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User’s Guide
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OM-DAQ-USB-2401
Multiple Channel USB Data
Acquisition Module
OM-DAQ-USB-2400
Multiple Channel USB Data Acquisition Module
TABLE OF
CONTENTS
Page
Section 1 - Introduction ....................................................................... 1-1
1.1 Precautions ................................................................................................ 1-1
1.2 Safety Warnings and IEC Symbols ......................................................... 1-2
1.3 Statement on CE Marking ........................................................................ 1-2
1.4 General Description and System Components .................................... 1-2
Section 2 - Hardware .......................................................................... 2-1
2.1 Package Inspection ................................................................................... 2-1
2.2 Included Items .......................................................................................... 2-1
Section 3 - Hardware Setup ................................................................. 3-1
3.1 OM-DAQ-USB-2400 Components ......................................................... 3-1
3.2 USB Hubs and Power Adaptors ............................................................. 3-1
3.2.1 USB-powered Hubs .................................................................... 3-2
3.2.2 Self-powered Hubs ..................................................................... 3-2
3.2.3 Power Adaptors .......................................................................... 3-2
3.3 Connecting Your OM-DAQ-USB-2401 Acquistition Systems To PC ... 3-3
3.4 Connecting Various Hardware Setups .................................................. 3-4
3.4.1 Direct Connection To Computer USB Port(s) ......................... 3-4
3.4.2 Connection To USB-powered Hub ........................................... 3-5
3.4.3 Connections To Self-powered and USB-powered Hubs ........ 3-5
3.5 OM-DAQ-USB-2401 Mounting .............................................................. 3-6
3.5.1 OM-DAQ-USB-2401 Wall Mounting ........................................ 3-7
3.5.2 OM-DAQ-USB-2401 DIN Rail Mounting ................................ 3-8
Section 4 - Software ............................................................................ 4-1
4.1 Getting Started .......................................................................................... 4-1
4.2 Software Installation ................................................................................ 4-1
4.2.1 System Requirements ................................................................. 4-1
4.2.2 Software Setup ............................................................................. 4-2
4.3 DAQ Central Software Operation .......................................................... 4-4
4.3.1 Main Control Window Pull-Down Operations ...................... 4-6
4.3.2 Device Configuration ................................................................. 4-8
4.4 Power Line Rejection .............................................................................. 4-14
4.5 Optical Isolation ....................................................................................... 4-14
4.6 A/D Conversion ..................................................................................... 4-14
4.7 Input Ranges .................................................................................................... 4-15
4.8 Analog Input Configuration .................................................................. 4-15
4.9 Measurement Duration, Scan Time, and Resolution ......................... 4-16
4.10 Automatic Calibration ...........................................................................4-17
4.11 Thermocouple Measurements ............................................................ 4-18
Section 5 - Signal Management ............................................................ 5-1
5.1 Channel Control and Expansion ............................................................ 5-1
5.2 Scan Time and Resolution ....................................................................... 5-1
5.2.1 Scan Time ..................................................................................... 5-1
5.2.2 Resolution [Effective Number of Bits (ENOB, RMS)] .............5-1
5.3 Under Sampling and Aliasing ................................................................ 5-2
i
OM-DAQ-USB-2400
Multiple Channel USB Data Acquisition Module
TABLE OF
CONTENTS
Page
5.4 Triggering ................................................................................................... 5-4
5.5 Signal Modes ............................................................................................. 5-4
5.6 System Noise ............................................................................................. 5-6
5.7 Averaging ................................................................................................... 5-6
5.8 Analog Filtering ........................................................................................ 5-6
5.9 Input and Source Impedance .................................................................. 5-7
5.10 Crosstalk .................................................................................................. 5-7
8.1 Service and Calibration ............................................................................ 7-1
Section 6 - CE Conformity ..................................................................... 6-1
6.1 OM-DAQ-USB-2401 Design for CE Conformity .................................. 6-1
Section 7 - Troubleshooting .................................................................. 7-1
7.1 Basic Checklist ........................................................................................... 7-1
7.2 Symptoms and Solutions ......................................................................... 7-1
Section 8 - Service and Calibration ....................................................... 8-1
8.1 Service and Calibration ............................................................................ 8-1
Section 9 - Specifications ..................................................................... 9-1
Section 10 - Approvals and Regulatory Compliance ........................... 10-1
10.1 International Usage and CE Marking ................................................ 10-1
ii
OM-DAQ-USB-2400
Multiple Channel USB Data Acquisition Module
LIST OF
FIGURES
List of Figures
Section
Figure
1-1
Description .............................................................. Page
IEC Symbols ............................................................... 1-2
System Components ................................................. 1-3
Section 1
1-2
Section 3
3-1
3-2
OM-DAQ-USB-2401 Hardware and Dimensions ... 3-1
Connection of an OM-DAQ-USB-2401 System
to a Computer USB Port ........................................... 3-3
3-3
3-4
3-5
Direct Connection to Computer USB Port ............. 3-4
Connection to USB-powered Hub .......................... 3-5
Connection to Self-powered Hub
and to USB-powered Hub ........................................ 3-6
3-6
3-7
OM-DAQ-USB-2401 Wall Mounting ...................... 3-7
OM-DAQ-USB-2401 Wall Mounting
Dimensions ................................................................ 3-7
3-8
OM-DAQ-USB-2401 Rail Mounting ....................... 3-8
Section 4
4-1
4-2
4-3
Welcome Screen ......................................................... 4-2
Select Install Screen ................................................... 4-2
Confirm Installation Screen ..................................... 4-3
Main Control Window ............................................. 4-4
Toolbar Buttons ......................................................... 4-5
File Menu .................................................................... 4-6
Device Menu .............................................................. 4-6
Tools Menu ................................................................. 4-7
Help Menu ................................................................. 4-7
Configuration Mode Channels Tab Screen ............ 4-8
Scan Options .............................................................. 4-9
Unit Options .............................................................. 4-9
Automatic Calibration .............................................. 4-9
Trigger Options ....................................................... 4-10
"Start Trigger" Options ............................................ 4-10
"Stop Trigger" Options ........................................... 4-10
Data Tab .................................................................... 4-11
Data "Save Behavior" Option ................................. 4-11
Main Window Screen ............................................. 4-12
Gauges Screen .......................................................... 4-12
Bars Screen ............................................................... 4-12
Digital Screen ........................................................... 4-12
Table Screen .............................................................. 4-12
Waveform Screen .................................................... 4-13
Sample Options Screen ........................................... 4-13
4-4
Table 4-1
4-5
4-6
4-7
4-8
4-9
4-10
4-11
4-12
4-13
4-14
4-15
4-16
4-17
4-18
4-19
4-20
4-21
4-22
4-23
4-24
iii
OM-DAQ-USB-2400
Multiple Channel USB Data Acquisition Module
LIST OF
FIGURES
List of Figures
Section
Figure
4-25
Description ............................................................. Page
OM-DAQ-USB-2400 Block Diagram .................... 4-14
4-26
OM-DAQ-USB-2401 Single-ended and Differential
Conections to Analog Input Channels Diagram ... 4-16
4-27
4-28
Calibration/Scan Arrangement ............................ 4-17
Thermocouple Wiring ............................................ 4-18
Section 5 Table 5-1
Scan Rate vs Resolution (ENOB, RMS) .................. 5-2
Examples of Under Sampling ................................. 5-3
Trigger Source Diagram ........................................... 5-4
Noise Reduction in Differential Mode ................... 5-5
Example of Floating Differential Circuit .................5-5
Analog to Digital Converter .................................... 5-7
5-1
5-2
5-3
5-4
5-5
Section 6
6-1
6-2
OM-DAQ-USB-2401 With Ferrite Cores Installed .. 6-1
Ferrite Core ................................................................ 6-2
Section 9 Table 9-1
Thermocouple Accuracy (C) for
OM-DAQ-USB-2400 .................................................. 9-1
iv
1
Introduction
Section 1 - Introduction
Please read this manual completely before installing and operating your Omega
data acquisition system. It’s important to read and follow all notes, cautions,
warnings and safety precautions before operating this device. “Device” refers to
your data acquisition unit.
1.1 Precautions
• This device is not designed for use in any medical or nuclear applications.
• Do not operate this device in flammable or explosive environments.
• Never operate with a power source other than the one recommended in this
manual or listed on product labels.
• This device has been designed for dry, moisture free indoor applications only.
• Do not operate this device outside of the recommended use outlined in this
manual.
• Never use your data acquisition unit as a portable device. Your unit has been
designed to be operated in a permanent installation only.
NOTE:
There are no user serviceable parts inside your device.
Attempting to repair or service your unit may void your
warranty.
NOTE:
The discharge of static electricity can damage some electronic
components. Semiconductor devices are especially susceptible
to ESD damage. You should always handle components
carefully, and you should never touch connector pins or
circuit components unless you are following ESD guidelines in
an appropriate ESD controlled area. Such guidelines include
the use of properly grounded mats and wrist straps, ESD
bags and cartons, and related procedures.
NOTE:
Never remove a USB cable from an active OM-DAQ-USB-
2401 unit while an acquisition is in progress. An active unit is
any unit that is currently open and has channels configured
for scanned input. Such disconnection may require you to exit
and then re-launch Omega DAQ Central, after the USB cable
has been connected.
1-1
1
Introduction
NOTE:
When using OM-DAQ-USB-2401 unit to acquire data,
computer energy save modes can cause false data readings.
Prior to using the unit, ensure your computer’s energy save
mode is disabled. If needed, consult your PC user’s manual to
disable energy save (power suspension) modes.
1.2 Safety Warnings and IEC Symbols
This device is marked with international safety and hazard symbols in
accordance with IEC standards. It is important to read and follow all precautions
and instructions in this manual before operating or commissioning this device as
it contains important information relating to safety and EMC. Failure to follow
all safety precautions may result in injury and or damage to your device. Use of
this device in a manner not specified will void your warranty.
IEC symbols
Description
Caution, refer to accompanying documentation
EU’s Waste Electrical and Electronic Equipment
Compliance
Figure 1-1. IEC Symbols
1.3 Statement on CE Marking
®
It is the policy of OMEGA to comply with all worldwide safety and EMI/EMC
regulations that apply. OMEGA is constantly pursuing certification of its
products to the European New Approach Directives. OMEGA will add the CE
mark to every appropriate device upon certification. For additional information
see Section 10 - Approvals & Regulatory Compliance.
1.4 General Description & System Components
The OM-DAQ-USB-2401 is a USB 2.0 full speed thermocouple/voltage input
data acquisition module (fully compatible with both USB 1.1 and USB 2.0 ports).
This stand-alone module draws power from the USB port to operate. An external
(optional) power supply can be used. All configurable options (including
individual channel input type and range) are software programmable.
The OM-DAQ-USB-2401 has user programmable voltage inputs that range from
30 mV to 10V, full scale. The compact, modular packaging ensures ease of use
in a variety of applications. Units can be DIN rail or wall mounted with the
included hardware or easily operated on a bench. All analog input channels can
be measured sequentially at about 1 ms per channel. A total of 1000 samples per
second can be taken, divided across all active channels.*
1-2
1
Introduction
NOTE:
*At highest scan rate, 1000 samples/sec +/- 1% with one
channel on, +/- 5% with all channels on.
The main items you will be using in your data acquisition system are the
OM-DAQ-USB-2401 unit, its USB cable, and power adaptor.
POWER
ADAPTER
(OPTIONAL)
OM-DAQ-USB-2401
MODULE
USB
PC WITH USB CONNECTION (NOT INCLUDED)
Figure 1-2. System Components
1-3
2
Hardware
Section 2 - Hardware
It is important that you read this manual completely and follow all safety
precautions before operating this instrument.
2.1 Package Inspection
Remove the packing list and verify that you have received all your equipment. If
you have any questions about the shipment, please call our Customer Service
Department at 1-800-622-2378 or 203-359-1660. We can also be reached on the
Internet at omega.com, e-mail: [email protected]. When you receive the
shipment, inspect the container and equipment for any signs of damage. Note
any evidence of rough handling in transit. Immediately report any damage to
the shipping agent.
NOTE:
The carrier will not honor any damage claims unless all
shipping material is saved for inspection. After examining
and removing contents, save packing material and carton in
the event reshipment is necessary.
2.2 Included Items
The following items are supplied in the box:
• 1 Omega OM-DAQ-USB-2401 data acquisition module
• 1 Omega DAQ Central software CD
• 1 USB Cable
• 1 9Vdc Power Adaptor
• 1 Mounting Kit (8 screws, 2 mounting brackets, 2 DIN rail adaptors)
• 1 Omega screwdriver
• 1 OM-DAQ-USB-2400 Series User Manual (this one, M-5025)
• 1 OM-DAQ-USB-2400 Series Quickstart Manual (MQS-5025)
• 2 Type K Thermocouples with Stripped Leads
2-1
3
Hardware Setup
Section 3 - Hardware Setup
3.1 OM-DAQ-USB-2401 System Components
127 (5.00)
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A N A L O G I N P U T
C H A N N E
A N A L O G I N P U T
C H A N N E L
1 2 V O U T
1 2 V O U T
107
(4.20)
!
7 & 8
5 & 6
97
(3.80)
OM-DAQ-USB-2400 SERIES
USB DATA ACQUISITION SYSTEM
CHANNEL 1 & 2
CHANNEL 3 & 4
12 V OUT
!
12 V OUT
ANALOG INPUT
ANALOG INPUT
A
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-
+
38
(1.5)
EXT
PWR
9V
1.0 A
PWR
IND
USB
STATUS
POWER SUPPLY
POWER LED
STATUS LED
USB PORT
DIMENSIONS mm (in)
Figure 3-1. OM-DAQ-USB-2401 Hardware and Dimensions
NOTE:
The external power port is used in applications which have
USB hubs that are not self-powered. See the next section for
more information.
NOTE:
The 'STATUS LED' blinking at Scan Rate means an acquisition
is in progress. At a fast scan rate, the 'STATUS LED' appears
solid. The 'POWER LED' in solid means the unit has power
3.2 USB Hubs and Power Adaptors
With the use of USB hubs you can connect up to 10 DAQ units to one PC. USB
hubs can be of the self-powered type, or of the USB-powered type. Both types of
hubs are available from a variety of vendors.
3-1
3
Hardware Setup
3.2.1 USB-powered Hubs
These hubs draw all power from the host USB connector’s power pins. The
power is used for hub internal functions and for the hub’s ports. Each port of a
USB-powered hub must be capable of supplying at least 100 mA.
3.2.2 Self-powered Hubs
These hubs draw power from a source other than the host USB connector, with
exception that they may draw up to 100 mA from their upstream connection for
hub internal functions. The external power is used for hub internal functions and
for the hub’s ports. Each port of a self-powered hub must be capable of
supplying 500 mA.
3.2.3 Power Adaptors
Power adaptors, also referred to as auxiliary power packs, are required for some
self-powered hubs, and for DAQ modules that are powered from USB-powered
hubs. In addition, DAQ units will require the use of a power adaptor when used
with certain laptops.
NOTE:
When using a power adaptor with your DAQ system, be sure
to supply power (from the adaptor to the DAQ unit) before
connecting the USB cable. This allows the DAQ to inform the
host computer (upon connection of the USB cable) that the
unit requires minimal power from the computer.
Power adaptors for use with the DAQ have a current limit of 500 mA (min.) and
a voltage range of +7.5 to +12 Volts DC. These specifications are provided on the
end-face of the DAQ unit.
If the computer does not recognize the DAQ unit, make sure the computer’s USB
port is properly enabled and is in good working order. If the computer still fails
to recognize the DAQ unit, the use of an external 9v DC power adaptor may be
required.
NOTE:
The use of certain notebook computers may require the use
of a power adaptor with your DAQ unit.
3-2
3
Hardware Setup
3.3 Connecting Your OM-DAQ-USB-2401 Acquisition System to PC
NOTE:
When using a power adaptor with your DAQ system, be sure
to supply power (from the adaptor to the DAQ) before
connecting the USB cable. This allows your DAQ to inform
the host computer (upon connection of the USB cable) that the
unit requires minimal power from the computer.
Use an approved high-speed USB cable to connect the DAQ system to one of the
host computer’s USB ports. There is no need for an additional power source in
this setup since the power pins (of the PC’s USB connection) supply 500 mA at 4
to 5.25 V. Additional setup examples are described in this chapter, some of which
involve USB hubs and/or power adaptors.
POWER
ADAPTER
(OPTIONAL)
USB
Figure 3-2. Connection of an OM-DAQ-USB-2401 System to a Computer USB Port
NOTE:
Certain notebook computers require the use of a power
adaptor with your DAQ unit.
3-3
3
Hardware Setup
3.4 Connecting Various Hardware Setups
ON-DAQ-USB-2401 data acquisition systems range from simple to complex. One
example of a simple system is that of one OM-DAQ-USB-2401 connected to a
PC’s USB connector. A much more complex system is one that contains 10 OM-
DAQ-USB-2401 units and a combination of USB-powered and self-powered
hubs. Despite the wide range of possibilities in between, use of the following
examples should enable you to properly connect your system.
NOTE:
In the examples that follow, the USB hubs have four external
ports (downstream ports). The USB hubs used in your system
may have more. Connections can be adjusted accordingly.
3.4.1 Direct Connection to Computer USB Port(s)
In this example, one DAQ unit is connected by cable to one of the computer’s
USB ports. The number of USB connectors may vary from PC to PC. When you
connect DAQ units directly to a USB connector in this manner, no additional
power source is required since the computer’s USB connector power pins supply
the DAQ with adequate power (500 mA at 4.75 to 5.25 V).
POWER
ADAPTER
(OPTIONAL)
USB
Figure 3-3. Direct Connection to a Computer USB Port(s)
3-4
3
Hardware Setup
3.4.2 Connection to USB-powered Hub
In this example, two OM-DAQ-USB-2401s are connected by cable to individual
ports of a single USB-powered hub. Since the hub receives all its power from the
computer’s USB, the hub cannot supply adequate power to the DAQ units.
Because of this aspect of insufficient power, each unit is connected to its own
power adaptor.
POWER
ADAPTER
POWER
ADAPTER
USB
HUB
USB
Figure 3-4. Connection to USB-Powered Hub
NOTE:
The power adaptors used must be capable of supplying at
least 500 mA and have a voltage rating of +7.5 to +12 Vdc.
3.4.3 Connections to Self-Powered and USB-powered Hubs
This example illustrates a system that makes use of four DAQ units and two
different style USB hubs. Two DAQs are connected by cable to individual ports
of a self-powered USB hub. In addition, the self-powered hub is connected to a
downstream USB-powered hub, which is also connected to two DAQ units.
Notice that the DAQ units connected to the self-powered hub have no adaptors
connected to them. This is because the hub receives external power (in addition
to the PC supplied USB power), which is capable of supporting the downstream
devices connected directly to it. In comparison, the three OM-DAQ-USB-2401s
connected to the USB-powered hub each require their own power adaptor. As in
example 3.4.2, the power adaptors used must be capable of supplying at least
500 mA and have a voltage rating of +7.5 to +12 Vdc.
3-5
3
Hardware Setup
POWER
ADAPTER
POWER
ADAPTER
USB
HUB
USB
POWER
ADAPTER
USB
HUB
Figure 3-5. Connections to Self-Powered Hub and to USB-Powered Hub
NOTE:
USB port locations vary from PC to PC.
3.5 OM-DAQ-USB-2401 Mounting
The OM-DAQ-USB-2401 mounting kit contains the following accessories:
• 2 mounting brackets (to be used for either wall or DIN rail)
• 4 long screws (to be used for either wall or DIN rail)
• 4 short screws (to be used for the DIN rail)
• 2 DIN rail plastic adaptors
3-6
3
Hardware Setup
3.5.1 OM-DAQ-USB-2401 Wall Mounting
In order to mount the OM-DAQ-USB-2401 to the wall, you will need to:
1. Remove the rear screws from the OM-DAQ-USB-2401.
2. Align the mounting brackets with the rear holes on the DAQ unit (make sure
that the ears are facing outwards, like in the figure below).
3. Use the longer screws to reconnect the mounting brackets to the body of the
enclosure, in the same direction as the screws that were removed from the
DAQ unit.
4. Drill 2 holes for #4 screws, 5.50" apart. Tip: Hold the DAQ unit with mounting
brackets attached, up against the wall; use the holes as a guide to mark where
you will drill holes in the wall.
5. Install the two screws into the wall.
6. Mount the DAQ unit on the wall by passing the screw head through the larger
mounting bracket holes and then sliding it down.
Figure 3-6. OM-DAQ-USB-2401 Wall Mounting
146 (6.00)
133 (5.50)
MOUNTING HOLE DISTANCE
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!
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5 & 6
Ø3
2 PLACES
(0.125)
OM-DAQ-USB-2400 SERIES
107
(4.20)
USB DATA ACQUISITION SYSTEM
Ø6
2 PLACES
(0.25)
CHANNEL 1 & 2
CHANNEL 3 & 4
12 V OUT
!
12 V OUT
ANALOG INPUT
ANALOG INPUT
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Figure 3-7. OM-DAQ-USB-2401 Wall Mounting Dimensions
3-7
3
Hardware Setup
3.5.2 OM-DAQ-USB-2401 DIN Rail Mounting
In order to mount the OM-DAQ-USB-2401 to a DIN-Rail, you will need to:
1. Attach the DIN-rail plastic adaptors to the mounting brackets, using the four
shorter screws.
2. Remove the rear screws from the OM-DAQ-USB-2401.
3. Align the mounting brackets with the rear holes on the DAQ unit (make sure
that the ears are facing inwards, like in the figure below).
4. Use the longer screws to reconnect the mounting brackets to the body of the
enclosure, in the same direction as the screws that were removed from the
DAQ unit.
5. Attach the DAQ unit to the DIN rail, using the plastic adaptors attached to the
mounting brackets.
Figure 3-7. OM-DAQ-USB-2401 Rail Mounting
3-8
4
Software
Section 4 - Software
4.1 Getting Started
The following program files are included on the Omega DAQ Central User
Software CD supplied with your data acquisition unit. These files can also be
downloaded from the omega.com website should you misplace your CD.
• DAQ Central data logging software installer
• Omega.DAQ .NET API
NOTE:
When using Omega DAQ modules to acquire data, computer
energy save modes can cause false data readings. Prior to
using Omega DAQ modules, ensure your computer’s energy
save mode is disabled. If needed, consult your PC user’s
manual to disable energy save (power suspension) modes.
4.2 Software Installation
4.2.1 System Requirements
Minimum Requirements:
• Processor: 800 MHz
• Hard Drive Space: 300 megabytes
• Ram: 512 megabytes or higher
• 1 Available USB Port
• CD-ROM Drive or Internet connection
• Windows XP Service Pack 3 (32-bit), Windows Vista (32-bit), Windows 7 (32-
bit), or Windows 7 (64-bit)
Recommended Requirements:
• Processor: 1.5 GHz
• Hard Drive Space: 300 megabytes
• Ram: 1.5 gigabytes
• 1 Available USB Port
• CD-ROM Drive or Internet connection
• Windows XP Service Pack 3 (32-bit), Windows Vista (32-bit), Windows 7 (32-
bit), or Windows 7 (64-bit)
4-1
4
Software
4.2.2 Software Setup
Insert the DAQ Central Software CD that was included with your DAQ unit into
the CD-ROM drive on your PC. Your system should begin the installation
process automatically. If the software installation does not start automatically:
open: "My Computer", double-click your CD-ROM drive, and run "setup.exe".
Figure 4-1. Welcome Screen
This welcome screen should be visible on your computer screen. To continue
with installing the program click the “Next >” button.
From this screen you select the folder were you want the program files installed
on your PC. The default setting will install the software under your “Program”
folders in a new folder named “Omega” To continue with installing the program
click the “Next >” button.
Figure 4-2. Select Install Screen
4-2
4
Software
Figure 4-3. Confirm Installation Screen
The setup wizard now has all the information to complete the installation of the
software on your PC. To continue with installing the program click the “Next >”
button.
During the install process, a Windows Command Prompt may pop up. No
interaction is required in this window; it is automatically installing or updating
the device’s USB drivers. Please let this process complete before closing the
software installation wizard.
Congratulations! You have just successfully installed the DAQ Central Program
on your PC. To end installing the program and close the setup wizard click the
“Close” Button.
4-3
4
Software
4.3 DAQ Central Software Operation
Below is the basic flow of operation when using the software:
1. Highlight desired device.
2. Open Device Configuration window.
3. Set channels, sample rate, triggering, and data output file.
4. Click “OK” to confirm Device Configuration.
5. Open any desired Data Displays.
6. Click the Start button.
Details on the various windows and options can be found in the rest of this
chapter.
Figure 4-4. Main Control Window
4-4
4
Software
TOOLBAR BUTTONS
Start Button
Initiates data acquisition for the
highlighted device. Even if a Start
Trigger is set, this must be pressed
to Arm the device.
Stop Button
Stops data acquisition for the
highlighted device. If a Stop
Trigger is set, this will cancel the
trigger.
Device
Configuration
Icon
Accesses the Device Configuration
window for the selected device.
The Device Configuration window
is used to set up all device options,
including channels, sample rate,
triggers, and data output file.
Gauges Display Opens a Gauges window.
Button
Displays measurements in analog
meter format.
Bars Display
Button
Opens a Bars window. Displays
measurements in a bar graph
format.
Digital Display
Button
Opens a Digital meter window.
Displays measurements in a digital
meter format.
Table Display
Button
Opens a Table window. Displays
measurements in a table format.
Waveforms
Display Button
Opens a Waveform window.
Displays the measurements in a
scrolling chart.
Device Display
List
Displays:
- The available connected DAQ
devices - DAQ2401DEMO –
Demo/simulation device for testing
software features without
hardware.- LEDs – Will flash green
during the data acquisition.
Table 4-1. Toolbar Buttons
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4.3.1 Main Control Window Pull-Down Operations
Below are the operations that are available in the Pull-Down Menus of the DAQ
Central Main Control Window.
Figure 4-5. File Menu
Open Configuration
Opens Device Configuration settings from a saved file
Save Configuration As Saves current Device Configuration settings to a new file name
These settings files contain all of the data that is found in the Device
Configuration window.
Figure 4-6. Device Menu
Detect Devices
Configuration
Detects available OM-DAQ-USB-2401 devices which are currently
connected to the computer through the USB.
Same function as Configuration button
Accesses the device
.
Configuration window to configure ‘Channels’ settings, ‘Triggers’
settings, and ‘Data’ settings.
Start Acquisition Same function as Start button
. Initiates data acquisition for
.
the highlighted device. Even if a Start Trigger is set, this must be
selected to Arm the device.
Stop Acquisition Same function as Stop button
. Stops data acquisition for the
highlighted device. If a Stop Trigger is set, this will cancel the trigger.
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Figure 4-7. Tools Menu
Export Data File – To convert data file from binary file to .csv file
Fgure 4-8. Help Menu
Check for Updates To check for the latest Omega DAQ Central software update
information through the Internet connection.
About
To view software version.
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Section 4.3.2 Device Configuration
The Device Configuration window contains the Channel, Triggers, and Data
tabs. Details for these tabs are below. When finished making changes, press
“OK” to confirm the changes or “Cancel” to abandon the changes.
Figure 4-9. Configuration Mode - Channels Tab Screen
Channels Tab
The Channels tab contains a spreadsheet designed for setting up channels for
data acquisition. Depending on the column, you can make changes to the
information contained in a cell by placing the mouse cursor in the cell.
All columns except “Channel” are editable. Those with drop-down arrows are
limited to the choices in the drop-down list.
You can use your PC’s keypad arrow and tab keys to select new “active cells” in
the spreadsheet.
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Software
Configuration Parameter Settings
Channel The input channel’s name (not editable)
AN1D = analog channel 1, differential input
AN1H = analog channel 1, single-ended high input
AN1L = analog channel 1, single-ended low input
Etc.
Nickname You can specify the Nickname (e.g., Oven 1, Monitor
Room)
Units
You can specify the Engineering Unit. When switching
between voltage and thermocouple ranges, this will
automatically switch to the default units for that range.
However, any units label may be typed in here.
On/Off
To turn on or turn off the selected input channel
Single/Diff You can select input channel as Single-ended or
Differential input.
Range
You can select the voltage input range or thermocouple
type for each input channel. Thermocouples must
always be used with Differential input.
Scale and You can rescale the input signal. This scaled/offset
Offset
value will appear in all data displays, and in any saved
data files.
Sampling can be set in terms of “Scan Rate” or “Scan Time”.
Scan Rate = 1/(Scan Time).
For example, if you are acquiring 4 voltage inputs at 250 Hz, you will receive 250
complete scans per second. Meaning each channel will send 250 pieces of data
every second, for a total of (4 x 250) = 1000 pieces of data.
The maximum scan rate is affected by the number of channels turned on.
Selecting thermocouple input also lowers the maximum scan rate.
Figure 4-10. Scan Options
Figure 4-11. Units Options
Figure 4-12. Automatic Calibration
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Figure 4-13. Trigger Options
The Triggers tab is used to set up triggers for starting and stopping data
acquisition. The Start Trigger and the Stop Trigger each have a different set of
available trigger types:
Figure 4-14. "Start Trigger" Options
Figure 4-15. "Stop Trigger" Options
Trigger Types
Manual
Acquisition is manually started/stopped.
Level
Set trigger to stop/start acquistition when the input level is either above or below a certain threshold.
Date/Time Set trigger to stop/start acquistition at a certain date and time, as per the PC’s clock.
Time Span Set trigger to stop acquistition after a certain elapsed time.
Scan Count Set trigger to stop acquistition after a certain number of scans have been acquired.
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NOTE:
For all Start Trigger types, the device must be armed by pushing the Start Button on the main window.
Data storage and display will not begin until the device triggers.
Data Tab
Figure 4-16. Data Tab
To save data to a file on the PC, select the Data tab and choose a filename. This data
can be saved in Binary or Delimited (.csv) format.
• Binary format is faster, and is recommended for slower PCs. Binary format also
creates files that are about 50% smaller than Delimited files. Binary files can be
converted to “.csv” format later by selecting Tools --> Export Data File.
• Delimited format can use either commas or tabs as the delimiter, and the time can
be saved as Elapsed Time or as a Date/Time stamp.
There are three “Save Behavior” options:
FIG 4-17. Data ‘Save Behavior’ Options
Auto-overwrite
If a file with the same name already exists, it will be automatically overwritten when
the Start Acquisition button is pressed.
Prompt for
overwrite
If a file with the same name already exists, a prompt
will appear when the Start Acquisition button is pressed.
Add creation
time to
filename
A timestamp is added to the filename, in the format
YYYY-MM-DD-hhmm-ss. For example, MyFile.bin
becomes MyFile-2011-1031-1121-03.bin. The timestamp will be automatically added
every time the Start Acquisition button is pressed, so multiple acquisitions can be easily
stored to the same folder without revisiting the Device Configuration window.
Data Displays
From the Main Window, you can choose to view live data from any combination of Gauges, Bars,
Digital Displays, Tables, and Waveforms. These displays can be opened by clicking the appropriate
button in the Main Window.
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Software
Figure 4-18. Main Window Screen
Figure 4-19. Gauges Screen
Figure 4-20. Bars Screen
Figure 4-21. Digital Screen
Figure 4-22. Table Screen
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Software
Figure 4-23. Waveform Screen
Each Data Display can be customized by clicking the Options Icon
.
Each Data Display's Options screen lets you choose which device channels to
display in that window. Channels can be added or removed with the Add
Display
and Delete Display
buttons. Confirm changes by clicking the
OK button. Start Acquistion by clicking the Play button on the Main Window.
Acquistion can be stopped with the Stop button.
Figure 4-24. Sample Options Screen
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4.4 Power Line Rejection
The OM-DAQ-USB-2401 Series can take readings while making use of 50/60Hz
line cycle rejection. While in the line cycle rejection mode, the maximum sample
rate is as follows:
• 50 Hz rejection: Scan Rate (SR) Range: 0.153Hz < SR <= 1Hz
• 60 Hz rejection: Scan Rate (SR) Range: 1Hz < SR <= 1.667Hz
OMB-DAQ-USB-2401 Series Block Diagram
Power LED
Isolation
Barrier
Power Supply
Isolated
Power Supply
Power Jack
Local Power
USB
Jack
USB
Controller
MCU
32Bit
Activity LED
Digital Isolators
CJC
4
Analog Inputs
Gain =
x2, 1/8
+12v
+12v output
Excitation voltage
SE/
DI
MUX
PGIA
CJC
4
Analog Inputs
Gain =
x1,2,4,8,16
32,64
+12v output
Excitation voltage
24–Bit
A/D
PGA
MUX
1MΩ
1MΩ
CJC
4
Analog Inputs
Gain =
x2, 1/8
+12v
+12v output
Excitation voltage
SE/
DI
PGIA
MUX
CJC
4
Analog Inputs
+12v output
Excitation voltage
1MΩ
1MΩ
Figure 4-25. OM-DAQ-USB-2400 Block Diagram
4.5 Optical Isolation
Your DAQ unit is optically isolated from its host PC by up to 500 Vdc. This
means that an inadvertent application of such voltage to the DAQ unit will not
affect the PC. In addition to isolation, the device maintains all sensitive
acquisition-related circuitry external to the PC. This physical isolation of
circuitry from the PC results in less noise and more accurate measurements.
4.6 A/D Conversion
OM-DAQ-USB-2401 uses an extremely low-noise, 24-bit analog-to-digital (A/D)
converters. They provide complete high-resolution measurement solutions for
the most demanding applications.
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The converter is comprised of a 4th-order, delta-sigma (Δ∑) analog-to-digital
(A/D) converter modulator followed by a programmable digital filter. A flexible
input multiplexer handles differential or single-ended signals; the programmable
filter allows the user to optimize between a resolution of up to 23 bits noise-free.
Examples of scan sequences, with various channel resolutions and calibration
arrangements, appear in Table 5-1 on page 5-2.
4.7 Input Ranges
You can individually select the input range for each channel. For example, one
channel could be used for volts and another for temperature. Omega’s OM-
DAQ-USB-2401 automatically assigns the appropriate units depending on two
factors:
• The selected range and
• Measurement unit preferences
Measurement unit preferences can be modified from the Omega DAQ Central
‘Channels’ tag of the ‘Configuration’ window. Chapter 4 provides more detailed
information.
NOTE:
The maximum voltage input range (full scale) is –10 to +10
Vdc. The lowest programmable voltage input range is -30mV
to +30 mV. A complete list of the OM-DAQ-USB-2401’s
programmable ranges appears on page 8-1.
Each analog input channel has the following user-specified measurement
parameters:
• Signal type: volts, or thermocouple type J, K, T, E, R, S, B, or N
• Full scale voltage: from -10 to + 10 Vdc; with programmable ranges as
indicated on page 8-1.
• Resolution/sample period: from 22.5 bit RMS at 0.153 samples/sec, to 17 bit
RMS at 50 samples/sec or greater
NOTE:
These rates were obtained with a 16-channel scan.
4.8 Analog Input Configuration
The OM-DAQ-USB-2401 includes 16 analog signal inputs which may be used as
16 single-ended inputs, 8 differential inputs, or as a combination of single-ended
and differential inputs with up to 16 connections.
Single-ended inputs are used with signals that share the same common low
(COM), such as multiple batteries which have their negative sides connected in
common. Differential inputs are required when signals do not share the same
common low, such as in the typical use of thermocouples.
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NOTE:
In DAQ applications, thermocouples should not be connected
single-ended. Doing so can result in noise and false readings.
This is especially true when acquiring other high-amplitude
signals in conjunction with thermocouple signals that are
connected single-ended.
The DAQ units include built-in cold-junction compensation (CJC), which is
automatically invoked when you select TC measurements. The OM-DAQ-USB-
2401 automatically converts acquired voltage readings into compensated-
linearized temperature readings. This DAQ system can make thermocouple and
volts measurements concurrently.
OM-DAQ-USB-2401
TERMINAL BLOCK
(PARTIAL)
A
1
H
A
1
L
C
O
M
A
2
H
A
2
L
V1
V2
COM
V3+
V3
V
3-
Figure 4-26. OM-DAQ-USB-2401 Single-Ended and Differential Connections to
Analog Input Channels Diagram
Figure Notes: *V1 and V2 are single-ended inputs.
*V3 is a thermocouple and is a differential input.
4.9 Measurement Duration, Scan Time, and Resolution
In relation to sampling analog input, the terms measurement duration, sample
rate, and resolution have the following meanings:
Measurement duration (per channel) – the amount of time used for sampling a
channel’s input signal. The measurement durations for the OM-DAQ-USB-2401's
analog channels range from very slow (400 milliseconds for one measurement
duration) to very fast (1 millisecond for one measurement duration).
Scan Time (per scan) - The amount of time used for scanning (sampling) all
selected channels’ input signal. For the OM-DAQ-USB-2401, the scan rates range
from very slow (1 hour per scan) to very fast (1 milliseconds per scan).
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Resolution (Effective Number of Bits - ENOB, RMS) – The number of reliable
data bits that exist for a signal’s measurement. The greater the resolution, the
more detailed the reading. For example, with an increased resolution, a reading
of 5.12 V could become 5.11896 V. The DAQ actually provides for 24 bits of data
information; however, the accuracy of the least significant bits decreases as the
measurement duration speeds up.
NOTE:
When measuring variable input signals (as opposed to
relatively steady input signals), the variable signals will
require more samples/sec to obtain a realistic signal
representation.
At a scan time greater than 6.5 seconds, the last 1.5 bits are considered unreliable,
resulting in a resolution of 22.5 bits. At a very fast scan time (1 millisecond), the
seven least significant bits are unreliable, resulting in 17 bit accuracy. When you
select the Scan Time you also determine the scan (sample) rate and resolution for
the applicable channel. For the DAQ’s analog input applications, scan (sample)
rates range from 0.0002778 samples/sec (1 hr/scan) up to 1000 samples/sec
(m/scan), and corresponding resolution ranges from 22.5 to 17 bits.
4.10 Automatic Calibration
The DAQ unit contains a built-in source for performing automatic self-
calibrations. These calibrations can be performed between scans periodically
throughout the measurement process, as indicated in the following figure. Such
calibration ensures accurate measurements, even in environments that
experience significant temperature fluctuations. The figure below shows an
initial calibration followed by the scan/calibrate, scan/calibrate pattern.
NOTE:
The continuous calibration feature is built into the DAQ
system. With Auto-Calibration enabled, you may experience
slower sample rates especially with multiple chanels turned on.
INITIAL CALIBRATION
SCAN
CALIBRATION
SCAN PERIOD
SCAN
CALIBRATION
SCAN
CALIBRATION
TIME
0
Figure 4-27. Calibration/Scan Arrangement
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4.11 Thermocouple Measurements
The OM-DAQ-USB-2401 provides effortless thermocouple (TC) measurements.
The unit includes built-in cold-junction compensation (CJC), which is
automatically invoked when you select TC measurements. The DAQ unit
automatically converts acquired voltage readings into compensated-linearized
temperature readings. A DAQ system can make thermocouple and volts
measurements concurrently.
TIP: If you experience noise from thermocouple wires, you can connect a 100K
resistor from AxL to the COM to elimate some noise. Please reference the
following diagram:
CONNECT A 100K RESISTER
TO ELIMATE SOME
THERMOCOUPLE INPUT NOISE
A
1
H
A
1
L
C
O
M
A
2
H
A
2
L
100K
V3+
V3
V
3-
Figure 4-28. Thermocouple Wiring
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5
Signal Management
Section 5 – Signal Management
5.1 Channel Control and Expansion
In the OM-DAQ-USB-2401 system, the quantities and types of DAQ units used
determine the system’s channel capacity. Up to 10 OM-DAQ-USB-2401s can be
used with one host PC. See the Specifications for more detailed channel
information.
5.2 Scan Time and Resolution
5.2.1 Scan Time
Scan Time (per scan) - The amount of time used for scanning (sampling) all
selected channels’ input signal. For the OM-DAQ-USB-2401, the scan rates range
from very slow (1 hour per scan) to very fast (1 milliseconds per scan).
5.2.2 Resolution (Effective Number of Bits – ENOB, RMS)
Resolution (Effective Number of Bits - ENOB, RMS) – The number of reliable
data bits that exist for a signal’s measurement. The greater the resolution, the
more detailed the reading, for example, with increased resolution a reading of
5.12 V could become 5.11896 V. The DAQ actually provides for 24 bits of data
information; however, the accuracy of the least significant bits becomes less as
the measurement duration speeds up.
At a scan time greater than 6.5 seconds, the last 1.5 bits are considered unreliable,
resulting in a resolution of 22.5 bits. At a very fast scan time ( 1 milliseconds), the
seven most least significant bits are unreliable, resulting in 17 bit accuracy.
When you select the Scan Time you also determine the scan(sample) rate and
resolution for the applicable channel. For the DAQ’s analog input applications,
scan(sample) rates range from 0.0002778 samples/sec up to 1000 samples/sec
and corresponding resolution ranges from 22.5 to 17 bits.
5-1
5
Signal Management
2
Scan Rate vs. Resolution
Resolution
3,4
5
Scan Rate (Scans
(ENOB
1
Speed Designation
Scan Time (s)
per Second - SPS)
RMS)
Very Slow, 50 / 60 Hz rejection
3600s>=ST >= 6.5s
0.0002778=< SR <=
0.153
22.5
Slow, 50 Hz rejection
Slow, 60 Hz rejection
Medium, 60 Hz rejection
Medium, 50 Hz rejection
Medium
6.5s> ST >= 1s
1s> ST >=0.6s
0.153 < SR <=1
1 < SR <= 1.67
1.67 < SR <= 3.33
3.33 < SR <= 5
5 < SR <= 20
21
20.9
20.4
20.3
19.2
18.7
17
0.6s> ST >=0.3s
0.3s> ST >=0.2s
0.2s> ST >=0.05s
0.05s> ST >=0.02s
0.02s> ST >=0.001s
Fast
20 < SR <= 50
50< SR <= 1000
Very Fast
Table 5-1. Scan Rate vs. Resolution (ENOB, RMS)
Notes:
1. Scan Rate = 1/(Scan Time);
2. Each channel can have independent measurement duration and resolution.
3. The scan rates and resolutions shown were obtained with a 16-channel scan and with continuous
self-calibration.
4. When measuring TC input, the CJC measurements will be treated as a channel.
5. ENOB, Effective Number of Bits
5.3 Under Sampling and Aliasing
When you select the Scan Time you also determine the scan rate and resolution
for the applicable channel. As shown in the previous table, scan rates range from
0.0002778 scans/sec up to 1000 scans/sec and corresponding resolution ranges
from 22.5 to 17 bit (for the DAQ’s analog input applications).
When measuring highly variable input signals (as opposed to relatively steady
input signals), the variable signals will require more scans/sec to obtain a
realistic signal representation. When too few samples are taken, the term under
sampling is often used. Under sampling tends to lower the signal’s graphed
amplitude. This is also known as aliasing. In such cases, the inadequate number
of samples results in a “flattening” of the signal. Gross under sampling can even
result in a relatively flat line, even though the actual signal is a waveform.
For best results the sample rate (scan rate) should be at least 10 times the
measurement frequency. If possible it is recommended that you set the scan rate
to 20 times the frequency of the input signal.
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Signal Management
The following table provides general advice regarding the selection of Scan
Time. The concepts are further illustrated by the figure, Examples of Under
Sampling.
Scan Time
(Measurement
Duration)
Scan Rate
(Sample Rate)
Analog Input Signal
Resolution
High
Steady, or gradual
change
Long
Low
Highly variable
(unsteady)
Short
High
Low
Figure 5-1. Examples of Under Sampling
The above figure depicts three signals from the same temperature fluctuations.
Under Sampling (aliasing) is evident in two of the signals. Elaboration follows:
Signal 1:
This signal, based on 1 sample(scan) per division, is represented by a heavy solid
line and sample-points designated by polygon symbols. The signal represented
is a fairly accurate portrayal of the actual temperature fluctuations.
Signal 2:
This signal, based on 1 sample(scan) every 3 divisions, is represented by a heavy
dotted line and sample-points designated by squares. Under sampling has
resulted in a distortion, in effect, a lower amplitude than that exhibited by the
first signal, even though each measured point is accurate.
Signal 3:
This signal, based on 1 sample(scan) every 4 divisions, is represented by a
dotted/dashed line and sample-points designated by plus signs (+). Fewer
samples (a greater degree of under sampling) has resulted in a further distortion
and lowering of signal amplitude.
From these examples it should be realized that more samples(scans) will result in
a more accurate representation of the actual signal, and that under sampling will
tend to lower the amplitude of the signal, exhibiting a trend toward a “flat line”
state.
As stated earlier, the more variability a signal has, the more samples that are
needed to accurately portray it.
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Signal Management
5.4 Triggering
Triggering controls an acquisition cycle. Once the system is armed, a trigger is
required to collect the data.
The user must determine the triggering requirement based on the nature of the
measurement and the amount of data needed to satisfy the system’s purpose.
The trigger source can be a software command or an analog input channel on
reaching a specified voltage level can be used to trigger the system.
IMMEDIATE
TYPE OF
START TIME
TRIGGER SOURCE
CHANNEL VALUE - RISING
- FALLING
TRIGGER EVENT
POST-TRIGGER SCAN COUNT
SCAN GROUP
TIME
SCAN PERIOD
Figure 5-2. Trigger Source Diagram
5.5 Signal Modes
OM-DAQ-USB-2401 units operate in one of two modes, (1) single-ended mode,
or (2) differential mode. These terms (single-ended mode and differential mode)
apply to their use in this manual. In other sources these terms may be used in a
different manner.
Choosing between differential and single-ended inputs is made by software
command. The following text briefly describes the two signal modes.
Single-ended mode refers to a mode, or circuit set-up, in which a voltage is
measured between one signal line and common ground voltage (Vcm). The
measured voltage may be shared with other channels. The advantage of a single-
ended non-differential mode [over differential mode] is that it provides for a
higher channel count, for example: 16 channels instead of 8.
NOTE:
In DAQ applications, thermocouples should not be connected
single-ended. Doing so can result in noise and false readings.
This is especially true when acquiring other high-amplitude
signals in conjunction with thermocouple signals that are
connected single-ended.
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5
Signal Management
Differential mode refers to a mode, or circuit set-up, in which a voltage is
measured between two signal lines. The measured differential voltage is used for
a single channel. An advantage of using differential inputs is that they reduce
signal errors and the induction of noise resulting from ground current. The
following illustration is an example of how noise is reduced, or canceled-out,
when using the differential
Figure 5-3. Noise Reduction in Differential Mode
In the schematic, voltage signal S2 is subtracted from signal S1, resulting in the
output signal shown. The noise spikes (having the same polarity, phase, and
magnitude in each input signal) cancel each other out. This results in a clean
differential signal (S1 - S2).
Floating-differential measurements are made when low-level signals must be
measured in the presence of high levels of common-mode noise (e.g., a non-
grounded thermocouple). When the signal source has no direct connection to the
system analog common, one must be provided. In Omega Daq the connection to
analog common is provided in the circuitry with both the channel high and
channel low connected to analog common. Both of these connections to common
are made through 1 MΩ resistors. No additional connections of channel high and
low to common should be made.
Figure 5-4. Example of Floating Differential Circuit
NOTE:
Differential signal hookups do not provide isolation or any
kind of circuit protection.
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5
Signal Management
Resolution: An analog-to-digital converter (ADC) converts an analog voltage to
a digital number. The digital number represents the input voltage in discrete
steps with finite resolution. ADC resolution is determined by the number of bits
that represent the digital number. An n-bit ADC has a resolution of 1 part in 2n.
Thus, 12 and 16 bit resolutions are as follows:
• 12-bit resolution: 1 part in 4096 (212), corresponding to 2.44 mV in a 10 V
range.
• 16-bit resolution: 1 part in 65,536 (216), corresponding to 0.153 mV in a 10 V
range.
5.6 System Noise
Laboratory and industrial environments often have multiple sources of electrical
noise. An AC power line is a source of 50/60 Hz noise. Heavy equipment (air
conditioners, elevators, pumps, etc.) can be a source of noise, particularly when
turned on and off. Local radio stations are a source of high-frequency noise, and
computers and other electronic equipment can create noise in a multitude of
frequency ranges. Thus, an absolute noise-free environment for data acquisition
is not realistic. Fortunately, noise-reduction techniques such as averaging,
filtering, differential voltage measurement, and shielding are available to reduce
noise to an acceptable level.
5.7 Averaging
Certain acquisition programs apply averaging after several samples have been
collected. Depending on the nature of the noise, averaging can reduce noise by
the square root of the number of averaged samples. Although averaging can be
effective, it suffers from several drawbacks. Noise in measurements only
decreases as the square root of the number of measurements—reducing RMS
noise significantly may require many samples. Thus, averaging is suited to low-
speed applications that can provide many samples.
NOTE:
Only random noise is reduced or eliminated by averaging.
Averaging does not reduce or eliminate periodic signals.
5.8 Analog Filtering
A filter is an analog circuit element that attenuates an incoming signal according
to its frequency. A lowpass filter attenuates frequencies above the cutoff
frequency. Conversely, a high-pass filter attenuates frequencies below the cutoff.
As frequency increases beyond the cutoff point, the attenuation of a singlepole,
low-pass filter increases slowly. Multi-pole filters provide greater attenuation
beyond the cutoff frequency but may introduce phase (time delay) problems that
could affect some applications.
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Signal Management
5.9 Input and Source Impedance
As illustrated below, the input impedance (Ri) of an analog-to-digital converter
combines with the transducer’s source impedance (Rs) forming a voltage
divider. This divider distorts the voltage being read at the analog-to-digital
converter. The actual voltage read is represented by the equation:
VADC = VT x Ri / (Rs + Ri)
The input impedance (Ri) of most ADCs is at least 1 MΩ; low source impedance
(Rs) usually presents no problem. Some transducers, such as piezoelectric types,
have high source impedance, and should therefore be used with a charge-
sensitive amplifier of low output impedance. As described in the following
paragraphs, multiplexing can greatly reduce the effective input impedance of an
analog-to-digital converter.
Figure 5-5. Analog to Digital Converter
5.10 Crosstalk
Crosstalk is a type of noise related to source impedance and capacitance, in
which signals from one channel leak into an adjacent channel, resulting in
interference or signal distortion. The impact of source impedance and stray
capacitance can be estimated by using the following equation.
T = RC
Where T is the time constant, R is the source impedance, and C is the stray
capacitance.
High source (transducer) impedance can be a problem in multiplexed A/D
systems. When using more than 1 channel, the channel input signals are
multiplexed into the A/D. The multiplexer samples each signal and then
switches to the next input signal. A high-impedance input interacts with the
multiplexer’s stray capacitance and causes crosstalk and inaccuracies in the A/D
sample.
A solution to high source impedance in relation to multiplexers involves the use
of buffers. The term buffer has several meanings; but in this case, buffer refers to
an operational amplifier having high input impedance but very low output
impedance. Placing such a buffer on each channel (between the transducer and
the multiplexer) prevents the multiplexer’s stray capacitance from combining
with the high input impedance. This use of a buffer also stops transient signals
from propagating backwards from the multiplexer to the transducer.
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6
CE Conformity
Section 6 - CE Conformity
6.1 OM-DAQ-USB-2401 Design for CE Conformity
The OM-DAQ-USB-2401 has been designed to meet requirements as outlined in
European Community EMC Directive EN61326. Three ferrite cores are included
in the OM-DAQ-USB-2401 package. When powering the unit using the adapter,
the ferrite cores must be attached to both the USB cable and the power adapter to
meet EFT (Electrical Fast Transient) specifications. Refer to Figure 6-1.
POWER
ADAPTER
USB
(MIDPOINT OF CABLES)
Figure 6-1. OM-DAQ-USB-2401 with Ferrite Cores Installed
To maintain CE certification and install the ferrite cores, perform the following:
1. Using a small screw driver or other suitable instrument, unsnap the ferrite
core to open it (as shown in Figure 6-2).
2. Install one ferrite core on each far end of the USB cable, and one ferrite core in
the middle of the cable (as shown in Figure 6-1).
3. Install one ferrite core on each far end of the power adapter, and one ferrite
core in the middle of the cable (as shown in Figure 6-1).
6-1
6
CE Conformity
UNSNAP
FERRITE
CORES
HERE
Figure 6-2 Ferrite Core
The ferrite cores may be removed from the DAQ unit; however, in order to
conform to CE standards, all of the ferrite cores must be attached to the USB
cable and power adapter.
NOTE:
If the user is not using the power adapter but relying on
power from the host USB connection, no ferrites are required.
6-2
7
Troubleshooting
Section 7 – Troubleshooting
7.1 Basic Checklist
Power – Check USB cable connection. The green “PWR IND” LED should be lit
on the DAQ device. If using a powered USB hub, make sure its power cable is
plugged in.
Signal – Check signal lines and connections. Connectors must be free of
corrosion. Signal lines should be undamaged and free of sharp bends and twists.
Signal paths should avoid potential sources of noise (high voltage and
electromagnetic interference).
Device Selection – Make sure the serial number selected in the software matches
the serial number of your device. Each data display will show the serial number
(or Nickname, if assigned) of the device it is currently displaying.
“DAQ2401DEMO” is a software demo device which outputs a sine wave.
Software Updates – A software update may be available. In DAQ Central,
choose “Check For Updates” from the Help Menu on an Internet-connected PC.
7.2 Symptoms and Solutions
USB drivers are not found or hardware installation fails. This can happen if the
device is plugged into the computer’s USB port before software installation is
complete. The program “C:\Program Files\Omega\DAQ Central\USB
Drivers\CDM20814_Setup.exe” can be run to reinstall the USB drivers. All non-
critical USB devices should be unplugged while this program runs, including all
DAQ devices.
The “20814” portion of this filename may be different, and the “DAQ
Central\USB Drivers” directory may be in a different location if an alternate
directory was chosen during installation.
Data does not appear or data does not make sense. See “Device Selection”
under Basic Checklist.
Stop the acquisition and check the Triggers tab of the Device Configuration
window. A trigger may be set to start acquisition at a future date. Try setting
both Start and Stop triggers to manual and restarting acquisition.
The Device Configuration screen is grayed out. A data acquisition may be
running. A device’s configuration can not be edited during acquisition.
The waveform scale is too small/large The vertical scale can be adjusted by
clicking the max and min values on the y-axis. The horizontal scale can be adjusted
from the Waveform Options screen, which is accessed by clicking the Options button
at the top of the Waveform window. The “Scans to graph” setting determines how
many data points (scans) will appear along the x-axis. A higher number shows a
greater span of time, but uses more of the PC’s RAM and may slow it down.
The main DAQ Central window does not respond. A configuration window
may be open. Configuration windows must be closed before continuing to
interact with the software. Check your desktop and Windows taskbar for a
Device Configuration window or an Options window.
The device does not appear in the device list. Select “Detect Devices” from the
Device menu to re-scan for connected devices. See also “Power” under “Basic
Checklist” and “USB drivers…” in this section.
Thermocouple inputs are noisy. If you experience noise from thermocouple
wires, you can connect a 100K resistor from AxL to COM to eliminate some noise.
7-1
8
Service and Calibration
Section 8 – Service & Calibration
Your Omega DAQ components have been built and factory calibrated to meet or
exceed the specifications listed here in this manual. The following section
provides information on how to have your device serviced.
8.1 Service & Calibration
If any of your DAQ system components require service or calibration, please call
our Customer Service Department at 1-800-622-2378 or 203-359-1660. They will
assist you in arranging the return and service of your device. We can also be
8-1
9
Specifications
Section 9 – Specifications
General Isolation:
500V from PC
External Excitation Output Voltage: +12v DC Regulated,
Maximum total current output 67mA
Power Requirements:
Powered from USB port max 500 mA,
or from external 7.5 to 12 Vdc,
(1.0 A recommended)
Thermocouple Types:
J, K, T, E, R, S, B, N
Cold-Junction Compensation
Accuracy:
1.0°C
Isolation:
500 Vdc from PC common
Channel Capacities:
Volts Inputs: 8 DE, or 16 SE
Thermocouple Inputs: 8 DE
* DE = Differential Mode,
SE = Single ended mode
Environmental:
0 to 50°C (0 to 122°F)
95% RH (non-condensing)
Operating Temperature:
0 to 50°C (32 to 122°F),
0 to 95% RH non –condensing
Analog Input Accuracy
Differential Input:
(exclusive of noise)
0.015% of reading + .004% of range
(In very slow mode)+ 10uV
(exclusive of noise)
Single-end Input:
0.05% of reading + 0.01% of range
(In very slow mode) + 50uV
(exclusive of noise)
Storage Temperature:
Weight:
-40 to 85°C (-40 to 185°F)
0.5 lbs (0.23 kg)
Dimensions:
107 W x 128 L x 39mm H (4.2 x 5.1 x 1.5")
Input Voltage Range:
Software-programmable On A Per-
channel Basis
Differential/Single-ended:
-10 to 10V
-5 to 5V
-2.5 to 2.5V
-2 to 2V
-1 to V -500 to 500 mV
-250 to 250 mV
-125 to 125 mV
-75 to 75 mV
-30 to 30 mV
9-1
9
Specifications
Thermocouple Input Range:
Type J: -18 to 1200°C (0 to 2192°F)
Type K: -129 to 1372°C (-200 to 2502°F)
Type T: -101 to 400°C (-150 to 752°F)
Type E: -184 to 1000°C (-300 to 1832°F)
Type R: 204 to 1768°C (400 to 3214°F)
Type S: 204 to 1768°C (400 to 3214°F)
Type B: 538 to 1820°C (1000 to 3308°F)
Type N: -129 to 1300°C (-200 to 2372°F)
Cold Junction
Compensation Accuracy:
1.0°C
Input Voltage Range Relative
To Analog Common (COM):
Input Resistance:
-10 to +10 Vdc
1MΩ (single ended);
2MΩ (differential); 5%
Absolute Maximum Input Voltage:
20 V maximum,
relative to analog common
Warm-up:
1 hour to rated specifications
USB 2.0 (full-speed)
USB Device Type:
Device Compatibility:
Power Supply:
USB 1.1, USB 2.0
From USB(Port) or 9 Vdc adaptor
External Power Source:
Required when used with a bus-powered
hub;
DIN Rail Mounted For
Rack Application:
Optional
Open Thermocouple Detect:
Automatically enable when a channel is
configured for a thermocouple sensor.
Limitations of the Total Recording
Memory Size:
1 G or 500M (in PC)
32 bit
MCU:
NOTE:
All temperature specifications assume unit is held in relatively
still air environment.
NOTE:
UNIV-AC-100/240, the external power supply is a Universal
Power Adaptor. It is a 100-240 VAC to+9 Vdc output
adaptor
9-2
9
Specifications
Table 9-1. Thermocouple Accuracy (ºC) for OM-DAQ-USB-2401
TC Type
Temp.
(°C)
Typical
Slow
Fast
-18
0
1200
1.3
1.1
0.9
3.8
3
2.5
J
-129
0
1.8
1.4
1.3
5
3.9
3.7
K
T
E
R
1372
-101
0
400
1.6
1.4
1
4.5
4
2.9
-184
0
1000
1.2
0.9
0.7
3.4
2.6
1.9
204
700
1768
5.2
4.6
3.9
14.8
13.1
11
204
700
5.6
5.2
4.6
16
14.7
12.8
S
B
1768
538
1820
7.9
4.8
13.7
13.7
-129
0
1300
2.6
2
1.4
7.3
5.9
4
N
NOTE:
Thermocouple accuracy excludes cold junction compensation
error.
9-3
10
Approvals and Regulatory Compliance
10.1 International Usage & CE Marking
The OM-DAQ-USB-2401 multiple channel USB data acquisition module is CE
marked and certified for use in several European countries. Please contact
OMEGA for information on International Regulatory Compliance for each
country.
It is your (the user’s) responsibility to insure that these products are operated
within the guidelines here in this manual and in conformance with all local or
national regulations and laws.
10-1
NOTES:
10-2
NOTES:
10-3
NOTES:
10-4
WARRANTY/DISCLAIMER
OMEGA ENGINEERING, INC. warrants this unit to be free of defects in materials and workmanship for a
period of 13 months from date of purchase. OMEGA’s WARRANTY adds an additional one (1) month
grace period to the normal one (1) year product warranty to cover handling and shipping time. This
ensures that OMEGA’s customers receive maximum coverage on each product.
If the unit malfunctions, it must be returned to the factory for evaluation. OMEGA’s Customer Service
Department will issue an Authorized Return (AR) number immediately upon phone or written request.
Upon examination by OMEGA, if the unit is found to be defective, it will be repaired or replaced at no
charge. OMEGA’s WARRANTY does not apply to defects resulting from any action of the purchaser,
including but not limited to mishandling, improper interfacing, operation outside of design limits,
improper repair, or unauthorized modification. This WARRANTY is VOID if the unit shows evidence of
having been tampered with or shows evidence of having been damaged as a result of excessive corrosion;
or current, heat, moisture or vibration; improper specification; misapplication; misuse or other operating
conditions outside of OMEGA’s control. Components in which wear is not warranted, include but are not
limited to contact points, fuses, and triacs.
OMEGA is pleased to offer suggestions on the use of its various products. However,
OMEGA neither assumes responsibility for any omissions or errors nor assumes liability for any
damages that result from the use of its products in accordance with information provided by
OMEGA, either verbal or written. OMEGA warrants only that the parts manufactured by the
company will be as specified and free of defects. OMEGA MAKES NO OTHER WARRANTIES OR
REPRESENTATIONS OF ANY KIND WHATSOEVER, EXPRESSED OR IMPLIED, EXCEPT THAT OF
TITLE, AND ALL IMPLIED WARRANTIES INCLUDING ANY WARRANTY OF MERCHANTABILITY
AND FITNESS FOR A PARTICULAR PURPOSE ARE HEREBY DISCLAIMED. LIMITATION OF
LIABILITY: The remedies of purchaser set forth herein are exclusive, and the total liability of
OMEGA with respect to this order, whether based on contract, warranty, negligence,
indemnification, strict liability or otherwise, shall not exceed the purchase price of the
component upon which liability is based. In no event shall OMEGA be liable for
consequential, incidental or special damages.
CONDITIONS: Equipment sold by OMEGA is not intended to be used, nor shall it be used: (1) as a “Basic
Component” under 10 CFR 21 (NRC), used in or with any nuclear installation or activity; or (2) in medical
applications or used on humans. Should any Product(s) be used in or with any nuclear installation or
activity, medical application, used on humans, or misused in any way, OMEGA assumes no responsibility
as set forth in our basic WARRANTY/DISCLAIMER language, and, additionally, purchaser will indemnify
OMEGA and hold OMEGA harmless from any liability or damage whatsoever arising out of the use of the
Product(s) in such a manner.
RETURN REQUESTS/INQUIRIES
Direct all warranty and repair requests/inquiries to the OMEGA Customer Service Department. BEFORE
RETURNING ANY PRODUCT(S) TO OMEGA, PURCHASER MUST OBTAIN AN AUTHORIZED RETURN
(AR) NUMBER FROM OMEGA’S CUSTOMER SERVICE DEPARTMENT (IN ORDER TO AVOID
PROCESSING DELAYS). The assigned AR number should then be marked on the outside of the return
package and on any correspondence.
The purchaser is responsible for shipping charges, freight, insurance and proper packaging to prevent
breakage in transit.
FOR WARRANTY RETURNS, please have the
following information available BEFORE
contacting OMEGA:
FOR NON-WARRANTY REPAIRS, consult OMEGA
for current repair charges. Have the following
information available BEFORE contacting OMEGA:
1. Purchase Order number under which the product
was PURCHASED,
1. Purchase Order number to cover the COST
of the repair,
2. Model and serial number of the product under
warranty, and
3. Repair instructions and/or specific problems
relative to the product.
2. Model and serial number of the product, and
3. Repair instructions and/or specific problems
relative to the product.
OMEGA’s policy is to make running changes, not model changes, whenever an improvement is possible. This affords
our customers the latest in technology and engineering.
OMEGA is a registered trademark of OMEGA ENGINEERING, INC.
© Copyright 2012 OMEGA ENGINEERING, INC. All rights reserved. This document may not be copied, photocopied,
reproduced, translated, or reduced to any electronic medium or machine-readable form, in whole or in part, without the
prior written consent of OMEGA ENGINEERING, INC.
Where Do I Find Everything I Need for
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OMEGA…Of Course!
Shop online at omega.comSM
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