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PHE/ORE Series
pH/ORP Electrodes
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OMEGA PHE/ORE Series pH/ORP Electrode Instructions
SAFETY INSTRUCTIONS
1. Depressurize and vent system prior to installation or removal.
2. Confirm chemical compatibility before use.
3. Do not exceed maximum temperature/pressure specifications.
4. Wear safety goggles or faceshield during installation/service.
5. Do not alter product construction.
6. When using chemicals or solvents care should be taken and appropriate eye, face, hand, body,
and/or respiratory protection should be used.
1. Technical Data
1.1 General
Compatibility:
OMEGA PH-2720-PA Twist-Lock Preamplifier
75
50
25
5
Pipe Size Range:
1
•
/
2
in. and up.
•
•
•
Use OMEGA installation fittings to 4 in.
Use pipe adapter in pipes over 4 in.
3
2
3
Submersion with PH-2720-PA pre-amplifier requires /4 in.
3
NPT or ISO 7-R /4 in. male threaded extensions
Efficiency:
>97% @ 25°C (77° F)
0 10 25
50
75
°C
°F
Wetted Materials:
CPVC Body
50
32
77
122
167
Glass
FPM O-rings
1.4 Temperature and pressure specifications
Porous UHMW Polyethylene reference
junctions
ORP electrode operating Temperature/Pressure
•
•
6.89 bar @ 0°C to 65ºC (100 psi @ 32° to 149° F)
ORP: Platinum sensing surface
4.00 bar @ 66ºC to 85°C (58 psi @150° to 185°F)
Primary Functions:
PHE-3271, ORE-2715: Flat surface
PHE-2716 and PHE-2716-DI pH electrode operating Temperature/
resists fouling
Pressure
PHE-2716, ORE-2717: Bulb surface for
general use
•
•
6.89 bar @ 0°C to 65ºC (100 psi @ 32° to 149° F)
4.00 bar @ 66ºC to 85°C (58 psi @150° to 185°F)
PHE-3271-HF: Extended use in
applications with trace hydrofluoric acid
(<2%)
PHE-3271 pH electrode operating Temperature/Pressure
•
•
6.89 bar @ 10°C to 65ºC (100 psi @ 50° to 149° F)
PHE-2716-DI: Extended use in pure
waters (<100 µS)
4.00 bar @ 66ºC to 85°C (58 psi @150° to 185°F)
PHE-3271-HF pH electrode operating Temperature/Pressure
Secondary Junction:
Nylon Filament
•
6.89 bar @ 0°C to 50ºC (100 psi @ 32° to 122° F)
Element:
Ag/AgCl
Shipping Weight:
0.2 kg (0.4 lb)
Storage Temperature: > -12° C (11° F)
1.2 PHE-3271 and PHE-2716 pH Electrodes
1.5 Dimensions
Operating Range:
Reference:
0 to 14 pH (PHE-3271-HF: 0 to 12 pH)
Electrolyte: Solidified Acrylamide Gel
3.5M KCI (PHE-3271, PHE-3271-HF,
PHE-2716)
0.1 M KCl (PHE-2716-DI)
Temperature Sensor:
3KΩ Balco (3000Ω = 25°C)
<5 s for 95% of signal change
140 s (PHE-3271), 196 s (PHE-2716)
1.2 in.
1.2 in.
2.6 in.
ResponseTime:
(30.5 mm)
(30.5 mm)
(65 mm)
Response Time, τ:
4.1 in.
3.8 in.
(104 mm)
(97 mm)
1.3 ORE-2715/ORE-2717 ORP Electrodes
Operating Range:
Reference:
-999 to +999 mV
2.6 in.
Electrolyte: Solidified Acrlyamide Gel
3.5M KCL
(65 mm)
3.4 in.
3.4 in.
(86 mm)
(86 mm)
Response Time:
Application dependent
0.9 in.
(23 mm)
0.9 in.
(23 mm)
Flat electrode
Bulb electrode
page 3
OMEGA PHE/ORE Series pH/ORP Electrode Instructions
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pH/ORP electrodes are similar to batteries; they age with time and usage. The following information will help maximize electrode life.
2.1 Conditions to Avoid:
•
High temperatures, strong acids or caustics will elevate electrochemical reactions and speed electrode aging.
•
Coatings on the glass or junction surfaces (i.e. proteins) cause extended response time and inaccurate measurement.
•
Never store the electrode tip in deionized (DI) water.
•
Never expose electrode to temperatures below -12 °C (10 °F) or allow it to dehydrate. These conditions will damage the electrode.
•
Never scrape or sand the glass electrode surface.
•
Treat glass electrode surfaces with care. The glass is very thin and requires care to prevent accidental breakage.
2.2 Submersible Installation Tips:
•
Mount electrodes in a location with ample clearance for removal for
YES
YES
periodic cleaning and recalibration. Choose a location that keeps the
electrode glass completely submerged at all times.
•
•
Place the electrode tip in pH 4 buffer during system maintenance or
storage to avoid dehydration.
Mount the electrode near tank outlet away from reagent addition areas.
30°
30°
2.3 In-Line Installation Tips:
NO
NO
•
•
pH and ORP electrodes respond best in moving fluids.
The internal measuring electrode chamber contains a wire within a liquid
and a slight amount of air. The electrode must be mounted at least 30°
from horizontal to ensure proper sensing. Mounting angles less than 30°
will impede performance.
NO
3. pH Electrode Calibration
All pH electrodes are designed to ensure linearity during their lifespan. The following
sections define proper electrode operation.
Theoretical mV Values @ 25°C
pH
2
3
4
mV
+ 295 mV
+ 236 mV
+177 mV
+118 mV
+ 59 mV
0 mV
3.1 Offset (STD)
Electrode offsets occur due to:
5
6
7
8
•
•
Clogged reference junction
Aged or contaminated reference solution/wire
- 59 mV
Check offsets in a pH 7 buffer @ 25 °C. The theoretical output is 0 mV. Any deviation from
9
- 118 mV
- 177 mV
- 236 mV
- 295 mV
0 mV is the pH electrode offset.
10
11
12
pH Electrode Offset pH 7 buffer @ 25°C
Theoretical:
7.0 pH (0.0 mV)
New:
pH 7 ± 0.25 pH (±15 mV)
Reliable:
pH 7 ± 0.85 pH (± 50 mV)
Electrode offsets greater than 0.85 pH (50 mV) indicate the electrode requires cleaning or replacement. See section 5: Maintenance and
cleaning.
°C
pH Error
7
3.2 Slope (SLP)
2
3
4
5
6
8
9
10
11
12
Electrode slope is the number of mV per pH unit. At 25°C the
theoretical slope is 59.16 mV per pH. Temperature has an
appreciable affect on electrode slope. Reliable instrumentation
15 0.15 0.12 0.09 0.06 0.03
0
0
0
0
0
0.03 0.06 0.09 0.12 0.15
25
0
0
0
0
0
0
0
0
0
0
35 0.15 0.12 0.09 0.06 0.03
0.03 0.06 0.09 0.12 0.15
includes temperature compensation. The graph below illustrates
potential pH error when a temperature compensated instrument
is not used.
45 0.3
0.24 0.18 0.12 0.06
0.06 0.12 0.18 0.24
0.3
55 0.45 0.36 0.27 0.18 0.09
0.09 0.18 0.27 0.36 0.45
Recommendations:
•
Calibrate temperature before calibrating the standard and slope.
•
The mV offset will track across the entire pH range. The slope is usually not affected by offset changes.
(i.e. pH 7= +10 mV, pH 4= +187 mV); slope = 59 mV
•
Coatings on the glass may affect sensor slopes. See section 5 maintenance and cleaning.
•
A constant output near 0 mV in all buffer solutions indicates a shorted electrode that must be replaced.
3.3 Response Time/Stability
Response time and stability are affected by the condition of the pH electrode's glass surface (ORP electrode - Platinum surface),
reference junction, and reference solution. Restoration to acceptable levels can often be accomplished by cleaning the electrode's glass
surface (ORP electrode - Platinum surface) and reference junction.
Electrode mV values should remain stable ±3 mV. Conditions that may cause fluctuations are:
1. Electrode coating
2. Ground fault: If proper operation is observed in the beaker, but is unstable in the application, a ground fault probably exists.
•
Using instrumentation with isolated inputs and outputs may restore stable operation.
•
Solution grounding may also restore stable operation.
page 4
OMEGA PHE/ORE Series pH/ORP Electrode Instructions
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All ORP electrodes are designed to ensure linearity during their lifespan. The following sections define proper electrode operation.
4.1 Offset (STD)
Electrode offsets occur due to:
•
•
Clogged reference junction
Aged or contaminated reference solution/wire
Offsets are easily checked in pH 7 buffer saturated with quinhydrone @ 25 °C; since the theoretical output is +87 mV. Any deviation
from +87 mV is the ORP electrode offset (i.e. +90 mV). Quinhydrone is the oxidizer measured by the ORP electrode and is required for
calibration. To guarantee buffer saturation, mix 1/8g quinhydrone per 50 mL of pH buffer.
ORP Electrode Offset:
Solution: pH 7 or pH 4 buffer saturated with Quinhydrone @ 25 °C
pH 7 + Quinhydrone
pH 4 + Quinhydrone
Theoretical mV:
+ 87 mV
+ 264 mV
New:
87 ± 15 mV
+264 ± 15 mV
Reliable:
87 ± 50 mV
+264 ± 50 mV
Electrode offsets greater than ±50 mV indicate the electrode requires cleaning or replacement, see section 5.2.
4.2 Slope (SLP)
ORP slope errors are generally caused by contamination of the platinum electrode surface. Cleaning the electrode surface will usually
restore proper values, response time, and stability.
Common ORP Values
Reaction
mV
2+
-
Cr → Cr + 2e
- 913
- 440
- 407
- 401
- 400
- 370
- 250
- 126
- 37
2+
-
Fe→ Fe + 2e
2+
3+
-
Cr →Cr + e
-
4OH → O2 + 2H2O + 4e
-
-
2I → I2 + 2e
2+
3+
-
Ti → Ti + e
2+
-
Ni → Ni + 2e
2+
-
Pb → Pb + 2e
3+
-
Fe → Fe + 3e
+
-
H2 → 2H + 2e
0
2+
3+
-
-
Fe → Fe + e
+ 771
+ 799
+ 800
+ 1060
+ 1066
+ 1160
+ 1188
+ 1369
+
-
Ag → Ag + e
4+
Pb → Pb + 4e
-
-
-
3Br → Br3 + e
-
-
2Br → Br2 + 2e
-
-
ClO2 → ClO2 + e
2+
-
Pt → Pt + 2e
2+
-
Ag → Ag + 2e
Many systems require both pH and ORP calibration. To conserve calibration reference solutions, use pH 7 and 4 buffers for pH
calibration first. ORP calibration can be performed with the same buffers by adding quinhydrone.
5. Maintenance and Cleaning
5.1 Maintenance
Variables can affect long term pH or ORP electrode life. For this reason, a maintenance log is recommended for trend analysis. When
storing boxed sensors, lay the sensor flat to maximize hydration of the glass surface. Keep the glass surface wet at all times. Soak the
sensor tip in pH 4.0 buffer during system maintenance intervals. In-line applications should be plumbed with a depression (trap) so liquid
is maintained around the sensor tip. If the sensor dehydrates, soak the sensor tip in pH 4 buffer for 24 to 48 hours, then visually inspect
the electrode for surface cracks, swelling, or discoloration. Severely dehydrated electrodes cannot be restored to normal operation.
page 5
OMEGA PHE/ORE Series pH/ORP Electrode Instructions
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Cleaning techniques vary depending on the type of coating present on the glass electrode surface or reference junction.
•
Soft coatings can be removed by vigorous stirring, or with directed spray of an applicable detergent or solvent onto the glass
electrode surface. Chlorine bleach or mild detergent may be used to remove soft coatings. Always rinse electrode tip in clean water
after cleaning.
•
•
•
Hard coatings can be chemically removed. Use the least harsh chemical which will remove the contaminant within two (2) minutes
without attacking the materials of construction. e.g. calcium carbonate may be removed with a 5% HCL (muriatic acid) solution.
Oily or organic coatings can be removed with detergents or an appropriate solvent that does not attack the materials of
construction e.g. isopropyl alcohol may be used but acetone must be avoided to prevent damage to the CPVC sensor body.
ORP electrode surface (platinum rod) can be gently sanded with 600 grit wet and dry silicone or carbide sandpaper, jewelers rouge,
crocus cloth, or very fine steel wool.
WARNING!
Wear appropriate eye, face, hand, body, and respiratory protection when using chemicals or solvents.
6. Replacement parts and accessories
Mfr. Part No.
Description
PHE-3271
Flat pH Electrode
PHE-3271-HF
Flat pH Electrode, HF Resistsant
ORE-2715
Flat ORP Electrode
PHE-2716
Bulb pH Electrode
PHE-2716-DI
ORE-2717
Bulb pH Electrode, DI Resistant
Bulb ORP Electrode
3
PH-270-PA
Preamplifier, /4 in. NPT
P31515-0V200
PVDF Pipe Adapter
FPP-1220-0021
O-ring, FPM (standard)
FPP-1224-0021
FPP-1228-0021
O-ring, EPR
O-ring, Kalrez
a
b
c
o
n
m
CAUTION!
d
Apply O-ring lubricant to sensor O-rings prior to assembly.
Unlubricated O-rings may score the sealing surface in the 2720.
c
Technical Features
l
a)
b)
Male BNC connector
i)
j)
3K Balco thermistor
k
Keyed for a simple sure fit
Solidified acrylamide reference
j
i
c)
d)
e)
Viton® O-rings
electrolyte
Silicone-bushing seal
k)
Ag/AgCl measuring element
e
f
Double junction
l)
Large reference volume
f)
Ag/AgCl reference element
m) Epoxy seal
g)
h)
Platinum sensing surface (ORP) or flat pH glass
Porous UHMW polyethylene reference junction
n)
o)
Shielding
h
g
10KΩ I.D. resistor for ORP sensor
page 6
OMEGA PHE/ORE Series pH/ORP Electrode Instructions
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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 which wear are not warranted, including but 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 it
will be as specified and free of defects. OMEGA MAKES NO OTHER WARRANTIES OR
REPRESENTATIONS OF ANY KIND WHATSOEVER, EXPRESS 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 to cover the COST of
the repair,
2. Model and serial number of the product, and
3. Repair instructions and/or specific problems
relative to the product.
1. Purchase Order number under which the
product was PURCHASED,
2. Model and serial number of the product under
warranty, 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 2000 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.
page 7
OMEGA PHE/ORE Series pH/ORP Electrode Instructions
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Where Do I Find Everything I Need for
Process Measurement and Control?
OMEGA…Of Course!
TEMPERATURE
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6-2714.090-OM/(H-4/03)
M-2922/0403
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