Advanced Instruments GPR-2500 User manual

2855 Metropolitan Place, Pomona, CA 91767 USA ♦Tel: [phone], Fax: [phone], www.aii1.com, e-mail: [email protected] Rev 10/15
Technical Specifications *
Accuracy: < 2% of FS range under constant conditions
Analysis: 0-1%, 0-5%, 0-10%, 0-25% FS ranges; auto-ranging or
fixed single range
Application: Oxygen analysis in inert, hydrocarbon, helium, hydrogen,
mixed and acid (CO2) gas streams
Area Classification: General purpose
Calibration: Max interval—3 months. Air calibrate with clean source
of certified span gas, compressed, or ambient (20.9%
O2) air on 0-25% range.
Compensation: Temperature
Connections: 1/8" compression tube fittings
Controls: Water resistant keypad; menu driven range selection,
calibration and system functions
Display: Graphical LCD 2.75” x 1.375”; resolution 0.001%;
displays real time ambient temperature and pressure
Enclosure: Painted aluminum, 4 x 9 x 3", 8 lbs.
Flow Sensitivity: Not flow sensitive, 1-2 SCFH recommended
Linearity: ±1% of full scale
Pressure: Inlet - regulate to 5-30 psig to deliver 1-2 SCFH flow;
vent - atmospheric
Power: 18-24 VDC
Response Time: 90% of final reading in 13 seconds
Sample System: None
Sensitivity: < 0.5% of FS range
Sensor Model: GPR-11-32-RTS for non-acid (CO2) gas streams;
XLT-11-24-RTS for gases containing > 0.5% CO2
Sensor Life: GPR-11-32-RTS 32 months in air at 25ºC and 1 atm
XLT-11-24-RTS 24 months in air at 25ºC and 1 atm
Signal Output: 4-20mA non-isolated
Operating Range: 5ºC to 45ºC (GPR sensor), -10ºto 45ºC (XLT sensor)
Warranty: 12 months analyzer; 12 months sensor
Wetted Parts: Stainless steel
Optional Equipment
Sample conditioning system - Contact factory.
* Subject to change without notice
GPR-2500
Oxygen Transmitter
2 Wire Loop Powered O2 Transmitter
With Optional Sample Systems
Advanced Sensor Technology
Longer Life with No Maintenance
Excellent Compatibility in 0-100% CO2
Extended Operating Temperature –10⁰C
18-24 VDC Loop Power
4-20 mA Signal Output
Sensitivity 0.5% Full Scale
4 Ranges Standard
Auto Ranging or Single Fixed
Stainless Steel Wetted Parts
ISO 9001:2008 Certified
INTERTEK Certificate No. 485

2855 Metropolitan Place, Pomona, CA 91767 USA ♦Tel: [phone], Fax: [phone], www.aii1.com, e-mail: [email protected] Rev 10/15
Technical Specifications *
Accuracy: < 2% of FS range under constant conditions, e.g.
constant temperature, flow rate and ambient pressure
Analysis: 0-100% FS range
Application: Continuous monitoring of oxygen levels up to 100% O2
Area Classification: General purpose
Calibration: Max interval—3 months. Use certified span gas with 97-
100% O2 (balance N2). To comply with FDA require-
ments for medical grade O2, zero calibrate with not less
than 99.9% N2 (balance O2) or span calibrate with not
less than 99.99% O2 (balance N2). For Oxygen 93
(transfilling), calibrate with 93% +0.1% O2 (balance
N2).
Compensation: Temperature
Connections: 1/8" compression tube fittings
Controls: Water resistant keypad; menu driven range selection,
calibration and system functions
Display: Graphical LCD 2.75” x 1.375”; resolution 0.1%;
displays real time ambient temperature and pressure
Enclosure: Painted aluminum, 4 x 9 x 3", 8 lbs.
Flow Sensitivity: Not flow sensitive, 1-2 SCFH recommended
Linearity: ±1% of full scale
Pressure: Inlet - regulate to 5-30 psig to deliver 1-2 SCFH flow;
vent - atmospheric
Power: 18-24 VDC two wire loop
Response Time: 90% of final reading in 13 seconds
Sample System: None
Sensitivity: < 0.5% of FS range
Sensor Model: GPR-11-120-RTS
Sensor Life: 24 months in 100% O2 at 25ºC and 1 atm
Signal Output: 4-20mA non-isolated
Operating Range: 5ºto 45ºC
Warranty: 12 months analyzer; 12 months sensor
Wetted Parts: Stainless steel
Optional Equipment
Sample conditioning system - Contact factory.
* Subject to change without notice
GPR-2500 MO
Oxygen Purity Transmitter
18-24 VDC Loop Powered
Advanced Galvanic Sensor Technology with
Optional Sample Systems
Proprietary Long Life Sensor
18-24 VDC Loop Power
4-20 mA Signal Output
Sensitivity 0.5% Full Scale
0-100% Full Scale Range
Stainless Steel Wetted Parts
ISO 9001:2008 Certified
INTERTEK Certificate No. 485

GPR-2500 / GPR-2500MO
Oxygen Transmitter
Owner’sManual
2855 Metropolitan Place, Pomona, CA 91767 USA ♦Tel: [phone], Fax: [phone], e-mail: [email protected], www.aii2.com

2
TableofContents
Introduction 1
Quality Control Certification 2
Safety 3
Features & Specifications 4
Operation 5
Maintenance 6
Spare Parts 7
Troubleshooting 8
Warranty 9
Material Safety Data Sheets 10
Drawings A/R

3
1 Introduction
Your new oxygen transmitter incorporated an advanced electrochemical sensor specific to oxygen along with state-
of-the-art digital electronics designed to give you years of reliable precise oxygen measurements in variety of
industrial oxygen applications.
To obtain maximum performance from your new oxygen transmitter, please read and follow the guidelines
provided in this Owner’s Manual.
Every effort has been made to select the most reliable state of the art materials and components, to design the
transmitter for superior performance and minimal cost of ownership. This transmitter was tested thoroughly by the
manufacturer prior to shipment for best performance.
However, modern electronic devices do require service from time to time. The warranty included herein plus a staff
of trained professional technicians to quickly service your transmitter is your assurance that we stand behind every
transmitter sold.
The serial number of this transmitter may be found on the inside the transmitter. You should note the serial
number in the space provided and retains this Owner’s Manual as a permanent record of your purchase, for future
reference and for warranty considerations.
Serial Number: _______________________
Advanced Instruments Inc. appreciates your business and pledges to make every effort to maintain the highest
possible quality standards with respect to product design, manufacturing and service.

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2 QualityControlCertification
Date: Customer: Order No.: Pass
Model ( ) GPR-2500 Oxygen Transmitter
( ) GPR-2500MO Oxygen Purity Transmitter
Sensor ( ) GPR-11-32-4 Oxygen Sensor (GPR-2500)
( ) XLT-11-24-4 Oxygen Sensor (GPR-2500)
( ) GPR-11-120-OP Oxygen Purity Sensor (GPR-2500MO)
( ) Other _____________________
Serial Nos.: Analyzer: Sensor:
Accessories: Owner’s Manual
Configuration: ( ) A-1151-E-L2 PCB Assembly Main / Display (GPR-2500)
( ) A-1151-E-L3 PCB Assembly Main / Display (GPR-2500MO)
Software rev:
( ) Ranges GPR-2500: 0-1%, 0-5%, 0-10%, 0-25%
( ) Range GPR-2500MO: 0-100%
Power: 12-36V DC two wire loop power
NEMA 4 rated wall mount enclosure
Barometric pressure compensation
Test: Default zero (without sensor)
Default span @ 40uA (GPR-2500) or 20uA (GPR-2500MO)
Analog signal output 4-20mA full scale
Calibrates with adequate span adjustment within 10-50% FS
Baseline drift on zero gas < ±2% FS over 24 hour period
Noise level < ±1.0% FS
Span adjustment within 10-50% FS
Final: Overall inspection for physical defects
Options:
Notes: 1 of 1 analyzer due ASAP

5
3 Safety
General
This section summarizes the essential precautions applicable to the GPR-2500/2500MO Oxygen Transmitter.
Additional precautions specific to individual transmitter are contained in the following sections of this manual. To
operate the transmitter safely and obtain maximum performance follow the basic guidelines outlined in this
Owner’s Manual.
Caution: This symbol is used throughout the Owner’s Manual to CAUTION and alert the user to recommended
safety and/or operating guidelines.
Danger: This symbol is used throughout the Owner’s Manual to identify sources of immediate DANGER such as
the presence of hazardous voltages.
Read Instructions: Before operating the transmitter read the instructions.
Retain Instructions: The safety precautions and operating instructions found in the Owner’s Manual should be
retained for future reference.
Heed Warnings: Follow all warnings on the transmitter, accessories (if any) and in this Owner’s Manual.
Follow Instructions: Observe all precautions and operating instructions. Failure to do so may result in personal
injury or damage to the transmitter.
PressureandFlow
Inlet Pressure: GPR-2500/2500MO ppm Oxygen Transmitters are designed for flowing samples, equipped with
1/8” bulkhead tube fitting connections on the side of the unit (unless otherwise indicated, either fitting can serve as
inlet or vent) and are intended to operate at positive pressure regulated to between 5-30 psig.
Caution: If the GPR-2500 is equipped with the optional H2S sample system, the inlet pressure must not exceed 30
psig.
Outlet Pressure: The sample gas vent pressure should be atmospheric.
Installation
Oxygen Sensor: DO NOT open the sensor. The sensor contains a corrosive liquid electrolyte that could be
harmful if touched or ingested, refer to the Material Safety Data Sheet contained in the Owner’s Manual appendix.
Avoid contact with any liquid or crystal type powder in or around the sensor or sensor housing, as either could be a
form of electrolyte. Leaking sensors should be disposed of in accordance with local regulations.
Mounting: The transmitter is approved for indoor or outdoor use. Mount as recommended by the manufacturer.
Power: Supply power to the transmitter only as rated by the specification or markings on the transmitter
enclosure. The wiring that connects the transmitter to the power source should be installed in accordance with
recognized electrical standards and so they are not pinched particularly near the power source and the point where
they attach to the transmitter. Never yank wiring to remove it from an outlet or from the transmitter.
Operating Temperature: The maximum operating temperature is 45º C.
Heat: Situate and store the transmitter away from sources of heat.
Liquid and Object Entry: The transmitter should not be immersed in any liquid. Care should be taken so that
liquids are not spilled into and objects do not fall into the inside of the transmitter.

6
Handling: Do not use force when using the switches and knobs. Before moving your transmitter be sure to
disconnect the wiring/power cord and any cables connected to the output terminals located on the transmitter.
Maintenance
Serviceability: Except for replacing the oxygen sensor, there are no parts inside the transmitter for the operator
to service.
Only trained personnel with the authorization of their supervisor should conduct maintenance.
Oxygen Sensor: DO NOT open the sensor. The sensor contains a corrosive liquid electrolyte that could be
harmful if touched or ingested, refer to the Material Safety Data Sheet contained in the Owner’s Manual appendix.
Avoid contact with any liquid or crystal type powder in or around the sensor or sensor housing, as either could be a
form of electrolyte. Leaking sensors should be disposed of in accordance with local regulations.
Troubleshooting: Consult the guidelines in Section 8 for advice on the common operating errors before
concluding that your transmitter is faulty.
Do not attempt to service the transmitter beyond those means described in this Owner’s Manual. Do not attempt to
make repairs by yourself as this will void the warranty as per Section 10 and may result in electrical shock, injury or
damage. All other servicing should be referred to qualified service personnel.
Cleaning: The transmitter should be cleaned only as recommended by the manufacturer. Wipe off dust and dirt
from the outside of the unit with a soft damp cloth then dry immediately. Do not use solvents or chemicals.
Nonuse Periods: If the transmitter is equipped with a range switch advance the switch to the OFF position and
disconnect the power when the transmitter is left unused for a long period of time.
4 Features & Specifications
See last page, this page left blank intentionally.

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5 Operation
PrincipleofOperation
The GPR-2500/2500MO oxygen transmitter incorporates a variety of ppm range advanced galvanic fuel cell type
sensors. The transmitter is configured in a general purpose NEMA 4X rated enclosure and meets the intrinsic safety
standards required for use in Class 1, Division 1, Groups A, B, C, D hazardous areas when operated in conjunction
with the manufacturer’s recommended optional intrinsic safety barriers.
Advanced Galvanic Sensor Technology:
The sensors function on the same principle and are specific for oxygen. They measure the partial pressure of
oxygen from low ppm to 100% levels in inert gases, gaseous hydrocarbons, helium, hydrogen, mixed gases, acid
gas streams and ambient air. Oxygen, the fuel for this electrochemical transducer, diffusing into the sensor reacts
chemically at the sensing electrode to produce an electrical current output proportional to the oxygen concentration
in the gas phase. The sensor’s signal output is linear over all ranges and remains virtually constant over its useful
life. The sensor requires no maintenance and is easily and safely replaced at the end of its useful life.
Proprietary advancements in design and chemistry add significant advantages to an extremely versatile oxygen
sensing technology. Sensors for low ppm analysis recover from air to ppm levels in minutes, exhibit longer life and
reliable quality. The expected life of our new generation of percentage range sensors now range to five and ten
years with faster response times and greater stability. Another significant development involves expanding the
operating temperature range for percentage range sensors from -30°C to 50°C.
Electronics:
The signal generated by the sensor is processed by state of the art low power micro-processor based digital
circuitry. The first stage amplifies the signal. The second stage eliminates the low frequency noise. The third stage
employs a high frequency filter and compensates for signal output variations caused by ambient temperature
changes. The result is a very stable signal. Sample oxygen is analyzed very accurately. Response time of 90% of
full scale is less than 10 seconds (actual experience may vary due to the integrity of sample line connections, dead
volume and flow rate selected) on all ranges under ambient monitoring conditions. Sensitivity is typically 0.5% of
full scale low range. Oxygen readings may be recorded by an external device via the 0-1V signal output jack.
A 4-20mA signal output is provided from a two-wire 12-36VDC loop power source such as a PLC and is represented
on full scale oxygen readings to an external device. When operated in conjunction with the manufacturer’s
recommended optional intrinsic safety barriers the GPR-2500/GPR-2500MO meets the intrinsic safety standards
required for use in Class 1, Division 1, Groups A, B, C, D hazardous areas.
Sample System:
The GPR-2500/2500MO is supplied without a sample conditioning system for maximum portability. However the
sample must be properly presented to the sensor to ensure an accurate measurement. Users interested in adding
their own sample conditioning system should consult the factory. Advanced Instruments Inc. offers a full line of
sample handling, conditioning and expertise to meet your application requirements. Contact us at 909-392-6900 or
e-mail us at [email protected]

8
Pressure & Flow
All electrochemical oxygen sensors respond to partial pressure changes in oxygen. The inlet pressure must always
be higher than the pressure at the outlet vent which is normally at atmospheric pressure.
Flow Through Configuration:
The sensor is exposed to sample gas that must flow or be drawn through
metal tubing inside the transmitter. The GPR-2500/2500MO internal
sample system includes 1/8” compression tube inlet and vent fittings, a
stainless steel sensor housing with an o-ring seal to prevent the leakage
of air and stainless steel tubing.
Flow rates of 1-5 SCFH cause no appreciable change in the oxygen
reading. However, flow rates above 5 SCFH generate backpressure and
erroneous oxygen readings because the diameter of the integral tubing
cannot evacuate the sample gas at the higher flow rate. The direction the
sample gas flows is not important, thus either tube fitting can serve as the
inlet or vent – just not simultaneously.
A flow indicator with an integral metering valve upstream of the sensor is
recommended as a means of controlling the flow rate of the sample gas.
A flow rate of 2 SCFH or 1 liter per minute is recommended for optimum
performance.
Caution: Do not place your finger over the vent (it pressurizes the
sensor) to test the flow indicator when gas is flowing to the sensor.
Removing your finger (the restriction) generates a vacuum on the sensor
and may damage the sensor (voiding the sensor warranty).
To avoid generating a vacuum on the sensor (as described above) during operation, always select and install the
vent fitting first and remove the vent fitting last.
Application Pressure - Positive:
A flow indicator with integral metering valve (GPR-2500/2500MO option) positioned upstream of
the sensor is recommended for controlling the sample flow rate between 1-5 SCFH. To reduce the
possibility of leakage for low ppm measurements, position a metering needle valve upstream of
the sensor to control the flow rate and position a flow indicator downstream of the sensor.
If necessary, a pressure regulator (with a metallic diaphragm is recommended for optimum
accuracy, the use of diaphragms of more permeable materials may result in erroneous readings)
upstream of the flow control valve should be used to regulate the inlet pressure between 5-30
psig.
Application Pressure - Atmospheric or Slightly Negative:
For accurate ppm range oxygen measurements, an optional external sampling pump should be positioned
downstream of the sensor to draw the sample from the process, by the sensor and out to atmosphere. A flow
meter is generally not necessary to obtain the recommended flow rate with most sampling pumps.
Caution: If the transmitter is equipped with an optional flow indicator with integral metering valve or a metering
flow control valve upstream of the sensor - open the metering valve completely to avoid drawing a vacuum on the
sensor and placing an undue burden on the pump.
If pump loading is a consideration, a second throttle valve on the pump’s inlet side may be necessary to provide a
bypass path so the sample flow rate is within the above parameters.

9
To avoid erroneous oxygen readings and damaging the sensor:
¾Do not place your finger over the vent (it pressurizes the sensor) to test the flow indicator when gas is flowing
to the sensor. Removing your finger (the restriction) generates a vacuum on the sensor and may damage the
sensor (voiding the sensor warranty).
¾Assure there are no restrictions in the sample or vent lines
¾Avoid drawing a vacuum that exceeds 14” of water column pressure – unless done gradually
¾Avoid excessive flow rates above 5 SCFH which generate backpressure on the sensor.
¾Avoid sudden releases of backpressure that can severely damage the sensor.
¾Avoid the collection of particulates, liquids or condensation collect on the sensor that could block the diffusion
of oxygen into the sensor.
¾If the transmitter is equipped with an optional integral sampling pump (positioned downstream of the sensor)
and a flow control metering valve (positioned upstream of the sensor), completely open the flow control
metering valve to avoid drawing a vacuum on the sensor and placing an undue burden on the pump.

10
Calibration & Accuracy
Single Point Calibration: As previously described the galvanic oxygen sensor generates an electrical current
sensor exhibiting an absolute zero, e.g. the sensor does not generate a current output in the absence of oxygen.
Given these linearity and absolute zero properties, single point calibration is possible.
Pressure: Because sensors are sensitive to the partial pressure of oxygen in the sample gas their output is a
function of the number of molecules of oxygen 'per unit volume'. Readouts in percent are permissible only when
the total pressure of the sample gas being analyzed remains constant. The pressure of the sample gas and that of
the calibration gas(es) must be the same (reality < 1-2 psi).
Temperature: The rate oxygen molecules diffuse into the sensor is controlled by a Teflon membrane otherwise
known as an 'oxygen diffusion limiting barrier' and all diffusion processes are temperature sensitive, the fact the
sensor's electrical output will vary with temperature is normal. This variation is relatively constant 2.5% per ºC. A
temperature compensation circuit employing a thermistor offsets this effect with an accuracy of +5% or better and
generates an output function that is independent of temperature. There is no error if the calibration and sampling
are performed at the same temperature or if the measurement is made immediately after calibration. Lastly, small
temperature variations of 10-15º produce < +1% error.
Accuracy: In light of the above parameters, the overall accuracy of an transmitter is affected by two types of
errors: 1) those producing 'percent of reading errors', illustrated by Graph A below, such as +5% temperature
compensation circuit, tolerances of range resistors and the 'play' in the potentiometer used to make span
adjustments and 2) those producing 'percent of full scale errors', illustrated by Graph B, such as +1-2% linearity
errors in readout devices, which are really minimal due to today's technology and the fact that other errors are
'spanned out' during calibration.
Graph C illustrates these 'worse case' specifications that are typically used to develop an transmitter's overall
accuracy statement of +1% of full scale at constant temperature or +5% over the operating temperature range.
QC testing is typically <+0.5% prior to shipment.

11
Example: As illustrated by Graph A any error, play in the multi-turn span pot or the temperature compensation
circuit, during a span adjustment at 20.9% (air) of full scale range would be multiplied by a factor of 4.78
(100/20.9) if used for measurements of 95-100% oxygen concentrations. Conversely, an error during a span
adjustment at 100% of full scale range is reduced proportionately for measurements of lower oxygen
concentrations.
Recommendation: Calibrating with a span gas approximating 80% of the full scale range one or two ranges
higher than the full scale range of interest is recommended for 'optimum calibration accuracy'. Always calibrate at
the same temperature and pressure of the sample gas stream.
Start-up
The GPR-2500/2500MO Oxygen Transmitters has been calibrated at the factory prior to shipment and is fully
operational from the shipping container. The ppm oxygen sensor has been removed and packaged in a nitrogen
atmosphere to assure optimum performance. Once installed, we recommend the user allow the transmitters to
stabilize for 30 minutes and then recalibrate the device as instructed below.
Installation Considerations:
The GPR-2500/2500MO consists of an electronic module, sensor housing and sample 1/8” sample inlet and vent
connections housed in a 4”W x 9”H x 3”D enclosure NEMA 4 rated enclosure suitable for wall mounting.
For optimum accuracy zero and calibrate a ppm transmitter after it has been allowed to stabilize, typically 24-36
hours after installation. Assuming the initial zero is performed according to the procedure described herein, the
analyzer should not require zeroing again until the either the sensor is replaced or a change is made to the sample
system or gas lines. Following the initial zero and calibration, the analyzer should not require span calibration again
for up to 3 months under “normal” application conditions as described in the published specifications.
Note: As described below, zeroing the transmitter is recommended for measurements below 1 ppm. The low end
sensitivity (zero capability) has been verified at the factory; however, no ZERO OFFSET adjustment has been
made. A factory adjustment would be meaningless because of the difference in sample systems and leakage
factors between the factory set-up and the actual application conditions
¾Assemble the necessary hardware for mounting the transmitter and optional components - such as coalescing
or particulate filters and pumps, 1/8” metal or plastic tubing for interconnecting the transmitter and optional
components.
¾Review the application conditions to ensure the sample is suitable for analysis.
¾Temperature: The sample must be sufficiently cooled before it enters the transmitter and any optional
components. A coiled 10 foot length of ¼” stainless steel tubing is sufficient for cooling sample gases as high
as 1,800ºF to ambient.

12
¾Pressure & Flow: As described above.
¾Moisture & Particulates: Prevent water and/or particulates from entering the sample system. They can clog the
tubing and damage the optional components such as pumps, scrubbers or sensors. Installation of a suitable
coalescing or particulate filter is required to remove condensation, moisture and/or particulates from the
sample gas to prevent erroneous analysis readings and damage to the sensor or optional components. Consult
the factory for recommendations concerning the proper selection and installation of components.
¾Contaminants: A gas scrubber and flow indicator with integral metering valve are required upstream of the
transmitter to remove interfering gases such as oxides of sulfur and nitrogen or hydrogen sulfide that can
produce false readings and reduce the expected life of the sensor. Installation of a suitable scrubber is required
to remove the contaminant from the sample gas to prevent erroneous analysis readings and damage to the
sensor or optional components. Consult the factory for recommendations concerning the proper selection and
installation of components.
¾Gas connections: Inlet and outlet vent gas lines require 1/8” diameter tubing preferably metal.
¾Power connection: Locate a source of AC power to meet area classification and to plug in the charging adapter.
¾Zero calibration (required only for very low percentage range measurements).
¾Span calibration – Users are responsible for certified span gas cylinder, regulator and flow control valve.
Mounting the Transmitter:
The GPR-2500/2500MO enclosure is 4”Wx9”Hx3”D configuration is
designed to be mounted directly to any flat vertical surface, wall or
bulkhead plate with the appropriate screws. To facilitate servicing
the interior of the transmitters, position it approximately 5 feet off
the floor.
1. Remove the four (4) screws securing the top section of the
enclosure, set them aside for reinstallation and raise the hinged
top section 180º until it locks in place.
2. Locate the mounting holes cast into the bottom section of the
enclosure and the black sensor. Orient the enclosure by locating
the sensor at six (6) o’clock.
3. Secure the bottom section of the enclosure to a vertical surface
approximately 5 feet from the floor or a level accessible to
service personnel. This requires the user to supply four (4)
additional proper size screws and anchors.
4. Caution: Do not remove or discard the gaskets from either the
enclosure or junction box. Failure to reinstall either gasket will
void the NEMA 4 rating and RFI protection.
5. The transmitters design provides protection from RFI that is
maintained by leaving specific mating areas of the enclosure unpainted to maintain conductivity the gasket, top
and bottom sections of the enclosure. These unpainted areas are protected by gaskets and contribute to
maintaining the NEMA 4 rating. Do not paint these areas. Painting will negate the RFI protection.
6. As described below the power connection is made through the junction box on the left side of the enclosure.

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Gas Connections:
The GPR-2500/2500MO with its standard flow through configuration is designed for positive pressure samples and
requires connections for incoming sample and outgoing vent lines. Zero and span inlet ports are offered as part of
the optional sample systems. The user is responsible for calibration gases and the required components, see
below.
With the pressure regulated to between 5-30 psig, flow rates of 1-5 SCFH cause no appreciable change in the
oxygen reading. However, flow rates above 5 SCFH generate backpressure and erroneous oxygen readings
because the diameter of the integral tubing cannot evacuate the sample gas at the higher flow rate. A flow
indicator with an integral metering valve upstream of the sensor is recommended as a means of controlling the
flow rate of the sample gas. A flow rate of 2 SCFH or 1 liter per minute is recommended for optimum performance.
Caution: Do not place your finger over the vent (it pressurizes the sensor) to test the flow indicator when gas is
flowing to the sensor. Removing your finger (the restriction) generates a vacuum on the sensor and may damage
the sensor (voiding the sensor warranty).
Procedure:
1. Caution: Do not change the factory setting until instructed to do in this manual.
2. Designate one of the bulkhead tube fittings as the VENT and the other SAMPLE.
3. Regulate the pressure as described in Controlling Pressure & Flow above.
4. Connect a 1/8” vent line to the compression fitting to be used for venting the sample.
5. Connect a 1/8” ZERO, SPAN or SAMPLE line to the fitting designated SAMPLE.
6. If equipped with optional fittings and/or sample system, connect the ZERO and SPAN gas lines.
7. Allow gas to flow through the transmitters and set the flow rate to 2 SCFH.

14
Power Connection:
Remove the front cover of the junction box located on left side of the transmitters by removing the four (4) screws
securing the cover and set them aside for reinstallation.
To assure proper grounding, connect the 4-20mA signal output to the external device (PLC, DCS, etc.) before
attempting any zero or span adjustments.
Power requirements consist of a two wire shielded cable and a 12-36V DC with negative ground power supply.
Procedure:
1. Loosen the nut on the cable gland.
2. Separate the shielding from the wires of the cable.
3. Thread the wires through the cable gland into the inside of the
junction box.
4. Connect the two wires to the two (2) screw type terminals of the
barrier strip inside the junction box.
5. Ensure the positive and negative terminals of the power supply are
connected to the appropriate terminals of the barrier strip as
marked.
6. Connect the shielding of the cable to the copper ground screw inside
the junction box.
7. Replace the junction box cover ensuring the gaskets are in place and
tighten the four (4) screws.
8. Tighten the cable gland to maintain NEMA 4 rating.
Hazardous Area Installation:
The GPR-2500/2500MO transmitters may be installed in a hazardous
area with specific intrinsic safety barriers and a barrier enclosure
approved for use with the safety barrier selected.
MTL 702 type barriers and a 24VDC power supply with two (2) wire shielded cable are recommended.
Requirements include a 4-20mADC two (2) wire signal and a power requirement of 20mADC per channel at 24VDC
minimum.
Refer to drawing A-2439 for wiring instructions. The following chart identifies the required wire based on the
distance from the safety barriers to the two wire transmitters.
4,500 ft. – 22 AWG
7,200 ft. – 20 AWG
11,500 ft. – 18 AWG
18,500 ft. – 16 AWG
29,500 ft. – 14 AWG

15
Connections – Optional Intrinsic Safety Barrier:
1. Non-hazardous area: Barrier terminals (1), (2)
2. Hazardous area: Barrier terminals (3), (4)
3. Direct measurement of 4-20mA: Reference (C1), connect the current measuring device at terminal (2) of the
barrier and the negative (-) terminal from the power source as shown below.
4. Convert 4-20mA current to voltage: Reference (C2), connect a resistor (RL) maximum value 850Ωbetween
terminal (2) of the barrier and the negative (-) terminal from the power source and measure the voltage across
the resistor.
5. Example: To convert the 4-20mA current for output to a PLC requiring 1-5V, follow the above procedure using
a 250Ωresistor (RL).
Hazardous Area Operation:
When used in conjunction with the optional MTL 702, third party certified, intrinsic safety barriers, the design of
the GPR-1500/2500 Series Oxygen Transmitters meet recognized standards as intrinsically safe for operation in
Class I, II, III; Division I, II; Groups A-G hazardous areas.
Note: Locate the optional intrinsic safety barrier as close to the power source in the non-hazardous area as
possible.

16
Output connection:
The 4-20mA current output is obtained by connecting the current measuring device between the negative terminal
of power source and the negative terminal, marked (-), located in the junction box of the transmitters. The positive
current flow is from pin 1 to pin 2 and from pin 2 to ground through the external load.
To check the signal output of the 4-20mA E/I integrated circuit connect an ammeter, as illustrated below, as the
measuring device and confirm the output is within +0.1mA of 4mA.
Power 12-36V DC To Transmitters
Terminal Strip
Caution: To assure proper grounding, connect the 4-20mA signal output to the external device (PLC, DCS, etc.)
before attempting any zero or span adjustments.

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Installing the Oxygen Sensor
The GPR-2500/2500MO Oxygen Transmitter is normally equipped with an integral oxygen sensor. It has been
tested and calibrated by the manufacturer prior to shipment and are fully operational from the shipping container.
However, when the application requires a remote sensor (external to the electronics enclosure) or other special
circumstances, the oxygen sensor will be packaged separately and must be installed prior to operating the
transmitter. If the sensor has not been installed at the factory, it will be necessary to install the sensor in the field.
Caution: All transmitters must be calibrated once the installation has been completed and periodically thereafter
as described below. Following the initial installation and calibration, allow the transmitters to stabilize for 24 hours
and calibrate with certified span gas.
Caution: DO NOT open the oxygen sensor. The sensor contains a corrosive liquid electrolyte that could be harmful
if touched or ingested, refer to the Material Safety Data Sheet contained in the Owner’s Manual appendix. Avoid
contact with any liquid or crystal type powder in or around the sensor or sensor housing, as either could be a form
of electrolyte. Leaking sensors should be disposed of in manner similar to that of a common battery in accordance
with local regulations.
Caution: Do not change the factory settings until instructed to do in this manual.
Integral Oxygen Sensor:
1. Remove the four (4) screws securing the top section of
the enclosure, set them aside for reinstallation and raise
the hinged top section 180º until it locks in place.
2. Caution: Do not remove or discard the gaskets from
either the enclosure or junction box. Failure to reinstall
either gasket will void the NEMA 4 rating and RFI
protection.
3. The transmitters design provides protection from RFI
that is maintained by leaving specific mating areas of the
enclosure unpainted to maintain conductivity the gasket,
top and bottom sections of the enclosure. These
unpainted areas are protected by gaskets and contribute
to maintaining the NEMA 4 rating. Do not paint these
areas. Painting will negate the RFI protection.
4. Remove the oxygen sensor from the bag.
5. Screw the oxygen sensor into the sensor flow housing,
equipped with elbows and tubing, finger tighten plus one
half (1/2) turn to ensure a good seal from the o-ring
affixed to the sensor.
6. Remove the shorting device (looped wire) from the receptacle located at the rear of the sensor. Minimize the
time the sensor is exposed to ambient air.
7. Assure the keyway registration of the female plug on the cable and male receptacle on the sensor match up.
8. Push the female plug (including the knurled lock nut) molded to the cable into the male receptacle attached to
the new sensor.
9. Screw the knurled lock nut attached the cable onto to the male connector attached to the sensor, tighten
finger tight plus ¼ turn.

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10. Replace the front cover of the transmitter and ensure that the gasket is replaced as well to maintain CE
approval and NEMA 4 rating.
11. Tighten the four (4) screws to secure the front cover.
12. Connect the gas lines, vent line first, as previously described.
13. Proceed to calibration.
Remote Oxygen Sensor:
Applications requiring the sensor to be located remotely from the electronics dictate the
separate packaging and shipment of the electronics enclosure, oxygen sensor and
sensor flow housing. The appropriate length of cable to connect the sensor to the
electronics is supplied and connected to the electronics. To install the remote sensor:
1. Locate the sensor flow housing and note the through holes in the flanged sections.
2. Identify the spot for installation.
3. Using two (2) 6/32 screws of the appropriate type and length secure the sensor flow
housing to a flat surface, the position illustrated at the right is recommended for
optimum performance.
4. Remove the oxygen sensor from the bag.
5. Screw the oxygen sensor into the sensor flow housing, equipped with elbows and
tubing, finger tighten plus one half (1/2) turn to ensure a good seal from the o-ring
affixed to the sensor.
6. Remove the shorting device (looped wire) from the receptacle located at the rear of
the sensor. Minimize the time the sensor is exposed to ambient air.
7. Assure the keyway registration of the female plug on the cable and male receptacle
on the sensor match up.
8. Push the female plug (including the knurled lock nut) molded to the cable into the
male receptacle attached to the new sensor.
9. Screw the knurled lock nut attached the cable onto to the male connector attached
to the sensor, tighten finger tight plus ¼ turn.
10. Connect the 1/8” diameter gas lines, vent line first, as previously described.
11. Proceed to calibration.