Analytical Industries GPR-2500 A User Manual

GPR-2500A

Oxygen Transmitter

Owner’s Manual

2855 Metropolitan Place, Pomona, CA 91767 USA ♦ Tel: [phone], Fax: [phone], e-mail: [e-mail], www.aii2.com

2

Table of Contents

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 state­of-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 Quality Control Certification

Date:

Customer: Order No.: Pass

Model:

GPR-2500A Oxygen Transmitter

Sensor:

( ) GPR-11-32-4 Oxygen Sensor
( ) XLT-11-24-4 oxygen Sensor

Serial Nos.:

Transmitter ______________________ Sensor ______________________

Accessories:

Owner’s Manual
ENCL-1071-KIT Y-Fitting Packing Fiber, Sealing Cement, Stick Stirrer

Configuration:

A-1151-E-A2 PCB Assembly Main Processing
A-1153-A2 PCB Assembly Alarms/Power Connection
Software rev:
Ranges: 0-1%, 0-5%, 0-10%, 0-25%
Power: 12-36V DC two wire loop power
Barometric pressure and temperature compensation
NEMA 4X rated wall mount enclosure

Test: Pass Pass

Set default zero
Set default span @ 40uA Alarm delay
Zero calibration Alarm bypass
Span Calibration Alarm configurations; ALARM 1, ALARM 2
Analog signal output 4-20mA full scale Alarm function; ALARM 1, ALARM 2
Calibrates with adequate span adjustment within 10-50% FS Alarm relays; ALARM 1, ALARM 2
Baseline drift on zero gas < ± 2% FS over 24 hour period Alarm system fail, dry contact
Noise level < ± 1.0% FS Overall inspection for physical defects

Options:
Notes:

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3 Safety

General

This section summarizes the essential precautions applicable to the GPR-2500A 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.

Pressure and Flow

Inlet Pressure: GPR-2500A 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 equipped with a H2S scrubber as part of an optional sample conditioning system, 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.
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.

6

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

Principle of Operation

The GPR-2500A oxygen transmitter incorporates a variety of advanced galvanic fuel cell type sensors. The
transmitter is a compact efficient package configured with the oxygen sensor and separate circuits boards for
signal processing and terminals for incoming power, power supply, signal output and alarm relay contacts housed
in a general purpose NEMA 4X rated enclosure.

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 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.

The circuit for the 4-20mA signal output and two adjustable alarms is powered by a DC/DC transformer that
requires a 12-36VDC power source and separate wiring for the outputs. A loop power source is not sufficient to
power to the circuit. The 4-20mA output is also represented on full scale oxygen readings to an external device.

Sample System:

The GPR-2500A is supplied without a sample conditioning system thereby giving users the option of adding their
own or purchasing a factory designed sample conditioning system. Whatever the choice, 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

[e-mail]

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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 or Tygon tubing inside the transmitter. The GPR-2500A 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 positioned upstream of the sensor is recommended
for controlling the sample flow rate between 1-5 SCFH. 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.

Caution: If equipped with a H2S scrubber as part of an optional sample conditioning system, inlet
pressure must not exceed 30 psig.

Application Pressure - Atmospheric or Slightly Negative:

For accurate oxygen measurements, an optional external sampling pump should be positioned upstream of the
sensor to draw the sample from the process and push the sample by the sensor and out to atmosphere. A flow
meter is not necessary if the discharge of the sampling pump approximates the recommended 2SCFH flow rate.

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.

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To avoid erroneous oxygen readings and damaging the sensor:

¾ 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).

¾ Assure there are no restrictions in the sample or vent lines
¾ Avoid drawing a vacuum that exceeds 14” of water column pressure – unless done gradually
¾ Avoid excessive flow rates above 5 SCFH which generate backpressure on the sensor.
¾ Avoid sudden releases of backpressure that can severely damage the sensor.
¾ Avoid the collection of particulates, liquids or condensation collect on the sensor that could block the diffusion

of oxygen into the sensor.

¾ If 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 +2% of full scale at constant temperature or +5% over the operating temperature range.
QC testing is typically <+0.5% prior to shipment.

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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-2500A Oxygen Transmitter has been tested, calibrated at the factory prior to shipment with the sensor
installed and is fully operational from the shipping container. Allow the transmitters to stabilize for 30 minutes and
then recalibrate the device as instructed below.

Installation Considerations:

The GPR-2500A consists of a two circuit boards, sensor housing and sample 1/8” sample inlet and vent connections
housed in a NEMA 4X rated enclosure. The complete transmitter package measures 9Hx4Wx3.5”D and is suitable
for mounting on any vertical flat surface.

For optimum accuracy zero and calibrate a 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 only for measurements below 1% and not
practical for measurement ranges above 1%. 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.

¾ Assemble 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.

¾ Temperature: 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.

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¾ Pressure & Flow: As described above.
¾ Moisture & 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.

¾ Contaminants: 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.

¾ Gas connections: Inlet and outlet vent gas lines require 1/8” diameter tubing preferably metal.
¾ Power connection: Locate a source of AC power to meet area classification and to plug in the charging adapter.
¾ Zero calibration (required only for very low percentage range measurements).
¾ Span calibration – Users are responsible for certified span gas cylinder, regulator and flow control valve.

Mounting the Transmitter:

The GPR-2500A is housed in a 9Hx4Wx3.5”D NEMA4X rated
enclosure. This configuration is designed to be mounted
directly to any flat vertical surface, wall or bulkhead plate with
four (4) of the appropriate size screws. To facilitate servicing
the interior of the transmitters, position it approximately 5 feet
off ground level.

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 hole s cast into the enclosure.

3. Secure 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.

13

Gas Connections:

The GPR-2500A with its standard flow through configuration is designed for positive pressure samples and requires
connections for incoming sample and outgoing vent lines. The user is responsible for calibration gases and the
required components, see below.

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 SAMPL E.

3. Regulate the pressure as described in Pressure and 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.

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.