Gas Detection GDA 2500 Series User manual

Gas Detection (Australia) Pty Ltd
GDA 2500 Series
Loop Powered Sensor
Operating Manual
Manual Revision: 1.0
Hardware Version: 2.6
© Copyright Gas Detection (Australia) Pty Ltd 2019

Gas Detection (Australia) Pty Ltd Page 2 of 20 M-GDA-2500 V2.6 Rev 1.0
Thank you for purchasing this product from Gas Detection (Australia) Pty Ltd
This manual contains information about the method of installation and operation of the GDA
2500 series of gas sensors. Please read it carefully and keep it nearby for further reference.
If you have any further question about the product, please contact us.
Location: Unit K1, USQ, Baker Street Toowoomba, QLD 4350
Address: PO BOX 597, Darling Heights, QLD 4350
Phone: [phone]
Web: www.gasdetectionaustralia.com.au
Email: [e-mail]
Note:
The calibration period for a sensor will depend on a number of factors such as the
environment in which it is used, operating temperature, humidity, atmospheric pressure and
environmental pollutants.
In all cases we recommend sensors are calibrated in line with target market legislation.
In order for these sensors to maintain operational efficiency and performance it is
recommended that the sensors are checked for calibration on a periodic cycle.
An appropriate bump test gas used according to the period stated in Table 2.
Calibration should be carried out according to the periods stated in Table 2 with the
appropriate Calibration gas.
The calibration should be carried out by fully trained and authorised and approved technicians
approved by GDA.
It is a further manufacturer’s recommendation that sensor head assembly be replaced every
2-3 years or earlier if the calibration or periodic test fails.

Gas Detection (Australia) Pty Ltd Page 3 of 20 M-GDA-2500 V2.6 Rev 1.0
WARNINGS
The GDA 2500 Series Sensors are only to be used in areas classified as SAFE AREAs. The
sensor is not designed for use in classified HAZARDOUS AREAs.
If GDA 2500 Series Sensors are used for safety critical applications the Calibration/Bump test
period should be evaluated according to risk management procedure associated the area the
sensor is installed.
The GDA 2500 Series Sensors use an electrochemical sensor, the chemical is used up when
the target gas is present. Therefore the chemical in the sensor will be used up at a faster rate,
shorting its life. From the time of calibration at the GDA factory the sensors output accuracy
will have degraded and may require re-calibration if some time has elapsed.
The sensor element contains substances that can be harmful to health. In the unlikely event of
a sensor element leaking, the sensor contents should not be touched. If the sensor contents
come in contact with eyes or skin, please seek immediate medical attention.
The sensor is designed to work only with the GDA transmitter. Connection to any other
transmitter will damage the sensor.
It is important not to exceed the specified DC voltage as indicated in this manual.
PROPRIETARY RIGHTS
No part of the hardware or documentation may be reproduced, transmitted, transcribed, stored
in a retrieval system, or translated into any language or computer language, in any form or by
any means, without prior written permission of GDA.
While great efforts have been made to ensure the accuracy and clarity of this document, GDA
assumes no liability resulting from any omissions in this document, or from misuse of the
information contained herein. The information in this document has been carefully checked
and is believed to be entirely reliable with all of the necessary information included. GDA
reserves the right to make changes to any products described herein to improve reliability,
function, or design, and reserves the right to revise this document and make changes from
time to time in content hereof with no obligation to notify any persons of revisions or changes.
GDA does not assume any liability arising out of the application or any use of any product or
circuit described herein; neither does it convey license under its patent rights or the rights of
others.

Gas Detection (Australia) Pty Ltd Page 4 of 20 M-GDA-2500 V2.6 Rev 1.0
Table of Contents
1. Overview:...................................................................................................................................................5
1.1. Introduction.............................................................................................................................................. 5
1.2. Specifications: .......................................................................................................................................... 6
1.3. Sensor Specifications: ............................................................................................................................... 7
2. Sensor Placement:......................................................................................................................................8
3. Wiring Instructions: ....................................................................................................................................9
4. Operation:................................................................................................................................................10
5. Calibration and Functional Test: ...............................................................................................................11
5.1. Zero point Calibration ............................................................................................................................ 12
5.2. Span point Calibration............................................................................................................................ 13
5.3. Test mA Output ...................................................................................................................................... 14
6. Sensor Head Replacement (25xx-002): ..................................................................................................... 15
7. Revision History .......................................................................................................................................20

Gas Detection (Australia) Pty Ltd Page 5 of 20 M-GDA-2500 V2.6 Rev 1.0
1. Overview:
1.1. Introduction
The GDA 2500 Series gas sensors have a loop powered 4-20 mA transmitter with an
electrochemical gas sensor module.
The gas sensor transmitter is a current loop powered device which provides a 4-20 mA current
value corresponding to the target gas concentration present. It accepts a range of
electrochemical sensor modules see Table 2 for gas types and ranges. The electrochemical
sensor cell is enclosed in a Brass or PTFE sensor module which is replaceable.
The transmitter is housed in an IP56 PVC plastic enclosure with the sensor module protruding
from the enclosure base with an IP53 (PTFE IP22).
The electronics of the transmitter are calibrated to the target gas and will not require alteration
when received from the GDA factory.
The sensor element will expire after approximately 24 months in Standard Ambient
Temperature and Pressure (SATP 25°C @ 101.325 kPa) conditions and is easily replaced by
disconnecting the plug on the transmitter and unscrewing the sensor module.
The sensor should be connected as per the wiring diagram in Figure 4 on page 9.
It is important when wiring the sensor that the cables screen/shield is connected to the
sensor transmitter connector labelled Earth and is only earthed to the system earth at
the controller end of the sensor cable.
Label interpretation:
1. Product: Model, Name of detectable gas and its chemical formula
2. Part Number: Product part number of detector, sensor head, controller, ...
3. Serial Number: Serial number of detector, sensor head, controller, ...
4. Sensor Serial No.: Serial Number of the Sensor module (May not appear on same
label)
5. Range: Range of sensor and units (ppm, %vol., %LEL)
6. Date of Manufacture: Date of Manufacture/ Date of Calibration
1:
2:
3:
5:
6:
4:
Figure 1: Label interpretation

Gas Detection (Australia) Pty Ltd Page 6 of 20 M-GDA-2500 V2.6 Rev 1.0
1.2. Specifications:
Series
GDA 2500
Operating Voltage
+24 VDC from a regulated power supply
Output Type
4-20 mA Loop Powered
Power Consumption
<25 mA @ 24 VDC
Connection
3 pin plug connector; 24 VDC, mA O/P & Earth
Wiring
2 core 18 AWG with overall screen
Output Specifications
Max loop impedance 680 Ω @ 24 VDC
Detection Type
Diffusion
Sensor Technology
Electrochemical Cell
Cable Entry
2 x M20 top entry
Enclosure Material
PVC plastic & Brass C385 / PTFE
Dimensions
122/115 x 85 x 62 mm (H, W, D)
IP Rating of Enclosure
IP56 with sensor module IP53, PTFE IP22
Weight
320g, PTFE 260g
Table 1: Specifications
Figure 2: Sensor dimensions

Gas Detection (Australia) Pty Ltd Page 7 of 20 M-GDA-2500 V2.6 Rev 1.0
1.3. Sensor Specifications:
Table 2: Gas Sensor specifications
1Accuracy of Calibration does not include calibration bottle accuracy.
2To remain within an allowed drift of #% of Full Scale output. If target gas is expected to be present
during normal operation the calibration period of the sensing element will be reduced.
Model
2525
2526
2527
2528
2529
2530
2531
Detection Gases
Carbon
Monoxide
Ammonia
Nitrogen
Dioxide
Oxygen
Hydrogen
sulphide
Sulphur
Dioxide
Chlorine
Chem. Formula
CO
NH3
NO2
O2
H2S
SO2
Cl2
Ranges
0-100
0-150
0-200
0-100
0-300
0-1000
0-30
0-25
0-100
0-10
0-10
Units
ppm
ppm
ppm
% vol.
ppm
ppm
ppm
Maximum Gas
concentration
Overload
5000
200
500
1500
200
30
500
150
100
Accuracy of
calibration1
< 0.5%
F/S
< 0.5%
F/S
< 0.5%
F/S
< 0.5%
F/S
< 0.5%
F/S
< 0.5%
F/S
< 0.5%
F/S
Response Time T90
at SATP
<30 sec
<60 sec
~30 sec
<10 sec
~30 sec
<30 sec
~60 sec
Linearity
Linear
Linear
Linear
Linear
Linear
Linear up
to 20 ppm
and within
±5%
Linear
Repeatability
<±2% CO
±10%
<±2%
NO2
-
< ±2%
H2S
< ±2%
SO2
< ±2% Cl2
Warm Up Time
~ 30
seconds
~ 30
seconds
~ 30
seconds
~ 30
seconds
~ 30
seconds
~ 30
seconds
~ 30
seconds
Output Drift per
annum at SATP in
Fresh Air
< 5%
< 20%
< 20%
< 5%
< 15%
< 15%
< 20%
Recommended time
between Calibration
operated at SATP in
Fresh Air
Annually
@ ~ 5%
allowed
drift2
6 months
@ ~ 10%
allowed
drift2
6 months
@ ~ 10%
allowed
drift2
Annually
@ ~ 5%
allowed
drift2
6 months
@ ~ 10%
allowed
drift2
6 months
@ ~ 10%
allowed
drift2
6 months
@ ~ 10%
allowed
drift2
Recommended time
between Bump Test
operated at SATP in
Fresh Air
6 months
@ ~ 3%
allowed
drift2
3 months
@ ~ 5%
allowed
drift2
3 months
@ ~ 5%
allowed
drift2
6 months
@ ~ 3%
allowed
drift2
3 months
@ ~ 5%
allowed
drift2
3 months
@ ~ 5%
allowed
drift2
3 months
@ ~ 5%
allowed
drift2
Filter Capacity
-
-
-
-
-
1000 ppm
hours @
25 ppm
H2S
-
Operating
Temperature
-10°C to
40°C
-10°C to
40°C
-10°C to
40°C
-10°C to
40°C
-10°C to
40°C
-10°C to
40°C
-10°C to
40°C
Operating Humidity,
peak non condensing
15% to
90% RH
15% to
90% RH
15% to
90% RH
5% to
95% RH
15% to
90% RH
15% to
90% RH
15% to
90% RH
Operating Pressure
800 to
1200
mbar
800 to
1200
mbar
800 to
1200
mbar
800 to
1200
mbar
800 to
1200
mbar
800 to
1200
mbar
800 to
1200
mbar
Gas density
compared to Air
(1.205 kg/m3) @ NTP
Approx.
1.165
Lighter
0.717
Heavier
-
Approx.
1.331
Heavier
1.434
Heavier
2.279
Heavier
2.994

Gas Detection (Australia) Pty Ltd Page 8 of 20 M-GDA-2500 V2.6 Rev 1.0
2. Sensor Placement:
The recommended sensor instillation height is determined from:
The properties of the target gas (Table 2).
Properties of other gases present.
The temperature of the gasses present.
Air flow in the detection space.
If the space is occupied or unoccupied.
For heavier gas the sensor should never be mounted with the sensor head pointing upwards,
as gas can pool in the sensor and cause constant high or false readings. Take into account
drafts and air movements when mounting the sensor.
The three recommended instillation heights depending on the target gas and the environment
are;
Lighter gases within 300 mm of the ceiling
The Breathing Zone is 1.0m to 1.8m from the ground.
Heavier gases 300 mm from ground
Below shows allowable mounting orientations for the GDA 2500 depending on the target gas.
Note the IP rating is only maintained in the normal orientation.
Figure 3: Sensor mounting orientation.
Normal orientation
Heavier gases: YES
Recommended
Lighter gases: NO
Not Recommended
Heavier gas: YES
Lighter gases: YES
Heavier gas: YES
Lighter gases: YES
Heavier gas: NO
Not Recommended
Lighter gases: YES
Recommended

Gas Detection (Australia) Pty Ltd Page 9 of 20 M-GDA-2500 V2.6 Rev 1.0
3. Wiring Instructions:
The sensor is a two-wire loop-powered 4-20 mA device. The sensor is designed to work with
24 VDC from a regulated power supply. The sensor transmitter is wired to the GDA range of
control units with a 2 core cable with an overall screen/shield or a 3 core 18 AWG cable.
The screen or third wire should be connected to the Earth connection of the sensor.
The +24 VDC is wired to +VDC (indicated on the PCB).
The 4-20mA output of the sensor which connects to the controller is wired to O/P.
The screen of the 2 core cable is wired to Earth of the three way connector.
Brass sensor modules provided with an earth wire must be wired to Earth of the three way
connector as shown below.
It is important that the Screen/Shield of the sensor cable is connected to the power
supply earth at the control unit.
+24 VDC
Cable Screen/Shield
Output 4-20mA
Replaceable
Sensor module
Sensor module
Connector
Brass Sensor
Module Earth Wire
(If Provided)
+VDC
Earth
O/P
Function LEDs
see Table 3
Figure 4: Sensor Wiring

Gas Detection (Australia) Pty Ltd Page 10 of 20 M-GDA-2500 V2.6 Rev 1.0
4. Operation:
The sensor has three LEDs which indicate the status of the sensor. After an initial warm up
period.
LED
Sensor output
Function
>12.00mA to 20.00mA
The red and amber LEDs indicate that the sensor
has detected the target gas at half scale or above.
<12.00 mA to 4.00mA
The amber LED indicates that the sensor has
detected the target gas at below half scale and zero
units of the target gas.
<4.00 mA
The green LED indicates that the sensor detects
zero units of the target gas.
Table 3: LED Status
The GDA 2500 transmitter gas type selection jumper is factory set for the required target gas.
Oxygen (O2)
Nitrogen Dioxide (NO2)
Toxic Gases;
CO, NH3, H2S, SO2& Cl2
Figure 5: JP1 gas type selection jumper

Gas Detection (Australia) Pty Ltd Page 11 of 20 M-GDA-2500 V2.6 Rev 1.0
5. Calibration and Functional Test:
Sensors are issued tested & pre-calibrated under controlled lab conditions. Changes to
humidity, temperature, and other environmental factors affect the sensor accuracy and may
need an adjustment of the Zero point when introduced to new environments.
THE SENSOR MUST BE FULLY POWERED FOR A MINIMUM OF ONE (1) HOUR BEFORE
CALIBRATION IS CARRIED OUT.
Zero
Adjustment Pot
Span (Gain)
Adjustment Pot
4-20 mA output Test points
I- (-mA), I+ (+mA)
LEDs
Factory set
Do not remove
or add Jumpers
Figure 6: Calibration adjustment pots and rang selection

Gas Detection (Australia) Pty Ltd Page 12 of 20 M-GDA-2500 V2.6 Rev 1.0
5.1. Zero point Calibration
The Zero point is when there is none of the target gas present (e.g. 0 ppm CO, 0% vol. O2).
A Zero point calibration adjusts the 4.0 mA point of the transmitter to correspond to a zero
target gas concentration.
Calibrate using the 4-20 mA test points and a multimeter see Figure 6 for mA output test
points and adjustment pots.
The 4-20 mA current output of the sensor can be monitored with a current meter set to the 30
mA range.
1. Use the GDA 2500 gassing cap and introduce 100% vol. nitrogen at a rate of
approximately 0.5 L/min or in Fresh Air which contains none of the target gas.
2. Apply the multimeter to the sensors 4-20 mA current test points see Figure 6
(observing the polarity).
a. To adjust the sensors zero point turn the ZERO pot until the current meter value is
4.00 mA note the value may vary ± 0.05 mA.
b. Observe the multimeter value, If the value is above 4.00 mA turn the ZERO POT
SLOWLY in the anti clockwise direction till the value is bellow 4.00 mA.
c. The recommended Zero point current should be equal to or below 4.00 mA and
above 3.90 mA.
d. The Zero point is now set, the Green LED should be illuminated;
3. Turn off nitrogen gas.

Gas Detection (Australia) Pty Ltd Page 13 of 20 M-GDA-2500 V2.6 Rev 1.0
5.2. Span point Calibration
The Span point is set when the sensor is exposed to a known concentration of the target gas.
This is normal at half or full scale of the sensor (e.g. 100 ppm CO, 18% vol. O2).
Calibration using the 4-20 mA test points and a multimeter see Figure 6 for mA output test
points and adjustment pots.
The 4-20 mA current output of the sensor can be monitored with a current meter set to the 30
mA range.
1. Use the GDA 2500 gassing cap and introduce the calibration gas (e.g. 100ppm CO) at
a rate of 0.5 L/min for approximately 120 seconds (Sensor dependent). With the
multimeter on the mA test points.
a. When the current meter value stabilises (the value may flicker ±0.05 mA) adjust
the SPAN (Gain see Figure 6) pot until the required mA value is displayed on the
current meter. See Table 4 below calculations to determine the correct mA value
for the calibration gas.
b. The Red and Orange LEDs should be illuminated when the mA value is above
12.0 mA
c. The SPAN is now set,
2. turn off the gas and replace sensor cover
Gas concentration calculations:
Example calculation for a 0-200 ppm sensor using calibration gas of 100 ppm, the transmitter
board output will be 12.00mA.
1.     
    
2. 󰇛  󰇜   
󰇛  󰇜   
Table 4: Calibration mA example calculations
Chem. Formula
CO
NH3
NO2
O2
H2S
SO2
Cl2
Sensor Range
0-200
ppm
0-100
ppm
0-30 ppm
0-25%
vol.
0-100
ppm
0-10 ppm
0-10 ppm
Calibration
gas
value
100 ppm
50 ppm
10 ppm
18% vol.
25 ppm
5 ppm
2 ppm
mA
12.0 mA
12.0 mA
9.3 mA
15.5 mA
8.0 mA
12.0 mA
7.2 mA
Full
Range
Calibration
gas
value
200 ppm
100 ppm
30 ppm
20.9%
vol. (Fresh
Air)
-
10 ppm
-
mA
20.0 mA
20.0 mA
20.0 mA
17.4 mA
-
20.0 mA
-
TWA
25 ppm
25 ppm
3 ppm
-
10 ppm
2 ppm
1 ppm
peak
STEL
-
35 ppm
5 ppm
-
15 ppm
5 ppm
-

Gas Detection (Australia) Pty Ltd Page 14 of 20 M-GDA-2500 V2.6 Rev 1.0
5.3. Test mA Output
The sensor transmitter board has a current output test function. This is used to simulate the
current output signal of the transmitter board for functional testing of the system.
The simulated mA current has an adjustable range from 4 to 20 mA. To use the test current
function, set jumper JP2 to the Test position see Figure 7 below. The Test current pot
adjustment screw can be rotated with a small flat screw driver to increase or decrease the mA
output.
Ensure that the JP2 jumper is repositioned to its Normal operating position after functional
testing to ensure sensing operation (Figure 8).
mA Output Test
Adjustment Pot
Jumper in Test
position
mA Output Test
Adjustment Pot
Jumper in Norm position
Figure 7: JP2 Jumper in Test position
Figure 8: JP2 Jumper in Normal operation

Gas Detection (Australia) Pty Ltd Page 15 of 20 M-GDA-2500 V2.6 Rev 1.0
6. Sensor Head Replacement (25xx-002):
When the sensor head is being replaced, the replacement sensor heads are supplied tested
but will require calibration when installed, follow these instructions on how to remove used
sensor and install new sensor without damaging the sensor. Gloves are recommended
when removing the brass sensor head to protect your hand from cuts.
1. Remove the lid of the enclosure (4 screws).
2. Disconnect Incoming Cable Connector (green 3 pin) located on the left of the main
board.
3. Disconnect the Sensor Assembly Connector (Figure 4).
4. Disconnect the sensor earth wire from the Incoming Cable Connector.
5. Gently pull the sensor cable towards the top of the case to clear any obstructions from
the main board and the incoming power cable.
6. Rotate the sensor head anti-clockwise, while checking that the sensor cable in the
enclosure is not catching on anything or that cable is not twisting, until sensor head is
removed. Caution: the brass thread can be sharp, use caution when loosening the
sensor.
7. When installing the new sensor head, guide the sensor cable into the enclosure
through the sensor mounting hole.
8. Rotate the new sensor head clockwise, while checking that the sensor cable in the
enclosure is not catching on anything or that cable is not twisting, until hand tight.
Caution: the brass thread can be sharp, use caution when tightening the sensor.
9. Connect the sensor cable from the sensor head in to the Sensor Assembly Connector
without putting stressful bends on the sensor cable.
10. Reconnect the replacement sensor Earth cable to the Incoming Cable Connector.
11. Reconnect the Incoming Cable Connector into the socket on main board.
12. Proceed to calibration of sensor.
Figure 9: Replacement Sensor

Gas Detection (Australia) Pty Ltd Page 16 of 20 M-GDA-2500 V2.6 Rev 1.0
4-20 mA
Test Point
See Figure 6
LEDS
See Table 3
mA Output Test
Adjustment Pot
See Figure 7
JP2 Jumper
See Figure 5
JP1 Jumper
See Figure 5
Incoming Cable
Connection
See Figure 4
Zero Adjustment
Pot See Figure 6
Span Adjustment
Pot See Figure 6
Figure 10: Feature location.
Jumpers JP4 &
JP3 See Figure 6

Gas Detection (Australia) Pty Ltd Page 17 of 20 M-GDA-2500 V2.6 Rev 1.0

Gas Detection (Australia) Pty Ltd Page 18 of 20 M-GDA-2500 V2.6 Rev 1.0

Gas Detection (Australia) Pty Ltd Page 19 of 20 M-GDA-2500 V2.6 Rev 1.0

Gas Detection (Australia) Pty Ltd Page 20 of 20 M-GDA-2500 V2.6 Rev 1.0
7. Revision History
Version
Contents
Date
1
Initial revision of the 2500 Manual HW: V2.6
20 Feb, 2019
This product and operating manual are subject to change without prior notice for the
improvement of product performance and ease of use.
Gas Detection (Australia) Pty Ltd
Unit K1, USQ, Baker Street Toowoomba, QLD 4350
PO BOX 597, Darling Heights, QLD 4350 [phone]
www.gasdetectionaustralia.com.au [e-mail]