l-com SRAQ-G208 User manual

LIQUEFIED NATURAL GAS & LIQUEFIED PETROLEUM GAS TRANSMITTER
User Guide for SRAQ-G208
Thank you for choosing L-com product. To ensure safe, accurate performance and product longevity, please take a moment to familiarize yourself
with this manual before powering the device. Please keep it handy for future reference. In case of any questions regarding the installation or use of
product, please call us at 800.341.5266.
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M_L-com_SRAQ-G208_11/2022_R1.0
1
Product Description
The SRAQ-G208 gas transmitter detects the presence and concentration of liquefied petroleum gas as well as liquefied natural gas. Integrated
circuitry produces a non-linear voltage signal corresponding to the gas concentrations. With high sensitivity to butane, propane and methane, the
SRAQ-G208 has a detection range of 300 to 10000 ppm. It is well suited for detecting LPG and LNG leaks and triggering alarms.
Features
 High sensitivity to LNG / LPG
 24 VDC power supply
 Wide detection range 300  10000 ppm
 Analog and TTL level outputs
 Wall or DIN rail mountable
Applications
 Industrial settings
 Chemical manufacturing
 Portable gas detectors
 Anywhere LNG or LPG concentration is a concern

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Technical Parameters
Detection Range 300  10000 PPM
Measured Gas LPG, Methane, Propane, Butane, Hydrogen
Working Voltage 24 VDC ± 0.2 V
Output Method 0  10 V (Non-linear)
Response Time ≤1 sec
Recovery Time ≤30 sec
Working Temperature -20~65 °C
Working Humidity <95% RH (Non condensing)
Preheat Time >30 mins
Mounting Diagram
1. Wall mount, hole diameter 4 mm, pitch 36 mm
2. DIN 35mm rail mount
Notes
1. Confirm the polarity and the voltage of the power supply before powering ON the sensor.
2. The analog output of this module is non-linear. When connect to microcontroller, it should be connected to ADC interface of the microcontroller.
3. The relationship between the resistance ratio and the concentration is a logarithmic relationship.

3
Electrical Diagram
1. 24V and GND are the power interface, D1 is the power indicator.
2. Aout is the analog output interface, VR2 is the signal trimmer potentiometer.
3. VR1 is the magnification (the output of 0-5V and 0-10V can be adjusted freely through this potentiometer).
4. The load resistance of the sensor composed of R7 and RP2 potentiometer is in parallel relationship (can be changed by user).
5. Different sensors use different parameters. The parameters are based on the PCB board.
Typical Sensitivity Curve
The calculation of the resistance ratio according to the output voltage is as follows:
The sensor is energized in relatively clean air for more than half an hour and after measure the output voltage value of Aout.
VCC is the power supply voltage, 5 VDC
RL is the load resistance
VRL = Aout = Vair value
When the sensor detects gas, the RS value can be calculated after measuring the value of Aout.
The VRL value at this time is the Aout value after gas is detected. It is different from the value of the above formula. The VCC value and the RL value
are the same as above.
The R0 and RS values are obtained, and the specific concentration value of the gas is converted by the RS / R0 value of the Sensitivity Characteristic
Curve (To get 0-10V output, through 0-5V, the circuit is enlarged 2 times, so use the calculation method accordingly. VCC is based on 5V as the
benchmark).
The ordinate in the figure is the resistance ratio of the sensor (Rs/R0). The abscissa is the gas concentration. Rs represents the resistance value of the
sensor in different concentrations of gas, and R0 represents the resistance value of the sensor in clean air. All tests in the figures were done under
standard test conditions.