Daviteq GCB Gas Sensor
GCB
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1. Giới thiệu
GCB is a sensor module, designed to measure flammable or toxic gas concentrations. It features high-performance, ultra-low-power gas sensing technology to accurately detect specific gas concentrations in the air.
The CH₄, C₃H₈ sensor modules apply high performance Non-Dispersive Infrared (NDIR) measurement technology while CO, Cl₂, H₂S, H₂, NH₃ gases are integrated with high performance Electro-Chemical measurement technology.
It has ultra-low power consumption to allow it to be integrated with Wireless Devices such as Sub-GHz transmitter, Sigfox transmitter, LoRaWAN transmitter, RS485 output transmitters, etc.
The sensor module is ideal for monitoring gas concentrations in industrial or commercial buildings in the areas of kitchens, parking garages, boiler rooms, laboratories, basements, HVAC rooms, utility rooms, industrial workspaces and more.
Specification:
Type of measuring gas: Choose 1 of CH₄, C₃H₈,CO, Cl₂, H₂S, H₂, NH₃ gases
Measurement technology: High performance Non-Dispersive Infrared (NDIR) sensor or high performance Electro-Chemical sensor
Measuring range: CH₄ 0-100% LEL, C₃H₈ 0-100% LEL, CO 0-500ppm, H₂S 0-100ppm, H₂ 0-1000ppm, NH₃ 0-100ppm, Cl2 0-20 ppm
Resolution: 0.1% or 0.1ppm, 0.01ppm
Reading stability:
For C3H8 and CH4, refer Daviteq's NIDR gas sensor link:
https://daviteq.com/en/manuals/books/gas-measurement-list/page/daviteq-ndir-gas-sensor
For CO, Cl₂, H₂S, H₂, NH₃, refer Daviteq's Electro-Chemical gas sensor link :
https://daviteq.com/en/manuals/books/gas-measurement-list/chapter/electro-chemical-gas-sensors
Sensor working temperature: -20∼60°C
Sensor Working humidity: 15-90% RH, non-condensing
Operating pressure: 80kPa to 120kPa
2. Nguyên tắc hoạt Ä‘á»™ng
NIDR measurement technology's operation principle for CH₄, C₃H₈ sensor
When infrared radiation interacts with gas molecules, infrared light is absorbed by the gas molecules at a particular wavelength, causing vibration of the gas molecules. NDIR (Non-Dispersive Infrared) gas sensors detect a decrease in transmitted infrared light which is in proportion to the gas concentration. This transmittance, the ratio of transmitted radiation energy to incident energy, is dependent on the target gas concentration.
NDIR gas sensor consist of an infrared source, detector, optical filter, gas cell, and electronics for signal processing. A single light source, dual wavelength type gas sensor has two detectors and two optical filters of different wavelengths which are placed in front of each detector. The infrared light that is absorbed by a target gas passes through the active filter with a particular bandwidth for the detection of the target gas. The infrared light that does not interact with the target gas passes through the reference filter. The difference between transmitted light intensities in these two bandwidths is converted into gas concentration. The dual wavelength sensor ensures stable measurements for a long period of operation as the aging effects of the light source or the gas cell are automatically compensated by output signals at the reference wavelength.
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Mid-infrared radiation through sample gas causes a resonance of gas molecules at their natural frequency with the infrared light in the spectrum region where the energy level of infrared is equivalent to the natural frequency of gas molecules, resulting in the absorption of infrared by gas molecules in the form of molecular vibration.
The relationship between infrared transmittance and gas concentration is expressed by the Lambert-Beer law:
Where T is transmittance, I is the intensity of light passed through sample gas and an optical filter, Io is the initial light intensity emitted from the source, ε is the molar attenuation coefficient, c is gas concentration, and d is the light path length.
Because ε of the target gas and the light pass length d are fixed with an NDIR sensor, gas concentration can be measured by measuring the transmittance within the spectrum region of the absorbed energy (wavelength) by the target gas.
The initial light intensity emitted from the light source Io is preset by calibration using zero gas which does not absorb infrared light. The initial value of the molar extinction coefficient ε is set by calibration using calibration gas of known concentration.
Eletro-chemical measurement technology operation principle for CO, Cl₂, H₂S, H₂, NH₃ sensor
The operation principle of an electrochemical sensor involves reacting with a specific gas of interest and producing an electrical signal proportional to the gas concentration. Here’s how it works:
Components:
Working Electrode: This electrode interacts directly with the gas being detected.
Counter Electrode: It balances the current flow in the system.
Reference Electrode: Provides a stable reference potential.
2. Electrolyte Layer:
The sensor has a thin layer of electrolyte through which charged molecules can pass.
3.Gas Interaction:
The target gas diffuses into the sensor through a gas-permeable membrane.
It reaches the working electrode, where it undergoes oxidation or reduction.
4.Electrochemical Reaction:
The oxidation or reduction of the gas at the working electrode generates an electric current.
This current flows through the external circuit.
5.Signal Output:
The magnitude of the current is directly proportional to the gas concentration.
The sensor translates this current into an observable signal, which can be measured and analyzed
3. Hiệu chuẩn
The Daviteq GCB Gas Sensor must be connected to a reading device, it usually is a wireless transmitter like Sub-GHz, Sigfox, or LoRaWAN.
Why do we need to calibrate the gas sensor?
There are some reasons:
- The output value of a sensor is different from the other sensor. It is not the same value for all sensors after manufacturing.
- The output value of a sensor will be changed over time.
Therefore, users need to calibrate the sensor before use or in a pre-defined interval time (30 months for example).
How to calibrate the GCB Flammable Gas sensor?
Please follow steps for Instruction to attach the calibration cap onto the sensor module to get Zero or Span values:
Step 1. Remove the sensor filter by pulling the filter by hand. The filter is attached to the sensor by 2 small magnetic points
Step 2. Prepare calibration cap
Step 3. Attach the calibration cap to the sensor head
Step 4. Installed the Regulator to the Gas cylinder
Step 5. Attach the tube to the regulator and calibration cap
Please select the flow regulator with a flow rate of 2.5 LPM or 5.0 LPM.
With the 2-point calibration method, the user can define the A and B factors. Please find below the steps of calibration.
Step 1. Get the Zero value.
- Power ON the device;
- Place the device in a clean-air environment (the target value is nearly zero) at a temperature from 20∼30℃, in at least 60 minutes.
- After 60 minutes, force the device to send data, read and record the Raw_Gas_Concentration, so now you got the Zero_value = Raw_Gas_Concentration value.
Recommendation: Record many Raw_Gas_Concentration values ​​at least 10 minutes apart (10 values). Zero value is the average of the recorded Raw values.
Note:Â The Raw_Gas_Concentration values can be positive or negative;
Step 2. Get the Span value
Note:Â Keep the sensor Power ON all the time
- Use the standard gas cylinder with a known concentration (for example C3H8 Air 1.05% volume is equivalent to 50% LEL ) to supply the gas to the sensor;
- Use the calibration cap as above pictures to attach to the sensor and connect the tubing to the gas cylinder;
- Open the valve on the Cylinder slowly and make sure the gas has reached the sensor. The flow regulator should be 2.5 LPM or 5.0 LPM.
Notes:Â The tube length is short as possible to reduce the gas loss.
- Press a timer to start counting the time;
- After 2 minutes, force the device to send data once every minute, and stop forcing at 5 minutes;
- The highest Raw_Gas_Concentration is the Span value.
Note:Â Just get one value for Span.
- After that, immediately turn OFF the valve to save the gas;
- Remove the calibration cap from the sensor;
- Place the sensor in clean air again.
Note: Always keep the sensor Power ON all the time.
Step 3. Calculate the new A and B
The calculation of new A, B value based on basic linear formula:
y = A * x + B
Where:
A, B is calibration coefficients
x is the sensor process value (example gas level in ppm) read on reading device such as on application server/network server, on offline tool. The process value is the RAW_VALUE in the payload
y is the correct value. y is the value of standard gas/standard condition
Which condition of Zero value: y₀ = A * x₀ + B
Which condition of Span value: yâ‚› = A * xâ‚›+ B
From the two formulas, the calculation of A, B as below
A = (y₀ - yₛ) / (x₀ - xₛ)
B = (yₛ * x₀ - y₀ * xₛ) / (x₀ - xₛ)
Example of A, B calculation for LoraWAN Ammonia Gas sensor (item code WSLRW-G4-NH3-100-01):
* With condition of clean-air environment at a temperature from 20∼30℃, there is no ammonia gas (y₀ = 0); while the NH₃ level on reading device (RAW_VALUE in the payload) is -0.25 (x₀ = -0.25)
* When the sensor is connected to standard gas cylinder having ammonia level of 25 ppm (yₛ = 25); while the NH₃ level on reading device (RAW_VALUE in the payload) is 18.66 (xₛ = 18.66)
The calculation of A, B for the Ammonia gas sensor:Â Â Â Â Â Â
A = (0 - 25) / (-0.25 - 18.66) = 1.32205
B = (yₛ * x₀ - y₀ * xₛ) / (x₀ - xₛ) = (25 * (-0.25) - 0 * 18.66) / (-0.25 - 18.66) = 0.33051
The factory default A = 1 and default B = 0
The RAW_VALUEÂ in the payload is used for calibration
Step 4. Configure the new A and B into the device
- User can use the off-line tool or downlink to write the values of A and B;
- Writing the new A and B successfully meant you had done the calibration process.
4. Ghi chú ứng dụng
5. Installation Notes
Notes: If a sensor has been kept in transport containers at temperatures below zero centigrade, leave it at 10∼35℃ for not less than one hour.* if the Sensor is intended to install outdoors, please use a rain guard to protect the sensor from rain and direct sunlight. Please contact us to buy this accessory.
Place the sensor in the area to monitor the target gas concentration. Please always check the gas molecular weight v.s the air.
Do not use a damaged sensor. It must be repaired only by personnel authorized by the manufacturer.
Keep the sensor out of contact with aggressive substances, e.g., acidic environments, which can react with metals, and solvents, which may affect polymeric materials.
Diffusion holes of the sensor should be protected against the ingress of sprayed liquid or waterdrops, buy using the Splash guard or Rain guard.
The sensor is not intended to measure the target gas concentration contained in fluids.
Correct measurement is provided when the ambient temperature changes not faster than 0.6℃/ min.
Inspection and maintenance should be carried out by suitably trained personnel.
Persons, who have studied this guide, must be briefed on safety precautions when operating electrical equipment intended for use in explosive areas in due course.
When dealing with a cylinder containing a gas mixture under pressure, it is necessary to follow safety regulations.
There is no risk of pollution or negative impact on human health. The sensor does not contain any harmful substances that may be released during its normal operation.
6. Troubleshooting
1. The measured value is not within the expected value
The sensor is drifted over time: Re-calibrate the sensor
The sensor was in a high humidity environment (> 90% RH) for more than 03 days continuously: Place the sensor in low humidity for its recovery. It may take up to 30 days to recover. If the sensor cannot recover after 30 days, please replace the new sensor module.
2. The measured value is always zero or near zero
The sensor module was removed: Please check the sensor;
The sensor is at the end of its life: Replace the sensor module.
3. Error code list
Please refer below table for error code, priority level, and recommendations