Contents
Winsen MH-T7042A Combustible Gas Sensor
INSTRUCTION MANUAL
Model: MH-T7042A
Zhengzhou Winsen Electronics Technology Co., Ltd.
MH-T7042A is a universal type intelligent sensor to detect CH4 gas, utilizing non-dispersive infrared (NDIR) principle. It offers high selectivity, no oxygen dependence, high performance, and long lifespan features. The sensor includes built-in temperature compensation and is compact and high-performance based on infrared absorption of gas detection technology, micro-machining, and sophisticated circuit design.
Features
- High sensitivity, high resolution, low power consumption
- Output method: IIC, analog voltage signal, etc.
- Quick response
- Temperature compensation, excellent linear output
- Excellent stability, Long lifespan
- Anti-poisons, anti-vapor interference
- Detect combustible gas concentration in explosive
environments
Statement
This manual copyright belongs to Zhengzhou Winsen Electronics Technology Co., LTD. Without the written permission, any part of this manual shall not be copied, translated, stored in database or retrieval system, also can’t spread through electronic, copying, record ways.
Thanks for purchasing our product. In order to keep customers using it better and reduce the faults caused by misuse, please read the manual carefully and operate it correctly in accordance with the instructions. If users disobey the terms or remove, disassemble, change the components inside of the sensor, we shall not be responsible for the loss.
The specific such as color, appearance, sizes etc., please in kind prevail.
We are devoting ourselves to products development and technical innovation, so we reserve the right to improve the products without notice. Please confirm it is the valid version before using this manual. At the same time, users’ comments on optimized using way are welcome.
Please keep the manual properly, in order to get help if you have questions during the usage in the future.
MH-T7042A Infrared CH4 Gas Sensor
1. Product Description
MH-T7042A is a universal type intelligent sensor to detect CH4 gas, taking advantage of non-dispersive infrared (NDIR) principle. With high selectivity, no oxygen dependence, high performance and long lifespan features, MH-T7042A also has built-in temperature compensation feature. MH-T7042A is a compact and high-performance sensor based on infrared absorption of gas detection technology,
2. Features
➢ High sensitivity, high resolution, low power consumption
➢ Output method: IIC, analog voltage signal, etc.
➢ Quick response
➢ Temperature compensation, excellent linear output
➢ Excellent stability, Long lifespan
➢ Anti-poisons, anti-vapor interference
➢ Detect combustible gas concentration matching with flame-proof marked detector in area 1&2 explosive environments which mix of ⅡA, ⅡB, ⅡC and T1-T6 flammable gases, vapors and air
3. Application
Widely used for industrial field instrumentation, industrial-process control and safety protection 4. Specification
Table 1: Technical Index
| Product Model | MH-T7042A | |||||||||||||||||
| Gas Detected | Combustible gas (see Table 2) | |||||||||||||||||
| Working Voltage | 4.5~5.5V DC | |||||||||||||||||
| Average Current | < 100mA | |||||||||||||||||
| Interface Level | 3.3V | |||||||||||||||||
| Measurement Range | 0~100%VOL optional (table 2) | |||||||||||||||||
| Output Signal | UART | |||||||||||||||||
| Warm-up Time | <2 minutes | |||||||||||||||||
| Response Time | T90 < 30s | |||||||||||||||||
| Working Temperature | -40℃ ~ 70℃ | |||||||||||||||||
| Working Humidity | 0 to 95%RH, non-condensing | |||||||||||||||||
| Dimension | Φ51×65mm | |||||||||||||||||
| Weight | 450g | |||||||||||||||||
| Lifespan | >5 years | |||||||||||||||||
| Explosion-proof sign | Ex db ⅡC T6 Gb | |||||||||||||||||
| Protection Grade | IP65 | |||||||||||||||||
Table 2
| Gas Name | Molecular Formula |
Detection Range |
Resolution | Precision | Note | ||||||||||||||||||||||||||
| Methane | CH4 | 0-5% Vol | 0.01% Vol | 0~50% FS | With | ||||||||||||||||||||||||||
| Methane | CH4 | 0-10% Vol | 0.01% Vol | (±3%FS) | Temperature | ||||||||||||||||||||||||||
| Methane | CH4 | 0-100% Vol | 0.1% Vol | 50%~100% FS | compensation | ||||||||||||||||||||||||||
| Propane | C3H8 | 0-2.2% Vol | 0.01% Vol | (±5%FS) | |||||||||||||||||||||||||||
| Chloromethane | CH3CL | 0-8.1% Vol | 0.01% Vol | ||||||||||||||||||||||||||||
| Acetylene | C2H2 | 0-2.3% Vol | 0.02% Vol | ||||||||||||||||||||||||||||
| Ethane | CH3CH3 | 0-3.0% Vol | 0.03% Vol | ||||||||||||||||||||||||||||
| Isobutene | C4H10 | 0-1.8% Vol | 0.018% Vol | ||||||||||||||||||||||||||||
| Gasoline | C3-C12 | 0-1.1% Vol | 0.01% Vol | 0~50% FS | No | ||||||||||||||||||||||||||
| Methanol | CH3OH | 0-5.5% Vol | 0.06% Vol | (±5%FS) | Temperature | ||||||||||||||||||||||||||
| Dichloromethane | CH2CL2 | 0-15% Vol | 0.15% Vol | 50%~100% FS | compensation | ||||||||||||||||||||||||||
| Toluene | C7H8 | 0-1.2% Vol | 0.012% Vol | (±10%FS) | |||||||||||||||||||||||||||
| Alcohol | C2H5OH | 0-3.3% Vol | 0.033% Vol | ||||||||||||||||||||||||||||
| Oxirane | C2H4O | 0-3.0% Vol | 0.03% Vol | ||||||||||||||||||||||||||||
| Acetic acid | CH3COOH | 0-4.0% Vol | 0.04% Vol | ||||||||||||||||||||||||||||
| Ethyl acetate | CH3COOC2H5 | 0-2.0% Vol | 0.02% Vol | ||||||||||||||||||||||||||||
Note: The range in the above table is the common range, users can customize according to their own needs.
Substances that are liquid at room temperature cannot be temperature compensated. Please be careful when selecting.
5. Dimension Drawing
(No dimensional tolerance is ±0.2)
Table 3 Pin Definition
6. UART Output
Hardware connection
Connect the Vin-GND-RXD-TXD of the sensor to the user’s 5V-GND-TXD-RXD. (The user end must use TTL level, and if it is RS232 level, conversion must be performed). The detector can directly read the gas concentration value through the UART interface of the sensor, without the need for calculation.
Software connection
Set the serial port baud rate to 9600, data bit to 8, stop bit to 1, and parity bit to none.
| 0x86 | Read Gas Concentration | |||||||||||||||||||||||||||
| 0x87 | Calibrate zero point（ZERO） | |||||||||||||||||||||||||||
| 0x88 | Calibrate span point（SPAN） | |||||||||||||||||||||||||||
0 x86 – Gas Concentration Reading
| 1 | 0x86 | Gas Concentration Reading | ||||||||||||||||||||||||||||||
| Send | 0 | 1 | 2 | 33 | 4 | 5 | 6 | 7 | 8 | |||||||||||||||||||||||
| Start Byte | Sensor Number |
Command | — | — | — | — | — | Check Code |
||||||||||||||||||||||||
| 0xFF | 0x01 | 0x86 | 0x00 | 0x00 | 0x00 | 0x00 | 0x00 | 0x79 | ||||||||||||||||||||||||
| Return Value | ||||||||||||||||||||||||||||||||
| Return | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |||||||||||||||||||||||
| Start Byte | Command | Concentration high level |
Concentration low level |
— | — | — | — | Check Code |
||||||||||||||||||||||||
| 0xFF | 0x86 | 0x02 | 0x60 | 0x47 | 0x00 | 0x00 | 0x00 | 0XD1 | ||||||||||||||||||||||||
Gas concentration= high *256 + low
0 x87 – Calibrate Zero Point
| Send | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | ||||||||||||||||||||||
| Start Byte | Sensor Number |
Command | — | — | — | — | — | Check Code |
|||||||||||||||||||||||
| 0xFF | 0x01 | 0x87 | 0x00 | 0x00 | 0x00 | 0x00 | 0x00 | 0x78 | |||||||||||||||||||||||
| Sensor no return value | |||||||||||||||||||||||||||||||
0 x88 – Calibrate Span Value
| Send | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | ||||||||||||||||||||||
| Start Byte | Sensor Number |
Command | High span value |
Low span value |
— | — | — | Check Code |
|||||||||||||||||||||||
| 0xFF | 0x01 | 0x88 | 0x07 | 0xD0 | 0x00 | 0x00 | 0x00 | 0XA0 | |||||||||||||||||||||||
| Sensor no return value | |||||||||||||||||||||||||||||||
Checksum & calculation method
The checksum = (invert (byte0 +… + byte7)) + 1 For example, Gas Concentration Reading
| Command Sent | ||||||||||||||||||||||||||||||||
| Byte0 | Byte1 | Byte2 | Byte3 | Byte4 | Byte5 | Byte6 | Byte7 | Byte8 | ||||||||||||||||||||||||
| Start byte | Sensor Number | Command | – | – | – | – | – | Check Value | ||||||||||||||||||||||||
| 0xFF | 0x01 | 0x86 | 0x00 | 0x00 | 0x00 | 0x00 | 0x00 | Checksum | ||||||||||||||||||||||||
A. Add all the bytes together except byte 0
0x01 + 0 x86 + 0 x00 + 0 x00 + 0 x00 + 0 x00 + 0 x00 = 0x87
B. Get the value from step A, then invert it.
0xFF– 0x87 = 0x87
C. Plus one based on the value of step B
0x78 + 0x01 = 0x79
C Language Calibrate & Calculate and Routine
char getCheckSum(char *packet)
{
char i, checksum;
for( i = 1; i < 8; i++)
{
checksum += packet[i];
}
checksum = 0xff – checksum;
checksum += 1;
return checksum;
}
7. Ordering instructions
In order to be able to provide a sensor that meets the needs of the customer, the customer is requested to provide the following details.
1. Sensor Model Name.
2. Sensor detection range and resolution (refer to Table 2)
8. Matters needing attention
➢ Sensors should be calibrated regularly, with a recommended calibration cycle of 6 months.
➢ Do not use sensors for a long time in environments with high dust density.
➢ Please use the sensor within its power supply range.
9. Cautions
➢ Sensors can only be used in conjunction with detectors with explosion-proof markings and are strictly prohibited from being used alone.
➢ It is prohibited to disassemble or replace sensors in hazardous areas. Sensor disassembly and replacement must be carried out in a safe environment.
➢ It is prohibited to install and fix sensors in a way that affects their explosion-proof performance, such as drilling holes.
➢ The working voltage of the sensor is 4.5-5.5V DC, and the recommended voltage is 5V. If the power supply voltage exceeds 5.5V, it will cause permanent damage to the sensor. If the voltage is lower than 4.5V, the DC sensor will not function properly.
➢ Sensors and detectors with explosion-proof markings can only be connected through explosion-proof threads, and must be sealed with sealing rings that meet explosion-proof requirements. The connection between explosion-proof threads must take anti loosening measures.
Specifications
| Product Model | Gas Detected | Working Voltage | Average Current | Interface Level | Measurement Range | Output Signal | Warm-up Time | Response Time | Working Temperature | Working Humidity | Dimension | Weight |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| MH-T7042A | Combustible gas (see Table 2) | 4.5~5.5V DC | < 100mA | 3.3V | 0~100%VOL optional (table 2) | UART | 5 years |
Zhengzhou Winsen Electronics Technology Co., Ltdμ
Add: No.299, ~ Road, National Hi-Tech Zone,
Zhengzhou 450001 Chinaμ
Tel: +86-371-67169097 /67169670μ
Fax: +86-371-60932988μ
E-mail: [email protected]μ
Website: www.winsen-sensor.com
FAQ
Q: What gases can the MH-T7042A sensor detect?
A: The MH-T7042A sensor can detect a variety of gases including methane, propane, acetylene, ethanol, and more. Refer to Table 2 for a detailed list of detectable gases and their detection ranges.
Q: What is the working voltage range of the MH-T7042A sensor?
A: The working voltage range of the MH-T7042A sensor is 4.5 to 5.5 volts DC.