Intelligent Infrared CO2 Gas Sensor (Model: MH-711A) Manual Version: 3.5 Valid from: 5th,May 2016 Zhengzhou Winsen Electronics Technology Co., Ltd.

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...

Zhengzhou Winsen Electronics Technology Co., Ltd. MH-711A is a universal type intelligent sensor to detect CO2 in air taking advantages of non-dispersive infrared (NDIR) principle. With high selectivity, no oxygen dependence, high performance and long lifespan features, MH-711A also has built-in temperature compensation feature. MH-711A is a compact and high-performance sensor based on infrared absorption of gas detection technology, micro-machining and sophisticated circuit design. Long lifespan High Sensitivity and resolution 5V constant power supply, low power consumption Output method: UART,...

Zhengzhou Winsen Electronics Technology Co., Ltd. Measurement Range Temperature compensation Temperature compensation Temperature compensation Temperature compensation Temperature compensation Temperature compensation Temperature compensation Table 2: Measurement Range and Accuracy Figure 1 Structural Drawing of Sensor Email: [email protected]

Zhengzhou Winsen Electronics Technology Co., Ltd. Figure 2: Pin Definition Pin Description Pad1 Vin (input voltage 4.5V～5.5V) Pad4 GND Pad5 Vout (0.4～2V) Pad2 IIC(SCL) clock Pad3 IIC(SDA) data Pad6, Pad7, Pad8 Reserved, do not connect Pad10, Pad11, Pad12 Table 3: Definition of Pin Figure 3 Application Circuit Explanations: 6.1: Analogue Voltage Output Voltage output range 0.4 to 2V, relatively stands for 0 to F.S. Pad1 connect with 5V supply, Pad4 connect with VSS and Pad5 connect with input side of ADC. Then warm-up the sensor, the Vout will show a voltage value which stands for the gas concentration....

Zhengzhou Winsen Electronics Technology Co., Ltd. Figure 4 Analogue Voltage Output 6.2 IIC output Hardware connection The sensor Vin is terminated at 5V, GND is terminated at the power ground, the CLK of the user communication interface is terminated at the CLK of the detector, and SDA is terminated at the SDA of the detector. The detector can directly read the gas concentration value through the sensor's IIC interface (Note: The user's SCL and SDA signal lines must use a pull-up resistor of no more than 10K to ensure the normal operation of the IIC communication interface) without calculation...

Zhengzhou Winsen Electronics Technology Co., Ltd. Figure 5 IIC Sequence Chart 3) Command Every frame number data of IIC communication command contains 10 bytes. Different host orders lead to different data and the last byte of data is the proof test value. Table 5 Command List 0x96 Calibrate zero point（ZERO） Calibrate span point（SPAN） Check Code return value Return High Range Gas concentration= high density *256 + low density Calibrate Zero 1 Email: sales@winsenso

Zhengzhou Winsen Electronics Technology Co., Ltd. EXP. Comma Send SPAN Value The checksum = (invert (byte0 +... + 8)) + 1 For example, Gas Concentration Reading Command Sent Byte0 Command Check Value 1. Add from Byte0 to Byte8: 0x96 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 = 0x96 2. Invert: 0xff – 0x96 = 0x69 3. Add 1:0x69 + 0x01 = 0x6A after inversion 6.2.3 Example Program C Language Calibrate & Calculate and Routine Email: sales@winsenso

Zhengzhou Winsen Electronics Technology Co., Ltd. char getCheckSum(char *packet) { char i, checksum; for( i = 1; i < 9; i++) { checksum += packet[i]; } checksum = 0xff – checksum; checksum += 1; return checksum; } 7.1 The sensor should be calibrated regularly. Recommended cycle time is once per 6 months. 7.2 Do not use the sensor in the high dusty environment for long time. 7.3 Please use the sensor with correct power supply. Warning: 1. Sensors can only be used with detectors that have a flameproof mark and must not be used alone. 2. Do not disassemble or replace the sensor in hazardous locations....