Intelligent Infrared Carbon Dioxide Module (Model: MH-Z14A) User’s Manual V1.4 Issue Date. Mar. 31st,2021 Zhengzhou Winsen Electronics Technology CO., LTD.

Statement The copyright of this manual 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 enable customers to better use the product 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...

MH-Z14A NDIR CO2 Module 1. Profile MH-Z14A NDIR Infrared gas module is a common type, small size sensor, using non-dispersive infrared (NDIR) principle to detect the existence of CO2 in the air, with good selectivity, non-oxygen dependent and long life. Built-in temperature sensor can do temperature compensation; and it has digital output and PWM output. This common type infrared gas sensor is developed by the tight integration of mature infrared absorbing gas detection technology, Precision optical circuit design and superior circuit design. 3. Main Features Chamber is gold plated, water-proof...

Measuring Range

HD(for zero-point calibration, low level lasting for over 7 sec is effective) UART（RXD） TTL data input UART（TXD）TTL data output 7. Two Output ways ●PWM

Take 400~2000ppm for example CO2 output range Cycle start high level output cycle end low level output CO2 concentration: Cppm=2000×(TH-2ms)/(TH+TL-4ms) Cppm: CO2 concentration could be calculated by PWM output TH high level output time during cycle TL low level output time during cycle ●Serial port output (UART) Hardware connection Connect module’s Vin-GND-RXD-TXD to users’ 5V-GND-TXD-RXD. (Users must use TTL level. If RS232 level, it must be converted.) Software setting Set serial port baud rate be 9600, data bit 8 bytes, stop bit 1byte, parity bit null. Calibrate zero point（ZERO） Calibrate...

0x86- Read CO2 concentration Sending command Byte0 Start Byte Start Byte Return value CO2 concentration = HIGH * 256 + LOW For example: Send command FF 01 86 00 00 00 00 00 79, Return value FF 86 02 20 00 00 00 00 58 How to calculate concentration: convert hexadecimal 02 into decimal 2, hexadecimal 20 into decimal 32, then 2*256+32=544ppm 0x79- On/Off Self-calibration for Zero Point Send command-No return value Byte0 Start Byte For example: ON this function, send command: FF 01 79 A0 00 00 00 00 E6 OFF this function, send command: FF 01 79 00 00 00 00 00 86 NOTE: This function is on when Byte3...

1. Checksum calculation method Checksum = (Negative (Byte1+Byte2+Byte3+Byte4+Byte5+Byte6+Byte7))+1 For example: Byte0 Start Byte char getCheckSum(char *packet) { char i, checksum; for( i = 1; i < 8; i++) { checksum += packet[i]; } checksum = 0xff – checksum; checksum += 1; return

8.Zero Point Calibration About zero point calibration: This module has three methods for zero point calibration: hand-operated method, sending command method and self-calibration. All the zero point is at 400ppm CO2. Hand-operated method: Connect module’s HD pin to low level(0V), lasting for 7 seconds at least. Before calibrating the zero point, please ensure that the sensor is stable for more than 20 minutes at 400ppm ambient environment. Sending command method: Zero and Span point calibration can be achieved by sending a calibration command to the sensor via the serial port (URAT). Zero and...

9.4 The module should be calibrated termly, the suggested period is not longer than 6 months. 9.5 Do not use the sensor in the high dusty environment for long time. 9.6 To ensure the normal work, the power supply must be among 4.5V~5.5V DC rang, the power current must be not less than 150mA. Out of this range, it will result in the failure of the sensor. (The concentration output is low, or the sensor can not work normally.) 9.7 During the zero point calibration procedure by manual, the sensor must work in stable gas environment (400ppm) for over 20 minutes. Connect the HD pin to low level (0V)...