Technical Parameters
| Technical parameter | Parameter value |
| Brand | KLHA |
| CO2 range | 0~5000ppm |
| CO2 accuracy | ±100ppm |
| Communication Interface | RS485 |
| Default baud rate | 9600 8 n 1 |
| Power | DC9~24V 1A |
| Running temperature | -30~85℃ |
| Working humidity | 5%RH~90%RH |
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Communication Protocol
The product uses RS485 MODBUS-RTU standard protocol format, all operation or reply commands are hexadecimal data. The default device address is 1 when the device leaves the factory, and the module or NON-Recorder default baud rate is 9600,8,n,1 ,but data recorder default baud rate is 115200 .
1. Read data (function code 0x03)
Inquiry frame (hexadecimal), sending example: query 1 data of 1# device, the upper computer sends the command: 01 03 00 00 00 01 84 0A .
| Address | Function Code | Start Address | Data Length | Check Code |
| 01 | 03 | 00 00 | 00 01 | 84 0A |
For the correct query frame, the device will respond with data: 01 03 02 00 79 79 A6 , response format:
| Address | Function Code | Length | Data 1 | Check Code |
| 01 | 03 | 02 | 00 79 | 79 A6 |
Data description: The data in the command is hexadecimal, take data 1 as an example, 00 79 is converted to decimal value as 121, assuming the data magnification is 100, then the real value is 121/100=1.21, Others and so on.
2. Common data address table
| Configuration Address | Register Address | Register Description | Data Type | Value Range |
| 40001 | 00 00 | carbon dioxide | Read Only | 0~65535 |
| 40101 | 00 64 | Model Code | Read/Write | 0~65535 |
| 40102 | 00 65 | total number of measuring points | read/write | 1~20 |
| 40103 | 00 66 | device address | read/write | 1~249 |
| 40104 | 00 67 | baud rate | read/write | 0~6 |
| 40105 | 00 68 | communication mode | read/write | 1~4 |
| 40106 | 00 69 | protocol type | read/write | 1~10 |