Technical Parameters
| Technical parameter | Parameter value |
| Brand | XUNCHIP |
| CO2 range | 0~5000ppm |
| CO2 accuracy | ±100ppm |
| Interface | RS485/4-20mA/DC0-5V |
| Power | DC6~24V 1A |
| Running temperature | -30~80℃ |
| Working humidity | 5%RH~90%RH |
Product Selection
Product DesignRS485,4-20mA,DC0-5VMultiple output methods, the products are divided into the following models depending on the output method.
| Product model | output method |
| XM8171B | RS485总线 |
| XM8171M | 4-20mA |
| XM8171V5 | DC0-5V |
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Communication Protocol
The product uses the RS485 MODBUS-RTU standard protocol format, and all operation or reply commands are in hexadecimal data. When the device leaves the factory, the default device address is 1, and the default baud rate is: for modules and non-recording instruments: 9600, 8, n, 1 (for the recorder series products, the default is: 115200, 8, n, 1).
1. Read data (Function code 0x03)
The inquiry frame (in hexadecimal). Example of sending: To query 1 piece of data of device No. 1, the host computer sends the command: 01 03 00 00 00 01 84 0A .
| Address | Function code | Starting address | Data length | Checksum |
| 01 | 03 | 00 00 | 00 01 | 84 0A |
For a correct inquiry frame, the device will respond with data: 01 03 02 02 18 B9 2E , and the response format is:
| Address | Function code | Length | Data 1 | Checksum |
| 01 | 03 | 02 | 02 18 | B9 2E |
Data description: The data in the command is in hexadecimal. Taking Data 1 as an example, 02 18 converted to decimal value is 536. Assuming the data magnification factor is 100, then the true value is 536/100 = 5.36, and the others can be deduced by analogy.
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-only | 0~59999 |
| 40102 | 00 65 | Total Number of Measuring Points | Read-only | 1~1600 |
| 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 Query |
| 2 Active Upload | 40106 | 00 69 | Protocol Type | Read/Write |
| 1 MODBUS-RTU | Others Unused |
For example, the range is 400~5000ppm, the analog output is 4~20mA current signal, carbon dioxide and current The calculation relationship is as shown in the formula: C = (A2-A1) * (X-B1) / (B2-B1) + A1, where A2 is carbon dioxide range upper limit, A1 is the lower limit of the range, B2 is current output range upper limit, B1 is the lower limit, X is the currently read carbon dioxide value, and C is the calculated current value. The list of commonly used values is as follows:
| current(mA) | carbon dioxideValue (ppm) | Calculation Process |
| 4 | 400.0 | (5000-400)*(4-4)÷(20-4)+400 |
| 5 | 687.5 | (5000-400)*(5-4)÷(20-4)+400 |
| 6 | 975.0 | (5000-400)*(6-4)÷(20-4)+400 |
| 7 | 1262.5 | (5000-400)*(7-4)÷(20-4)+400 |
| 8 | 1550.0 | (5000-400)*(8-4)÷(20-4)+400 |
| 9 | 1837.5 | (5000-400)*(9-4)÷(20-4)+400 |
| 10 | 2125.0 | (5000-400)*(10-4)÷(20-4)+400 |
| 11 | 2412.5 | (5000-400)*(11-4)÷(20-4)+400 |
| 12 | 2700.0 | (5000-400)*(12-4)÷(20-4)+400 |
| 13 | 2987.5 | (5000-400)*(13-4)÷(20-4)+400 |
| 14 | 3275.0 | (5000-400)*(14-4)÷(20-4)+400 |
| 15 | 3562.5 | (5000-400)*(15-4)÷(20-4)+400 |
| 16 | 3850.0 | (5000-400)*(16-4)÷(20-4)+400 |
| 17 | 4137.5 | (5000-400)*(17-4)÷(20-4)+400 |
| 18 | 4425.0 | (5000-400)*(18-4)÷(20-4)+400 |
| 19 | 4712.5 | (5000-400)*(19-4)÷(20-4)+400 |
| 20 | 5000.0 | (5000-400)*(20-4)÷(20-4)+400 |
As shown in the above formula, when measuring 8mA, current current is 1154ppm。
For example, the range is 400~5000ppm, the analog output is 0~5V DC0-5Vvoltage signal, carbon dioxide and DC0-5Vvoltage The calculation relationship is as shown in the formula: C = (A2-A1) * (X-B1) / (B2-B1) + A1, where A2 is carbon dioxide range upper limit, A1 is the lower limit of the range, B2 is DC0-5Vvoltage output range upper limit, B1 is the lower limit, X is the currently read carbon dioxide value, and C is the calculated DC0-5Vvoltage value. The list of commonly used values is as follows:
| DC0-5Vvoltage(V) | carbon dioxideValue (ppm) | Calculation Process |
| 0 | 400.0 | (5000-400)*(0-0)÷(5-0)+400 |
| 1 | 1320.0 | (5000-400)*(1-0)÷(5-0)+400 |
| 2 | 2240.0 | (5000-400)*(2-0)÷(5-0)+400 |
| 3 | 3160.0 | (5000-400)*(3-0)÷(5-0)+400 |
| 4 | 4080.0 | (5000-400)*(4-0)÷(5-0)+400 |
| 5 | 5000.0 | (5000-400)*(5-0)÷(5-0)+400 |
As shown in the above formula, when measuring 2.5V, current DC0-5Vvoltage is 2300ppm。