Reference

Communication Protocol Description

1. Basic communication parameters

2. Data frame format definition

Using Modbus-RTU communication protocol, the format is as follows:

Initial structure ≥4 bytes of time

Address code = 1 byte

Function code = 1 byte

Data area = N bytes

Error check = 16-bit CRC code

End structure ≥4 bytes of time

Address code: The address of the sensor, which is unique in the communication network (factory default 0x01).

Function code: The function indication of the command sent by the host. This sensor reads the register function code 0x03/0x04 and writes the register function code 0x06/0x10

Data area: The data area is the specific communication data. Note that the high byte of 16-bit data is in front!

CRC code: A two-byte check code.

Register address

3. Communication Protocol Examples and Explanation

3.1 Reading Ammonia Nitrogen, pH, and Temperature

Query Frame:

Response Frame:

Ammonia nitrogen calculation: 0CF5H=3317 =>NHN=33.17mg/L
pH calculation: 0316H=790 =>pH=7.90
Temperature calculation: 0109H=265=>Temperature=26.5℃

3.2 Correcting the deviation value of ammonia nitrogen

Query frame: If the current device outputs an ammonia nitrogen value of 33.17, to increase the value by 7.25 (multiply by 100 to 725=>02D5), write 02D5 to the register content.

Response Frame:

3.3 Ammonia Nitrogen Electrode Calibration

Calibration is performed by writing parameters to registers 0x1200 and 0x1201 using function code 0x10. This device uses two-point calibration and requires two known ammonia nitrogen standard solutions. Before each calibration point, the equipment must be thoroughly cleaned, excess water removed, and the device thoroughly shaken in the standard solution to accelerate the response. After standing for at least 15 minutes until the values ​​stabilize, the calibration operation can proceed. For the first calibration point, write 0x0001 to register 0x1200 and 100 times the standard ammonia nitrogen value of the first point to register 0x1201. For the second calibration point, write 0x0002 to register 0x1200 and 100 times the standard ammonia nitrogen value of the second point to register 0x1201. Calibration complete.

Query frame: Select a 10 mg/L ammonia nitrogen standard solution to calibrate the first point. 10 * 100 = 1000 = 03E8H

Response Frame:

Query frame: Select a 100 mg/L ammonia nitrogen standard solution to calibrate the second point. 100*100=10000=2710H

Response Frame:

3.4 pH Electrode Calibration

pH calibration is performed by writing parameters to registers 0x1100 and 0x1101 using function code 0x10. This device uses a two-point pH calibration, requiring two known pH standard solutions. For the first calibration point, write 0x0003 to register 0x1100 and 100 times the standard pH value of the first point to register 0x1101. For the second calibration point, write 0x0004 to register 0x1100 and 100 times the standard pH value of the second point to register 0x1101. Calibration complete.

Query frame: Select a pH standard solution of 4.01 to calibrate the first point. 4.01 * 100 = 401 = 0191H

Response Frame:

Query frame: Select a pH standard solution of 9.18 to calibrate the second point. 9.18 * 100 = 918 = 0396H

Response Frame:

3.5 Change the current address to 0x02

Query Frame:

Response Frame:

3.6 Modify the current baud rate to 9600

Query Frame:

Response Frame: