DR-DO1, DR-DO2 -- Dissolved Oxygen Sensor

1. Introduction

1.1 Specification

DO1 and DO2 have the same functions

• Applicable environment

  • DO1 is for use in ordinary waters.
  • DO2 is suitable for seawater.

• Measuring range: 0-20mg/L, 0--50°C

• Accuracy: 3%, ±0.5°C

• Resolution: 0.01 mg/L, 0.01°C

• Maximum operating pressure: 6 bar

• Output signal: A: 4-20mA (current loop); B: RS485 (standard Modbus-RTU protocol, device default address: 01)

• Power supply voltage: 5-24V DC

• Working environment:

  • Ambient Temperature: 0--60°C
  • Relative Humidity: <85% RH(Specifically refers to the cable male and female)

• Power consumption: ≤0.5W

• Wire length: 5 meters

1.2 wiring

1.3 Impedance requirements for current signals

Supply Voltage	9V	12V	20V	24V
Max Impedance	<250Ω	<400Ω	<500Ω	<900Ω

1.4 Mechinical Drawing

DO1:

DO2(Seawater version):

1.5 Instructions for use and maintenance

• It can be directly put into water without adding a protective tube, ensuring the long-term stability, reliability and accuracy of the sensor.

• If the water conditions are complex and you want accurate data, you need to wipe the sensor probe frequently.

1.6 RS485 Commands

RS485 signaldefault address 0x14 Standard Modbus-RTU protocol, baud rate: 9600; check bit: none; data bit: 8; stop bit: 1

1.6.1 Query address

send:

Original address	Function code	Register address high	Register address low	Register length high	Register length low	CRC16 low	CRC16 high
0XFF	0X03	0X00	0X0A	0X00	0X02	0XF1	0XD7

If you forget the original address of the sensor, you can use the broadcast address 0XFF instead. When using 0XFE, the host can only connect to one slave, which can be used as a method of address query.

response:

Register 0 data high and register 0 data low indicate the actual address of the sensor: 1 Register 1 data high and register 1 data low indicate the sensor version

Address	Function code	Data length	Register 0 Data high	Register 0 Data low	Register 1 Data high	Register 1 Data low	CRC16 low	CRC16 high
0XFF	0X03	0X04	0X00	0X01	0X00	0X00	0XB4	0X3C

1.6.2 Change address

For example: Change the address of the sensor with address 1 to 2(address range: 1-119), master → slave

Original address	Function code	Starting register address high	Starting register address low	Register length high	Register length low	Data length	Start address high	Start address low	Sensor version	Sensor version	CRC16 high	CRC16 low
0X01	0X10	0X00	0X0A	0X00	0X02	0X04	0X00	0X02	0X00	0X00	0XD2	0X10

response:

Address	Function code	Starting register address high	Starting register address low	Register length high	Register length low	CRC16 low	CRC16 high
0X01	0X10	0X00	0X0A	0X00	0X02	0X61	0XCA

1.6.3 Query data

Query the data (dissolved oxygen) of the sensor (address 14), host → slave

Address	Function code	Starting register address high	Starting register address low	Register length high	Register length low	CRC16 low	CRC16 high
0X14	0X03	0X00	0X14	0X00	0X01	0XC6	0XCB

If the sensor receives correctly, the following data will be returned, slave → host

Address	Function code	Data length	Register 0 Data high	Register 0 Data low	CRC16 low	CRC16 high
0X14	0X03	0X02	0X03	0X78	0XB5	0X55

After the query, 7 bytes will be returned. For example, the returned data is 14 03 02 03 78 B5 55. 03 78 is the value of dissolved oxygen.

Converted to decimal, it is 888. Add two decimal places to get the actual value. 03 78 means the current dissolved oxygen is 8.88mg/L

Query the data (temperature) of the sensor (address 14), host → slave

Address	Function code	Starting register address high	Starting register address low	Register length high	Register length low	CRC16 low	CRC16 high
0X14	0X03	0X00	0X11	0X00	0X01	0XD6	0XCA

If the sensor receives correctly, the following data will be returned, slave → host

Address	Function code	Data length	Register 0 Data high	Register 0 Data low	CRC16 low	CRC16 high
0X14	0X03	0X02	0X09	0XA4	0XB2	0X6C

After the query, 7 bytes will be returned. For example, the returned data is 14 03 02 09 A4 B2 6C. 03 78 is the value of dissolved oxygen temperature.

Converted to decimal, it is 2468. Add two decimal places to get the actual value. 09 A4 means the current dissolved oxygen temperature is 24.68°C

The following is the command for CO2

Query the data of the sensor (address 21), host → slave

Command Frame:

Address Code	Function Code	Register Address	Register Content	Checksum (Low Byte)	Checksum (High Byte)
0x21	0x03	0x00 0x00	0x00 0x06	0xc2	0xA8

Response Frame:

Address Code	Function Code	Byte Count	Register Content	Checksum (Low Byte)	Checksum (High Byte)
0x21	0x03	0x0c	0x3f 0x6a 0xeb 0x52 0x40 0xe2 0x48 0xb0 0x41 0xe5 0x85 0xc5	0xc5	0x87

Big-endian float 3f 6a eb 52 is 0.917653, representing a dissolved oxygen saturation of 91.8%. Big-endian float 40 e2 48 b0 is 7.071373, representing a dissolved oxygen concentration of 7.07 mg/L. Big-endian float 41 e5 85 c5 is 28.690317, representing a temperature of 28.7°C.

Example 2: Write atmospheric pressure

Command Frame: Write atmospheric pressure of 101.35 kPa to the device with address 1.

Write 10135 (hexadecimal 2797) to register 0x1022.

Address Code	Function Code	Register Address	Register Content	Checksum (Low Byte)	Checksum (High Byte)
0x21	0x06	0x10 0x22	0x27 0x97	0x70	0x3e

Response Frame: (According to the ModBus standard, the response is a mirror of the command frame)

Address Code	Function Code	Register Address	Register Content	Checksum (Low Byte)	Checksum (High Byte)
0x21	0x06	0x10 0x22	0x27 0x97	0x70	0x3e

Example 3: Zero-point calibration

After the sensor reading stabilizes in oxygen-free water, write 0x0001 to register 1010H.

Address Code	Function Code	Register Address	Register Content	Checksum (Low Byte)	Checksum (High Byte)
0x21	0x06	0x10 0x10	0x00 0x01	0x4a	0x6f

Response Frame: (According to the ModBus standard, the response is a mirror of the command frame)

Address Code	Function Code	Register Address	Register Content	Checksum (Low Byte)	Checksum (High Byte)
0x21	0x06	0x10 0x10	0x00 0x01	0x4a	0x6f

2. Water Quality Sensor Datasheet

• Water Quality Sensor Transmitter Datasheet