1. Overview

This product adopts advanced fluorescence quenching principle to measure the dissolved oxygen concentration in water without loss, and has the advantages of no pollution, long service life, good stability, and low maintenance difficulty. The unique optical detection method of the measuring probe can effectively eliminate the interference of pH fluctuations, chemical substances such as ammonia nitrogen, or heavy metals in water, thereby providing more stable and accurate measurement results over a longer period of time. This product is suitable for industries that require measurement and control of dissolved oxygen concentration in water bodies, such as aquaculture (such as South American white shrimp, eel, osmanthus fish, etc.), environmental water treatment, etc. 2.3 ModBus Communication and Register Detailed Explanation

1.1. Performance indicators

Dissolved oxygen measurement probe
Measurement range (dissolved oxygen):	0～20 mg∕L； 0~200%
Accuracy:	< ±0.5 mg/L
Measurement repeatability:	< 0.3mg/L
Zero offset:	< 0.2 mg/L
Resolution:	0.01mg/L； 0.1%
Temperature measurement range:	0～60℃
Temperature resolution:	0.01℃
Temperature measurement error:	< 0.5℃
Power supply:	10~30VDC
Working temperature:	0～40℃
Storage temperature:	-20～70℃
anti-interference:	Not affected by the following substances: H2S, pH, K+1, Na+1, Mg+2 , Ca+2 , NH4 +1, Al+3 , Pb+2 , Cd+2, Zn+2 , Cr (tot), Fe+2, Fe+3, Mn+2 , Cu+2 ,Mi+2 , Co+2 , CN-1 , NO3 -1 , SO4 -2 , S-2 , PO4 +3, Cl-1 , Anionic surfactant, crude oil, Cl2-1

1.2. Equipment selection

S-					Company Code
	DO-				Dissolved Oxygen Sensor
		N01-			RS485. MODBUS protocol
			1-		stainless steel casing
				20	0~20.00mg/L (0~200% saturation, 25 ℃)

2. Equipment installation

The sensor should be immersed below the liquid level for fixed installation. During installation and use, avoid collision or scratching of the surface of the fluorescent film head. The fluorescent film head should be avoided from being attached by sediment at the bottom of the water. The rubber protective cover should be removed during use.
Submerged installation:
Comes with a rubber tube and a hose clamp, which can be used with our waterproof tube. The rubber tube is fitted onto the top of the probe and the hose clamp is used to connect the probe to the waterproof tube.

3. Sensor usage and precautions

1. Wiring definition: ① Power supply positive VCC (red line); ② Negative GND of power supply (black line); ③ Communication line A (green); ④ Communication line B (blue).
2. As shown in the figure, insert the protective cover into the sensor in the direction indicated by the arrow until the sensor is securely fastened.


3. It is best to install the sensor at a distance of 5-6 meters from the aerator. If the distance is too close, the measured data may deviate from the actual situation of the water body.
4. Avoid touching the fluorescent film on the sensor head with nails or sharp objects. Before use, remove the rubber sleeve and put on a plastic protective cover. After use, remove the plastic protective cover and put on the rubber sleeve again. Please use the matching brush to clean the fluorescent film.
During storage and transportation, first add a thin sponge pad as a protective cover at the bottom of the sensor.
6. Sensors are precision instruments, please handle them with care.
After prolonged use, sensors may experience varying degrees of blockage. Lift the sensor out of the water surface and gently clean the bottom of the sensor with a clean cloth and water.
If there is a significant deviation in the dissolved oxygen sensor, it can be cleaned and left to stand in the air for 15 minutes. The displayed value can be compared with the air data at different temperatures in the appendix. If there is a significant deviation, the product can be corrected according to the on-site calibration operation method.

4. Basic parameters of device communication

code	8-bit binary
data bit	8 digits
parity bit	none
stop bit	1 person
Error verification	CRC (Redundant Cyclic Code)
Baud rate	2400bit/s, 4800bit/s, 9600 bit/s can be set, and the factory default is 4800bit/s

4.1. Definition of Data Frame Format

Adopting Modbus RTU communication protocol, the format is as follows:
The time for the initial structure to be ≥ 4 bytes
Address code=1 byte
Function code=1 byte
Data area=N bytes
Error check=16 bit CRC code
Time to end structure ≥ 4 bytes
Address code: It is the address of the transmitter and is unique in the communication network (factory default 0x01).
Function code: The instruction function indication issued by the host.
Data area: The data area contains specific communication data, please note that the high byte of 16 bits data comes first! CRC code: a two byte checksum.

4.2. register address

register address	operation	Instructions
0000H、0001H	03	Dissolved oxygen saturation (%; floating point high end)
0002H、0003H	03	Dissolved oxygen concentration (mg/L; floating point high end)
0004H、0005H	03	Temperature (℃; floating point big end)
1020H	03	Salinity (ppt; shaping)
1022H	03	Atmospheric pressure (kPa; shaping)

4.3. Example and Explanation of Communication Protocol

Read the current dissolved oxygen saturation (%), dissolved oxygen concentration (mg/L), and temperature of the device with address 01
Issued frame:

address code	function code	register address	Register content	Low bit of verification code	High bit of verification code
0x01	0x03	0x00 0x00	0x00 0x06	0xc5	0xc8

Response frame:

address code	function code	Effective byte count	Register content	Low bit of verification code	High bit of verification code
0x01	0x03	0x0c	0x3f 0x6a 0xeb 0x52 0x40 0xe2 0x48 0xb0 0x41 0xe5 0x85 0xc5	0xa7	0x49

The floating-point number 3f 6a eb 52 is 0.917653, indicating a dissolved oxygen saturation of 91.8%
Floating point number big end 40 e2 48 b0 is 7.071373 Dissolved oxygen concentration is 7.07mg/L
The floating-point number 41 e5 85 c5 is 28.690317, indicating a temperature of 28.69 ℃

4.4. On site calibration and parameter setting of equipment

The data writing of this product uses transparent transmission function, and the specific format is as follows

address code	Transparent transmission function code	Distribute frame content	Transparent verification code low bit	Transparent transmission verification code high bit
0x01	0xab		0x**	0x**

The corresponding response frame format is as follows

address code	Transparent transmission function code	Response frame content	Transparent verification code low bit	Transparent transmission verification code high bit
0x01	0xac		0x**	0x**

The content of the issued frame includes the CRC check code of the issued frame.
The transparent transmission check code is a CRC check code that includes an address code, a transparent transmission function code, and the content of the transmitted frame.
The specific content of the issued frame is as follows:
(1) On site calibration
Function: Write the atmospheric pressure value, calculate the corresponding dissolved saturated oxygen in the air, and require the product to be placed in a saturated dissolved oxygen environment until the reading stabilizes before sending this command (if the requirement is not high, take out the product from the water and let it sit in the air for half an hour, and send this command after the reading stabilizes).
Taking the atmospheric pressure value of 101.33kPa 0x2795=10133 as an example, the issuance frame and response frame of the command to set the dissolved oxygen correction curve will be explained.
Issued frame:

slaveid	function code	register address	number of registers	byte count	Register content	Low bit of verification code	High bit of verification code
0x01	0x10	0x00 0x11	0x00 0x01	0x02	0x95 0x27	0x8a	0x5b

Response frame:

slaveid	function code	register address	number of registers	Low bit of verification code	High bit of verification code
0x01	0x10	0x00 0x11	0x00 0x01	0x51	0xcc

(2) Revoke on-site calibration
Function: Cancel the user's on-site calibration correction curve and restore the factory calibration curve
Issued frame:

slaveid	function code	register address	number of registers	byte count	Register content	Low bit of verification code	High bit of verification code
0x01	0x10	0x00 0x21	0x00 0x01	0x02	0x02 0x14	0xa1	0x8e

Response frame:

slaveid	function code	register address	number of registers	Low bit of verification code	High bit of verification code
0x01	0x10	0x00 0x21	0x00 0x01	0x51	0xc3

(3) Write salinity
Function: Write salinity in ppt.
Taking the example of writing a salinity of 10ppt 000a=10.
Issued frame:

slaveid	function code	register address	number of registers	byte count	Register content	Low bit of verification code	High bit of verification code
0x01	0x10	0x00 0x62	0x00 0x01	0x02	0x0a 0x00	0xa8	0xb2

Response frame:

slaveid	function code	register address	number of registers	Low bit of verification code	High bit of verification code
0x01	0x10	0x00 0x62	0x00 0x01	0xa0	0x17

5. Maintenance and fault diagnosis

In order to achieve good performance, improve stability and reliability, please pay attention to the following maintenance work:
If the sensor has scale, soak it in 10% dilute hydrochloric acid for 3 minutes, and then rinse it with clean water. If there are organic pollutants, soak in 80% alcohol for 10 minutes and rinse with clean water. Processing does not affect usage.
2. Due to the long-term operation of sensors in water bodies, sudden changes in water quality caused by weather or human factors, as well as the braking flow rate of oxygenation equipment, result in the formation of flocs in the water, leading to sensor membrane blockage. Therefore, sensors need to be cleaned regularly, usually every 10 days as a cleaning cycle.
3. When the dissolved oxygen value remains unchanged or the data fluctuates too much, take the sensor out of the water surface to check the surface condition of the sensor and observe the dissolved oxygen value to see if the product is working properly.