1. Product Introduction

This product is a device for measuring the pH value (hydrogen ion concentration index, acidity/alkalinity) of a solution. It has an automatic temperature compensation function and can switch between automatic and manual temperature compensation at will. This product is suitable for industrial wastewater, domestic wastewater, agriculture, aquaculture industry and other scenarios in non corrosive weak acid and weak alkali environments.

1.1 Functional Features

• The pH measurement range is 0-14pH, with a resolution of 0.01pH.
• Temperature measurement range: 0~80 ℃, resolution: 0.1 ℃ (limited to devices with optional temperature compensation function).
• Equipped with automatic temperature compensation function, manual compensation and automatic compensation can be switched freely.
• S485 communication interface: MODBUS RTU communication protocol can be easily connected to a computer for monitoring and communication.
• The ModBus communication address can be set and the baud rate can be modified.
• The equipment can be powered by a wide voltage supply of DC 10-30V.

1.2 Equipment Technical Parameters

power supply	DC 10~30V
power consumption	0.6W
communication interface	S485； Standard MODBUS-RTU protocol; Communication baud rates: 2400, 4800, 9600 can be set
PH measurement range	0~14.00pH ; Resolution: 0.01pH
PH measurement error	±0.15pH
repeatability error	±0.02pH
Temperature measurement range	0~80℃; Resolution: 0.1 ℃ (When manually compensating for temperature, it is set to 25 ℃ by default.)
Temperature measurement error	±0.5℃
Equipment working conditions	Environmental temperature: 0-60 ℃ Relative humidity:<85%
Suitable temperature for electrodes	0~80℃
Electrode withstand voltage	0.6MPa
Electrode wire length	Default 5m (10m, 15m, 20m can be customized)
Electrode usage cycle	1 year

1.3 Product selection

S-					Company Code Name
	PH-				Industrial PH transmitter
		N01-			S485 (Modbus RTU protocol)
			2-		Wall mounted king shaped shell
				201	Conventional composite electrode without temperature compensation
				201T	Conventional composite electrode with temperature compensation

1.4 Product List

One industrial pH transmitter
◆ 1 PH electrode (with or without temperature compensation optional)
◆ Certificate of conformity, warranty card, etc
◆ 2 expansion plugs and 2 self tapping threads
◆ One pack each of pH buffer 4.01, 6.86, and 9.18 (not included by default, can be purchased separately)

1.5 Equipment size

1.6 Electrode size and installation

1.6.1 Electrode type and size

This product uses conventional composite electrodes and is suitable for measuring solutions such as conventional sewage, tap water, environmentally friendly sewage, and domestic sewage.

1.6.2 Electrode Installation

1. Submerged installation: The lead of the pH electrode is threaded out of the stainless steel tube, and the 3/4 thread at the top of the pH electrode is connected to the stainless steel 3/4 thread with a raw tape. Ensure that the top of the electrode and the electrode wires are not flooded with water.
3. Pipeline installation: Connect to the pipeline through the 3/4 thread of the pH electrode.

2. Equipment usage instructions

2.1 Wiring Instructions

	Instructions	Instructions
electricity source	brown	Positive power supply (10~30V DC)
	black	Negative power supply
through message	green	485-A
	blue	485-B

2.2 Parameter Configuration Instructions

Open the package, select "Debugging Software" ->"485 Parameter Configuration Software", and find
Just open it.
1) Select the correct COM port (check the COM port in "My Computer - Properties - Device Manager - Ports"), and the following figure lists the driver names of several different 485 converters.

2) Connect only one device separately and power it on. Click on the software's test baud rate, and the software will test the current device's baud rate and address. The default baud rate is 4800bit/s and the default address is 0x01.
3) Modify the address and baud rate according to usage needs, and also query the current functional status of the device.
4) If the test is unsuccessful, please recheck the device wiring and 485 driver installation.

2.3 Electrode Calibration Instructions

1) Prepare two different pH standard buffer solutions. If measuring acidic solutions, use standard buffer solutions of 4.01 and 6.86. If measuring alkaline solutions, use standard buffer solutions of 6.86 and 9.18. If measuring general solutions, use standard buffer solutions of 4.01 and 9.18.

1. Open the configuration software.

3) Select the corresponding serial port number, choose the correct device address (default address is 1) and baud rate (default baud rate is 4800), then open the serial port, find the PH tab, and check the automatic option.

4) Place the pH electrode in a standard buffer solution with a relatively low pH value at room temperature (around 25 ℃) (for example, choose 4.01 when using two buffer solutions, 4.01 and 9.18). Enter the pH value of the standard buffer solution at calibration point one, wait for the value to stabilize, and then cancel the automatic mode. Click "Calibrate" at calibration point one to perform the first point calibration.

5) After completing the calibration of the first point, clean the pH electrode and use a tissue or soft cloth to absorb excess water (do not damage the glass bulb of the electrode, otherwise the electrode will fail). Check the automatic option again and place it in a standard buffer solution with a relatively high pH value (for example, choose 9.18 when using two buffer solutions, 4.01 and 9.18). Enter the pH value of the standard buffer solution at calibration point one, and cancel automatic when the value stabilizes. Click "Calibration" at calibration point two to calibrate the second point. Calibration completed.

2.4 ModBus Communication and Register Detailed Explanation

2.4.1 Basic parameters of equipment 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

2.4.2 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.

2.4.3 Register Address

register address	operation	Instructions
0x0000	0x03/0x04	PH value (100 times the actual value)
0x0001	0x03/0x04	Temperature (10 times the actual value)
0x0050	0x03/0x04/0x06	PH deviation value (100 times the actual value)
0x0051	0x03/0x04/0x06	Temperature deviation value (10 times the actual value)
0x0060	0x03/0x04/0x06	Whether to manually compensate (1: Yes 0: No)
0x0061	0x03/0x04/0x06	Manually compensate for temperature (10 times the actual value)
0x0120、0x0121	0x10	Electrode calibration (100 times the actual value)

2.4.4 Communication Protocol Examples and Explanations

Example 1: Read the current pH value and temperature of the device with address 01
Issued frame:

address code	function code	register address	Register content	Low-order check digit	high-order check digit
0x01	0x03	0x00 0x00	0x00 0x02	0xc4	0x0b

Response frame: (For example, reading pH value of 7.90 and temperature of 26.5 ℃)

address code	function code	valid byte count	Register content	Low-order check digit	high-order check digit
0x01	0x03	0x04	0x03 0x16 0x01 0x09	0xb8	0xbe

PH calculation: 316H (hexadecimal)=790=>pH=7.90
Temperature calculation: 109H (hexadecimal)=265=>Temperature=26.5 ℃
Example 2: Numerical correction of the deviation value set for the current pH value of the device with address 01
Issued frame: (If the current device output pH is 7.90, the value needs to be corrected to 8.00, with a difference of 8.00-7.90=0.10, multiplied by 100 times to 10=>0xa (hexadecimal), and the register content should be written as 000a)

address code	function code	register address	Register content	Low-order check digit	high-order check digit
0x01	0x06	0x00 0x50	0x00 0x0a	0x09	0xdc

Response frame: (according to the MODBUS standard, the response is a mirror message of the issued frame)

address code	function code	register address	Register content	Low-order check digit	high-order check digit
0x01	0x06	0x00 0x50	0x00 0x0a	0x09	0xdc

2.4.5 Register Calibration Electrode

If electrode calibration is required, parameters can be written to the 0x0120 and 0x0121 registers through the 0x10 function code for calibration.
This device adopts two-point calibration and requires the preparation of two known pH standard solutions. When calibrating the first point, write 0x0001 to the 0x0120 register and write 100 times the standard pH value of the first point to the 0x0121 register; When calibrating the second point, write 0x0002 to the 0x0120 register and write 100 times the standard pH value of the second point to the 0x0121 register. Calibration completed.
Example: Select a pH standard solution of 4.01 and calibrate the first point.
Issued frame: 4.01 * 100=401 converted to hexadecimal as 0x191

address code	function code	register address	register length	byte length	Register content	Low-order check digit	high-order check digit
0x01	0x10	0x01 0x20	0x00 0x02	0x04	0x00 0x01 0x01 0x91	0x6d	0xdb

Response frame: (according to the MODBUS standard, the response is a mirror message of the issued frame)

address code	function code	register address	register length	Low-order check digit	high-order check digit
0x01	0x10	0x01 0x20	0x00 0x02	0x41	0xfe

Select a pH standard solution of 9.18 and calibrate the second point.
Issued frame: 9.18 * 100=918 converted to hexadecimal 0x396

address code	function code	register address	register length	byte length	Register content	Low-order check digit	high-order check digit
0x01	0x10	0x01 0x20	0x00 0x02	0x04	0x00 0x02 0x03 0x96	0xdd	0x79

Response frame: (according to the MODBUS standard, the response is a mirror message of the issued frame)

address code	function code	register address	register length	Low-order check digit	high-order check digit
0x01	0x10	0x01 0x20	0x00 0x02	0x41	0xfe

3. Precautions and Maintenance

The equipment itself generally does not require daily maintenance. In case of obvious malfunctions, please do not open it for self repair and contact us as soon as possible!
In principle, electrodes should be calibrated before each measurement, and electrodes should be calibrated regularly for long-term use.
There is an appropriate amount of soaking solution in the protective bottle at the front end of the electrode, and the electrode tip is soaked in it to maintain the activation of the glass bulb and liquid interface. When measuring, loosen the bottle cap, remove the electrode, and rinse with pure water before use.
Preparation of electrode soaking solution: Take a packet of pH 4.00 buffer and dissolve it in 250ml of pure water. Add 56g of analytical grade potassium chloride, heat it appropriately in an electric furnace, and stir until completely dissolved. Alternatively, a 3.3M potassium chloride solution can be used for soaking, prepared as follows: Dissolve 25 grams of analytical grade potassium chloride in 100 milliliters of pure water.
The glass bulb at the front end of the electrode should not come into contact with hard objects. Any damage or scratching will cause the electrode to fail.
Before measurement, the bubbles inside the electrode glass bubble should be thrown away, otherwise it will affect the measurement. During measurement, the electrode should be stirred in the measured solution and placed still to accelerate the response.
Clean the electrodes with deionized water before and after measurement to ensure accuracy.
After long-term use, the pH electrode will become passivated, resulting in a decrease in sensitivity gradient, slow response, and inaccurate readings. At this time, the bottom bulb of the electrode can be soaked in 0.1M dilute hydrochloric acid for 24 hours (0.1M dilute hydrochloric acid preparation: 9 milliliters of hydrochloric acid are diluted to 1000 milliliters with distilled water), and then soaked in 3.3M potassium chloride solution for 24 hours. If the passivation of the pH electrode is severe and soaking in 0.1M hydrochloric acid is ineffective, the bulb end of the pH electrode can be soaked in 4% HF (hydrofluoric acid) for 3-5 seconds, washed with pure water, and soaked in 3.3M potassium chloride solution for 24 hours to restore its performance.
Glass bulb contamination or liquid interface blockage can also cause electrode passivation. In this case, appropriate solution cleaning should be carried out according to the properties of the pollutant, as shown in the table below (for reference)
Pollutant: Cleaning agent:
Inorganic metal oxides below 1M dilute acid
Organic oil-based detergent (weakly alkaline)
Resin polymer substances such as alcohol, acetone, and ether
Protein blood sediment acidic enzyme solution
Dilute bleaching solution of pigment substances, hydrogen peroxide