KWS-700 Online pH Sensor

Introduction

KWS-700 online pH sensor is used in environmental water quality monitoring, acid/alkali/salt solution, chemical reaction process, industrial production process, it can meet the requirments of online pH measurement for most industrial applications.

Feature

Signal output: RS-485 (Modbus/RTU protocol).
Convenient connection to third-party equipment such as PLC, DCS, industrial control computer,general controller, paperless recording instrument or tounch screen.
Double high-impedance differential amplifier with strong anti-interference and fast response.

The patented pH probe, the internal reference solution oozes very slowly from the microporous salt bridge under the pressure of at least 100KPa (1Bar), and its forward bleed continues for more than 20 months. Such a reference system is very stable and the electrode life is extended by a factor of two compared to conventional industrial electrodes.
Easy to install: 3/4 NPT pipe thread for easy submersible installation or installation in pipes and tanks.

Technical Specifications

Dimension

Installation and Electrical Connection

Installation

Note: The sensor should not be installed upside down or horizontally when installed, at least at an angle of 15 degrees or more.

Wiring

a) Red line - power cord (12 ~ 24V)
b) Black line - ground (GND)
c) Blue line - 485A
d) White line - 485B
e) Bare wire - shielded wire
After wiring is completed, it should be carefully checked to avoid incorrect connections before powering up.

Cable specification: Considering that the cable is immersed in water (including sea water) for a long time or exposed to the air,the cable has certain corrosion resistance.The outer diameter of the cable is Φ6 mm and all interfaces are waterproof.

Maintenance

Use and maintenance

When measuring the pH sensor, it should be cleaned in distilled water (or deionized water), and the filter paper should be used to absorb moisture to prevent impurities from being introduced into the liquid to be tested. 1/3 of the sensor should be inserted into the solution to be tested.
The sensor should be washed when not in use, inserted into a protective sleeve with a 3.5 mol/L potassium chloride solution, or the sensor inserted into a container with a 3.5 mol/L potassium chloride solution.
Check if the terminal is dry. If it is stained, wipe it with absolute alcohol and dry it. Avoid long-term immersion in distilled water or protein solution and prevent contact with silicone grease. With a longer sensor, its glass film may become translucent or with deposits, which can be washed with dilute hydrochloric acid and rinsed with water. The sensor is used for a long time. When a measurement error occurs, it must be calibrated with the meter for calibration.
When the calibration and measurement cannot be performed while the sensor is being maintained and maintained in the above manner, the sensor has failed. Please replace the sensor.

Standard Buffer Ph Reference Table

The actual reading and standard of the instrument sometimes have an error of ±1 digit.

Calibration

Note: the sensor has been calibrated at the factory, if not exceeding the measurement error, the calibration should not be random.

a) Zero calibration
Use 250 mL of distilled water in a measuring cylinder,pour into a beaker, add a packet of calibration powder with pH=6.86 , stir evenly with a glass rod until the powder is completely dissolved, configure the solution with pH=6.86 , put the sensor into the solution, wait for 3 ~ 5 minutes, after the value is stable, see if the displayed value is 6.86 . If not, you need to perform zero calibration. Refer to the appendix for calibration instructions .

b) Slope calibration
For acidic solution: Take 250 mL of distilled water in a measuring cylinder , pour into a beaker, add a packet of calibration powder with pH=4.00 , stir evenly with a glass rod until the powder is completely dissolved, and configure the solution topH=4.00 ; In the solution, wait for 3 to 5 minutes. After the value is stable, see if the value is 4.00 . If not, the slope calibration is required. Refer to the appendix for the calibration instructions.

For alkaline solution: Take 250 mL of distilled water in a measuring cylinder , pour into a beaker, add a packet of calibration powder with pH=9.18 , stir evenly with a glass rod until the powder is completely dissolved, and configure the solution to pH=9.18 ; Into the solution, wait for 3 to 5 minutes. After the value is stable, see if the display is 9.18 . If not, the slope calibration is required. Refer to the appendix for the calibration instructions.

Quality assurance

Quality inspection departments have standardized inspection procedures, with advanced detection equipment and instruments, and in strict accordance with the test procedures for products that do 72 hours aging test, stability test, not asubstandard products factory.

The receiving party directly returns the product batch with a failure rate of 2% , and all the costs incurred are borne by the supplier. The reference standard refers to the product description provided by the supplier.

Guarantee the quantity of goods and the speed of shipment.

Service commitment

The company provides local after-sales service within one year from the date of sale, but does not include damage caused by improper use. If repair or adjustment is required, please return it, but the shipping cost must be conceited. Damaged on the way, the company will repair the damage of the instrument for free.

Appendix data communication

1. Data Format

The default data format for Modbus communication is: 9600, n, 8, 1 (baud rate 9600bps, 1 start bit, 8 data bits, no parity, 1 stop bit).
Parameters such as baud rate can be customized.

2. Information Frame Format

a) Read data instruction frame
06 03 xx xx xx xx xx xx
Address Function code Register address Number of registers CRC check code (low byte first)
b) Read data response frame
06 03 xx xx...... xx xx xx
Address Function code Bytes Answer data CRC check code (low byte first)
c) Write data instruction frame
06 06 xx xx xx xx xx xx
Address Function code Register address Write data CRC check code (low byte first)
d) Write data response frame (same data command frame)
06 06 xx xx xx xx xx xx
Address Function code Register address Write data CRC check code (low byte first)

3. Register Address

Note:
a) Modbus register address according to the protocol defined with the register type register start address (16 hex represents the actual starting address register in parentheses).
b) When changing the sensor address, the sensor address in the return command is the changed new address.
c) The data definition that returns the measured value when reading data:
xx xx xx xx xx xx Xx xx

2- byte measurement 2 bytes measurement value scale number 2 bytes temperature value 2 bytes temperature scale

The data type defaults to: double-byte integer, high byte first; others are optional as floating-point types.
4. Command example

a) Read data instruction:
Function: Obtain the pH and temperature of the measuring probe; the unit of pH is pH; the unit of temperature is °C.
Request frame: 06 03 00 00 00 04 45 BE ;
Response frame: 06 03 08 00 62 00 02 01 01 00 01 24 59

Example of reading:

pH: 00 62 indicates the hexadecimal reading pH value, 00 02 indicates that the pH value has 2
decimal places and is converted to a decimal value of 0.98 .
Temperature value: 01 01 indicates the hexadecimal reading temperature value, 00 01 indicates that
the temperature value has 1 decimal place and is converted to a decimal value of 25.7 .

b) Calibration instructions:

Zero calibration
Function: Set the pH zero calibration value of the electrode. The zero value is based on the 6.86 pH standard. The examples are as follows
Request frame: 06 06 10 00 00 00 8C BD
Response frame: 06 06 10 00 00 00 8C BD
Slope calibration
Function: Set the pH slope calibration value of the electrode; the slope calibration is divided into high point and low point calibration, and the alkaline solution is measured at the high point; the acidic solution is measured at the low point, where the standard solution is high here.
point 9.18pH, low 4.00pH standard solution of the calibration reference, examples are as follows:
High point standard solution 9.18 pH calibration:
Request frame: 06 06 10 04 00 00 CD 7C
Response frame: 06 06 10 04 00 00 CD 7C
Low standard solution 4.00 pH calibration:
Request frame: 06 06 10 02 00 00 2D 7D
Response frame: 06 06 10 02 00 00 2D 7D

c) Set the device ID address:

Role: set the MODBUS device address of the electrode;
Change the device address 06 to 01. The example is as follows
Request frame: 06 06 20 02 00 01 E3 BD
Response frame: 06 06 20 02 00 01 E3 BD

5. Error response

If the sensor does not execute the host command correctly, it will return the following format information:

a) CODE : 01 – function code error
03 – data is wrong
b) COM : Received function code

Company Information