Check for package damage before opening and contact support if
needed.
Clean and calibrate the sensor head if dirt or scaling is
present to ensure accurate measurements.

Sensor Wiring

Follow wiring instructions carefully to prevent damage.
Do not supply power until all cables are correctly
connected.

Double-check wiring before supplying power to avoid any
risks.

Preparing Standard Turbidity Solution

Sensor Calibration

The sensor supports two calibration methods: precise and rough
calibration. Rough calibration is recommended for regular use, and
calibration should be done every 3 months. Calibration can be done
via RS485 using the MODBUS-RTU communication protocol.

FAQ

Is the sensor pre-calibrated before leaving the factory?

Generally, the sensor has been precisely calibrated before
leaving the factory, and users may only need to perform rough
calibration.

“`

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Intelligent Turbidity Sensor
IQTB-NTU
Product Manual
(V1.2)

Important statement
Thank you very much for choosing our products. Our company pursues excellent quality and pays more attention to excellent after-sales service.
Please hand over this manual to the end user and read it carefully before using the product. And please keep it in a safe place for reference when needed. The company reserves the right to modify this manual due to product technology and process updates. If there is any change, no further notice will be given, and the final interpretation of this manual is reserved.
Product overview
This intelligent water quality turbidity sensor is designed and manufactured based on the principle of scattered light turbidity measurement. When a beam of light is projected into a water sample, the light is scattered due to the turbidity substances in the water sample. The turbidity in the water sample is calculated by measuring the intensity of the scattered light in the direction perpendicular to the incident light and comparing it with the internal calibration value. After linearization, the final value is output.
Features
90° scattered light principle, built-in temperature sensor. RS-485 interface, Modbus-RTU protocol. Dual high-impedance differential amplifier, strong anti-interference, fast response speed. Protection grade IP68. Small size, more convenient installation, can monitor water quality online continuously.
2

Technical indicators

Measuring range Accuracy Output Power supply Resolution Operating temperature Case material Installation method Signal line length Load Protection level Operating pressure Calibration method

0-400NTU, 0-4000NTU (customizable) ±1%FS 4~20mA and RS485 9-30VDC 0.01NTU, 0.1NTU, 0.1NTU, 0.1NTU 0~50 Stainless steel Flow-through, immersion 5m (customizable) < 750 IP68 0.4MPa Multi-point calibration

Note: The product technical indicators shall be subject to the order, and the actual wiring method shall be subject to the actual product.

Dimensions

Instructions before use
1. Please read this instruction carefully before use. 2. This instruction applies to the smart turbidity series sensor.

3. The sensor is a fragile item and cannot be repaired once damaged. 4. Please check whether the package is damaged before opening it. If the outer package is damaged, please do not continue to open the package and contact us immediately. 5. During the measurement process, if there is dirt, adhesive or scaling on the sensor head, it will cause inaccurate or fluctuating measurement values, and it should be cleaned and calibrated in time.
Sensor wiring
1. Please follow the instructions carefully for wiring. Incorrect wiring will cause complete damage to the product.
2. It is strictly forbidden to supply power before all cables are connected to avoid danger. Before supplying power, please be sure to carefully check all system wiring and confirm that it is completely correct before supplying power.

1 foot 2 foot 3 foot 4 foot 5 foot

Pin definition Power positive RS485A GND RS485B Iout

Wire color Red Green Black White Blue

Method for preparing standard turbidity solution
1. Formazine turbidity standard substance issued by the State Administration of Technical Supervision is used in the calibration of turbidity sensor, with a fixed value uncertainty of ±3% and a valid period of 1 year.
2. Standard solutions of different turbidities are obtained by accurately diluting Formazine turbidity standard substance in proportion with zero turbidity water and qualified volumetric instruments.
3. Formazine turbidity standard substances above 400 NTU need to be stored in the refrigerator (48°C) at low temperature and away from light. Standard solutions diluted to low turbidity values are unstable and should not be stored. They should be prepared as needed.
When it is difficult to obtain standard solutions, they can be prepared according to the method specified in ISO7027, strictly controlling the conditions and reagent dosage. The method is as follows:

Required solution concentration (NTU)
10

Total preparation volume is 50ml

400NTU absorption volume of stock solution (ml)

4000NTU absorption volume of stock solution (ml)

1.25

0.125

Total preparation volume is 100ml

400NTU absorption volume of stock solution (ml)

4000NTU absorption volume of stock solution (ml)

2.5

0.25

100

12.5

1.25

2.5

200

2.5

300

37.5

3.75

7.5

400

100

500

–

6.25

–

12.5

600

–

7.5

–

700

–

8.75

–

17.5

800

–

900

–

11.25

–

22.5

1000

–

12.5

–

Sensor calibration

Sensor calibration supports two methods: precise calibration and rough calibration. Precise calibration requires 4 points, while rough calibration requires only 2 points. Generally, the sensor has been precisely calibrated before leaving the factory, and the user only needs to do rough calibration. It is recommended that the sensor be calibrated once every 3 months. It can be calibrated via RS485 using the MODBUS-RTU communication protocol. For the communication protocol, see the next chapter.
1. Precise calibration operation method: Use the standard solution configuration method described in the previous chapter to evenly configure 4 numerical solutions. Assuming that the sensor range is 0-1000NTU, it is recommended to configure the standard solutions of 0, 200, 500, and 1000NTU respectively (other numerical standard solutions can also be configured according to actual conditions). Write the configured standard solution values to the floating-point registers 0x30, 0x34, 0x38, and 0x3c respectively (refer to the sensor communication protocol section). Place the sensor in a standard solution with a value of 0NTU. After the data stabilizes for 3-5 minutes, enter 1 in the corresponding floating-point register 0x32 to complete the first point calibration. Place the sensor in a standard solution with a value of 200NTU. After the data stabilizes for 3-5 minutes, enter 1 in the corresponding floating-point register 0x36 to complete the second point calibration. Place the sensor in a standard solution with a value of 500NTU. After the data stabilizes for 3-5 minutes, enter 1 in the corresponding floating-point register 0x3a to complete the third point calibration. Place the sensor in a standard solution with a value of 1000NTU. After the data stabilizes for 3-5 minutes, enter 1 in the corresponding floating-point register 0x3e to complete the fourth point calibration. 2. Rough calibration operation method: (1) Zero point calibration: Configure a standard turbidity solution with a value of 0NTU, place the sensor in it, wait for 3-5 minutes for the data to stabilize, and enter 1 in the corresponding floating-point register 0x2c to complete the zero point calibration. (2) Slope calibration: Place the sensor in 500NTU (or other numerical fluid), wait for 3-5 minutes for the data to stabilize, and then enter 500 (the actual configured standard fluid value) in the corresponding floating-point register 0x2e to complete the slope calibration.
Sensor installation
The installation method is as shown below:

1-Flow cell installation

2-Submerged installation

Installation precautions: The turbidity sensor needs to be at least 30mm away from the bottom and

the wall.

Sensor communication

1. Address description:

Tag name
Measurement value Temperature measurement value

Current output value

0X 00 04

Temperature upper limit alarm
Temperature lower limit alarm

0X 00 06 0X 00 08

Data type Floating point
Floating point
Floating point
Floating point
Floating point

Length Read/Write Description

Read

Turbidity measurement value storage location

Read

Temperature value storage location

Current output based on

Read

turbidity measurement

value

Read/Write

Temperature upper limit alarm

Read/Write

Temperature lower limit alarm

Measurement upper limit alarm
Measurement lower limit alarm
Temperature offset

0X 00 0A 0X 00 0C 0X 00 10

Device address 0X 00 20

Baud rate

0X 00 21

Filter coefficient 0X 00 25

Brush operating frequency

0X 00 26

Brush opening mode

0X 00 29

Floating point

Integer 1

Integer 1 Integer 1

Integer 1

Warning

0X 00 2A

Integer 1

Zero point calibration (rough calibration) Slope calibration (rough calibration)
First point calibration value
First point ADC value
Second point calibration value
Second point ADC value
Third point calibration value
Third point ADC value
Fourth point calibration value
Fourth point ADC value

0X 00 2c
0X 00 2e
0X 00 30 0X 00 32 0X 00 34 0X 00 36 0X 00 38 0X 00 3A 0X 00 3C 0X 00 3E

Floating point

Read/Write

Measurement upper limit alarm

Read/Write Read/Write

Measurement lower limit alarm
Corrected temperature value

Read/Write 1-255
24=2400, 48=4800 , Read/Write 96=9600, 192=19200 ,
384=38400
Read/Write 4-15

Read/Write Unit: minutes

Read/Write Read

0 = automatic scraping, 1 = manual scraping, 3 = disabled
01: Turbidity measurement value exceeds the upper limit; 02: Turbidity measurement value exceeds the lower limit; 03: Temperature value exceeds the upper limit; 04: Temperature value exceeds the lower limit.

Write

Enter 1 to complete zero point calibration

Write

Enter the calibration liquid value to complete slope calibration

Read/Write 0

Read/Write

Enter 1 to complete the first point calibration

Read/Write 100

Read/Write

Enter 1 to complete the second point calibration

Read/Write 500

Read/Write

Enter 1 to complete the third point calibration

Read/Write 1000

Read/Write

Enter 1 to complete the fourth point calibration

2. Factory default communication parameters: Factory default communication parameters

Baud rate

9600

Data bits

Stop bits

Parity bits

None

Address

1 (default)

3. Host computer sending format:

Device ID address
Slave ID

Function code
Function

Data address

Addres Addre

s H

ss L

Data quantity

CRC16

Quantit Quanti CRC. CRC.

y _H ty_L L

Length

1byte

Example 1 Read the measured value
Example 2 Read the temperature value

0X 01 0X 01

1byte 0X 03 0X 03

1byte 1byte 2byte 0X 00 0X 01 0X 00

2byte 1byte 1byte

0X 02

0X 95

0X CB

0X 00

0X 03 0X 00

0X 02

0X 34

0X 0B

4. Sending format of the lower computer:

Device ID address
Slave ID

Function code
Function

Data quantity
Quantity

Data content

Data_L

Data_ H

CRC16

CRC. CRC.

Length

1byte

Example 1 Measurement value return
Example 2 Measurement value return

0X 01 0X 01

1byte 0X 03 0X 03

1byte 0X 04 0X 04

2byte 2byte 1byte 1byte

0X 2C 0X 81

0X 40 0X 91

0X 52

0X E7

0X 72 0X 37

0X 41 0X DB

0X 20

0X 8E

Note: (1) Data starting with 0X represents hexadecimal; (2) The check code is 16CRC, with the low byte first and the high byte last; (3) Float (floating point number) occupies four bytes; (4) Convert the data content, Data_L and Data_H to floating point numbers in the order of Data_H and Data_L, i.e. the measured value 40 912C 81, to floating point is 4.53; the temperature return value 41 DB 7237, to floating point is 27.4.

Maintenance, care and storage
1. Daily cleaning. Use a clean, soft cloth or sponge with a small amount of detergent to wipe. Avoid using detergents containing abrasives to avoid scratching the surface of the turbidity sensor lens;
2. Circulation pool cleaning. If it is installed in a circulation pool, the bottom and surrounding areas of the circulation pool should be cleaned regularly to avoid scale residue or blockage, which will affect the accuracy of the readings;
3. The cable connectors must be kept clean and cannot be exposed to moisture or water; 4. Calibration operation. Before calibration, check whether the power supply voltage is stable to ensure that the instrument is normal. Before calibration, a water sample with known turbidity should be measured first so that the calibration point can be correctly selected. The calibration method and operating steps provided in this manual should be followed during calibration to ensure accuracy and reliability. During calibration, standard solution should be used for calibration. After the calibration operation is completed, the measured values should be recorded and the records should be saved for verification.

Troubleshooting
1. Modbus troubleshooting:

Problem
Modbus not responding
Modbus response abnormal

Possible causes

Solution

The baud rate or stop bits do not match the Modbus master device settings

Verify that the settings match the Modbus master settings, verify that the Modbus master parity is set to None

The RS485 cable is faulty

Replace/repair the cable

No network offset and termination, or the network offset and termination are not suitable.
The slave address is incorrect, or the slave address is different from the address of another bus device

Check the termination or offset settings of all network devices. Only the end points of the network should have termination turned on, and there should be only one point on the network providing offset.
Verify that all addresses are unique and between 1 and 247.

Unsupported register

Verify that registers are supported

Incorrect data type

Verify that the requested register data type matches the Modbus master request, for example, you cannot use a 2byte integer to access a float. When requesting a float (2 registers/4 bytes), you must request both registers.

Precautions
1. After opening the product package, please check whether the product appearance is intact, verify whether the relevant content of the product manual is consistent with the product, and properly keep the product manual for more than one year; 2. Strictly connect the wires according to the product wiring diagram, and work under the allowable

excitation voltage of the product. Do not use overvoltage; 3. Do not knock the product to avoid damage to the appearance and internal structure; 4. The measured medium is not allowed to freeze, otherwise it will damage the sensor measuring diaphragm and cause damage to the sensor. If necessary, the sensor needs to be temperature protected to prevent freezing; 5. The product has no customer self-repair parts. Please contact our company in case of failure; 6. If the company’s products fail under normal use, the warranty period is one year (12 months from the date of shipment from our company to the date of return). Whether it is a normal failure is based on the inspection of our quality inspectors. If the repair exceeds the period, the company will charge the cost fee. All products of our company are repaired for life; 7. For any unfinished matters, please refer to our company’s website or call us for inquiries.

Documents / Resources

IOT Store IQTB-NTU Intelligent Turbidity Sensor [pdf] Instruction Manual
IQTB-NTU Intelligent Turbidity Sensor, IQTB-NTU, Intelligent Turbidity Sensor, Turbidity Sensor, Sensor

References

User Manual

IOT Store IQTB-NTU Intelligent Turbidity Sensor Instruction Manual

IQTB-NTU Intelligent Turbidity Sensor

Product Information

Specifications

Product Overview

Dimensions

Instructions Before Use

Sensor Wiring

Preparing Standard Turbidity Solution

Sensor Calibration

FAQ

Is the sensor pre-calibrated before leaving the factory?

Documents / Resources

References

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