• LF-0020 water temperature sensor

LF-0020 water temperature sensor

Short Description:

LF-0020 water temperature sensor (transmitter) uses high-precision thermistor as the sensing component, which has the characteristics of high measurement accuracy and good stability. The signal transmitter adopts advanced circuit integrated module, which can convert the temperature into the corresponding voltage or current signal according to different needs of users. The instrument is small in size, easy to install and portable, and has reliable performance; it adopts proprietary lines, good linearity, strong load capacity, long transmission distance, and strong anti-interference ability. It can be widely used for temperature measurement in the fields of meteorology, environment, laboratory, industry and agriculture.


Product Detail

Product Tags

Technique Parameter

Measurement range -50~100℃
-20~50℃
Accuracy ±0.5℃
Power supply DC 2.5V 
DC 5V 
DC 12V 
DC 24V 
Other
Out-put Current: 4~20mA 
Voltage: 0~2.5V 
Voltage: 0~5V    
RS232
RS485
TTL Level: (frequency; Pulse width)
Other
Line length Standard: 10 meters
Other  
Load capacity Current output impedance≤300Ω
Voltage output impedance≥1KΩ
Operating environment Temperature: -50℃~80℃
Humidity: ≤100%RH    
Produce weight Probe 145 g, with collector 550 g
Power dissipation 0.5 mW

Calculation Formula

Voltage type (0~5V):
T=V / 5 × 70 -20
(T is the measured temperature value (℃), V is the output voltage (V), this formula corresponds to the measurement range -20 ~ 50 ℃)
T=V / 5 × 150 -50
(T is the measured temperature value (℃), V is the output voltage (V), this formula corresponds to the measurement range -50 ~ 100 ℃)
Current type (4~20mA)
T=(I-4)/ 16 × 70 -20
(T is the measurement temperature value (℃), I is the output current (mA), this type corresponds to the measurement range -20 ~ 50 ℃)
T=(I-4)/ 16 × 150 -50
(T is the measured temperature value (℃), I is the output current (mA), this formula corresponds to the measurement range -50 ~ 100 ℃)
Note: The calculation formulas corresponding to different signal outputs and different measurement ranges need to be recalculated!

Wiring Method          

1. If equipped with a weather station produced by our company, directly connect the sensor to the corresponding interface on the weather station using the sensor cable.
2. If the transmitter is purchased separately, the matching cable sequence of the transmitter is:

Line color

Output signal

Voltage type

Current type

Communication type

Red

Power+

Power+

Power+

Black (green)

Power ground

Power ground

Power ground

Yellow

Voltage signal

Current signal

A+/TX

Blue

 

 

B-/RX

3. Transmitter voltage and current output wiring:

LF-0020 water temperature sensor5

Wiring for voltage output mode 

LF-0020 water temperature sensor6

Wiring for current output mode

Structure Size

LF-0020 water temperature sensor7

(Water temperature sensor)

Sensor Size 

LF-0020 water temperature sensor8

(Water temperature sensor)

MODBUS-RTUProtocol

1. The serial format
Data bits 8 bits
Stop bit 1 or 2
Check Digit None
Baud rate 9600 Communication interval is at least 1000ms
2. Communication format
[1] Write device address
Send: 00 10 Adress CRC (5 bytes)
Returns: 00 10 CRC (4 bytes)
Note: 1. The address bit of the read and write address command must be 00.
2. Adress is 1 byte and the range is 0-255.
Example: Send 00 10 01 BD C0
Returns 00 10 00 7C
[2] Read device address
Send: 00 20 CRC (4 bytes)
Returns: 00 20 Adress CRC (5 bytes)
Explanation: Adress is 1 byte, the range is 0-255
For example: Send 00 20 00 68
Returns 00 20 01 A9 C0
[3] Read real-time data
Send: Adress 03 00 00 00 02 XX XX
Note: as shown below:

Code

Function definition

Note

Adress

Station number (address)

 

03

Function code

 

00  00

Initial address

 

00  01

Read points

 

XX XX

CRC Check code,front low later high

 

Returns: Adress 03 02 XX XX XX XX

Code

Function definition

Note

Adress

Station number (address)

 

03

Function code

 

02

Read unit byte

 

XX  XX

Soil temperature data (high before, low after)

Hex

XX  XX

Soil humidity data (high before, low after)

 

To calculate the CRC code:
1. The preset 16-bit register is FFFF in hexadecimal (that is, all are 1). Call this register the CRC register.
2. XOR the first 8-bit data with the lower bit of the 16-bit CRC register and put the result in the CRC register.
3. Shift the contents of the register to the right by one bit (toward the low bit), fill the highest bit with 0, and check the lowest bit.
4. If the least significant bit is 0: repeat step 3 (shift again), if the least significant bit is 1: the CRC register is XORed with the polynomial A001 (1010 0000 0000 0001).
5. Repeat steps 3 and 4 until 8 times to the right, so that the entire 8-bit data has been processed.
6. Repeat steps 2 to 5 for the next 8-bit data processing.
7. The CRC register finally obtained is the CRC code.
8. When the CRC result is put into the information frame, the high and low bits are exchanged, and the low bit is first.

RS485 Circuit

LF-0020 water temperature sensor9

Instructions for use

Connect the sensor according to the instructions in the wiring method, and then insert the sensor probe into the soil to measure the temperature, and supply power to the collector and the sensor to obtain the water temperature at the measurement point.  

Precautions

1. Please check whether the packaging is intact and check whether the product model is consistent with the selection.
2. Do not connect with power on, and then power on after checking the wiring.
3. Do not arbitrarily change the components or wires that have been soldered when the product leaves the factory.
4. The sensor is a precision device. Please do not disassemble it by yourself or touch the surface of the sensor with sharp objects or corrosive liquids in order to avoid damaging the product.
5. Please keep the verification certificate and certificate of conformity, and return it with the product when repairing.

Troubleshooting

1. When the output is detected, the display indicates that the value is 0 or is out of range. Check whether there is obstruction from foreign objects. The collector may not be able to obtain the information correctly due to wiring problems. Please check whether the wiring is correct and firm.
2. If it is not the above reasons, please contact the manufacturer.

Selection table

Number

Power supply mode

Output signal

Explain

LF-0020

 

 

Water temperature sensor

 

5V-

 

5V powered

12V-

 

12V powered

24V-

 

24V powered

YV-

 

Other powered

 

0

No change

V

0-5V

V1

1-5V

V2

0-2.5V

A1

4-20mA

A2

0-20mA

W1

RS232

W2

RS485

TL

TTL

M

Pulse

X

Other

For example: LF-0020-24V-A1: water temperature sensor (transmitter)

24V power supply, 4-20mA output


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