JXCT JXBS-3001-NPK-RS User manual

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RS485 Modbus
JXBS-3001-NPK-RS Soil NPK Sensor User Manual
JXBS-3001-NPK-RS
Soil NPK Sensor User Manual
RS485 Modubus
Version: 2.0
Date: 2020-10-24
Status: Released
www.jxct-iot.com

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JXBS-3001-NPK-RS Soil NPK Sensor User Manual
Contents
1 Introduction …………………………………………………...….. 3
1.1 Product Overview.……………………………………………...3
1.2 Parameters …………………………………………………...3
1.3 Structure & Size……………………………………..................3
1.4 System Frame Diagram …………………………………….…4
2 Installation & Wiring ………….…………………………..…...... 5
2.1 Product & Accessories ……………………………………….5
2.2 Interface Description ………………………………………..... 6
2.3 Surface measurement method ...……………………………..6
2.4 Buried measurement method …………………………………7
2.5 Remarks ………………………………………………………...7
3 Software…….………….………………………………………….. 8
3.1 Sensor access to the computer………………………….……8
3.2 Use of sensor monitoring software……………………………8
3.3 Modify the baud rate and device ID…………………………. 9
4 Communication Protocol …………………………..................10
4.1 Communication Basic Parameters…………………………..10
4.2 Data Frame Format Definition………………………………. 10
4.3 Register Address …………………...………………………...11
4.4 Communication Protocol Examples…………………………11
RS485 Modbus
JXBS-3001-NPK-RS Soil NPK Sensor User Manual

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JXBS-3001-NPK-RS Soil NPK Sensor User Manual
1 INTRODUCTION
1.1 Product Overview
The NPK sensor is designed for detecting the content of nitrogen, phosphorus and
potassium in soil, determining the fertility of the soil and facilitating the evaluation of
the soil condition by the customer system.
The product can be widely used in rice fields, greenhouse cultivation, rice, vegetable
cultivation, orchard nursery, flowers and soil research.
1.2 Parameters
Parameters
Technical Specs
Measure Range
0-1999mg/kg
Accuracy
±2%F.s
Resolution
1mg/kg(mg/l)
Response Time (T90, Seconds)
<10s
Working Temperature
5-45℃
Working Humidity
5-95%RH (Relative humidity), no condensation
Baud Rate
2400/4800/9600
Communication Port
RS485
Power Supply
12V-24V DC
1.3 Structure & Size
The sensors probes are made of 316 stainless steel for anti-rust and electrolysis
resistance, salt and alkali corrosion resistance purpose, to ensure the long-term
operation of the probe part. Sensor body is made IP68, filled with high-density epoxy
resin for high-temperature vacuum filling, effectively preventing moisture from. Rs485
Cable length is 0.6m by default. Can be customized.

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1.4 System Frame Diagram
The device can be connected directly to the PLC with 485 interface, and it can be
connected to the MCU through the 485 interface chip. The microcontroller and PLC
can be programmed to match the sensor by the modbus protocol specified later. User
can also connect the sensor to the computer by using USB to 485 converter, and use
the sensor configuration tool provided by JXCT for configuration and testing.
This product can also be used in combination with multiple sensors on one 485 bus.
Please observe the “485 Bus Field Wiring Code” when performing 485 bus
combination (see Appendix). In theory, one bus can connect more than 16 485
Picture 1: Single Sensor Working Diagram
316 Stainless Steel
7cm
High-density Epoxy Resin
IP68

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sensors. If you need to connect more 485 sensors, you can use 485 repeater to
expand more 485 devices, and the other end to connect PLC with 485 interface and
pass 485 interface chip. Connect to the micro-controller, or use USB to 485 to connect
to the computer, use the sensor configuration tool provided by our company for
configuration and testing.
2 Hardware Connections
2.1 Product & Accessories
Check the list of devices before installation:
Product Name
Qty
Soil NPK Sensor
1 Pc
12V Power Adapter (Optional)
1 Pc
485 to USB Converter (Optional)
1 Pc
Picture 2: Multiple Sensors Working Diagram

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2.2 Interface Description
The power interface can be 12-24V for wide voltage power supply. When wiring the
485 signal line, note that the A/B lines cannot be connected in reverse, and the
addresses between multiple devices on the bus cannot conflict.
Function
Cable Color
Specs
Power
Brown
Power supply +
Black
Power supply -
Communication
Yellow (grey)
485-A
Blue
485-B
Note: Please be careful not to connect the wrong line sequence. The wrong wiring will
cause the device to burn out.
The factory default supply of 1.5 meters long wire, customers can extend the wire as
needed or in sequence.
Note that there is no yellow line in the line sequence that may be provided in some
factory batches, in which case the gray line is equivalently replaced by the yellow line.
2.3 Surface Measurement Method
Select the appropriate measurement location, avoid the stone, ensure that the steel
needle will not touch the hard object, throw off the topsoil according to the required
measurement depth, keep the original soil tightness under the ground, hold the
sensor vertically into the soil, insert It is not allowed to sway from side to side. It is
recommended to measure the average for multiple measurements within a small
range of one measurement point.
Power +
Power –
RS485B
RS485A

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2.4 Buried Measurement Method
Vertically dig pits with a diameter of >20cm, insert the sensor steel needle horizontally
into the pit wall at a given depth, fill the pits tightly, and stabilize for a period of time,
then measure and record for several days, months or even longer.
2.5 Remarks
1. The steel needle must be inserted into the soil during the measurement.
2. Avoid strong sunlight directly on the sensor for high temperature. Use in the field to

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prevent lightning strikes.
3. Do not violently bend the steel needle, do not pull the sensor lead wire, do not beat
or violently hit the sensor.
4. The sensor protection class IP68 can soak the sensor in the water.
5. Due to the presence of radio frequency electromagnetic radiation in the air, it is not
suitable to be energized in the air for a long time.
3 Configuration Tool Installation
JXCT provides the matching "SENSOR MONITORING SOFTWARE", which can
conveniently use the computer to read the parameters of the sensor, and flexibly
modify the device ID and address of the sensor.
3.1 Sensor access to the computer
After the sensor is properly connected to the computer via USB to 485 and powered,
find COM port in the computer ("My Computer - Properties - Device Manager - Port" to
view the COM port). Shown as in below screenshot:
As shown in above, serial port number is COM10 at this time. Please remember this
serial port. It shall be filled in the serial port number in the sensor monitoring software.
If the COM port is not found in the device manager, it means that you have not
plugged in the USB to 485 or did not install the driver correctly, please contact the
technical staff for assistance.
3.2 Use of sensor monitoring software
The configuration interface is as shown in the figure. First, obtain the serial port
number according to the method in section 3.1 and select the correct serial port, then
click to automatically obtain the current baud rate and address to automatically detect

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all devices and baud rates on the current 485 bus. . Please note that there is only one
sensor on the 485 bus that needs to be automatically acquired using the software.
Then click on the connected device to get sensor data information in real time.
If your device is a gas concentration sensor, please select “Gas Concentration Sensor” at
the sensor type, “Formaldehyde Transmitter” for the formaldehyde sensor, “Analog
Transmitter Module” for the analog transmitter, and “Atmospheric Pressure” for the
atmospheric pressure sensor. “Sensor”, the illuminance sensor selects “Optical Light
20W”, the oxygen sensor selects “Oxygen Transmitter”, and the other sensors select the
default “No Other Sensor”.
3.3 Modify the baud rate and device ID
In the case of disconnecting the device, click the device baud rate and setting address
in the communication settings to complete the relevant settings. Please note that after
the setting, please restart the device, and then "automatically obtain the current baud
rate and address", you can find the address. And the baud rate has been changed to
the address and baud rate you need.
If you need to modify the baud rate and address using the modbus command, you can
refer to the appendix "How to Modify the Baud Rate and Address Using the modbus
Command".

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4 Communication Protocol
4.1 Communication Basic Parameters
Parameters
Specs
Coding
8-bit binary
Data bit
8-bit
Parity bit
no
Stop bit
1-bit
Error check
CRC(redundant cyclic code)
Baud Rate
2400bps/4800bps/9600bps.Can customize.
Default 9600bps
4.2 Data Frame Format Definition
Adopt Modbus-RTU communication protocol, the format is as follows:
Initial structure ≥ 4 bytes of time
Address code = 1 byte
Function code = 1 byte
Data area = N bytes
Error check = 16-bit CRC code
End structure ≥ 4 bytes of time
Address code: is the address of the transmitter, which is unique in the communication
network (factory default 0x01).
Function code: The instruction function of the command sent by the host. This
transmitter only uses function code 0x03 (read register data).
Data area: The data area is the specific communication data. Note that the 16-bit data
high byte is in front!
CRC code: Two-byte check code.
Inquiry Frame
Address Code
Function Code
Register Start Address
Register Length
CRC_L
CRC_H
1bit
1bit
2bit
2bit
1bit
1bit

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JXBS-3001-NPK-RS Soil NPK Sensor User Manual
Answer Frames
Address
code
Function
Code
Effective number
of bytes
Data area
Second
data area
Nth
data area
Check
code
1bit
1bit
2bit
2bit
1bit
2bit
2bit
4.3 Register Address
Register
Address
PLC or configuration
address
Content
Operating
001E H
4001F（40021）
Nitrogen content (unit mg/kg)
Read-Only
001F H
40020（40022）
Phosphorus content(unit mg/kg)
Read-Only
0020 H
40021（40023）
Potassium content (unit mg/kg)
Read-Only
0100 H
40101
Device address(0-252)
Read/Write
0101 H
40102
Baud rate(2400/4800/9600)
Read/Write
4.4 Communication Protocol Examples
4.4.1 Read the Soil NPK Value from Device Address 0x01
Inquiry Frame
Address Code
Function
Code
Register
Start Address
Register Length
CRC_L
CRC_H
0x01
0x03
0x00 0x1E
0x00 0x03
0x34
0x0D
Answer Frame
Address
Code
Function
Code
Effective
number
of bytes
Nitrogen
content
Phosphorus
content
Potassium
content
CR
C_L
CRC_H
0x01
0x03
0x06
0x00
0x20
0x00
0x25
0x00
0x30
0x5
A
0x3D

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NPK content:
0020 H（hexadecimal ）=32=>Nitrogen=32mg/kg
0025 H（hexadecimal ）=37=>Phosphorus=37mg/kg
0030 H（hexadecimal ）=48=>Potassium=48mg/kg
4.4.2 Reading the value of soil nitrogen at device address 0x01
Inquiry Frame
Address
Code
Function
Code
Register
Start Address
Register
Length
CRC_L
CRC_H
0x01
0x03
0x00 0x1e
0x00 0x01
0xB5
0xCC
Answer Frame
Address
Code
Function
Code
Effective No. of
bytes
Nitrogen
content
CRC_L
CRC_H
0x01
0x03
0x02
0x00
0x20
0x5A
0x3D
Nitrogen content：0020 H（hexadecimal）=32=>Nitrogen=32mg/kg
4.4.3 Reading the Value of Soil Phosphorus in Device Address 0x01
Inquiry Frame
Address Code
Function
Code
Register start
address
Register length
CRC_L
CRC_H
0x01
0x03
0x00 0x1f
0x00 0x01
0xE4
0x0C
Answer Frame
Address Code
Function
Code
Effective No.
of bytes
Phosphorus
content
CRC_L
CRC_H
0x01
0x03
0x02
0x00 0x25
0x5A
0x3D

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Phosphorus content：0025 H（16hexadecimal）=37=>Phosphorus=37mg/kg
4.4.4 Reading the Value of Soil Potassium in Device Address 0x01
Inquiry Frame
Address
Code
Function
Code
Register start
address
Register length
CRC_L
CRC_H
0x01
0x03
0x00 0x20
0x00 0x01
0x85
0xC0
Answer Frames
Address
Code
Function
Code
Effective No. of
bytes
Potassium
content
CRC_L
CRC_H
0x01
0x03
0x02
0x00 0x30
0x5A
0x3D
Potassium ：0030 H（16hexadecimal）=48=>Potassium=48mg/kg