SENSECAP Soil Moisture Temperature EC Sensor User Manual

SENSECAP Soil Moisture Temperature EC Sensor User Manual

1 Introduction

This S-Temp&VWC&EC-02 soil moisture & EC & temperature sensor is provided with high accurate and high sensitive. It is an important tool to observe and study the occurrence, evolution, improvement and the dynamics water of saline soil. By measuring the dielectric constant of the reaction of soil, soil direct stable real moisture content. This S-Temp&VWC&EC-02 sensor can measure the volume of soil moisture. The soil moisture measurement method is in line with international standards at present. Apply to the soil moisture monitoring, scientific experiment, water-saving irrigation, greenhouse vegetables, flowers, grass, soil, plant cultivation, measured speed of sewage treatment, grain storage, greenhouse control, precision agriculture.

Features:

• Soil moisture content, electrical conductivity and temperature all in one
• One solution can also be used for fertilizer, and other nutrient solution conductivity matrix
• Electrode using special treatment of the alloy material, can withstand a strong external impact, not easy to damage
• Completely sealed, acid and alkali corrosion, can be buried in the soil or directly into the water for long-term dynamic testing
• High precision, fast response, good compatibility, the probe insert design to ensure accurate measurement, reliable performance
• Perfect protection circuit

2 Specifications

Soil Temperature

  Range|   -40 ℃ to +80 ℃
  Accuracy|   ±0.5℃
  Resolution|   0.1 ℃
Soil Moisture
  Range|   From completely dry to fully saturated (from 0% to 100% of saturation)
  Accuracy|   ±2% (0~50%); ±3% (50~100%)
  Resolution|   0.03% (0~50%); 1% (50~100%)

Electrical Conductivity

  Range|   0 ~ 10000 μs/cm
  Accuracy|   ±3%
  Resolution|   10 μs/cm
  Temperature Compensation|   Built in temperature compensation sensor, range 0-50℃
General Parameters
  Product Model|   S-Temp&VWC&EC-02
  Interface|   RS-485
  Protocol|   MODBUS-RTU RS485
  Power Supply|   3.6 ~ 30V DC
  Current Consumption|   6mA@24V DC (quiescent dissipation)
  IP Rating|   IP68
  Cable Length|   5 meters
Operating Temperature| -40 ~ 85℃
  The material of the probe|   Anti-corrosion special electrode
  Sealing material|   The black flame retardant epoxy resin
  Installation|   All embedded or probe inserted into the measured medium
  Device Weight|   210g

3 Wiring

Yellow|   RS485+/A/T+
  White|   RS485-/B/T-
  Red|   VCC+, power supply
  Black|   VCC-, power ground
  Green|    SET, V+ (power) when boot module into the “setting mode”. Not connected or connected with the     GND when boot into “mode of operation”.

Module configuration parameters such as Modbus address, baud rate, parity, communication                protocol is composed of module inside the EEPROM (power down storage device stores). The            specific configuration sometimes forget these parameters that cannot communicate with the module. In order to prevent this problem, the module has a special mode called “mode”. When the      module is based on the “mode” electric start, the module communicates with the following                  parameters:  Fixed Modbus address  Communication configuration is 9600, N, 8,1 (9600bps, no parity bit, 8 data bits, a stop bit) Communication protocol for Modbus-RTU Configuration                  parameters in EEPROM will not because the module into the

“mode” and “will change, when the module is in communication with in the EEPROM                        configuration   parameter is still running mode”.

4 Installation

Because of the direct determination of the soluble salt ions in the soil, the water content of the soil can be higher than about 20%, and the soluble ions in the soil can correctly reflect the electrical conductivity of the soil. In the long-term observation, after irrigation or rainfall measured values are close to the true level. If the velocity measurement, first in the tested soil watering, to be full of water permeability were measured.

1. Rapid measurement method: selected measurement locations, avoid the rocks, to ensure that the needle will not touch the stones like hard object, according to the required depth of cut open the surface soil, maintain the tightness degree of the original soil below the sensor body, clenched vertically inserted into the soil, can not be inserted before and after shaking, ensure the close contact with the soil. A measuring point within a small range test should repeatedly averaging.
2. Buried in the underground measurement method: vertical drilling diameter greater than 20 cm depth of pit, according to the measurement needs, then the sensor wire inserted into the pit wall in a given level of depth, the pit landfill compaction, ensure the close contact with the soil. Stable after a period of time, can be last for days, months or even longer to measure and record.

If the surface measurement is hard, should first hole (diameter should be less than the diameter of the probe), and then inserted into the soil and the soil compaction and measurement; sensor should prevent violent vibration and impact, but not with a hard object percussion. Because the sensor for black package, in the strong sunlight will make the sensor to make sharp warming (up to over 50 ℃℃), in order to prevent the temperature measurement of high temperature impact sensor, please pay attention to sun protection in the field or fields.

5 Modbus Communication Protocol

5.1 Serial communication parameters

Modbus is a serial communication protocol, Modicon programmable logic controller (PLC) for the use of published. It has become the industry standard communication protocols, and is now quite common connection between industrial electronic equipment. Modbus has ex-tensive application in the industrial field. Modbus protocol is a master slave framework agreement. A node is the master node, other nodes using the Modbus protocol in communication from node. Each slave device has a unique address.

S-Temp&VWC&EC-02 sensor with RS485 interface, support Modbus protocol. The communication parameters to factory default values for: baud rate 9600 BPS, one start bit, 8 data bits, no parity, one stop bit. Communication protocol is Modbus RTU protocol. Communication parameters can be changed by the setup program or MODBUS command, after the communication parameters are changed, the sensor is required to re – enter the sensor to be effective.

5.2 Modbus Register

Parameter name| Register address

**(HEX / DEC)**

| Parameter type| Modbus function

number

| Parameter range and description
---|---|---|---|---
  TEMPRATURE|   0x0000 /0|   INT16, read|   3/4|   -4000-8000 corresponds to -40.00 ~

**** 80.00℃.

  VWC|   0x0001 /1|   UINT16, read|   3/4|   0-10000 corresponds to 0-100%
EC| 0x0002 /2| UINT16, read|   3/4|   0-20000 corresponds to 0-20000us/cm
SALINITY| 0x0003 /3|   UINT16, read|   3/4|   0-20000 corresponds to 0-20000mg/L
  TDS|   0x0004 /4|   UINT16, read|   3/4|   0-20000 corresponds to 0-20000mg/L
  EPSILON|    0x0005 /5|   UINT16, read|  3/4

|   0-8200 corresponds to

0.00~82.00

  SOIL TYPE|    0x0020 /32|   UINT16, read-write|   3/6/16|   0-3

0: Mineral soil

1: sandy soil

2: clay

3: organic soil

  TEMP UNIT|   0x0021 /33|   UINT16, read-write|    3/6/16|   0:℃

1:℉

  EC&TEMP COFF|   0x0022 /34|   UINT16, read-write|   3/6/16|   0-100 corresponds to 0.0%-10.0%
  SALINITY COFF|   0x0023 /35|   UINT16, read-write|   3/6/16|   0-100 corresponds to 0.00-1.00
  TDS COFF|   0x0024 /36|   UINT16, read-write|   3/6/16|   0-100 corresponds to 0.00-1.00
  Modbus ADDRESS|   0x0200 /512|   UINT16, read-write|   3/6/16|   0-255
  BAUDRATE|   0x0201 /513|   UINT16, read-write|   3/6/16|     0-6

0:1200bps 1:2400bps 2:4800bps             3:9600bps 4:19200bps

| | | |   5:38400bps
---|---|---|---|---
PROTOCOL| 0x0202 /514| UINT16, read-write| 3/6/16|   0~1

0: Modbus RTU

1: Modbus ASCII

  PARITY|   0x0203 /515|   UINT16, read-write|   3/6/16|   0-2

0: No parity bit

1: even parity check 2: Odd Parity bit

   DATABITS|   0x0204 /516|   UINT16, read-write|   3/6/16|    1

1:8 data bits

  STOPBITS|   0x0205 /517| |

3/6/16

|   0-1

0:1 Stop bit

1:2 Stop bit

  RESPONSE    DELAY|   0x0206 /518|   UINT16, read-write|   3/6/16|   0-255 corresponds to the 0-2550   milliseconds sensor to receive the host   request for a period of time and then     the   delay response. The time delay for setting the value of 10 milliseconds.         Set to 0 when no delay.
 ACTIVE   OUTPUT   INTERVAL|   0x0207 /519|   UINT16, read-write|   3/6/16| 0-255 corresponds to 0-255 seconds        does not require the host to request,        the   sensor to send data at a fixed time     interval. The time interval is set value 1 second. Set to 0 when the active output

function is prohibited.

5.3 Detail of Modbus Register

TEMPERATURE

  Parameter range|   -4000-8000 corresponds to -40.00~80.00℃|   Default: none
  Parameter storage|   none|
  Meaning: the measured value of the temperature, negative for complement representation.

For example: if the return value is 0702H (of 16 hexadecimal, source code), the first byte is 07, the second byte and the low byte is   02h, then the temperature for the measured value (07H256 02h) /100=17.94℃.
If the return value is FF05H (16 – band, the complement), the first byte is FFH, low second byte is 05H, then temperature     measurement value ((FFH256 05H) -FFFFH-1H) / 100 = FF05H-FFFFH-1H Celsius /100=-2.5℃.

VWC — volumetric water content

  Parameter range|   0-10000 corresponds to 0-100%|   Default: none
Parameter storage|   None|
  Significance: volumetric water content measurements.
For example: if the return value is 071DH (16 Decimal), the first byte of the high byte is 07H, second bytes of low byte is 1DH,      then the measured value is (1DH 07H256) /10000= (7256 29) =1821. representative volume water content is 18.21%.
EC — electrical conductivity

  Parameter range|   0-20000 corresponds to 0-20000us/cm|   Default: none
  Parameter storage|   None|
    Significance: electrical conductivity measurement.

For example: if the return value is 071DH (in hexadecimal), the first byte is 07, the second byte and the low byte is 1dh, then          conductivity measurement value (07H256 1dh) / 10000 = (7256 29) on behalf of the =1821. soil conductivity 1821us/cm

SALINITY

  Parameter range|   0-20000 corresponds to 0-20000mg/L|   Default: none
  Parameter storage|   None|
  Significance: Salinity Measurement.

For example: if the value returned is 071DH (16 Decimal), the first byte of the high byte is 07H, the second byte low byte is   1DH, then the salinity measurement value (1DH 07H256) /10000= (7256 29)

=1821. on behalf of the soil salinity is 1821mg/L

TDS— total dissolved solids

  Parameter range|   0-20000 corresponds to 0-20000mg/L|   Default: none
  Parameter storage|   None|
  Significance: TDS measurement value.

For example: if the value returned is 071DH (16 Decimal), the first byte of the high byte is 07H, second bytes of low byte is           1DH, then the TDS measurement value (1DH 07H256) /10000= (7256 29) =1821. on behalf of TDS 1821mg/L.

EPSILON— dielectric constant

  Parameter range|   0-8200   corresponds to 0.00-82.00|   Default: none
  Parameter storage|   None|
  Meaning: dielectric constant.

For e xample: if the value returned is 071DH (16 Decimal), the first byte is 07H, the second byte low byte is 1DH, then the            measured value is (1DH 07H256) /10000= (7256 29) =1821. to represent the dielectric constant of 18.21.

TEMP UNIT— degree unit

  Parameter range|   0：℃

1：℉

|   Default: 0
  Parameter storage|   None|
  Significance: unit of temperature.
EC TEMP COFF

  Parameter range|   0-100   corresponds to 0.0%-10.0%|   Default: 20（2%）
  Parameter storage|   None|
  Significance: the temperature compensation coefficient of electrical conductivity
SALINITY COFF

  Parameter range|   0-100 corresponds to 0.00-1.00|   Default: 55（0.55）
  Parameter storage|   None|
  Significance: Salinity / conductivity compensation coefficient
TDS COFF

  Parameter range|   0-100 corresponds to 0.00-1.00|   Default: 50（0.50）
  Parameter storage|   None|
  Significance: TDS/ conductivity compensation coefficient
SLAVE ADDR — Modbus address

  Parameter range|   0-255|   Default:1
  Parameter storage|   Immediate storage|
  Modbus address can be set to 0-255. When outside of the module address the dip switch setting to address 0, using the             contents   of the register as a slave address. After setting need to re power or use the rst command restart module, the entry into    force of this address. The use of the command to

change the module address does not need to open the cabinet can be arranged.

BAUDRATE

  Parameter range|   0-5

0:1200bps 1:2400bps 2:4800bps 3:9600bps

|   Default:3
|   4:19200bps

5:38400bps

|
---|---|---
  Parameter storage|   Immediate storage|
PROTOCOL — Serial communication Protocol

  Parameter range|   0~1

0:Modbus RTU 1:Modbus ASCII

|   Default:0
   Parameter storage|   Immediate storage|
PARITY — Serial communication Check bit

  Parameter range|   0-2

0:none

1: even parity check 2: Odd parity check

|   Default:0
  Parameter storage|   Immediate storage|
DATA BITS

  Parameter range|   1

1:8 data bits

|   Default:1,Only supports 8    data bits,

the other is invalid

  Parameter storage|   Immediate storage|
STOP BITS

Parameter range|   0-1

0:1 stop bit

1:2 stop bits

|   Default:0
Parameter storage| Immediate storage|
RESPONSE DELAY

  Parameter range|   0-255| Default:0
  Parameter storage|   Immediate storage|
  Serial communication delay response used in the following circumstances: when the host sends a request command, delay          module (RESPONSEDELAY10 milliseconds), then the response data is returned to the host. For example, to set up                RESPONSEDELAY=5, so delay module 510=50 millisecond response requesting host. Set to 0 for no delay an immediate     response. This command is mainly used to host from RS485 transmission switch state to the receiving state relatively slow speed of occasions.
ACTIVE OUTPUT INTERVAL

  Parameter range|   0-255|   Default:0
  Parameter storage|   Immediate storage|
Serial communication active output time interval used in the following circumstances: hosts that do not need to send a request command module active output response data and output interval for ACTIVEOUTPUTINTERVAL second, such as setting ACTIVEOUTPUTINTERVAL=5. So module every 5 seconds according to set up the communication protocol of a debate output data. Set to 0 when the active output is invalid, the main request before response. This command is mainly used in GPRS wireless transmission, terminal active node data transmission occasions.
Note: when the active output data is set, only one module can be connected on the RS485 bus.

5.4 Communication Sample

In the following instructions, the data at the beginning of the 0x or the ending of the H is a 16 – band data. Modbus protocol with two common types of registers:
(1) To maintain the register, storage data is not lost, it is read and write. Usually with function number 3 (0x03) read, use function number 6 (0x06) or 16 (0x10) write.
(2) The input registers are used to store a number of read – only physical variables, such as temperature values, that are read – only and usually read with a function number 4 (0x04).

5.4.1 Function number 3 communication sample

Common request format：AA 03 RRRR NNNN CCCC

Common request format：AA 03 MM VV0 VV1 VV2 VV3… CCCC

For example: to read register 0x0200-0x0201, namely from the machine address and baud rate for example

  Start register

address

|   2byte|   0x0200
  Register number|   2byte|   0x0002
---|---|---
  Check|   2byte|   0xC5B3

Respond：01 03 04 00 01 00 03 EB F2

  Effective byte

number

|   1byte|   0x04
  Slave address

register value

|   2byte|   0x00 (From machine address high byte)
|   0x01 (From machine address low byte)
  The baud rate

register value

|   2byte|   0x00 (High baud rate byte)
|   0x03 (low baud rate byte)
  Check|   2byte|   0xEBF2

5.4.2 Function number 4 communication sample

Common request format：AA 04 RRRR NNNN CCCC

Common request format：AA 04 RRRR NNNN CCCC

  Start register

address

|   2byte|   0x0000
  Register number|   2byte|   0x0003
  Check|   2byte|   0xB00B

Common request format：AA 04 MM VV0 VV1 VV2 VV3… CCCC

  Effective byte

number

|   1byte|   0x06
  Temperature

register value

|   2byte|   0x08
|   0x90
  Volume water

content register value

|   2byte|   0x0E
|   0x93
  Conductivity

register value

|   2byte|   0x02
|   0x4E
  Check|   2byte|   0xD257

For example: to read the register 0x0000-0x0003, that reads the temperature, water content, electrical conductivity value
Ask：01 04 0000 0003 B00B

the front

Common request format：AA 06 RRRR VVVV CCCC

in the front

  CCCC|   2byte|   CRC CHECK

Respond：01 04 06 08 90 0E 93 02 4E D2 57

  Start register

address

|   2byte|   0x0021
  Register number|   2byte|   0x0001
  Check|   2byte|   0x1800

5.4.3 Function number 6 communication sample

Common request format：AA 06 RRRR VVVV CCCC

front

  MM|   1byte|   The number of byte to write the value of the

register

 VVVV1|   2byte|   To write the value of the first register, the high

byte is in the front.

 VVVV2|   2byte|   To write the value of the second register, the high

byte is in the front.

…| …| To write the value of the “N” register, the high byte

is in the front. N=MM/2

CCCC|   2byte| CRC CHECK

For example: to write register 0x0021, namely the temperature unit for Fahrenheit cases Ask：01 06 0021 0001 1800

Start register

address

|   2byte|   0x0021
Register number|   2byte|   0x0001
Check|   2byte|   0x1800

Respond：01 06 0021 0001 1800

  Start register

address

|   2byte|   0x0021
  Register number|   2byte|   0x0001
  Check|   2byte|   0x1800

For example: to write register 0x0021, namely the temperature unit for Fahrenheit cases
Ask：01 06 0021 0001 1800

5.4.4 Function number 16 communication sample

Common request format：AA 10 RRRR NNNN MM VVVV1 VVVV2 …CCCC

front

MM| 1byte|   The number of byte to write the value of the

register

  VVVV1|   2byte|   To write the value of the first register, the high

byte is in the front.

VVVV2|   2byte|   To write the value of the second register, the high

byte is in the front.

…| …|   To write the value of the “N” register, the high byte

is in the front. N=MM/2

  CCCC|   2byte|   CRC CHECK

Common request format：AA 10 RRRR NNNN CCCC

front

  CCCC|   2byte|   CRC CHECK

Common request format：AA 10 RRRR NNNN CCCC

front

CCCC|   2byte| CRC CHECK
  AA|   1byte|   Address, 0-255
---|---|---
  10(HEX)|   1byte|   Function number16 (10 binary system)
  RRRR|   2byte|   Start register address, High byte in front
  NNNN|   2byte|   To read the number N Register, high byte in the

front

  CCCC|   2byte|   CRC CHECK

For example: to write register 0x0200-0x0201 is set from the machine address is 1, the baud rate is 19200bps as an example
Ask：01 10 0200 0002 04 0001 0004 BACC

front

  0x04|   1byte|   The number of byte to write the value of the

register

  0x0001| 2byte|   To write such as from the station address register

value is 1

  0x0004|   2byte|   To write such as from the station address register
| |   value is 4
---|---|---
  0xBACC|   2byte|   CRC CHECK

Respond：01 10 0200 0002 4070

front

  0x4070|   2byte|   CRC CHECK

5.5 CRC16 Check Algorithm

// CRC calculation of C51 language function is as follows
// Enter the parameter 1:snd, to be the name of the byte Check array
// Input parameters 2:num, the total number of Check to be byte
// Function return value: Check and
//—————————————————————————–
unsigned int calc_crc16 (unsigned char *snd, unsigned char num)
{
unsigned char i, j;
unsigned int c,crc=0xFFFF;
for(i = 0; i < num; i ++)
{
c = snd[i] & 0x00FF;
crc ^= c;
for(j = 0;j < 8; j ++)
{
if (crc & 0x0001)
{
crc>>=1;
crc^=0xA001;
}
else
{
crc>>=1;
}
}
}
return(crc);

For example: to read the register 0x0000-0x0002, that reads the temperature, water content, electrical conductivity value
Host Ask:01 0400000003 B00B (8 byte)

When the host needs to send data to the sensor, it will need to send Check data stored in the snd array. (01 04 00 00 00 03 A total of 6 byte), Among them num=6
Pseudo code as follows:
unsigned char request[8]={01,04,00,00,00,03,00,00};// The last two 00,00 are CHECK CRC
unsigned char num=6;// Calculate the array of the first 6 CRC CHECK byte
unsigned int crc16=0;
crc16= calc_crc16 (request, num);
request[6]= crc16%256;// Store check CRC in an array to be sent
request[7]= crc16/256;
Comm Port .Send(request, 8);// Send data through serial port

Sensor Respond:01 04 06 08 90 0E 93 02 4E D2 57 (11 byte)

When the host receives the 11 byte data returned by the sensor, the following CRC calculation is performed, where num=11
Pseudo code as follows：
unsigned char response[11]={ 01 04 06 08 90 0E 93 02 4E D2 57};// The last two byte are the CHECK CRC that the sensor returns
unsigned char num=11;// Calculate the entire return of the 11 CRC CHECK byte
unsigned int crc16=0;
crc16= calc_crc16 (response, num);
if(crc16==0)
{
// Check CRC correctly, you can use the returned data }
else
{
// Check CRC error, can not be used to return the data }
To get results back to 0 so the success of Check, if Check fails to return to a nonzero value.If the Check does not succeed, it shows that the transmission process is wrong, should give up the collected data, re collection.
The success of the Check, use the following formula to calculate the temperature (negative to complement representation) and conductivity of H at the end of the 16 hexadecimal data：
temperature=（08H256+90H）/100=2192/100=21.92 ℃
volumetric water content =（0EH256+93H）/100=3731/100=37.31%
conductivity =02H256+4EH=2256+78 =590 μs/cm

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