SLM-THM-4

SLM-THM-4

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Channels: 4
Thermocouples Types: J, E, K, R, S, T, B, N, and C
Voltage Ranges: 0-39.0625 mVDC, ±39.0625 mVDC, ±78.125 mVDC, 0-156.25 mVDC, ±156.25 mVDC,
0-1250 mVDC
Resolution: ±0.1 °C or °F
Voltage: 16 bit (Formatted as a 32-bit float)
Data Type: IEEE-754 32-bit floating point OR Integer and Decimal (16-bit each)
Register Type: Analog Input/Input Registers

Specifications:
Download SLM-THM-4 Datasheet

Description

• 4-channel thermocouple input module.

• Supports multiple thermocouple types (J, K, T, E, R, S, B, N).

• Provides accurate temperature measurement for industrial applications.

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Configuration Options

Burnout Detection

The module will monitor the thermocouple for a burnout condition (i.e. open circuit or short circuit) and will perform the following actions to the corresponding channel:

• Low Side Burnout: Set the channel to minimum range.

• High Side Burnout: Set the channel to maximum range.

Temperature Units

• Celsius: °C

• Fahrenheit: °F

Float Behavior

This option will determine the format of the data that is returned by the SLM-MX. Both are returned with MSB first.

• IEEE-754: This is the default behavior and will return the temperature in 32-bit floating point format across two 16-bit registers.

• Integer and Decimal: This will return the temperature in a 16-bit integer and 16-bit decimal format, each in their own register.

Channel Select

Enable or disable the channels to be read. The first channel cannot be disabled.

Thermocouple Type

Select the type of thermocouple to be used.

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Modbus Mapping

Note

The following register mappings assumes that it is the only module connected. Actual mapping may vary depending on the configuration of the system.

Modbus Register Mapping

Channel	Modbus Register	Access	Register Type	Data Length
THM1	30001	Read-Only	Input Register	32-bit
THM2	30003	Read-Only	Input Register	32-bit
THM3	30005	Read-Only	Input Register	32-bit
THM4	30007	Read-Only	Input Register	32-bit

Notes:

• Thermocouple inputs (THM1-THM4) are read-only and correspond to Modbus Input Registers (30001 - 30008).

• Each channel are mapped across two 16-bit registers, in IEEE-754 32-bit floating point format or Integer and Decimal (16-bit each).

• Each channel supports various thermocouple types for versatile temperature measurement.

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Status Register Mapping

Note: The status registers are read-only booleans and are mapped to Discrete Input Status registers (101001 - 101014).

Status	Modbus Register	Access	Register Type	Data Length
Module diagnostics failure	101001	Read-Only	Input Register	1-bit
Module not ready	101002	Read-Only	Input Register	1-bit
Ch1 Burnout	101003	Read-Only	Input Register	1-bit
Ch2 Burnout	101004	Read-Only	Input Register	1-bit
Ch3 Burnout	101005	Read-Only	Input Register	1-bit
Ch4 Burnout	101006	Read-Only	Input Register	1-bit
Ch1 Under Range	101007	Read-Only	Input Register	1-bit
Ch2 Under Range	101008	Read-Only	Input Register	1-bit
Ch3 Under Range	101009	Read-Only	Input Register	1-bit
Ch4 Under Range	101010	Read-Only	Input Register	1-bit
Ch1 Over Range	101011	Read-Only	Input Register	1-bit
Ch2 Over Range	101012	Read-Only	Input Register	1-bit
Ch3 Over Range	101013	Read-Only	Input Register	1-bit
Ch4 Over Range	101014	Read-Only	Input Register	1-bit

Example Usage

Note

The following examples assume that it is the only module connected. Actual mapping may vary depending on the configuration of the system.

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IEEE-754 32-bit Floating Point

Python

import time
from pyModbusTCP.client import ModbusClient
import struct

client_ip = '192.168.1.255'  # Replace with your device's IP
client = ModbusClient(host=client_ip, port=502, auto_open=True)

while True:
    regs = client.read_input_registers(0, 2)
    combined_int = (regs[1] << 16) | regs[0] # 
    float_value = struct.unpack('f', struct.pack('I', combined_int))[0]
    print(float_value)
    time.sleep(1)

Arduino

#include <ArduinoModbus.h> // Include Modbus library

float readThermocoupleTemp() {
  float temp = 0.0;
  if (!ModbusRTUClient.requestFrom(0x21, INPUT_REGISTERS, 0, 2)) { // Request 2 registers starting at address 0 from slave 0x21
    Serial.print("- Failed to read temperature! ");
    Serial.println(ModbusRTUClient.lastError());
  } else {
    uint16_t highWord = ModbusRTUClient.read(); // Read high word
    uint16_t lowWord = ModbusRTUClient.read();  // Read low word
    uint32_t combinedValue = ((uint32_t)highWord << 16) | lowWord; // Combine into 32-bit value

    // Interpret the 32-bit value as a float (assuming IEEE 754)
    memcpy(&temp, &combinedValue, sizeof(float)); // Copy bytes to temp variable
  }
  return temp;
}

Note

The above code uses the ArduinoModbus library and is not a complete program.

Codesys

Under Modbus_TCP_Server -> Modbus Server Channel Under Modbus_TCP_Server -> Modbus Server Channel -> I/O Mapping Usage

VAR
    THMCH1 AT %IW0 : REAL;
    THMCH2 AT %IW2 : REAL;
END_VAR

Productivity Suite

Tag

Tag Name	Type
thmch1	Float, 32 Bit

Usage

Integer and Decimal

Python

import time
from pyModbusTCP.client import ModbusClient
import struct

client_ip = '192.168.1.255'  # Replace with your device's IP
client = ModbusClient(host=client_ip, port=502, auto_open=True)

while True:
    ch1 = client.read_input_registers(0, 2)
    ch1_int = ch1[0]
    ch1_dec = ch1[1]
    print("Channel 1 Integer:", ch1_int, "Decimal:", ch1_dec)
    time.sleep(1)

Arduino

#include <ArduinoModbus.h> // Include Modbus library

int* readThermocoupleTemp() {
  int ch1[2];
  if (!ModbusRTUClient.requestFrom(0x21, INPUT_REGISTERS, 0, 2)) { // Request 2 registers starting at address 0 from slave 0x21
    Serial.print("- Failed to read temperature! ");
    Serial.println(ModbusRTUClient.lastError());
  } else {
    ch1[0] = ModbusRTUClient.read(); // Read integer part
    ch1[1] = ModbusRTUClient.read();  // Read decimal part
  }
  return &ch1;
}

Note

The above code uses the ArduinoModbus library and is not a complete program.

Codesys

Under Modbus_TCP_Server -> Modbus Server Channel Under Modbus_TCP_Server -> Modbus Server Channel -> I/O Mapping Usage

VAR
    THMCH1_INT AT %IW0 : WORD;
    THMCH1_DEC AT %IW1 : WORD;
END_VAR

Productivity Suite

Tag

Tag Name	Type
thmch1_int	Integer, 16 Bit
thmch1_dec	Integer, 16 Bit

Usage

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Specifications

Download SLM-THM-4 Datasheet

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Safety Precautions

• Do not add or remove modules while field power is applied.

• Ensure proper grounding and wire connections to prevent electrical hazards.

• Follow all local and national electrical codes.

• Maintain adequate ventilation to prevent overheating.

For more details and technical support, visit Synergy Logic or contact support@synergy-logic.com.