# SLM-THM-4 `````{margin} ````{card}
SLM-THM-4
^^^ ```{image} /images/modules/SLM-THM-4.png :alt: SLM-THM-4 :width: 70% :align: center ``` --- +++ **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}`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**. --- ## Configuration Options ```{image} /images/modules/config/SLM-THM-4-config.png :alt: SLM-THM-4 Config Menu :width: 70% ``` ```{admonition} Burnout Detection :class: note, dropdown 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. ``` ```{admonition} Temperature Units :class: note, dropdown - **Celsius**: °C - **Fahrenheit**: °F ``` ```{admonition} Float Behavior :class: note, dropdown 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. ``` ```{admonition} Channel Select :class: note, dropdown Enable or disable the channels to be read. The first channel cannot be disabled. ``` ```{admonition} Thermocouple Type :class: note, dropdown Select the type of thermocouple to be used. ``` --- ## 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. --- ### 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. ``` --- ### IEEE-754 32-bit Floating Point `````{tab-set} ````{tab-item} Python ```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) ``` ```` ````{tab-item} Arduino ```arduino #include // 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](https://docs.arduino.cc/learn/communication/modbus/) and is not a complete program. ``` ```` ````{tab-item} Codesys Under Modbus_TCP_Server -> Modbus Server Channel ![Codesys Modbus Server Channel](/images/modules/example/SLM-THM-4-codesys-config.png) Under Modbus_TCP_Server -> Modbus Server Channel -> I/O Mapping ![Codesys Modbus Server I/O Mapping](/images/modules/example/SLM-THM-4-codesys-io.png) **Usage** ``` VAR THMCH1 AT %IW0 : REAL; THMCH2 AT %IW2 : REAL; END_VAR ``` ```` ````{tab-item} Productivity Suite **Tag** | Tag Name | Type | |:---------:|:----:| | thmch1 | Float, 32 Bit | **Usage** ![Productivity Suite Modbus Config](/images/modules/example/SLM-THM-4-prod-config.png) ```` ````` ### Integer and Decimal `````{tab-set} ````{tab-item} Python ```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) ``` ```` ````{tab-item} Arduino ```arduino #include // 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](https://docs.arduino.cc/learn/communication/modbus/) and is not a complete program. ``` ```` ````{tab-item} Codesys Under Modbus_TCP_Server -> Modbus Server Channel ![Codesys Modbus Server Channel](/images/modules/example/SLM-THM-4-codesys-config.png) Under Modbus_TCP_Server -> Modbus Server Channel -> I/O Mapping ![Codesys Modbus Server I/O Mapping](/images/modules/example/SLM-THM-4-codesys-io.png) **Usage** ``` VAR THMCH1_INT AT %IW0 : WORD; THMCH1_DEC AT %IW1 : WORD; END_VAR ``` ```` ````{tab-item} Productivity Suite **Tag** | Tag Name | Type | |:---------:|:----:| | thmch1_int | Integer, 16 Bit | | thmch1_dec | Integer, 16 Bit | **Usage** ![Productivity Suite Modbus Config](/images/modules/example/SLM-THM-4-prod-config-intdec.png) ```` ````` --- ## Specifications [Download SLM-THM-4 Datasheet](/docs/SLM-THM-4-DS_1stEdition_08272025.pdf) --- ## 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](https://www.synergy-logic.com)** or contact **support@synergy-logic.com**.