Home » Eight Thermocouples DAQ 8-Layer Stackable HAT for Raspberry Pi
Eight Thermocouples DAQ 8-layer stackable HAT for Raspberry Pi with RS485, supports multiple thermocouple types, DIP switches, and 24-bit A/D converters.
Eight Thermocouples DAQ 8-layer stackable HAT with RS485 ports and DIP switch for Raspberry Pi temperature sensor data acquisition.
Eight Thermocouples DAQ 8-Layer Stackable HAT module mounted on Raspberry Pi board with green terminal blocks and red DIP switch
Eight thermocouples data acquisition stackable HAT for Raspberry Pi with multiple terminal connectors and DIP switch configuration
Eight thermocouples data acquisition stackable HAT for Raspberry Pi with multiple input connectors and DIP switch configuration.
Eight Thermocouples DAQ 8-layer stackable HAT circuit board for Raspberry Pi with multiple integrated chips and connectors.
8 THERMOCOUPLES HAT 360 VIEW
Eight Thermocouples DAQ 8-layer stackable HAT for Raspberry Pi with RS485, supports multiple thermocouple types, DIP switches, and 24-bit A/D converters.
Eight Thermocouples DAQ 8-layer stackable HAT with RS485 ports and DIP switch for Raspberry Pi temperature sensor data acquisition.
Eight Thermocouples DAQ 8-Layer Stackable HAT module mounted on Raspberry Pi board with green terminal blocks and red DIP switch
Eight thermocouples data acquisition stackable HAT for Raspberry Pi with multiple terminal connectors and DIP switch configuration
Eight thermocouples data acquisition stackable HAT for Raspberry Pi with multiple input connectors and DIP switch configuration.
Eight Thermocouples DAQ 8-layer stackable HAT circuit board for Raspberry Pi with multiple integrated chips and connectors.
8 THERMOCOUPLES HAT 360 VIEW
SKU: SM-I-019

Eight Thermocouples DAQ 8-Layer Stackable HAT for Raspberry Pi

Read eight thermocouples type J, K, T, N, E, B, R and S; 0.1% accuracy through calibration; RS485, Watchdog.

In stock
$95.00

Overview

Compact, stackable temperature data acquisition HAT for Raspberry Pi. Monitors up to eight thermocouple channels per card — 64 when stacked — using high-resolution 24-bit delta-sigma ADCs with automatic cold-junction compensation. Supports J, K, T, N, E, B, R, and S thermocouple types. Includes RS485/MODBUS RTU interface, hardware watchdog, and onboard 5V supply for the Raspberry Pi.

  • Eight thermocouple inputs with automatic cold-junction compensation
  • Supports J, K, T, N, E, B, R, and S thermocouple types
  • 24-bit delta-sigma ADC — ±1% factory accuracy, ±0.01% after calibration
  • RS485/MODBUS RTU — operates standalone or under Raspberry Pi control
  • Up to 8 cards stackable for 64-channel monitoring
  • Uses only I²C — all remaining GPIO pins stay free

Works with Open Automation Software

Compatible with widely used tools for control, monitoring, and system integration.

Command Line Python Node-RED CODESYS Open PLC Arduino

INTERFACES AND I/O

I/O's Communication Software Integration
• Eight Thermocouple Inputs (J, K, T, N, E, B, R, S) • I²C Port to Raspberry Pi • Command Line
• 24-bit Delta-Sigma ADC Resolution • RS485/MODBUS RTU Port • Python Library
• Automatic Cold-Junction Compensation • Node-RED nodes
• CODESYS Driver
• OpenPLC Module
• Arduino Library
Other Features
• User-programmable threshold LEDs for all eight channels
• Integrated 5V power supply for Raspberry Pi
• Maximum acquisition rate: 40 samples per second
• Factory-calibrated accuracy: ±1% — up to ±0.01% after field calibration • Pluggable connectors for 26–16 AWG field wiring
• PLC-ready via RS485/MODBUS RTU — no Raspberry Pi required • Onboard hardware watchdog and resettable fuse
• General-purpose programmable pushbutton • Eight-level stackable — up to 64 thermocouple channels

DESCRIPTION

The Eight Thermocouples DAQ HAT provides a compact, high-accuracy solution for monitoring thermocouple sensors directly from Raspberry Pi.

Thermocouple Inputs

Eight inputs supporting J, K, T, N, E, B, R, and S thermocouple types for industrial and scientific temperature measurement applications.

24-bit Resolution

High-resolution 24-bit delta-sigma A/D converters with ultra-low-drift (0.005 µV/°C), low-offset (50 µV) amplifiers deliver factory accuracy of ±1%, improving to ±0.01% after field calibration.

Cold-Junction Compensation

Automatic cold-junction compensation removes the need for isothermal blocks or manual compensation calculations, simplifying sensor wiring and installation.

RS485 / MODBUS RTU

Standard RS485 transceiver with IN and OUT ports. Operates as MODBUS RTU slave under Raspberry Pi control or as a standalone device connected directly to a PLC, with no Raspberry Pi required.

Threshold LEDs

Eight user-programmable LEDs illuminate when the corresponding thermocouple channel exceeds a configurable temperature threshold, providing instant visual status at a glance.

Hardware Watchdog

The hardware watchdog automatically power-cycles the Raspberry Pi if the software becomes unresponsive, ensuring continuous operation in unattended deployments.

Programmable Pushbutton

A general-purpose pushbutton routed to GPIO 26 enables safe Raspberry Pi shutdown without requiring a keyboard, monitor, or remote login — essential for headless field deployments.

Stacking

Up to eight cards can be stacked on a single Raspberry Pi, sharing only the I²C bus (two GPIO pins) for monitoring up to 64 thermocouple channels simultaneously.

TECHNICAL DETAILS

CARD LAYOUT

Eight Thermocouples DAQ HAT board layout showing connector positions and DIP switch for Raspberry Pi

MECHANICAL SPECIFICATIONS

Eight Thermocouples DAQ HAT Mechanical Specifications

DIP SWITCH AND STACKING

The onboard six-position DIP switch configures both the stack address and the RS485 port behavior. Cards of different Sequent HAT types can be freely mixed in the same stack.

Switch Name Function
TERM RS485 termination Enable on the last card in an RS485 chain to prevent signal reflections
TX RS485 TX select ON: Raspberry Pi drives RS485 directly
RX RS485 RX select ON: Raspberry Pi receives RS485 directly
ID0 Stack ID bit 0 Binary stack address bit 0 (LSB) — sets card level 0–7
ID1 Stack ID bit 1 Binary stack address bit 1
ID2 Stack ID bit 2 Binary stack address bit 2 (MSB)

ELECTRICAL SPECIFICATIONS

Power
Power supply 5V from Raspberry Pi GPIO bus or pluggable connector
Power consumption 50 mA
Onboard resettable fuse Yes
Thermocouple Inputs
Channels 8
Thermocouple types J, K, T, N, E, B, R, S
ADC resolution 24-bit delta-sigma
Maximum sample rate 40 SPS
Factory accuracy ±1%
Accuracy after calibration ±0.01%
Amplifier drift 0.005 µV/°C
Amplifier offset 50 µV max
Cold-junction compensation Automatic
General
Operating temperature −40°C to 85°C
Wire gauge (connectors) 26–16 AWG

POWER REQUIREMENTS

Power supply: The card is powered from the Raspberry Pi GPIO bus (5V) or from its own pluggable 2-pin connector. Operating current is 50 mA. An integrated 5V supply delivers power to the Raspberry Pi when used as a HAT, eliminating the need for a separate Raspberry Pi power supply.

FIELD CALIBRATION

All thermocouple inputs are factory-calibrated. Firmware commands allow the user to recalibrate the board or perform higher-precision calibration if required.

Calibration is performed using a two-point method with an external high-precision voltage reference. The two calibration points should be placed as far apart as possible within the measurement range to maximize accuracy.

Calibration values are stored in non-volatile flash memory. If an incorrect value is entered during calibration, a RESET command can restore factory calibration values and the procedure can be repeated.

For a full list of calibration commands, run: smtc -h

COMMUNICATION INTERFACES

RS485 / MODBUS RTU

The Eight Thermocouples DAQ HAT includes a standard RS-485 transceiver that can be accessed either by the onboard processor or by the Raspberry Pi. The operating mode is configured using the TX and RX switches on the onboard DIP switch.

When TX and RX are set to ON, the Raspberry Pi communicates directly with any device that has an RS-485 interface. In this mode the card functions as a passive bridge, implementing only the hardware signal levels required by the RS-485 protocol. To use this configuration, the onboard processor must first release control of the RS-485 bus:

~$ smtc [0] wcfgmb 0 0 0 0

When TX and RX are set to OFF, the card operates as a MODBUS RTU slave. Any MODBUS master — PLC, SCADA, or HMI — can read all thermocouple input values using standard MODBUS commands, with no Raspberry Pi required. A full list of supported MODBUS registers is available on GitHub.

In both modes, the onboard processor must be configured to either release or control the RS-485 signals accordingly. Refer to the command-line help for further details.

HARDWARE WATCHDOG

The Eight Thermocouples DAQ HAT includes a hardware watchdog that ensures your system automatically recovers if the Raspberry Pi software becomes unresponsive. The watchdog is disabled at power-up and activates after it receives the first reset command from the Raspberry Pi.

Watchdog Parameters
Initial timeout period Configurable — allows time for Raspberry Pi to boot and start the application
Running timeout period Configurable — normal operating timeout
Off period Configurable — duration the Raspberry Pi power is cut when timeout triggers
Reset counter Stored in non-volatile flash; can be read or cleared at any time

For a full list of watchdog commands, run: smtc -h

COMPATIBILITY

Interface I²C
GPIO used GPIO2 (SDA), GPIO3 (SCL) — 2 pins only; remaining 24 GPIO pins stay free
Max stack 8 cards — up to 64 thermocouple channels
Compatible with All Raspberry Pi versions from Zero to 5 (40-pin GPIO header)

FIRMWARE UPDATE

The onboard microcontroller firmware can be updated in the field. The update tool downloads the latest firmware from Sequent Microsystems' servers and flashes it to the board over I²C.

WARNING: Stop all processes that access the card (Node-RED flows, Python scripts, cron jobs) before starting a firmware update. Accessing the card during an update may corrupt the firmware.

Running the Update

~$ cd ~/smtc-rpi/update/

~/smtc-rpi/update$ ./update <id>

Replace <id> with the board stack address (0–7). Full instructions including recovery procedures are available at:

https://github.com/SequentMicrosystems/smtc-rpi/blob/main/update/README.md

ERRATA

ERRATA — VER2.0: Polarity is reversed on the channels 5–8 silkscreen markings. Connect wires according to the schematic, not the silkscreen.

DOWNLOADS

User's Guide (PDF) Schematics (PDF) CAD Software & Integrations
User's Guide V1.1 Schematic V1.1 3D STEP Model V1.1 Command Line
User's Guide V2 Schematic V2.0 3D Printing Enclosure Python Library
Node-RED nodes
MODBUS interface
CODESYS Library
Arduino Library

WHAT'S INCLUDED

When you purchase the card you will receive the following items:

1. Eight Thermocouples DAQ HAT for Raspberry Pi
Eight Thermocouples DAQ HAT for Raspberry Pi
2. Mounting Hardware
Mounting hardware for Eight Thermocouples DAQ HAT
  • Four M2.5×18mm male-female brass standoffs
  • Four M2.5×5mm brass screws
  • Four M2.5 brass nuts
3. Connector Plugs for all Inputs and Power
Connector plugs for Eight Thermocouples DAQ HAT
  • One 2-pin female mating connector plug for power
  • Two 3-pin female mating connector plugs

QUICK START

  1. Plug your card on top of your Raspberry Pi and power up the system.
  2. Enable I²C communication on Raspberry Pi using raspi-config.
  3. Install the software from GitHub:
    ~$ git clone https://github.com/SequentMicrosystems/smtc-rpi.git
    ~$ cd /home/pi/smtc-rpi
    ~/smtc-rpi$ sudo make install
    ~/smtc-rpi$ smtc

The program will respond with a list of available commands. To read more about the CLI, please refer to the README file. If you would rather use a different platform, you can access the same functionality through dedicated, ready-to-use integrations in the Downloads tab above.

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