MCC 134 Thermocouple DAQ HAT for Raspberry Pi Features Four isolated thermocouple inputs 24-bit A/D converter 1 second update interval, minimum Thermocouple types J, K, R, S, T, N, E, and B supported Cold junction compensation Linearization Screw terminal connections The MCC 134 is a 24-bit, 4-channel HAT add-on board for thermocouple measurements. Stack up to eight MCC HATs The board is shown here connected to a Raspberry Pi (not included). onto a single Raspberry Pi Software MCC DAQ HAT Library Overview available on GitHub The MCC 134 is a thermocouple measurement HAT (Hardware Attached on Top) designed for use with Raspberry Pi, the most popular single-board computer on Supported Operating Systems the market today. Linux A HAT is an add-on board with a 40W GPIO (general purpose input/output) con- Programming API nector that conforms to the Raspberry Pi HAT specification. C, C++, Python The MCC 134 HAT provides four isolated thermocouple inputs. Up to eight MCC DAQ HATs can be stacked onto one Raspberry Pi. Raspberry Pi Interface Thermocouple Input Power The MCC 134 header plugs into the 40-pin Users can connect up to four differential The MCC 134 is powered with 3.3 V and general purpose I/O (GPIO) connector on a thermocouples (TC) to the MCC 134 input 5 V provided by the Raspberry Pi through user-supplied Raspberry Pi. The MCC 134 channels. TC types are software-selectable the GPIO header connector. was tested for use with all Raspberry Pi per channel. TC values can be updated models with the 40-pin GPIO connector. every 1 second, minimum. MCC DAQ HAT Library Thermocouple inputs are electrically iso- The open-source MCC DAQ HAT Library HAT Configuration lated from the Raspberry Pi to minimize of commands in C/C++ and Python HAT configuration parameters are stored noise and provide protection from harsh allows users to develop applications on in an on-board EEPROM that allows the electrical environments. the Raspberry Pi using Linux. Raspberry Pi to automatically set up the The library is available to download from GPIO pins when the HAT is connected. Cold-Junction Compensation GitHub. Comprehensive API and hard- The MCC 134 has three high-resolution ware documentation is available. Stackable HATs cold-junction compensation (CJC) The MCC DAQ HAT Library supports Up to eight MCC DAQ HAT boards can be sensors. operation with multiple MCC DAQ HATs stacked onto a single Raspberry Pi. Users running concurrently. can mix and match MCC HAT models Open-Thermocouple in the stack. Console-based and user interface (UI) Detection example programs are available. The MCC 134 is equipped with open- thermocouple detection (OTD) for all TC input channels so users can monitor the board for broken or disconnected thermocouples. Measurement ComputingMeasurement Computing (508) 946-5100(508) 946-5100 info mccdaq.cominfo mccdaq.com mccdaq.commccdaq.com 11MCC 134 Block Diagram Isolation Barrier Isolated +5 V +3.3 V Power Supply Input Board Filters, SPI Raspberry Pi Digital Address 24-bit ADC ESD, Isolator Header Matching and OTD I2C HAT EEPROM CJC Sensors Best Practices for Accurate Thermocouple Measurements The MCC 134 should achieve results within the maximum thermocouple accuracy specifications when operating within the docu - mented environmental conditions. Operating in conditions with excessive temperature transients or airflow may affect results. In most cases, the MCC 134 will achieve the typical specifications. To achieve the most accurate thermocouple readings, MCC recommends the following practices: Reduce the load on the Raspberry Pi processor. Running a Provide a steady airflow, such as from a fan . A steady airflow program that fully loads all 4 cores on the Raspberry Pi can dissipate heat and reduce errors. processor can raise the temperature of the processor above When configuring multiple MCC DAQ Hats in a stack, posi - 70 C. Running a program that only loads 1 core will oper- tion the MCC 134 farthest from the Raspberry Pi board. Since ate approximately 20 C cooler. the Raspberry Pi is a significant heat source, placing the Minimize environmental temperature variations. Place the MCC 134 farthest from the Pi will increase accuracy. MCC 134 away from heat or cooling sources that cycle For additional information, refer to the Measuring Thermocouples on and off. Sudden environmental changes may lead to with the Raspberry Pi and the MCC 134 Tech Tip. increased errors. Stackable Connect up to eight MCC DAQ HATs onto a single Raspberry Pi. Configure onboard jumpers to identify each board in the stack. Measurement Computing (508) 946-5100 info mccdaq.com mccdaq.com 2 Screw Terminals