MCC 134
Thermocouple DAQ HAT for Raspberry Pi
The MCC 134 is a 24-bit, 4-channel HAT add-on board for thermocouple measurements.
The board is shown here connected to a Raspberry Pi (not included).
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Overview
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
the market today.
A HAT is an add-on board with a 40W GPIO (general purpose input/output) connector that conforms to the Raspberry Pi HAT specification.
The MCC 134 HAT provides four isolated thermocouple inputs. Up to eight MCC
DAQ HATs can be stacked onto one 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
• Stack up to eight MCC HATs
onto a single Raspberry Pi
Software
• MCC DAQ HAT Library;
available on GitHub
Supported Operating Systems
• Linux
Programming API
• C, C++, Python
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Raspberry Pi Interface
The MCC 134 header plugs into the 40-pin
general purpose I/O (GPIO) connector on a
user-supplied Raspberry Pi. The MCC 134
was tested for use with all Raspberry Pi
models with the 40-pin GPIO connector.
HAT Configuration
HAT configuration parameters are stored
in an on-board EEPROM that allows the
Raspberry Pi to automatically set up the
GPIO pins when the HAT is connected.
Stackable HATs
Up to eight MCC DAQ HAT boards can be
stacked onto a single Raspberry Pi. Users
can mix and match MCC HAT models
in the stack.
Thermocouple Input
Users can connect up to four differential
thermocouples (TC) to the MCC 134 input
channels. TC types are software-selectable
per channel. TC values can be updated
every 1 second, minimum.
Thermocouple inputs are electrically isolated from the Raspberry Pi to minimize
noise and provide protection from harsh
electrical environments.
Cold-Junction Compensation
The MCC 134 has three high-resolution
cold-junction compensation (CJC)
sensors.
Open-Thermocouple Detection
The MCC 134 is equipped with openthermocouple detection (OTD) for all
TC input channels so users can monitor
the board for broken or disconnected
thermocouples.
Power
The MCC 134 is powered with 3.3 V and
5 V provided by the Raspberry Pi through
the GPIO header connector.
MCC DAQ HAT Library
The open-source MCC DAQ HAT Library
of commands in C/C++ and Python
allows users to develop applications on
the Raspberry Pi using Linux.
The library is available to download from
GitHub. Comprehensive API and hard-
ware documentation is available.
The MCC DAQ HAT Library supports
operation with multiple MCC DAQ HATs
running concurrently.
Console-based and user interface (UI)
example programs are available.
Measurement Computing (508) 946-5100
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MCC 134
24-bit ADC
Input
Filters,
ESD,
and
OTD
Isolation Barrier
Raspberry Pi
Header
I2C
SPI
+5 V
+3.3 V
Board
Address
Matching
HAT
EEPROM
Digital
Isolator
Screw Terminals
CJC Sensors
Isolated
Power
Supply
Block Diagram
Best Practices for Accurate Thermocouple Measurements
The MCC 134 should achieve results within the maximum thermocouple accuracy specifications when operating within the documented 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
program that fully loads all 4 cores on the Raspberry Pi
processor can raise the temperature of the processor above
70 °C. Running a program that only loads 1 core will operate approximately 20 °C cooler.
• Minimize environmental temperature variations. Place the
MCC 134 away from heat or cooling sources that cycle
on and off. Sudden environmental changes may lead to
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.
• Provide a steady airflow, such as from a fan. A steady airflow
can dissipate heat and reduce errors.
• When configuring multiple MCC DAQ Hats in a stack, posi-
tion the MCC 134 farthest from the Raspberry Pi board. Since
the Raspberry Pi is a significant heat source, placing the
MCC 134 farthest from the Pi will increase accuracy.
For additional information, refer to the Measuring Thermocouples
with the Raspberry Pi and the MCC 134 Tech Tip.
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MCC 134
Example Programs
MCC DAQ HAT Examples
The MCC DAQ HAT Library includes example programs
developed in C/C++ and Python that users can run to become
familiar with the DAQ HAT library and boards; source code is
included.
Console-Based (C/C++)
The compiled console example reads and displays the value of
each thermocouple channel in a software timed loop.
Continuously read and display the value of each thermocouple input
User Interface
Example programs featuring a user interface are provided in
different formats. Examples of each are shown here.
DataLogger (C/C++)
The datalogger example acquires data from the MCC 134, displays the data on a strip chart, and logs the data to a CSV file.
This example can be run from the terminal.
Web Server (Python)
The web server example lets users configure acquisition options
and view acquired data from a browser window. This example
is written for Python (source included).
Configure options and view strip chart data from your browser
IFTTT Applet (Python)
IFTTT (If This Then That) is a free web-based service that interacts with apps and hardware to automate various functions. An
IFTTT account is required.
The DAQ HAT Library includes two IFTTT example programs
written for Python (source included):
• The logging example reads one channel at regular intervals
and writes the data to a Google Sheets spreadsheet. Users
can remotely monitor the spreadsheet from Google Drive
(shown below).
• The alarm example monitors one channel and sends an
email if the channel value meets specified criteria.
Configure options, plot data on a strip chart, and log data to a file
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Remotely monitor acquired data from your browser
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MCC 134
Specifications
All specifications are subject to change without notice.
Typical for 25 °C unless otherwise specified.
Thermocouple input
A/D converters: Delta-Sigma
ADC resolution: 24 bits
Number of channels: 4
Input isolation
Between input and Raspberry Pi ground: 500 Vpk withstand max
Differential input voltage range: ±78.125 mV
Common mode voltage range
Between any CHx+ or – input and any other input: 0.8 V max
Absolute maximum input voltage
Between any two TCx inputs: ±25 V (power on), ±25 V (power off)
Differential input impedance: 40 MΩ
Input current: 83 nA
Common mode rejection (fIN = 50 Hz or 60 Hz): 100 dB
Update interval: 1 second min
Open thermocouple detect response time: 2 seconds
Recommended Warm-up time: 15 minutes min
Calibration method: Factory
Compatible thermocouples
J: –210 °C to 1200 °C
K: –270 °C to 1372 °C
R: –50 °C to 1768 °C
S: –50 °C to 1768 °C
Accuracy
Thermocouple measurement accuracy
Thermocouple accuracy specifications, including typical CJC measurement error.
All specifications are (±).
Note 1: Thermocouple measurement accuracy specifications include polynomial
linearization, cold-junction compensation error, and system noise. Accuracies shown do not include inherent thermocouple error or large temperature
gradients across the board. Contact your thermocouple supplier for details on
the inherent thermocouple accuracy error. The accuracy specifications assume
the device has been warmed up for the recommended 15 minutes.
Note 2: To avoid excessive cold-junction compensation errors, operate the device
in a stable temperature environment and away from heat sources that could
cause temperature gradients across the board. Refer to the documentation for
ways to decrease this error.
Note 3: When thermocouples are attached to conductive surfaces, the voltage
differential between multiple thermocouples must remain within ±0.8 V. For
best results MCC recommends using electrically insulated thermocouples when
possible.
T: –270 °C to 400 °C
N: –270 °C to 1300 °C
E: –270 °C to 1000 °C
B: 50 °C to 1820 °C
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MCC 134
Specifications and Ordering
Memory
Non-volatile memory: 4 KB (ID and calibration storage, no user-modifiable
memory)
Power
Supply current
5 V supply: 16 mA typ, 24 mA max
3.3 V supply: 1 mA typ, 5 mA max
Interface
Raspberry Pi GPIO pins used:
GPIO 8, GPIO 9, GPIO 10, GPIO 11 (SPI interface)
ID_SD, ID_SC (ID EEPROM)
GPIO 12, GPIO 13, GPIO 26, (Board address)
Data interface type: SPI slave device, CE0 chip select
SPI mode: 1
SPI clock rate: 10 MHz, max
Environment
Operating temperature: 0 °C to 55 °C
Storage temperature: –40 ˚C to 85 °C max
Relative humidity: 0% to 90% non-condensing
Mechanical
Dimensions (L × W × H): 65 × 56.5 × 12 mm (2.56 × 2.22 × 0.47 in.) max
Order Information
Hardware
Part No. Description
MCC 134 4-channel thermocouple measurement DAQ HAT.
Software
Part No. Description
MCC HAT
Library
Measurement Computing (508) 946-5100
May 2020. Rev 3
DS-MCC-134 © Measurement Computing Corporation
Raspberry Pi model with the 40-pin GPIO connector
required.
Open-source library for developing applications in C, C++,
and Python on Linux for MCC DAQ HAT hardware.
Available for download on GitHub at https://github.com/
mccdaq/daqhats.
Accessories
Part No. Description
745690-E001 E-type thermocouples wire, fiberglass
745690-E002 E-type thermocouples wire, fiberglass
745690-J001 J-type thermocouples wire, fiberglass
745690-J002 J-type thermocouples wire, fiberglass
745690-K001 K-type thermocouples wire, fiberglass
745690-K002 K-type thermocouples wire, fiberglass
745690-T001 T-type thermocouples wire, fiberglass
745690-T002 T-type thermocouples wire, fiberglass
5
(0 °C to 482 °C, 32 °F to 900 °F), 1 m
(0 °C to 482 °C, 32 °F to 900 °F), 2 m
(0 °C to 482 °C, 32 °F to 900 °F), 1 m
(0 °C to 482 °C, 32 °F to 900 °F), 2 m
(0 °C to 482 °C , 32 °F to 900 °F), 1 m
(0 °C to 482 °C, 32 °F to 900 °F), 2 m
(0 °C to 260 °C, 32 °F to 500 °F), 1 m
(0 °C to 260 °C, 32 °F to 500 °F), 2 m
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