MCC 172
IEPE Measurement DAQ HAT for Raspberry Pi
The MCC 172 is a 24-bit DAQ HAT for making sound and vibration measurements from
IEPE sensors. The MCC 172 is shown connected to a Raspberry Pi (not included).
Overview
The MCC 172 is a voltage HAT (Hardware Attached on Top) board 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 172 HAT provides two analog inputs for sound or vibration measurements. Up to eight MCC HATs can be stacked onto one Raspberry Pi.
®
Features
• Two IEPE inputs
− Two 24-bit, 51.2 kS/s A/D
converters (one per channel)
− AC coupled at ±5 V
− 10-32 and screw terminal
connections for OEM support
• Synchronous ADC conversions
between multiple boards
• Onboard sample buffers allow
high-speed acquisition
• External digital trigger input
• Stack up to eight MCC HATs
onto a single Raspberry Pi
Software
• MCC DAQ HAT Library;
available on GitHub
Supported Operating Systems
• Linux®/Raspbian
Raspberry Pi Interface
The MCC 172 header plugs into the 40-pin
general purpose I/O (GPIO) connector on a
user-supplied Raspberry Pi. The MCC 172
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 HAT boards can be
stacked onto a single Raspberry Pi.
Users can mix and match MCC HAT
models in the stack.
Analog Input
The two 24-bit differential analog input
channels simultaneously acquire data at
rates up 51.2 kS/s. Users can turn IEPE
excitation current on or off.
Each channel has a dedicated A/D converter. Both ADCs share the same clock
and are synchronized to start conversions
at the same time for synchronous data.
Multiple HAT Synchronization
Multiple MCC 172 HATs can be synchronized to a single sampling clock. The clock is
programmable for sampling rates between
51.2 kS/s to 200 S/s.
Sample Rates
• Single-board: max throughput is
102.4 kS/s (51.2 kS × 2 channels)
• Stacked boards: max throughput is
307.2 kS/s aggregate1.
Digital Trigger
The trigger input (terminal TRIG) is used
to delay an input scan until a specified
condition is met at the trigger input.
The trigger input signal may be a 3.3V or
5V TTL or CMOS logic signal. The input
condition may be edge or level sensitive,
rising or falling edge, or high or low level.
This terminal may be used to trigger the
start of an acquisition on multiple synchronized MCC 172 HATs.
Power
The MCC 172 is powered with 5 V
provided by the Raspberry Pi through the
GPIO header connector.
1 Dependent on the load on the Raspberry Pi and
the SPI interface.
Programming API
• C, C++, Python
OEM Support
Users can connect analog input signals to
either the 10-32 coaxial inputs or to the
screw terminals. Only one source may be
connected to a channel at a time.
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 for each
API.
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MCC 172
SPI
SPI
I2C
+5V
Clock
Clock
Trigger Bus
Clock Bus
Raspberry Pi
Header
Digital
Trigger
Clock
Master/
Slave
26.2144
MHz
Oscillator
3.3V
Supply
Board
Address
Matching
HAT
EEPROM
32-bit
Microcontroller
IEPE
Supply
CH 0 Amp ADC
IEPE
Supply
CH 1 Amp ADC
Trigger
Master/
Slave
Block Diagram
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Stackable
Connect up to eight MCC DAQ HATs onto a single
Raspberry Pi.
Onboard jumpers identify each board in the stack.
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MCC 172
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++ and Python)
Console-based examples are provided that demonstrate how
to perform FFT on a block of data, acquire synchronous data
from multiple MCC 172 HATs using shared clock and trigger
options, trigger a finite scan, and synchronously acquire data
from multiple DAQ HATs. Source code is included.
The fft_scan example is shown here.
User Interface
Example programs featuring a user interface are provided in
different formats. Examples of each are shown here.
Data Logger (C/C++)
The data logger example shows how to acquire data from the
MCC 172, display the data on a strip chart, and log the data to
a CSV file. This example can be run from the terminal.
Peak frequency and harmonics display in a terminal window
FFT data is saved to a csv file
Configure options, plot data on a strip chart, and log data to a file
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
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MCC 172
Specifications
All specifications are subject to change without notice.
Typical for 25 ˚C unless otherwise specified.
Analog input
Number of channels: 2
ADC Resolution: 24 bits
A/D converter type: Delta sigma
Sampling mode: Simultaneous
Master timebase (fM):
Frequency: 26.2144 MHz
Accuracy: ±50 ppm max
Master timebase sources
Internal clock
Shared clock from another MCC 172
Data rates (fS)
(fM / 512) / n, n = 1, 2, …, 256
51.2 kS/s max
200 S/s min
Input coupling: AC
AC cutoff frequency
-3 dB: 0.78 Hz
-0.1 dB: 5.2 Hz max
Input voltage range: ±5 V
Common-mode voltage range
CHx to AGND: ±2 V max
Overvoltage protection
CHx+ to CHx-: ±35 V
CHx- to ground: ±2.5 V
IEPE compliance voltage: 23 V max
IEPE excitation current: 4.0 mA min, 4.1 mA typ
Input delay
1 kHz to 23 kHz input frequency: 4.5 µs + 39 / f
Channel-to-channel matching
Phase (200 Hz to 23 kHz): (fin * 0.022°) max
Gain (20 Hz to 23 kHz): 0.19 dB typ
Passband
Frequency: 0.453 * f
Flatness (20 Hz to 23 kHz): 52 mdB (pk-to-pk max)
Phase nonlinearity
fS = 51.2 kS/s, 200 Hz to 23 kHz input frequency: ±0.36° max
Stopband
Frequency: 0.547 * f
Rejection: 99 dB min
Alias-free bandwidth: 0.453 * fS
Alias rejection: 100 dB @ 51.2 kS/s
Oversample rate: 128 * f
Crosstalk
1 kHz: -122 dB
SFDR
fin = 1 kHz, -60 dBFS: 120 dB
Dynamic range
fin = 1 kHz, -1 dBFS: 100 dB
Input impedance
Differential: 202 kΩ
AI- (shield) to ground: 50 Ω
Throughput
Single board: 102.4 kS/s max (51.2 kS/s × 2 channels)
Multiple boards: Up to 307.2 kS/s aggregate
†
Depends on the load on the Raspberry Pi processor and the SPI interface.
Note: For best results, connect the signal source and the Raspberry Pi to a common
ground. If a floating source is required, connect the MCC 172 to earth ground via
the DGND screw terminal to minimize common mode noise.
S
S
S
S
†
Accuracy
Analog input AC voltage measurement accuracy
(all values are (±) and apply to calibrated readings)
Gain error,
max:
0.43% 5.10 mV 88 ppm/°C 184 µV/°C
Offset error,
max:
Gain temperature
coefficient, max:
Gain temperature
coefficient, max:
Noise performance
Idle Channel 51.2 kS/s
Noise 33 µVrms
Noise density 207 nV/√Hz
Total harmonic distortion (THD)
Input Amplitude 1 kHz 8 kHz
-1 dBFS -93 dB -91 dB
-10.96 dBFS -87 dB -87 dB
External digital trigger
Trigger source: TRIG input
Trigger mode: Software configurable for rising or falling edge, or high or low level
Trigger latency: 1 µs + 1 sample period (1/fS) max
Trigger pulse width: 100 ns min
Input type : Schmitt trigger, 100K pull-down to ground
Input high voltage threshold: 1.48 V min
Input low voltage threshold: 1.2 V max
Input hysteresis: 0.51 V min
Input voltage limits: 6.5 V absolute max, –0.5 V absolute min,
0 V recommended min
Memory
Data FIFO: 48 K (49,152) analog input samples
Non-volatile memory: 4 KB (ID and calibration storage, no user-modifiable
memory)
Power
Supply current, 5 V supply
Typical: 100 mA
Maximum: 140 mA
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)
GPIO 5, 6, 19, 16, 20 (Clock / trigger sharing, Reset, IRQ)
Data interface type: SPI slave device, CE0 chip select
SPI mode: 1
SPI clock rate: 18 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
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MCC 172
Ordering
Signal connectors
Connector types: 10-32 coaxial / screw terminal (in parallel; only one source may
be connected to a channel at a time)
Coaxial input signals
CH0: channel 0 input
CH1: channel 1 input
Screw terminal wire gauge range: 16 AWG to 30 AWG
Analog input screw terminal pinout (Connector J2)
Pin Signal name Pin description
1 CH0+ Channel 0 positive input
2 CH0- Channel 0 negative input
3 CH1+ Channel 1 positive input
4 CH1- Channel 1 negative input
Order Information
Hardware
Part No. Description
MCC 172 24-bit, 2-channel IEPE measurement DAQ HAT.
Raspberry Pi with the 40-pin GPIO connector required.
Accessories
Part No. Description
ACC-172 Coaxial cable, 3 ft, with 10-32 plug to BNC jack (2 qty)
Trigger input screw terminal pinout (Connector J5)
Pin Signal name Pin description
1 TRIG Digital trigger input
2 GND Digital ground
Software
Part No. Description
MCC DAQ
HAT Library
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.
Measurement Computing (508) 946-5100
April 2021. Rev 3
DS-MCC-172 © Measurement Computing Corporation
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