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MCC 172 IEPE Measurement DAQ HAT for 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 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. • 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 Multiple HAT Synchronization 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. 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. HAT Configuration • Single-board: max throughput is 102.4 kS/s (51.2 kS × 2 channels) 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. Sample Rates • Stacked boards: max throughput is 307.2 kS/s aggregate1. Digital Trigger 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. 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 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 hardware 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. 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. Measurement Computing (508) 946-5100 1 info@mccdaq.com mccdaq.com MCC 172 Block Diagram +5V IEPE Supply 3.3V Supply Clock CH 0 Amp Clock Master/ Slave IEPE Supply CH 1 Amp 26.2144 MHz Oscillator ADC Clock 32-bit Microcontroller SPI SPI Board Address Matching Raspberry Pi Header ADC HAT EEPROM Trigger Master/ Slave Digital Trigger I2C Trigger Bus Clock Bus Stackable Connect up to eight MCC DAQ HATs onto a single Raspberry Pi. Onboard jumpers identify each board in the stack. Measurement Computing (508) 946-5100 2 info@mccdaq.com mccdaq.com MCC 172 Example Programs MCC DAQ HAT Examples User Interface 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. Example programs featuring a user interface are provided in different formats. Examples of each are shown here. Console-Based (C/C++ and Python) 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. Data Logger (C/C++) 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. 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). Peak frequency and harmonics display in a terminal window Configure options and view strip chart data from your browser FFT data is saved to a csv file Measurement Computing (508) 946-5100 3 info@mccdaq.com mccdaq.com MCC 172 Specifications Accuracy All specifications are subject to change without notice. Typical for 25 ˚C unless otherwise specified. Analog input AC voltage measurement accuracy (all values are (±) and apply to calibrated readings) 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 / fS 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 * fS 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 * fS Rejection: 99 dB min Alias-free bandwidth: 0.453 * fS Alias rejection: 100 dB @ 51.2 kS/s Oversample rate: 128 * fS 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. (508) 946-5100 Offset error, max: Gain temperature coefficient, max: Gain temperature coefficient, max: 0.43% 5.10 mV 88 ppm/°C 184 µV/°C 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 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. Measurement Computing Gain error, max: Dimensions (L × W × H): 65 × 56.5 × 12 mm (2.56 × 2.22 × 0.47 in.) max 4 info@mccdaq.com mccdaq.com MCC 172 Ordering Signal connectors Trigger input screw terminal pinout (Connector J5) 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 Pin Signal name Pin description 1 TRIG Digital trigger input 2 GND Digital ground 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 Software 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. 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. Accessories Part No. Description ACC-172 Coaxial cable, 3 ft, with 10-32 plug to BNC jack (2 qty) Measurement Computing DS-MCC-172 (508) 946-5100 5 info@mccdaq.com mccdaq.com April 2021. Rev 3 © Measurement Computing Corporation