Today’s crop of data acquisition products offers a powerful range of modular products. They provide the flexibility for engineers to mix and match data capture, data conversion and I/O functions to fit user-specific needs.
Like all of today’s electronics, products for data acquisition (often abbreviated as “DAQ”) have exploited the benefits of integration. Decades ago, a typical data acquisition set up required large racks of slot-cards based on VXI, PXI or other form factors. Today such systems can be implemented with well-established desktop computing interfaces such as USB and PCI Express. All that said, most engineers have unique needs when it comes to specific sets of data acquisition functions. That’s driven data acquisition product vendors to continue to focus on modular sets of products.
Over the past 12 months, the latest trends revolve around increasing channel counts and embracing popular embedded architectures like Raspberry Pi. To keep pace, data acquisition product vendors are rolling out board-, module- and box-level solutions that leverage the best available interfacing and analog conversion technology—all in modular formats.
STANDALONE ETHERNET DAQ
Exemplifying these trends, in July ADLINK technology added the MCM-216 and MCM-218 models to its MCM-210 standalone Ethernet DAQ series. MCM-216/218 Ethernet DAQ, based on Arm Cortex-A9 processors with built-in 8- or 16-channel, 16-bit, provide voltage or current input and can function as a standalone edge device without a host PC (Figure 1). The standalone Ethernet DAQ supports edge computing and includes a built-in web console and RESTful API for periodic machine condition polling.
The MCM-216 and MCM-218 represent a simple, scalable, sustainable edge device to overcome the challenge of mass deployment in IIoT applications, says ADLINK. Dual daisy-chainable Ethernet ports eliminate additional networking equipment and extend the usable distance, reducing TCO and boosting overall ROI. Successful applications include semiconductor factory digitization, petrochemical plant monitoring and wafer feeder vacuum pump monitoring.
The standalone Ethernet DAQ system can perform the tasks of a DAQ system without the complexity and added cost of an embedded system. This means distributed and remote acquisition without distance restriction. The system converts data to information for edge analytics. Rich connectivity is provided for easier data transfer to a backend server or SCADA. The MCM-216/218 models complete the MCM-210 series and provide a full-spectrum edge DAQ solution for factory automation, IIoT and traditional testing and measurement. The simple, scalable edge device overcomes the challenge of mass deployment for IIoT applications.
DAQ SERIES FOR TEST
Also focusing on a modular data acquisition approach, in October Advantech released a series of data acquisition modules called the iDAQ series. The iDAQ series is comprised of modular DAQ modules and chassis including the iDAQ-900 series chassis and iDAQ-700 and 800 series DAQ modules. The iDAQ series splits traditional functions in PCI/PCIe cards and USB modules into several smaller functional units (Figure 2). Unlike traditional multi-function cards with I/O and functions that are fixed, each iDAQ module only has one type of function, like a digital input, analog input or even IEPE input. Customers can choose different module combinations and specifications for their iDAQ system to meet different test and measurement scenarios.
When an iDAQ module is integrated in a machine used as a measurement device, it will cumulatively incur damage after long periods of constant use. iDAQ modules are hot-swappable, which makes maintenance very simple. iDAQ-900 series chassis provides fast bus access on the backplane to connect iDAQ modules. There are triggers and pacer clocks in the timing signals, which control when the measurement cycle will start and stop, as well as the acquisition speed.
Each of the DAQ modules can be synchronized together using the same clock and trigger event via the bus. This makes synchronization easy with Advantech iDAQ systems because they only need to be configured in software, which also means no complicated wiring. On top of the backplane bus, programmable function pins (PFP) in the iDAQ-900 chassis provide an interface for timing control. The DAQ modules can be configured as either input or output signal types, and as either single pulse or clock types. This provides great flexibility for field applications needing to synchronize with external devices, or to be triggered by other devices simply with pulses.
Three factors make the iDAQ system rugged: anti-vibration, EMC immunity and wide-range temperature operation. The whole assembly is tested under 5Grms random vibration and 30G shock tests that are designed to survive the most extreme vibration scenarios. The iDAQ series uses an aluminum alloy as its enclosure, which provides better EMC performance. Finally, the operating temperature range is -20°C to 60°C.
The iDAQ-900 chassis provides different connectivity solutions depending on which module is installed. For example, the iDAQ-934 is a USB 3.0 chassis with four iDAQ slots and the iDAQ-964 is a chassis expansion of AMAX edge controllers. The iDAQ system relies on the DAQNavi/SDK as a development package. It provides a Navigator utility to configure the module and chassis, and test its functionalities. For example, the programs completed based on iDAQ-934 can be moved to iDAQ-964 directly with only slight modification on device names.
DAQ PCIe/104 BOARD
With today’s level of electronics integration, complete data acquisition functionality can even fit on a small form factor like PCIe/104. With exactly that in mind, in September Diamond Systems announced a rugged, PCIe/104 form factor SBC aimed at data acquisition tasks. Like Diamond’s Zeta board set, the Saturn SBC runs Linux or Windows on Intel’s Apollo Lake. It adopts the legacy PCIe/104 form factor and more specifically uses the stackable PCIe/104 OneBank expansion interface (Figure 3).
The Saturn SBC runs Ubuntu and Win 10 on Intel’s quad-core, 1.6GHz/1.8GHz Atom x5-E3940. Like other PCIe/104 and PC/104 boards, there are no typical real-world ports. The Saturn instead offers rugged latching connectors. The fanless SBC supports -40ºC to 85ºC temperatures with the help of a bottom-mounted heat spreader. There are no specific ruggedization claims beyond that, but Diamond says that durability is improved with the latching connectors and a thicker than usual PCB. In addition, the 4GB to 8GB of DDR3L is soldered. The 8GB model uses ECC RAM.
Data acquisition features depend on whether you purchase the “D” model, which is limited to digital I/Os or the “A” model, which also includes analog I/Os. The fully featured “A” model provides 16x single-ended and 8x differential analog inputs plus 4x analog outputs. There are also 24x digital I/Os, 8x counter/timers, 4x PWM interfaces and an external A/D trigger.
The data acquisition circuit features autocalibration, which maintains best accuracy of the A/D and D/A circuits regardless of time and temperature swings. Supplied drivers enable the circuit to be “quickly calibrated to within ±2LSB accuracy at any time, relative to the on-board precision reference voltage circuit.
The Saturn is equipped with 2x GbE, 2x HDMI, 2x USB 3.0, and 2x USB 2.0 ports. You also get 2x RS-232/422/485 and a single RS-232 port. There is HDA audio I/O based on a Realtek ALC662 plus dual-channel, 24-bit LVDS with backlight power. The Saturn has a 5VDC input, a battery connector, a TPM 2.0 chip, and LEDs. The SBC provides a SATA header for an external 2.5-inch HDD drive and an M.2 2242 socket for up to 1TB SSD storage. Further expansion is available via a full-sized mini-PCIe slot (PCIe/USB) and the PCIe/104 OneBank interface with 4x PCIe x1 and 2x USB 2.0 signals.
The Saturn is available with software or hardware development kits. The software kit provides a 64GB flash disk with a read-to-run installation of the selected OS plus a backup USB memory device. The Linux version includes “all the tools needed to rebuild the OS. The hardware kit adds a cable kit, and there are a variety of a la carte cable accessories.
RASPBERRY HATS FOR DAQ
The extreme popularity of Raspberry Pi SBCs has opened the door to a vast number of add-on modules for the Raspberry Pi, called “HATs.” HAT stands for “hardware attached on top,” a hardware specification for add-on modules for the Raspberry Pi model B+ SBC. HATS have a 40-pin GPIO (general purpose input/output) connector that conforms to the Raspberry Pi HAT specification. Up to eight HATs can be stacked onto one Raspberry Pi.
Data acquisition products are among these HAT offerings. As an example, in November Contec announced three new CPI Series HATs for the Raspberry Pi, bringing the total up to 10 and providing some analog I/O to complement the previous boards’ digital input and output capabilities (Figure 4).
The stackable HATs are designed for factory automation and measurement control applications, adding up to 8x stacking capability per the HAT spec for multi-stage connectivity for general-purpose usability. The HATs provide push-type terminal blocks, -20°C to 60°C support, and an API that is compatible with Python and PC expansion cards. A free downloadable Linux driver (API-TOOL for Linux) comes with sample Python and GCC programs.
The first of the HATs from Contec is the CPI-AI-1208LI, a 12-bit, 8-channel. analog input with bus isolation and multiple input range and types. Next is the CPI-AO-1602LC, a 16-bit, 2-channel analog output with inter-channel isolation, and support for various voltage output ranges and current output types. The third HAT is the CPI-CNT-3201I, a 32-bit up/down counter with opto-coupler bus isolation.
VOLTAGE MEASUREMENT HAT
Also offering data acquisition HAT products, Measurement Computing Corp. (MCC) offers its MCC 128 Voltage Measurement HAT for Raspberry Pi (Figure 5). The MCC 128 features 16-bit resolution and multiple analog input ranges. This makes it well suited for making precision voltage measurements. It includes eight single-ended or four differential-ended analog inputs with sample rates up to 100KSPS.
Up to eight MCC HATs can be stacked onto one Raspberry Pi providing up to 64 channels of data and a maximum throughput of 320KSPS. MCC offers a variety of DAQ HATs that allow users to configure multifunction, Pi-based solutions with voltage, thermocouple, or vibration inputs, voltage outputs and digital I/O.
Two versions of the MCC 128 are available. The MCC 128 features screw terminal signal connectors. The MCC 128-OEM is provided with unpopulated signal connections for users that want to add their own connectors. The open-source MCC DAQ HAT Library of commands in C/C++ and Python enables users to develop applications on Linux. The library is available to download from GitHub. Comprehensive API and hardware documentation are also provided.
PUBLISHED IN CIRCUIT CELLAR MAGAZINE • JANUARY 2022 #378 – Get a PDF of the issueSponsor this Article
Jeff served as Editor-in-Chief for both LinuxGizmos.com and its sister publication, Circuit Cellar magazine 6/2017—3/2022. In nearly three decades of covering the embedded electronics and computing industry, Jeff has also held senior editorial positions at EE Times, Computer Design, Electronic Design, Embedded Systems Development, and COTS Journal. His knowledge spans a broad range of electronics and computing topics, including CPUs, MCUs, memory, storage, graphics, power supplies, software development, and real-time OSes.