Dear Desktop Engineering Reader:
Your basic hand-built data acquisition systems come in as many forms and are used in as many applications as there are engineers and engineering teams. But, basically, there are two shapes: traditional setups and distributed setups. The image of a traditional data acquisition system has lots of wires running out from some centralized rack to some signal conditioning that’s wired to the sensors attached to whatever is under test. The rack holds the hardware that converts the analog signals to digital then ships them out over even more wires to a nearby computer for processing. Works like a charm. Trouble is that all those wires running everywhere gets complex and wiring jacks up costs big time.
Distributed data acquisition setups have wires too, but generally not the long runs. Distributed setups place the hardware as close to the UUT (unit under test) and often within the environment where the UUT operates. Here, you can create smaller, less expensive, and easier to replace subsystems. And a single wire or even a Wi-Fi link sends the data back to the computer for processing. Because you have less wiring, measurement accuracy can increase since shorter sensor wires are less prone to noise, interference, and signal loss. Works like a charm too. The trouble is that the environment where you place your distributed data acquisition equipment can be nasty hot, tooth rattling, capable of blowing up to your dismay, and what have you, so you need the right gear to do it right.
National Instruments designed the NI cDAQ-9188XT, the newest member of its CompactDAQ line of rugged, modular data acquisition systems, for distributed or remote measurements in extreme environments. Extreme means that the NI cDAQ-9188XT works in temperatures ranging from -40 to +70 Celsius. This 8-slot NI CompactDAQ Ethernet chassis can also handle 50 g of shock and 5 g of vibration, and it’s Class 1 Division 2 and Ex hazardous location certified.
The NI cDAQ-9188XT has a lot to offer you distributed data acquisition-ologists, but here are three neat features: a watchdog timer, NI-DAQmx driver software, and 50 electrical or sensor measurement modules. Let’s start with the modules.
The NI cDAQ-9188XT can use NI’s C Series modules. These self-contained measurement modules come with the connectivity and conditioning circuitry required for a given measurement. All A/D (analog-to-digital) and D/A (digital-to-analog) conversions happen in them before the data reaches the chassis. The modules are hot swappable, configure automatically, and connect with common sensor types directly.
NI-DAQmx driver software helps you with a bunch of stuff. For example, it provides a single interface for programming analog input, analog output, digital I/O, and counters. It has programming support for NI LabVIEW, ANSI C/C++, C#, and Visual Basic .NET. Its DAQ Assistant configuration tool helps you generate code for LabVIEW and NI Measurement Studio. It also supports NI Measurement & Automation Explorer for system configuration and test.
The NI cDAQ-9188XT’s onboard watchdog timer, a first in the NI CompactDAQ line, lets you define safe states that can help protect tests and equipment. You can configure the timer for any of the output channels (analog, digital, or counter) you use on the chassis. So, you can set specified output channels to voltage levels or logic states so that you have a fail-safe mechanism.
The short of it is that the NI cDAQ-9188XT sounds like a highly capable, highly flexible system that can give you a robust platform to build a distributed data acquisition system for gnarly environments. You can learn more about the NI cDAQ-9188XT in today’s Pick of the Week write-up and the resource links. Good stuff.
Thanks, Pal. — Lockwood
Anthony J. Lockwood
Editor at Large, Desktop Engineering
Read today's pick of the week write-up.
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