Sunday, December 9, 2007

Virtual Instruments

I said in a post last month that I would read & review Designing Next Generation Test Systems - An In-Depth Developers Guide from National Instruments. I'm practically done now & will post my thoughts in a couple of days. But parts of this manual neatly dovetailed with a conversation I had earlier this week about virtual instruments.

NI is big on the concept of a virtual instrument - use the computer in place of the benchtop instrument to do the measurements. I've used this concept for potentiometers and oscilloscopes. But I just don't think this works in all cases, or even most cases. I have two reasons to back this opinion.

Complicated real-world measurements
There are some properties that are more than just a voltage or current. You need a good deal of physical hardware to actually acquire the data. Several examples I'm familiar with include optical spectrometers, digital communications analyzers, and (more esoteric) high energy particle detectors. A good deal of additional circuitry, physical devices, and sometimes patented techniques are involved.

Test Expertise
Hardware companies that build test equipment often have a good deal of knowledge and experience making that kind of measurement. That information often is built into the desktop instrument that performs that measurement. In most of those sorts of situations I would rather have the actual instrument than spend time and effort trying to duplicate that expertise myself.

I am not saying that virtual instruments are invalid. I think they work well for any non-complicated measurements or measurement techniques that are well-established (i.e. - the modern triggered oscilloscope was invented over 60 years ago). But sometimes you need the actual hardware.

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