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PC Based Measuring Instruments

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It had to happen! Over the years Personal Computers (PCs) became faster, cheaper and more powerful. The range of their possible applications increased exponentially and it is not surprising that they are now well into the field of electronics measurement. Today we find an increasing number of measuring instruments designed to be used with a PC, taking advantage of the computer’s powerful functions.

How can this happen? Let’s take an oscilloscope as an example. What’s inside an oscilloscope that a PC can do as well or even better?

- Screen: The PC can display whatever you want, bigger, better and brighter than an oscilloscope and with more flexibility, changing colours, size etc…

- Controls: All those expensive buttons and switches can be replaced with “click- on’’ buttons on the screen and drop down menus.

- Functions: The software is the limit. I.e. virtually no limit! Most of the PC based oscilloscopes include a spectrum analyser and a function generator as additional functions.

- Data storage: Average PCs have a huge storage capacity that few oscilloscopes can match.

- Data format: PCs can output data in various forms such as pictures, PDF, Spread sheets etc…

Besides the software, all what we need is a hardware interface to convert the analogue signals into digital, then outputs the digital signals to the PC. It’s usually a small box with a few inputs (BNC connectors for the probes and external sync) and an output to connect to the PC.

PC Based Measuring InstrumentsThe output can be of various kinds. Some PC based measuring instruments are PCI cards that plug into your PC just like a modem or video card. Others connect to the PC through the printer port, or use the LAN (Ethernet) port or even communicate wirelessly using Bluetooth. The most common are the ones connecting through one of the PC’s USB ports. One of the advantages of using the USB ports is that the port will supply the 5V to power the interface. Thus there is no need for an external power supply, making the interface even cheaper.

Why only now? As PCs have been around for many years, we may wonder why this technology didn’t come earlier… The fact is that “real time” applications could not use standard PCs in the past because of this: Real Time. It’s all about the time it takes for a PC to respond to an input. Traditionally, PCs are multitasking and each task has defined priorities, and then takes place in a queue. The time it takes for a task to be processed depends on its priority and on how many tasks are running simultaneously. Therefore, the response to an input might take a few seconds. This is not a problem if you want to scan or print a document but it is critical when you need an immediate response to an input. That is why industrial control and instrumentation equipment used dedicated PCs or controllers running proprietary operating systems instead of standard computers. This would have made PC based measuring instruments too expensive to compete with their hardware equivalent.

PC Based Oscilloscope

With the increased speed and power of today’s PCs, “near real time” responses can now be achieved. Modern operating systems also took this timing issue into consideration and priorities can be set by the application software.

Today we find a wide range of PC based measuring instruments from oscilloscopes to multimeters and function generators including network analyzers etc…. They offer more functions and features than their hardware equivalent for a fraction of the price. The sky is the limit. Any measuring instrument can be built PC based, providing the right interface and software. Manufacturers can offer more functions simply by upgrading the software.

This technology is not limited to PCs only. We see projects to transform your iPad or mobile phone into a portable oscilloscope! The following video is a nice example:

There are other videos on the same page using different models of mobile phones to make oscilloscopes, quite funny!

It seems that this technology is here to stay and that’s how future measuring instruments will be. Be ready for a different look of your workplace; instead of those impressive (and beautiful) instruments you will only see a few boxes with connectors and a computer screen. For the nostalgic like me, we can be reassured with the fact that our faithful analogue multimeter will still remain on the bench for a while.

Gerald Musy
Penang 14-06-2011

Own experience

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Published in our category of Digital Oscilloscopes on Tuesday June 14, 2011 with the keywords , , , , .
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