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Why Calibrate Your Test Equipment?

During preparation of the Precision Voltage Reference project elsewhere in this issue, we consulted with Trio Smartcal on the subject of calibration. This article gives a brief overview.

By Tony Tong

You have invested in test equipment to allow you to measure something. It could be a multimeter to measure a power supply voltage, an oscilloscope to measure waveform amplitude or a spectrum analyser to measure RF power at a given frequency, etc. In any of these cases the big question is “how important is the result you get from your test equipment to you and your company?”

Many people consider calibration to be a necessary evil. However the implications and cost of using an inaccurate item of test equipment can be much greater.

For example, let’s take a production maintenance technician who is troubleshooting electronic control sys-
tems. Typically his multimeter has not been checked since new (several years ago) and has had a hard life in his toolbox, being dropped a few times. It now reads 5% low.

He is checking a control board for the manufacturing line and is checking the 5V board supply which has a tolerance of ±5% but it happens to be faulty and is high by 7%. The board is acting erratically but his meter tells him the supply is OK, comfortably inside tolerance. The technician then spends another four hours looking elsewhere for the problem. Not only does this cost the company money for his time but production has been down for four more hours and this cost the company $40,000 in lost output.

In a recent case here at TRIO Smartcal, we had a customer who was setting up CCTV systems. He owned a well-respected brand of TV signal generator, about three years old. He never suspected it to output anything other than the specified signals. He had set up several hundred systems in the last year and felt that his waveform monitor (not the signal generator) was out of spec because it was not showing the picture he expected.

We performance-verified the monitor and found it was well within spec. It turned out that the signal generator was out of spec instead and he had probably set up every system incorrectly for at least the last year; not what he wanted to hear!

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