How often should you calibrate?

The question isn’t whether to calibrate, it’s how often to. There is no “one size fits all” answer. Consider these possible calibration frequencies to help you decide what works best for you:

• Manufacturer-recommended calibration interval. Manufacturers’ specifications indicate how often to calibrate their tools, but critical measurements may require different intervals.
   
• Before a major critical measuring project. Suppose you are taking a plant down for testing that requires highly accurate measurements. Decide which instruments you will use for that testing. Send them out for calibration, then “lock them down” in storage so they are unused before the test.
   
• After a major critical measuring project. If you reserved calibrated test instruments for a particular test, send that same equipment for calibration after the testing. When the calibration results come back, you will know whether you can consider the test complete and reliable.
   
• After an event. If your instrument took a hit — something knocked out the internal overload protection or the unit absorbed a sharp impact — send it out for calibration and have the safety integrity checked, as well.
   
• Per requirements. Some measurement jobs require calibrated, certified test equipment — regardless of the project size. Note that this requirement may not be explicitly stated but simply expected — review the specs before the test.
   
• Monthly, quarterly, or semiannually. If you do mostly critical measurements and do them often, a shorter time span between calibrations means less chance of questionable test results. Many times, calibrating at shorter intervals will afford you with better specifications.
   
• Annually. If you do a mix of critical and non-critical measurements, annual calibration tends to strike the right balance between prudence and cost.
   
• Biannually. If you seldom do critical measurements and don’t expose your meter to an event, calibration at long frequencies can be cost-effective.
   
• Never. If your work requires just gross voltage checks (“Yep, that’s 480 V”), calibration seems like overkill. But what if your instrument is exposed to an event? Calibration allows you to use the instrument with confidence.

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