Verifying Equipment Calibration
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Verifying Equipment Calibration
When it comes to equipment calibration, thermographers often send their infrared instruments to the manufacturer at periodic intervals. To help ensure accuracy, thermographers should understand calibration procedures and review calibration documentation whenever possible.
Within the thermographic community it is common practice to periodically return infrared equipment to the manufacturer. Typical time frames range from 12 to 24 months depending upon one’s circumstances. As part of the calibration process, most manufacturers will provide a statement of calibration upon returning the subject instruments.
Recently, we sent two identical contact radiometers to their manufacturer for calibration. Both units had been providing inaccurate temperatures and were expected to need adjustment. The units were returned approximately two weeks later each with a calibration statement and the observation that neither needed adjustment.
In reviewing the accuracy statement for each of the radiometers, it was noted that the tolerances were not in accordance with the manufacturer’s published specifications. When asked about the discrepancy, the manufacturer stated the calibration forms that we received were outdated and had been used by mistake. The manufacturer apologized and faxed the correct formula.
Upon applying the correct formula to the calibration data, it was noted that the subject radiometers were out of tolerance for several temperature points. As a result, both radiometers were sent back to the manufacturer for proper calibration and adjustment.
The above experience underscores the need for thermographers to understand manufacturers’ calibration procedures and the resulting data. Had we blindly relied on the manufacturer’s initial calibration, it is likely that we would have introduced significant error into our measurements.
To help ensure equipment accuracy, it is always advisable to perform an in-house check of radiometric equipment on a regular basis, after manufacturer adjustments, or whenever equipment has experienced any physical shock. The Infraspection Institute Level II Certified Infrared Thermographer® training course teaches a simple method that may be used to check the calibration of infrared equipment. For more information on thermographer training or certification, visit us online at: www.infraspection.com.
Infraspection Institute and Kleinfeld Technical Services, Inc. are preparing Distance Learning Tutorials on a variety of topics. We would appreciate your feedback as to your interest areas for these tutorials. Please fill in the very short survey at this link: http://www.surveymonkey.com
