- calibration services are available for ELF/VLF Field Strength Meters, AC Power Measurement Equipment, Product Safety Equipment and Accessibility Probes.
- consulting services in Product Safety and Regulatory Compliance.
- testing services are offered in Acoustics, Magnetic
and Electric Field Surveys.
Calibration intervals are mentioned in most quality standards and literature. ISO9001 and ISO17025 are perhaps the most applicable for this topic. ISO9001, clause 7.2 states, "equipment shall be calibrated and verified at specific intervals". ISO17025 makes similar statements. The purpose of calibration is to verify compliance to specifications since test equipment may change with time and the amount of usage. If this change is great enough between calibrations to cause an out-of-specification condition, the measurement will be inaccurate sometime during the time interval. Both standards have provisions for a recall of all measurements made during the interval. If the equipment is used for regulatory compliance tests, this out-of-specification condition could be very important. According to the quality standards, the customers must be notified of the out-of-specification condition and the products verified. Depending on the situation, this could be quite costly.
What influences the interval between calibrations? Factors such as usage, the amount of equipment drift or change, tolerance of the specification and the cost of recall. Drift and usage are related and only the history over time can predict the normal time interval to assure specification compliance. Tight tolerances may require more frequent calibrations. Time interval is also selected by determining the risk of non-compliance and the cost of a product recall. The longer the time between calibrations, the more costly the recall.
Conclusion: Generally accepted times between calibrations for electronic devices are one year. Most companies and calibration authorities believe this balances the cost of calibration with the cost of recall. Time intervals between calibrations for other products are not so generally agreed upon and a statistical analysis of data and a business analysis of risk will determine the proper interval between calibrations.
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