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.

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.