Frequency of re-calibration should be based on the critical nature of those ESD sensitive items handled and the risk of failure for the ESD protective equipment and materials. In general, EMIT recommends that calibration be performed annually. Use the EMIT 50426 Limit Comparator to perform periodic verification (once every 6-12 months) of the Desco Combo Tester X3 and EMIT SmartLog Pro. The Limit Comparator can be used to check the test limits of these testers without removing them from the factory floor. The EMIT 50426 Limit Comparator is compatible with the following items: