nVent ERICO testers are designed for rapid testing of the integrity of surge protection device components. Because standard metal oxide varistors, gas arresters, and avalanche diodes do not provide the user with a visual indication of the integrity of the protection capacity, an external means of testing is required. It is impossible to predict when these failures will occur without some form of testing. As MOVs approach the end of their life cycle, they exhibit a change in tolerance levels. nVent ERICO testing products are specifically designed to identify these situations and allow the operator to effect remedial replacement to the devices which are nearing the end of their life cycle. They can test both components, as well as replacement modules such as the TDS or DSD.