Test device for easily testing of PTC-resistor relays for correct function Normal PTC-resistor relays can be tested by simply disconnecting the sensor. PTC-resistor relays with monitoring of sensor short-circuit and break need more sophisticated test-equipment. With help of the ZIEHL MS-Tester also these relays can be easily tested for correct function. The included cable is designed for the connection of relays type MSF 220 V(U). Also any other PTC-resistor relay can be connected to the MS-Tester. **Test** disconnect the PTC-resistor relay connect the MS-Tester (T/0, T/1 and/or T/3) to the sensor inputs switch on the relay increase the resistance with the potentiometer (turn slowly) until the appropriate Alarm switches reduce the resistance until the relay switches back (or a LED signals, that it is ready to switch back) if necessary, the values of the switching points can be measured at the terminals T/0, T/1, T/2 after disconnecting the relay. Typical values are 3000 Ω ... 4000 Ω for tripping and >1500 Ω for switching back. test break with push-button (only at relays with monitoring of sensor/line-break) test short circuit with push-button (only at relays with monitoring of sensor/lineshort-circuit) **ATTENTION:** At relay MSF 220 V(U), break or short-circuit in any sensor will result in an error message = ALARM 1. The LED "sensor" lights and the LED of the appropriate alarm blinks. HINT: cold PTCs have a resistance of 20...250 Ω, typical 50...120 Ω per sensor. Design: Mount in switchgear cabinet Applications: Protection of transformers