METROSIL - how to test?

Question

how can i test a disc type METROSL to determine if it is OK or it needs a new one

Answer 1

A Metrocil is a non-linear resistor.. Metrocil was the name given by their developer, Metropolitan Vickers in the UK in the 50s.
So, how would you test a NLR? I guess you would apply a current to the NLR and monitor the current decay. It should make no difference whether your supply was dc or ac. At some point the resistance of the NLR will become so high that the current will almost cease to flow
Hope this is of assistance.