Sharmasons sakova instruments offers portable contact resistance meter. It is a micro-ohm-meter. The input is 230 v, 1 phase, 50 hz, and output 0-100 a dc. The metering is41/2 digit millivoltmeter with range 0-200 mv/2000 mv and 31/2 digit ammeter 0-100 a. The contact resistance is measured on the principle of voltage drop. A current, variable up to 100 a is passed through the equipment under test is indicated by the ammeter and the potential drop across the contact is measured by the millivoltmeter. The contact resistance is obtained by dividing the mv reading by the current reading. The instrument comprises of a variac, loading transformer, a rectifier, ammeter and millivoltmeter housed in an insulated [fibre glass] cabinet.
