Resistance measurement circuit for corroded conductors - uses differential amplifier with one input connected to measurement contact, other to conductor at known press. contact

摘要

A circuit for measurement of the resistance between a measurement contact and a contaminated conductor includes allowance for the connection resistance of the measurement device. It is used after a contact material is prepared in an air conditioned cabinet. Very high measurement accuracy is achieved over a wide operating range. To avoid sintering, the test voltage and current are held at 20 millivolts and 20 milliamps. Thermo-diode effect on the corroded surface and other errors are excluded. A variable voltage source is connected to one end of the conductor and to the measurement contact. A differential amplifier has one input connected to the contact and the other to the other end of the conductor. Its output is processed in further circuitry whilst the contact is applied with known force.