The Keithley Model 502 is a battery operated, portable milliohmmeter
for measuring resistances from 0.00003 to 1000 ohms. The instrument
employs an AC testing method, eliminating zero drift and permitting
resistance readings in the presence of DC currents.
The reading is presented an a linear scale panel meter.
Typical applications of the instrument include measurement of contact
resistance, conductivity of semi-conductor samples, fuse and
squib testing, and electrolyte conductivity.
Maximum power dissipation in the sample is 2 microwatts, permitting
the measurement of detonator fuses without danger of detonation.
In the measurement of contact resistance, the model 502 may be
considered a "dry circuit" tester. However, the instrument may be
used in the presence of DC biasing currents to measure the change
in resistance caused by these currents.