The Keithley 580 Micro-ohmmeter combines high accuracy, resolution, and sensitivity. When measuring contact and connector resistances, it is important not to puncture oxides and films that may have formed. The Model 580 ensures this dry-circuit condition by clamping the open-circuit test voltage to 20mV on the 200mohm, 2ohm, and 20ohm ranges when the 20mV MAX button is pressed.The Model 580 can test more devices by enabling both test current polarity and waveform (DC or pulsed) to be selected. When using pulsed test current, the Model 580 automatically compensates for thermoelectric EMFs. Tests on inductive devices are best performed using DC test current, as this avoids the effects of time constants on pulsed current resistance measurements. For temperature-sensitive components, a single trigger mode of operation minimizes power delivered to the device. Resistance measurements can be made from 10uohm to 200kohm on seven ranges, with 41/2-digit resolution and accuracy to within 0.04% of reading. Ranging can be performed either manually or automatically.