ST2521 AC milliohmmeter is used to test contact resistance, internal resistance and battery voltage. The application of constant current source with 1 kHz frequency can greatly eliminate the potential error caused by thermoelectricity on DUT. This AC milliohmmeter has the function to automatically detect contact failures on test cable. There are three versions of milliohmmeter: ST2521, ST2521A and ST2521B with different ranges 1µOhm up to 4kOhm (400 Ohm) and 100µV up to 50V / 200V. With GO-NOGO-comparator and several interfaces (LAN, USB, RS232,...) this AC milliohmmeter is very convenient to be used in automatic production lines.