It is a series resistor inside capacitor, using 100kHz to remove the impedance 1/(2*pi*F*C).The impedance become small, and then measure the true series resistor value.Using this , measure the capacitor is / damaged or good in condition. ESR meter only applies less than 15mV DC or to on a good capacitor, as a use it as in circuit test.During repairing TV, LCD, Audio board, etc. in circuit testing the capacitor is good or not.Dual terminal, for fast and easy inspect general capacitor or resistor, a ESR table for fast check.RangeAccuracy(After zero,Refresh Time(Manual Mode)tested with 1,10,100RAuto mode take 0 to 2s, more timeresistor depends on capacitance value.0.000 to 1.000R1%+2Digit~0.4s1.000 to 10.00R1%+1Digit~0.4s10.00 to 100.0R2%+1Digit~0.4sAccuracy: Up to 1% (detail on above table)Wide Measurement Range: 1uFHigh Resolution: 4 digit, or 0.001Ohm @ 1 ohm rangeMeasuring voltage: Less than ~40mV (TESTING VOLTAGE)External Power: 5V -USBOperating Current: 0.02ABattery: 2 * AA 1.5V Battery (not included)Battery Life time: 80 HoursItem Size: 14.5 x 8 x 3cm / 5.7 x 3.1 x 1.2inItem Weight: 139.6g / 4.9ozColour:Orange-yellowMaterial:plasticPackage Contents:1x Capacitance Meter2x Test ClipsOnly the above package content, other products are not included.Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.