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 bad/ 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 printed ESR table for fast check. RangeAccuracy(After zero,Refresh Time(Manual Mode) tested with 1,10,100RAuto mode take 0 to 2s, more time resistor depends on capacitance value. 0.000 to 1.000R1%+2Digit~0.4s 1.000 to 10.00R1%+1Digit~0.4s 10.00 to 100.0R2%+1Digit~0.4s Accuracy: Up to 1% (detail on above table) Wide Measurement Range: 1uF High Resolution: 4 digit, or 0.001Ohm @ 1 ohm range Measuring : Less than ~40mV (TESTING ) External Power: 5V -USB Operating Current: 0.02A Battery: 2 * AA 1.5V Battery (not included) Battery Life time: 80 Hours Item Size: 14.5 x 8 x 3cm / 5.7 x 3.1 x 1.2in Item Weight: 139.6g / 4.9oz Colour:Orange-yellow Material:plastic Package Contents: 1x Capacitance Meter 2x Test Clips Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.