Patent ID: 8432172

Claim:
A measuring apparatus for capacitor applied to a charging power source and a capacitor to be measured, the measuring apparatus including: a microcontroller unit; an analog-digital converter unit, wherein the analog-digital converter unit is electrically connected to the microcontroller unit and the capacitor to be measured; a charging-side switch unit, wherein the charging-side switch unit is electrically connected to the microcontroller unit and the charging power source; a charging-side resistor unit, wherein the charging-side resistor unit is electrically connected to the charging-side switch unit; a discharging-side switch unit, wherein the discharging-side switch unit is electrically connected to the microcontroller unit and the charging-side resistor unit; and a discharging-side resistor unit, wherein the discharging-side resistor unit is electrically connected to the discharging-side switch unit, the charging-side resistor unit, the analog-digital converter unit and the capacitor to be measured, and the discharging-side resistor is directly connected between the charging-side resistor unit and the capacitor to be measured, wherein the capacitor to be measured is charged and discharged by the charging-side switch unit and the discharging-side switch unit, both of which are controlled by the microcontroller unit; charging and discharging voltage and time variation of the capacitor to be measured are measured by the analog-digital converter unit to calculate a capacitance value of the capacitor to be measured, and when charging the charging power source is electrically connected to the charging-side resistor unit by the charging-side switch unit and the discharging-side switch unit is not connected to a ground, so that the capacitance value is calculated as: C x =−T chg /{( R ref +R 1 )*ln [1=(Δ V/V DD )]} wherein, C x is capacitance value, T chg is a charging time, R ref is a resistance value of the charging-side resistor unit, R 1 is a resistance value of the discharging-side resistor unit, V DD is a voltage value of the charging power source and ΔV is a charging voltage variation, and when discharging, the charging power source is cut from the charging-side resistor unit by the charging-side switch unit and the discharging-side switch unit is connected to the ground, so that the capacitance value is calculated as: C x =−T disc /{R 1 *ln [1−( V 2 /V 1 )]} wherein, T disc is a discharging time, V 2 is a voltage after discharging and V 1 is a voltage before discharging.