Capacitance meter

From Wikipedia, the free encyclopedia

A capacitance meter is a piece of electronic test equipment used to measure capacitors. Depending on the sophistication of the meter, it may simple display the capacitance or it may also measure a number of other parameters such as leakage, equivalent series resistance, and inductance.

[edit] Simple meters

Many DVMs (digital volt meters) also contain a capacitance-measuring function. These usually operate by charging and discharging the capacitor under test with a known current and measuring the rate of rise of the resulting voltage; the slower the rate of rise, the larger the capacitor. DVMs can usually measure capacitors in the range of nanofarads to a few hundred microfarads.

[edit] Bridges

More sophisticated instruments use other techniques such as inserting the capacitor-under-test into a bridge circuit. By varying the values of the other legs in the bridge (so as to bring the bridge into balance), the value of the unknown capacitor is determined. The bridge usually can also measure the other parameters (series resistance and inductance) of interest to the electrical engineer. Through the use of Kelvin connections and other careful design techniques, these instruments can usually measure capacitors over a range extending from picofarads to farads. It's also common to find combined LRC meters that can measure all of: inductance, resistance, and capacitance.

It is also commonly possible to apply a DC bias voltage to the capacitor and measure the leakage current.

Modern instruments in this category usually include a digital display as well as some sort of Go/no go testing to allow simple automated use in a production environment. Beyond that, an IEEE-488 (GPIB) interface allows sophisticated computer control.