Editing Capacitance (section)

== Measuring capacitance ==
{{Main|Capacitance meter}}
A [[capacitance meter]] is a piece of [[electronic test equipment]] used to measure capacitance, mainly of discrete [[capacitor]]s. For most purposes and in most cases the capacitor must be disconnected from [[electronic circuit|circuit]].

Many DVMs ([[Voltmeter|digital volt meter]]s) have a capacitance-measuring function. These usually operate by charging and discharging the [[Device under test|capacitor under test]] with a known [[Electric current|current]] and measuring the rate of rise of the resulting [[voltage]]; the slower the rate of rise, the larger the capacitance. DVMs can usually measure capacitance from [[Farad|nanofarads]] to a few hundred microfarads, but wider ranges are not unusual.  It is also possible to measure capacitance by passing a known [[high-frequency]] [[alternating current]] through the device under test and measuring the resulting [[volt]]age across it (does not work for polarised capacitors).

[[Image:AH2700 cap br.jpg|thumb|right|An [http://www.andeen-hagerling.com Andeen-Hagerling] 2700A capacitance bridge]]

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. This method of ''indirect'' use of measuring capacitance ensures greater precision. Through the use of [[four-terminal sensing|Kelvin connection]]s and other careful design techniques, these instruments can usually measure capacitors over a range from picofarads to farads.