LCR meter
Encyclopedia
A LCR meter is a piece of electronic test equipment
used to measure the inductance
, capacitance
and, resistance
of a component. In the usual versions of this instrument these quantities are not measured directly, but determined from a measurement of impedance
. The necessary calculations are, however, incorporated in the instrument's circuitry; the meter reads L, C and R directly with no human calculation required.
Usually the device under test
(DUT) is subjected to an AC
voltage source
. The meter detects the voltage
over, and the current through the DUT. From the ratio of these the meter can determine the magnitude of the impedance. The phase angle
between the voltage and current is also detected and between that and the impedance magnitude the DUT can be represented as an L and R or a C and R. The meter must assume either a parallel or a series model for these two elements. The most useful assumption, and the one usually adopted, is that LR measurements have the elements in series (as would be encountered in an inductor coil) and that CR measurements have the elements in parallel (as would be encountered in measuring a capacitor with a leaky dielectric).It can also be used to judge the inductance variation with respect to the rotor position in permanent magnet machines.
Electronic test equipment
Electronic test equipment is used to create signals and capture responses from electronic Devices Under Test . In this way, the proper operation of the DUT can be proven or faults in the device can be traced and repaired...
used to measure the inductance
Inductance
In electromagnetism and electronics, inductance is the ability of an inductor to store energy in a magnetic field. Inductors generate an opposing voltage proportional to the rate of change in current in a circuit...
, capacitance
Capacitance
In electromagnetism and electronics, capacitance is the ability of a capacitor to store energy in an electric field. Capacitance is also a measure of the amount of electric potential energy stored for a given electric potential. A common form of energy storage device is a parallel-plate capacitor...
and, resistance
Electrical resistance
The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical...
of a component. In the usual versions of this instrument these quantities are not measured directly, but determined from a measurement of impedance
Electrical impedance
Electrical impedance, or simply impedance, is the measure of the opposition that an electrical circuit presents to the passage of a current when a voltage is applied. In quantitative terms, it is the complex ratio of the voltage to the current in an alternating current circuit...
. The necessary calculations are, however, incorporated in the instrument's circuitry; the meter reads L, C and R directly with no human calculation required.
Usually the device under test
Device under test
Device under test , also known as unit under test , is a term commonly used to refer to a manufactured product undergoing testing.-In semiconductor testing:...
(DUT) is subjected to an AC
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
voltage source
Voltage source
In electric circuit theory, an ideal voltage source is a circuit element where the voltage across it is independent of the current through it. A voltage source is the dual of a current source. In analysis, a voltage source supplies a constant DC or AC potential between its terminals for any current...
. The meter detects the voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
over, and the current through the DUT. From the ratio of these the meter can determine the magnitude of the impedance. The phase angle
Phase angle
In the context of vectors and phasors, the term phase angle refers to the angular component of the polar coordinate representation. The notation A\ang \!\ \theta, for a vector with magnitude A and phase angle θ, is called angle notation.In the context of periodic phenomena, such as a wave,...
between the voltage and current is also detected and between that and the impedance magnitude the DUT can be represented as an L and R or a C and R. The meter must assume either a parallel or a series model for these two elements. The most useful assumption, and the one usually adopted, is that LR measurements have the elements in series (as would be encountered in an inductor coil) and that CR measurements have the elements in parallel (as would be encountered in measuring a capacitor with a leaky dielectric).It can also be used to judge the inductance variation with respect to the rotor position in permanent magnet machines.