LCR Meters
LCR Meters, capacitance meters, impedance analyzers, inductance analyzers test components and materials in a variety of research and design applications and in component manufacturing. LCR Meters measure the inductance (L), capacitance (C) and resistance (R) of a component or Device Under Test (DUT).
These tests are usually done at a specific frequency (measured in Hz). The range of frequency that you test under should match that of the real-world frequencies the components will be used under. Other factors to consider in selecting an LCR meter include test voltage and test current. You may also want to record your measurement results to a PC or USB Memory stick. Or integrate the instrument into your production/test system, utilizing GPIB or an I/O port.
Other related measurements and calculations are usually also provided. Which ones and how many vary depending on model with bench instruments providing the most.
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AC Resistance (Rac)
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Admittance (Y) is the reciprocal of Impedance and measures how easily the electricity flows in an AC circuit. (Y = 1/Z)
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Capacitance (C) measures the amount of electronic charge stored between two terminals . Unit: F or Farad
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Conductance, (G = 1/R), is the reciprocal of Resistance and measures how easily the electricity flows
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DC Resistance (Rdc)
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Impedance (Z) measures the total amount of opposition between two terminals in an AC circuit
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Inductance (L) measures the amount of magnetic flux generated by an electrical current in a conductor or circuit. Changes in current induce an electromagnetic force. Unit: H or Henry
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Phase Angle (θ) measures the phase on which Impedance (Z), Admittance (Y), Quality factor (Q), and Dissipation factor (D) are measured
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Quality Factor (Q) and Dissipation Factor (D). Quality factor (Q) and its reciprocal, Dissipation factor (D = 1/Q), are used for measuring the rate of energy dissipation relative to the measurement frequency
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Low energy dissipation: High Q, low D
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High energy dissipation: Low Q, high D
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Reactance (X) measures the imaginary part of Impedance (Z) caused by capacitors or inductors
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Resistance (R) measures how difficult it is for the electricity to flow between two terminals. Unit: Ω or Ohms
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Susceptance (B) is the reciprocal of Reactance and measures the imaginary part of Admittance (Y)
In general, two items, primary and secondary, are combined in a single measurement. Not all combinations are possible. For measuring AC Resistance, Capacitance, Reactance, Inductance, and Susceptance, series and parallel equivalent circuit models are available.
Instruments with four terminal pairs will eliminate unwanted interference and facilitate more accurate measurements. These are known as “Kelvin” style interfaces. They may be in the form of probes or clips. Some LCR Meters also have test fixtures for loose or non-mounted components.
One of the most common applications for LCR meters is known as binning. This is a sorting method that allows you to quick pass/fail components based on their tolerance accuracy for one or two basic parameters.
Another way to characterize devices is to see how they react under a variety of conditions. This is a parameter sweep. A sweep will take into account a number of measurements, as defined by the user. The parameters typically involved include the start/stop frequency, volts and/or amps, as well as the number of step increments and if the data should be tabular or plotted on a graph.
Binning is a static test and sweeps are dynamic.
In order to simulate real time operating conditions, a bias voltage or current may need to be applied to the device under test. Some LCR meters have the ability to provide this directly from the instrument and others may offer an optional accessory to offer this functionality.
Hand held vs Bench LCR Meters
Hand held LCR meters typically have selectable test frequencies of up to 100kHz, while more advanced bench meters will go higher. Bench meters may even offer graphical displays and step programming. The multi-step function allows on-screen programming of customized measurement sequence with Pass/Fail indication. Under multi-step operation, a tedious work routine can be done step by step automatically just at a press of a button. In addition, bench meters allow the usage of special test fixtures.