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LCR meter working principle | LCR meter types, LCR meter measurements

This page describes LCR meter working principle and mentions LCR meter types and its measurements. It mentions LCR meter advantages and LCR meter manufacturers or vendors.

What is LCR meter ?:
As we know L stands for inductance, C stands for Capacitance and R stands for resistance. The device which measures these parameters is known as LCR meter.

Digital LCR meter type measures I(through DUT) and V (across DUT) and phase angle between measured I and V. From these measured parameters useful impedance parameters are calculated. LCR meter can also be used to measure impedance which is later converted to L, C or R for display.

LCR meter types

There are two LCR meter types viz. benchtop and handheld. Benchtop are developed for bench applications and hence are kept at fixed location without much of movement. Handheld are developed for portable applications and hence can be moved around for test and measurement purpose.

Handheld LCR meters are lightweight and are battery powered. It usually will have USB port to transfer data tothe PC/Laptop. It provides measurement of inductance and AC resistance. It will usually have measurement accuracy between 0.1% to 0.2%.

Benchtop LCR meter will have additional features compare to handheld type such as programmable frequency setting. It will have very higher measuement accuracy of about 0.01%. It provides advanced measurement capabilities such as DC bias current and voltage, sweep etc. This type of LCR meter is used for AC calibration of L, C and R. Typically measurements is performed at frequencies such as 100Hz, 120Hz, 1kHz and 10kHz.

Based on display formats LCR meter types are further categorized into analog and digital. Analog type are cheaper compare to digital type as they are made of basic discrete components. Digital type are costlier but are more accurate compare to analog counterpart.

LCR meter working principle | How LCR meter works

LCR meter working principle, How LCR meter works, LCR meter nulling bridge type

Before we move to understand how LCR meter works, let us understand concept of impedance first. As shown in the figure, impedance consists of two parts viz. resistance (i.e. real) and reactance(i.e. imaginary). Zs represents series impedance which is combination of resistance(Rs) and reactance(Xs).

Impedance can be expressed with magnitude |Z| and phase angle θ When θ>0 the reactance is inductive and when θ<0 the reactance is capacitive. There are two reactance types viz. inductive reactance (XL) and capacitive reactance (XC). They can be expressed as follows:
XL = 2*π * f * L
XC = 1/ (2* π * f * C)

Impedance can be measured either in series or in parallel mode. Impedance in parallel mode can be expressed as reciprocal of admittance(Y).
Here , Z=1/Y,
Y = G + j*B, where G = Conductance and B = Susceptance

There are various techniques for the measurement of impedance. The most common method is nulling type bridge as shown in the figure-1 above. When there is no current flow through detector(D), value of unknown impedance can be expressed as follows:
Zx = (Z1/Z2)*Z3

Different applications use different combinations of L, C and R as elements of the bridge. Hence LCR meter working principle depends on its application usage.

LCR meter Advantages

Following are the advantages of LCR meter:
• User friendly to operate.
• It measures passive components with minimal of errors.
• This instruments are very easy in calibration.
• There are many companies which manufactures the LCR meter and hence more features and options are available for user to purchase.

LCR meter manufacturers or vendors

Following are the best LCR meter manufacturers or vendors:
1. Keysight technologies
2. Meco Instruments P.Ltd (www.mecoinst.com)
3. IET Labs, Inc. (www.ietlabs.com)
4. Scientific Mes-Technik Pvt. Ltd. INDIA
5. Extech Instruments
6. InnovateUs Inc.
7. Stanford Research Systems, Inc.
8. Sigma Instruments

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