HOW TO MAKE PRECISE
CAPACITANCE AND INDUCTANCE
MEASUREMENTS USING AN LCR
METER
Name: M Khoza
Date: 13 October 2015

Table of Contents
 Overview
 Comparison Reported Results
 Definition of an LCR Meter
 LCR Meter Calibration
 LCR Meter Circuit Modes
 Equipment Setup and Connections
 Source of Errors & Preventative Action
 Aspects of Consideration

Overview
 Accredited laboratories participated in the 2011 inductance and 2013 capacitance interlaboratory comparisons.
 LCR meter used as a measuring and transfer standard.
 Laboratories imported traceability from the pilot laboratory,NMISA.
 The normalised error (E n
) values of the reported results were calculated as a measure of the proficiency. Values greater than plus or minus one required investigation.
 The outcome of investigation noted the incorrect use of the
LCR meter.

Comparison Reported Results

Definition of an LCR Meter
 LCR meter is an electronic piece of equipment that measures the inductance, capacitance and resistance of a passive component.
 The current through and voltage across the component, and phase difference between the voltage and current measured.
 Capacitance, inductance and resistance of the component calculated using measured quantities

LCR Meter Calibration
 Two types of LCR meter calibrations: open/short and traceable calibrations
 Open/short calibration
Compensates the residual capacitance, inductance and impedance of the test fixture and cables.

LCR Meter Calibration cont:
 Traceable calibration
Performed to check the accuracy of the instrument against calibrated reference standards.
Link the measurements performed by LCR to SI units
Standard capacitors (3T)
Standard inductors Standard capacitors (4T)

LCR Meter Circuit Modes
 Two types of circuit modes: Parallel and Series
 Parallel mode is the default for capacitance and resistance measurements
 When the reactance is large, the series resistance is negligible and then the parallel model is used
 Series mode is the default for inductance measurements
 When the reactance is small, the parallel resistance is negligible and then the series model is used

LCR Meter Circuit Mode cont:

Equipment Set up and connections
 Types of connections: 2-terminal, 3-terminal and 4-terminal
2-terminal 3-terminal 4-terminal
Errors: lead inductance, resistance and stray capacitance
NB: less accurate
Guad terminal elimanates the lead inductance and resistance, stray capacitance
NB: accurate
Effectively removes lead inducatnce and resistance, and stray capacitance
NB: precise and accurate

Equipment Set up and connections cont:
3 Terminal
2 Terminal
4 Terminal

Equipment Set up and connections cont:
3 Terminal: capacitance
2 Terminal: inductance
2 Terminal: capacitance
4 Terminal: capacitance

Source of Errors & Preventative Action
Two different reported results, which is correct?
Source of errors Preventative action signal signal

Aspects of consideration
 Open/short calibration
 Traceable calibration
 Test voltage, current and frequency
 Proper connections
 Accuracy specifications