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 (En) 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 capacitors (4T) Standard inductors

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: Guad terminal Effectively removes lead inductance, elimanates the lead inducatnce resistance and lead inductance and resistance, and stray capacitance and resistance, stray capacitance NB: less accurate stray capacitance NB: precise and accurate NB: accurate

Equipment Set up and connections cont:

2 Terminal

4 Terminal

3 Terminal

Equipment Set up and connections cont:

2 Terminal: capacitance

3 Terminal: capacitance

4 Terminal: capacitance

2 Terminal: inductance

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

Thank you