Reed Instruments R5001 - Resistance Measurement Types (DC vs AC); Understanding the Guard Terminal; Calibration Procedure for Accuracy

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Resistance
When measuring resistance of devices, it is important to know that there are
two types or ways of measurement. One type is DC resistance measurement.
Another type is AC resistance measurement. The LCR meter provides both
types of measurement.
Before using the meter to measure resistance, please verify whether
theDUT(deviceundertest)requiresDCorACresistancemeasurement
method. Depending on the method, results will vary greatly.
Guard Terminal
Oneoftheinputsocketsandterminalsislabeledas"GUARD".This
terminal does not have to be used in all instances for the meter to provide
measurements.Butinsomeinstances,itisveryuseful.Guardterminal
generally serves two purposes.
If user is using test leads, the guard terminal can be used to connect to
the shielding of the test leads. Doing so can be useful when making large
resistivecomponentmeasurements.Forexample,whenmeasuringa10
MΩresistorwithtestleads,atthehighrangethereadingmayseemtobe
unstableasafewdigitsmaycontinuouslybechanging.Havingtheshield
of the test leads connected to the guard terminal will help stabilize the
reading in some instances.
Guardterminalisalsousedtominimizenoiseandtohelpminimizeparasitic
effects coming from the component being measured, thus allowing high
precision results.
Calibration Mode
It is recommended to regularly calibrate this meter to improve the accuracy
ofhigh/lowimpedancemeasurements.
Note: You will need a shorting bar or a short piece of conductive metal
(i.e.paperclip)tocompletethecalibrationprocedure.
1. Be sure nothing is connected to the meter, and turn it on.
2. Press and hold down the CAL button for 2 seconds to enter
calibration mode.
3. Thescreenwilldisplay"OPEN",indicatingtheinputterminalshave
nothing connected.
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