CALIBRATION

Calibration is a comparison between measurements of known magnitude with one device and another measurement made in as similar a way as possible with a second device.

Defi nition

Calibration ???!!!

Digital multimeters usually have built-in processors that handle measurements using stable voltage references. Unlike digital multimeters, analog multimeters need to be calibrated to maintain accuracy.

Analog multimeters usually have adjustable resistors called trimmer resistors that may be used to compensate for different conditions.

Analog .vs. digital

Basic calibration processThe calibration process begins with the design

of the measuring instrument that needs to be calibrated.

voltmeter

Think how can we calibrate voltmeter?

Calibrating a voltmeter is a two step approach.

 

Think again now for Ammeter how to calibrate?

HINT Ohm’s

law

Ammeter calibration1 Connect the two

terminals of the voltmeter to across the resistor.

2Connect the two terminals of the ammeter in series with the resistor. This will allow the current flowing the resistor to be determined.

3Switch on the voltage supply, and set it to 1 V.

4Calculate the expected value of current using Ohm's law. Ohm's law states V=IR, In this case, the expected current is I=V/R. Compare this with the measured value shown on the ammeter. If the values are different, adjust the calibration knob on the ammeter to match 1mA.

Last one ohm meter how calibrate ?

Ohmmeter calibrationA rough calibration of an ohmmeter may be performed by

measuring a standard resistance and noting the reading

Do this similar standard procedure with different resistance values , This will allow one to obtain an indication of the correct measurements