Measurement of Resistance - PPT PDF

Electrical Measurements 

Measurement of Resistances;  Potentiometers;  AC Bridge Methods for Measurement Measurement of

Capacitance; 

Magnetic Measurements

Inductance &

Measurement of Resistances 1. Low Low Resis Resistan tancce: Up to 1Ω; 2. Medium edium Resis Resistan tance ce:: 1Ω to 100KΩ;  3. High Resistanc Resistance: e: Above Above 100K 100KΩ.

Measurement of Medium Resistances: 1. Ammet Ammeterer-V Voltmet oltmeter er Meth Method; od; 2. Subst Substitu itute te Metho Method; d;  3. Wheatstone Wheatstone Bridge Bridge Method; 4. Ohmmet Ohmmeter er Method. ethod.

1. Ammeter-V Ammeter-Voltmeter oltmeter Method:

 Rm1

V  R + V a = =    =  R + Ra  I   I  V 

   Ra     R =  Rm1   1 −    Rm1 

 Rm 2 =

V   I  R +  I V 

=

 R  R

1+

      1   R =  Rm 2    Rm 2   1− V     R  

 RV 

2. Substitution Method: Method:

 Accuracy of this method is greatly affected if there is any change in  Accuracy the th e ba batttery em emff. This method is not widely used for medium resistance measurements and is used in a modifi fie ed form for measurement of  high resi resistanc stances. es.

 3. Wheatstone Wheatstone Bridge Bridge Method: Method:  I 1 P  =  I 2 R  I 1 =  I    3 =

 I 2 =  I    4 =

P Q

=

 E  P+Q

 E   R + S 

 R S