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  • HOW CAN WE FIND ZERO ERROR AND LEAST COUNT  OF VOLTMETER AND AMMETER?

First inspect the voltmeter/ammeter indicator hand with no connection to it. If the indicator hand is in the zero position then the zero error  is 0. If it is it is showing 1 division then the zero error is 1 division and it should be added to the voltage/ current measurement after connecting to circuit.

 Above case is called +ve zero error
If the indicator hand is found beyond the 0 mark in off state of the meter, then the zero error is called negative zero error and the no. of divisions must be subtracted from the final reading
 

Least count is the lowest possible measurement possible by a device. If suppose a voltmeter has marks such that 10 small divisions make 1 volt then the least count will be 1/10 th of a volt. if 10 small divisions are shown 10 volt then the least count will be 1 volt
Similarly same follows for ammeter
 

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If the needle of ammeter or voltmeter is not on zero, then it is having zero error.

To find the least count, we should find the difference between two successive readings. Then we should count the no. of smaller readings between the two readings. then we should divide the difference between the two readings by the no. of smaller divisions.

 For example,  there is a voltmeter with readings - 0.1 , 0.2 , 0.3 , 0.4 and 0.5.  there are 10smaler divisions between 0.3 and 0.4. and the difference between 0.4 and 0.3 is 0.1.

then divide 0.1 by 10. =0.01

Hence 0.01 is the least count of the voltmeter.

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