A 0 to 200 V voltmeter has a guaranteed accuracy of 0.5 percent of full scale deflection. The voltage measured by the instrument is 50 V. Find the limiting error.

Concept:
Limiting error: The maximum allowable error in the measurement is specified in terms of true value, which is known as limiting error. It will give a range of errors. It is always with respect to the true value, so it is a variable error.

\({\rm{\% L}}imiting\;Error\;\left( {\% L.E.} \right){\rm{\;}} = \frac{{Limiting\;Error\;\left( {L.E.} \right)}}{{True\;value}} \times 100\)

Guaranteed accuracy error: The allowable error in measurement is specified in terms of full-scale value is known as guaranteed accuracy error. It is a variable error seen by the instrument since it is with respect to full-scale value.

\({\rm{\% Guaranteed\;accuracy\;error\;}} = \frac{{Limiting\;Error\;\left( {L.E.} \right)}}{{Full\;scale\;value}} \times 100\)

Calculation:

Full scale voltage = 200 V

Accuracy = 0.5%

Voltage to be measured = 50 V

The limiting error is given as:-

= \(\frac{0.5}{{100}} \times 200\times \frac{1}{{50}}\)

=2/100

= \(\frac{2}{{100}} \times 100 = 2\% \)