Electrical Engineering ⇒ Topic : Voltmeter Sensitivity

Voltmeter Sensitivity

The resistance offered per volt of full scale deflection by the voltmeter is called voltmeter sensitivity.

Voltmeter sensitivity indicates the internal resistance of the voltmeter. For example, if the total resistance of the meter is 5000 Ω and the meter is to read 5 volts full scale, then internal resistance of the meter is 1000 Ω per volt i.e. meter sensitivity is 1000 Ω per volt. Conversely, if the voltmeter sensitivity is 400 Ω per volt which reads from 0 to 100 V, then meter resistance is 40, 000 Ω. If the,voltmeter is to read r 'volts full scale and I_m is the full scale deflection (f.s.d.) current, then

Sensitivity is the most important characteristic of a voltmeter. If the sensitivity of a voltmeter is high, it means that it has high internal resistance. When such a meter is connected in the circuit to measure voltage, it will draw a very small current. Consequently, there will be practically no change in the circuit current due to the introduction of the meter. Hence, it will measure the voltage correctly.On the other hand, if the sensitivity of the voltmeter is low, it would cause serious error in voltage measurements. The sensitivity of voltmeters available in the market ranges from 5 kΩ per volt to 20 kΩ per volt.