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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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The multiplier and the meter coil in a voltmeter are in
Series
Parallel
Series-parallel
None of the above
Series
Quick Summary: In a voltmeter, the multiplier is a high-value resistor connected in series with the meter movement (usually a PMMC coil). This configuration is essential to limit the current flowing through the sensitive meter coil to a safe level, allowing it to measure higher voltage ranges than its basic full-scale deflection capability would otherwise permit.
In a voltmeter, the multiplier is a high-value resistor connected in series with the meter movement (usually a PMMC coil). This configuration is essential to limit the current flowing through the sensitive meter coil to a safe level, allowing it to measure higher voltage ranges than its basic full-scale deflection capability would otherwise permit.
V=Ifsd(Rm+Rs) — Total voltage drop across the voltmeter
Rs=Rm(VfsdV−1) — Value of multiplier resistor required for a desired voltage range
The basic meter coil has a very low internal resistance (Rm). By connecting a large resistor (Rs) in series, the total resistance of the voltmeter becomes Rv=Rs+Rm. According to Ohm's Law, I=V/Rv, which ensures that even at high input voltages, the current I remains proportional to the voltage but is maintained below the full-scale deflection current (Ifsd) of the meter.
The multiplier resistor is constructed from high-stability materials like Manganin or Constantan.
A voltmeter is always connected in parallel with the circuit element whose voltage is to be measured.
The sensitivity of the voltmeter is defined in Ω/V and is the reciprocal of the full-scale deflection current (S=Ifsd1).
Enables measurement of high voltages using a low-range meter.
Increases the input resistance of the voltmeter, minimizing loading effects on the circuit under test.
High-value resistors can lead to thermal drift if not temperature-compensated.
Increases the overall physical size of the instrument.
Analog Multimeters (VOM)
DC Voltmeter range extension
Switchboard panel meters
The multiplier must have high resistance to ensure the voltmeter draws negligible current from the circuit, preserving measurement accuracy.
Option B (Parallel) is incorrect because connecting a resistor in parallel with a meter movement would shunt current away from the coil, which is the principle used in Ammeters, not Voltmeters.
A is correct — The multiplier is connected in series with the meter coil to limit the current and extend the voltage range of the instrument.
Always remember: Ammeters use a parallel shunt to bypass current, while Voltmeters use a series multiplier to restrict current.