Voltmeter loading: On a higher voltage range, a voltmeter's internal resistance becomes smaller, increasing load effect on the circuit. True or false?

Introduction / Context:
Voltmeter loading refers to how much a measuring device disturbs the circuit under test. The internal resistance of the voltmeter largely determines this loading. Understanding how range switching affects internal resistance is crucial to obtain accurate measurements.

Given Data / Assumptions:

• Conventional analog DC voltmeters use a sensitive movement plus series multiplier resistors.
• Higher voltage ranges are selected by adding more series resistance.
• Digital voltmeters typically present a very high, nearly constant input resistance (e.g., 10 MΩ), independent of range for DC measurements.

Concept / Approach:

In analog meters, the total internal resistance R_in increases with selected range because more series resistance is inserted to limit current through the movement. Higher R_in means less loading (better). In digital meters, R_in is already very high and often remains effectively constant, minimizing loading regardless of range.

Step-by-Step Solution:

Verification / Alternative check:

Model the circuit: a source with Thevenin resistance Rs feeding a node. The measured node voltage with meter is V_meas = Vs * (R_in / (Rs + R_in)). As R_in increases (higher range for analog), V_meas approaches the true Vs with minimal drop, confirming reduced loading.

Why Other Options Are Wrong:

• Selecting “True” contradicts the behavior of multiplier resistors in analog meters and the near-constant high input resistance in DVMs.

Common Pitfalls:

Confusing current range switching (which lowers internal shunt resistance in ammeters) with voltage range switching (which increases series resistance in voltmeters). The two instruments behave in opposite ways regarding internal resistance.

Final Answer:

False