Ohmmeter usage and safety: When measuring resistance with a multimeter, how should the component or circuit be prepared for an accurate reading?

Introduction / Context:
An ohmmeter injects a small known current and measures the resulting voltage to calculate resistance. Measuring resistance on a live or connected circuit causes false readings and can damage the meter. Proper isolation ensures accuracy and safety.

Given Data / Assumptions:

• A standard digital multimeter with an ohms function is used.
• We want the resistance of a component, not the combined resistance of parallel paths.
• The circuit may otherwise be energized or have stored charge (capacitors).

Concept / Approach:

To measure resistance correctly, the component must be isolated from the rest of the circuit so that no alternate current paths exist. This is achieved by “breaking the circuit”—disconnecting at least one lead of the component—or by removing the component entirely. Power must be off; any residual voltage sources should be discharged to avoid meter damage and incorrect readings.

Step-by-Step Solution:

Verification / Alternative check:

Compare the measured value to the component’s color code or datasheet tolerance. Reconnect and test circuit function to confirm the component behaves as expected under operation.

Why Other Options Are Wrong:

• In parallel/in series: these describe circuit connections, not preparation steps for resistance measurement.
• After checking voltage/current: measuring voltage/current is useful, but it does not satisfy the isolation requirement for an accurate ohms reading.

Common Pitfalls:

Measuring resistance with power applied; not isolating one leg so parallel paths lower the reading; not accounting for lead resistance on very low ohm measurements; failing to discharge capacitors which can momentarily drive the meter.

Final Answer:

after breaking the circuit