Instrument selection: Which piece of test equipment is specifically designed to measure resistance values accurately in ohms (Ω)?

Introduction / Context:
Proper instrument choice prevents damage to equipment and improves measurement accuracy. Resistance measurement is common for verifying components, checking sensor elements, and troubleshooting open or short circuits. Knowing which meter function to use saves time and avoids misreadings.

Given Data / Assumptions:

• Standard benchtop or handheld digital multimeters (DMMs) are available.
• Device under test is unpowered during resistance measurements unless a specialized method is used.
• Leads are zeroed or compensated if very low resistances are being measured.

Concept / Approach:
An ohmmeter applies a small test current and measures the resulting voltage drop (or vice versa) to compute resistance via R = V / I internally. The ammeter measures current, and the voltmeter measures potential difference; these are not direct resistance measurement instruments, though resistance can be inferred indirectly with additional steps. A watt meter measures power and is not used for passive component value checks.

Step-by-Step Solution:

Verification / Alternative check:
Validate with Ohm’s law using a known current source and a voltmeter: apply a known I and measure V, then compute R = V / I. The indirect result should match the ohmmeter within tolerance.

Why Other Options Are Wrong:

• Ammeter: Measures current in amperes.
• Voltmeter: Measures voltage in volts.
• Watt meter: Measures power in watts.

Common Pitfalls:
Measuring resistance in-circuit while powered can damage the meter or produce incorrect readings. For low-ohm measurements, compensate for lead resistance using the REL/zero function or a 4-wire method.

Final Answer:
ohmmeter