Deep Dive: T7D06
The correct answer is C: Attempting to measure voltage when using the resistance setting. Attempting to measure voltage when using the resistance setting can damage a multimeter. When a multimeter is set to resistance (ohms), it applies a small voltage from its internal battery to measure resistance. If you then connect it to a circuit with external voltage (like a powered circuit), that external voltage can damage the meter's internal circuits, especially the resistance measurement circuitry. For amateur radio operators, this is a common mistake that can destroy expensive meters. Always ensure the meter is set to the correct function before making measurements.
Why Other Answers Are Wrong
Option A: Incorrect. Measuring resistance using the voltage setting won't damage the meter - it just won't give a correct reading. The meter is designed to handle this mistake. Option B: Incorrect. Not connecting a probe to ground won't damage the meter - it just means you won't get a measurement. Ground connection is for safety, not meter protection. Option D: Incorrect. Not allowing warm-up time might affect accuracy but won't damage the meter. Modern digital meters don't require warm-up.
Exam Tip
Voltage on resistance setting = damages meter. Think 'V'oltage on 'R'esistance setting = 'V'ery 'R'isky. External voltage applied when meter is in resistance mode can damage internal circuits. Always check the setting first.
Memory Aid
Voltage on resistance setting = damages meter. Think 'V'oltage on 'R'esistance = 'V'ery 'R'isky. External voltage damages resistance measurement circuitry. Check setting before connecting.
Real-World Example
You set your multimeter to resistance mode to check a resistor, but forget to change the setting. You then connect it to a powered circuit to measure voltage. The external voltage from the circuit flows into the meter's resistance measurement circuitry, which isn't designed to handle it, causing damage. The meter may stop working or give incorrect readings. Always verify the meter is on the correct setting before connecting.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T7D
Reference: 2022-2026 Question Pool · T7 - Practical circuits
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T7D topic.