Which of the following can damage a multimeter?
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.
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 Application
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.
Key Concepts
Why Other Options 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.
题目解析
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.
考试技巧
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.
记忆口诀
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.
实际应用示例
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.
错误选项分析
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.
知识点
Multimeter safety, Measurement errors, Meter damage, Proper meter use
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.