Question T0A12
From subelement T0 - T0A
Which of the following precautions should be taken when measuring high voltages with a voltmeter?
Why is this correct?
The correct answer is B because using test equipment rated below the voltage being measured can damage the meter or create serious safety hazards. A voltmeter rated for 50 volts could be destroyed when measuring 1000 volts, potentially causing injury. The other options are incorrect: low impedance isn't required for voltage measurements, grounding through the voltmeter creates unsafe conditions, and frequency settings don't apply to basic DC/AC voltage measurements.
Memory tip
When dealing with electrical measurements, always match your tool's ratings to the job. This 'rating matching' principle applies beyond voltmeters to all test equipment, connectors, and components. The equipment's maximum ratings aren't suggestions—they're safety and operational limits that protect both you and your equipment.
Learn more
High-voltage measurements require proper safety margins in your test equipment. Professional voltmeters often have CAT (Category) ratings that specify both voltage and energy levels they can safely handle. Using underrated equipment violates fundamental safety practices and can result in arc flash, equipment destruction, or personal injury. Part 97 emphasizes amateur station safety, making proper test equipment selection a regulatory as well as practical concern.
Think about it
Why do you think the voltage rating of test leads is just as critical as the voltmeter itself when measuring high voltages?