Which of the following precautions should be taken when measuring high voltages with a voltmeter?
Ensure that the voltmeter has very low impedance
Ensure that the voltmeter and its leads are rated for use at the voltages being measured✓Правильный ответ
Ensure that the circuit is grounded through the voltmeter
Ensure that the voltmeter is set to the correct frequency
Объяснение
Meters and test leads carry a maximum voltage rating covering both insulation and internal construction, and using them beyond that rating risks flashover, meter damage and injury to the person holding the leads. A very low meter impedance would load the circuit and give wrong readings, and grounding the circuit through the meter is not a safety measure.