Which device is used to scale down voltage and current for measurement while preserving the waveform?

Which device is used to scale down voltage and current for measurement while preserving the waveform?

• A. Auto transformer
• B. Megohmmeter
• C. Instrument transformer
• D. Variable transformer

Answer: (C)

Instrument transformers are designed to safely scale down high voltages or currents to levels that metering equipment and protective relays can handle, while keeping the waveform shape and phase information intact. A voltage transformer reduces high system voltage to a lower, proportional voltage, and a current transformer does the same for current, all with galvanic isolation so the measuring devices are protected from the live circuit. This accurate, linear scaling allows meters and relays to read true values without distortion or significant loading of the circuit. The other devices don’t fit this purpose. An auto transformer changes voltage without providing isolation, which can compromise safety and measurement accuracy in many applications. A megohmmeter measures insulation resistance, not for scaling signals for measurement. A variable transformer can adjust voltage levels but isn’t intended to provide safe, isolated, waveform-preserving scaling for measurement and protection.

Instrument transformers are designed to safely scale down high voltages or currents to levels that metering equipment and protective relays can handle, while keeping the waveform shape and phase information intact. A voltage transformer reduces high system voltage to a lower, proportional voltage, and a current transformer does the same for current, all with galvanic isolation so the measuring devices are protected from the live circuit. This accurate, linear scaling allows meters and relays to read true values without distortion or significant loading of the circuit.

The other devices don’t fit this purpose. An auto transformer changes voltage without providing isolation, which can compromise safety and measurement accuracy in many applications. A megohmmeter measures insulation resistance, not for scaling signals for measurement. A variable transformer can adjust voltage levels but isn’t intended to provide safe, isolated, waveform-preserving scaling for measurement and protection.