What is the best instrument to measure the current in a high-voltage supply line?

What is the best instrument to measure the current in a high-voltage supply line?

• A. Analog voltmeter
• B. Clamp-on ammeter
• C. Digital multimeter
• D. Wattmeter

Answer: (B)

A clamp-on ammeter is specifically designed to measure current without directly interrupting the circuit, making it ideal for high-voltage supply lines. This instrument achieves its measurement by using the principle of magnetic induction, allowing it to encircle the conductor and read the electromagnetic field produced by the current flow.

The advantage of this design is significant in high-voltage environments; it provides safety by allowing measurements from outside the circuit, preventing any need for disconnection and reducing the risk of electric shock. This feature is particularly crucial when working with potentially dangerous high-voltage systems, where direct contact could pose a substantial hazard.

While a digital multimeter is versatile and capable of measuring current as well, it typically requires a direct connection to the circuit, which can be impractical or unsafe in high-voltage scenarios. An analog voltmeter, on the other hand, primarily measures voltage and is not suitable for current measurement at all. A wattmeter’s function is to calculate power, which involves both voltage and current measurements, but it is not designed specifically for measuring current flow alone.

Overall, the clamp-on ammeter stands out as the most effective instrument for safely measuring current in high-voltage applications.