What instrument is known for measuring resistance across electrical contacts in EHV breakers?

The micro-ohm meter is specifically designed to measure low resistance values with high accuracy, making it ideal for testing electrical contacts in Extra High Voltage (EHV) breakers. EHV breakers require precise resistance measurements because even small variations can significantly impact their performance. The micro-ohm meter operates by passing a known current through the resistance being measured and then calculating the voltage drop across it, which allows for precise measurements of resistance in the micro-ohm range. This capability is essential for ensuring proper functioning and reliability of EHV equipment.

In contrast, a multimeter typically measures resistance but may not provide the same level of precision at low resistance levels as a micro-ohm meter. An oscilloscope is used for analyzing voltage waveforms and does not measure resistance. A clamp meter is primarily designed for measuring current and, while some may have resistance measurement capabilities, they are not as specialized for low-resistance measurements as a micro-ohm meter. Thus, the micro-ohm meter's focus on low resistance makes it the appropriate choice for measuring resistance across electrical contacts in EHV breakers.