What type of resistance should voltmeters have for accurate measurements?

For accurate measurements, voltmeters should have high resistance. This characteristic minimizes the influence of the voltmeter on the circuit being measured. When a voltmeter is connected across a component, if it has low resistance, it will draw significant current, which can alter the voltage drop across the component and lead to inaccurate readings. High resistance ensures that the voltmeter does not have a significant effect on the overall circuit, allowing it to measure the potential difference accurately while not loading the circuit down.

Therefore, high resistance is essential for voltmeters, as it preserves the integrity of the measurement by ensuring that the voltmeter itself does not draw current that can influence the voltage being measured. Understanding this principle is crucial for cathodic protection testing and other electrical measurements, ensuring the reliability of data collected during such assessments.