Cathodic Protection Tester Practice Exam

How is a voltmeter connected to take a reading?

1. In series with the circuit

2. In parallel with the circuit

3. Across shunts only

4. Connected to the ground

The correct answer is: In parallel with the circuit

A voltmeter is designed to measure the electrical potential difference between two points in a circuit. To obtain an accurate reading, it must be connected in parallel with the component or circuit segment whose voltage you are measuring. This configuration allows the voltmeter to measure the voltage across that component without significantly altering the overall resistance of the circuit, which could otherwise affect the circuit operation and the measurement itself. When connected in parallel, the voltmeter picks up the potential difference directly across the two points of interest, ensuring that the reading reflects the true voltage rather than something influenced by other circuit elements. This method of connection is essential in almost all electrical and electronic measurement scenarios, including cathodic protection systems, where voltage readings help assess the effectiveness of the protection being applied. If a voltmeter were connected in series, it would become part of the circuit, significantly altering the resistance and potentially leading to inaccurate readings, as the circuit's functioning could be impeded. The other choices also imply incorrect usage of the voltmeter, as measuring across shunts is not the absolute method of measuring voltage in general, nor is connecting it solely to the ground.