Cathodic Protection Tester Practice Exam

What is the DC voltage reading for shunt current measurements on a voltmeter?

1. 200 millivolts

2. 2 volts

3. 20 volts

4. 200 volts

The correct answer is: 200 millivolts

For shunt current measurements, a DC voltage reading of 200 millivolts is commonly used because it is within a suitable range for accurately measuring the small voltage drop across the shunt resistor. Shunt resistors are employed to allow a small current to flow through while enabling the measurement of higher currents using a low voltage drop. The 200 millivolt level ensures that the voltmeter can capture readings without exceeding its limits while providing sufficient resolution for low current applications. This range is especially useful in cathodic protection systems, where the current levels can be relatively low and precise measurements are vital for system performance assessments. The choice of 200 millivolts reflects a balance between sensitivity and accuracy, which is crucial for effective cathodic protection testing. Other options exceed this typical range for shunt measurements. Voltages considerably higher than 200 millivolts could lead to inaccuracies as they may not register correctly on equipment designed for lower voltage readings. This underscores the importance of using an appropriate voltage level for accurate monitoring in cathodic protection systems.