A meter is placed on wire 1 and wire 3. PB1 is closed. A reading of source voltage is given. What does this indicate?

• A. The circuit is working properly
• B. The Stop PB3 is open
• C. The Fwd PB1 is open
• D. None of these

Answer: (B)

A voltmeter wired between two points in a control circuit shows whether there is a complete path from the power source to the load through the switches. With Forward PB1 closed, the supply is connected up to the Stop pushbutton. If the meter reads the full source voltage between those two wires, it means the path past the Stop button is open — the Stop PB3 is not allowing current to continue. In other words, the source voltage is present on the supply side, but the circuit is interrupted at the Stop button, so current can’t reach the downstream elements. This is why the Stop button being open is the indication you’re getting.