To verify a motion detector's power, the meter should be set to which measurement?

To verify a motion detector's power, the meter should be set to which measurement?

• A. AC
• B. DC
• C. Ohms
• D. Hertz

Answer: (B)

The device is powered by direct current, so you verify its power by measuring DC voltage. Motion detectors in homes are typically fed with a low-voltage DC supply (like 12 V DC from the control panel or a battery). Using the meter on the DC volts setting lets you see the actual operating voltage at the detector. If you used AC, Ohms, or Hertz, you’d be checking something other than the supply voltage the detector needs—AC would not reflect the device’s DC power, Ohms tests resistance, and Hertz checks frequency, not power. A proper DC reading confirms the detector is getting the correct power; if the reading is too low or absent, inspect the power source or wiring or replace the battery.

The device is powered by direct current, so you verify its power by measuring DC voltage. Motion detectors in homes are typically fed with a low-voltage DC supply (like 12 V DC from the control panel or a battery). Using the meter on the DC volts setting lets you see the actual operating voltage at the detector. If you used AC, Ohms, or Hertz, you’d be checking something other than the supply voltage the detector needs—AC would not reflect the device’s DC power, Ohms tests resistance, and Hertz checks frequency, not power. A proper DC reading confirms the detector is getting the correct power; if the reading is too low or absent, inspect the power source or wiring or replace the battery.