When testing the CAD cell with the burner on, the ohmmeter reading should drop to between which range in ohms?

When testing the CAD cell with the burner on, the ohmmeter reading should drop to between which range in ohms?

• A. 100 to 200 ohms
• B. 600 to 1200 ohms
• C. 300 to 900 ohms
• D. 900 to 1500 ohms

Answer: (C)

The main idea is that a CAD cell acts as a light-driven sensor used to confirm flame presence. When the burner is on, the flame provides light that lowers the resistance of the cadmium sulfide cell, so an ohmmeter connected across it will read a relatively low value. In typical CAD-cell tests, this “on” reading should fall in the mid-hundreds of ohms, commonly around 300 to 900 ohms. This drop signals the control that a flame is present and the burner can continue operating. If the reading stays high or changes little when the flame is on, there may be a fault in the CAD cell, its wiring, or the flame reaching the sensor.

The main idea is that a CAD cell acts as a light-driven sensor used to confirm flame presence. When the burner is on, the flame provides light that lowers the resistance of the cadmium sulfide cell, so an ohmmeter connected across it will read a relatively low value. In typical CAD-cell tests, this “on” reading should fall in the mid-hundreds of ohms, commonly around 300 to 900 ohms. This drop signals the control that a flame is present and the burner can continue operating. If the reading stays high or changes little when the flame is on, there may be a fault in the CAD cell, its wiring, or the flame reaching the sensor.