What setting would you select on a multimeter to measure a flame signal?

To measure a flame signal, selecting the microamps DC setting on a multimeter is appropriate because flame sensors typically generate a small electrical current in the microamp range when a flame is present. This small direct current indicates the presence of the flame to the control system of a gas appliance.

In contexts such as gas burners or furnaces, the flame sensor sends a signal that helps maintain safe operation. The use of microamps DC specifically allows for the detection of very low current levels produced by the flame, which most accurately represents the activity of the flame safety system.

Other settings on the multimeter are not suitable for this application. Measuring volts AC would be useful for measuring alternating current voltage, commonly found in household wiring but not for a flame signal. The ohms setting is ideal for checking resistance in circuits, which is not relevant for measuring a signal current. Lastly, measuring amps AC would apply to alternating current usage, typically not related to the direct current signal outputs from flame sensors. Therefore, selecting microamps DC is essential and accurate for monitoring flame signals in plumbing and HVAC systems.