What scale should you set your meter on to measure a standing pilot?

To measure a standing pilot, the correct scale to set your meter on is millivolts direct current (mV DC). A standing pilot is a small flame that burns continuously to ignite gas in a furnace or heater, and it typically produces a very low electrical voltage due to the thermocouple or thermopile used in the system.

The millivolt scale is specifically designed to measure the low voltage output generated by these components, which can be generally in the range of a few hundred millivolts. Setting the meter to this scale allows you to accurately measure the voltage produced by the thermocouple or thermopile when it is generating electricity from the heat of the pilot flame.

Using the other scales, such as AC volts, DC volts, or amperes DC, would not be appropriate for this application. AC volts is used for measuring alternating currents, which are not present in standing pilot systems. DC volts could measure higher voltage outputs than what a standing pilot would produce, leading to inaccurate readings. Amperes DC measures current, not voltage, making it unsuitable for this context as well. Therefore, the mV DC setting is the most precise and appropriate choice for measuring the electrical output of a standing pilot.