What meter scale should be set to measure flame rectification?

To measure flame rectification, the appropriate meter scale to set is milliamps direct current (mA DC). Flame rectification refers to the ability of the flame to allow current to flow in one direction due to the ionization of the gases present in the flame when it is heated by a spark.

In this context, the flame acts as a rectifier, allowing small amounts of current to flow through an electrode. Measuring this current is essential for confirming that the flame is established and that the system is operating correctly. Since the current generated in this scenario is typically very low, the milliamps scale is ideal. It provides the sensitivity needed to accurately measure the small currents associated with flame rectification.

Other options, such as volts AC or amps AC, are not appropriate for this measurement because they do not relate to the direct current signals produced by the flame. Similarly, while millivolts DC is specific and sensitive, it does not convey the current flow that is needed to assess flame rectification effectively. Therefore, setting the meter to mA DC accurately aligns with the requirements for measuring the flame rectification process in HVAC systems.