What is a common way to check flame sensor functionality?

A common way to check flame sensor functionality is by observing current flow in microamps. Flame sensors operate by detecting the presence of a flame through the ionization of the combustion gases. When the flame is present, a small current flows through the sensor, typically measured in microamps. This current indicates that the flame sensor is functioning properly and that the system can safely maintain ignition.

If the current flow is below a certain threshold, it may indicate that the flame is not present or that the sensor is not operating correctly. This measurement is crucial because a functioning flame sensor is necessary for safe operation, as it prevents the gas valve from remaining open without a flame to ignite the gas, thus avoiding potential hazards like gas buildup and explosions.

Assessing circuit continuity and measuring output voltage are helpful diagnostic methods but do not provide the specific information needed to confirm that the flame sensor is detecting the flame correctly. Additionally, checking for physical damage can indicate if there are any obvious issues with the sensor itself, but it does not assess the sensor's functional performance under operational conditions.