What is used to confirm airflow through an evaporator coil in a correctly charged air conditioning system?

To confirm airflow through an evaporator coil in a correctly charged air conditioning system, measuring the temperature drop across the coil is essential. When air moves over the evaporator coil, it absorbs heat from the air, causing the temperature of the air to decrease. This temperature difference, or drop, is indicative of effective heat transfer and airflow. If the airflow is sufficient, the temperature drop should be within a certain range, indicating that the system is functioning efficiently.

The other options do not directly confirm airflow through the coil. While sound level measurement might provide an indication of system operation, it does not specifically measure airflow. Pressure gauges are useful for assessing refrigerant charge and system pressure but do not reveal how well the air is moving through the evaporator. A humidity meter can help determine moisture removal effectiveness but is not a direct measure of airflow. Thus, utilizing the temperature drop is the most relevant method for confirming airflow through the evaporator coil.