The TrueFlow® Air Handler Flow Meter is designed to provide a simple and accurate measurement of airflow through residential air handlers. The TrueFlow Meter temporarily replaces the filter in the air handler distribution system during the airflow measurement process. If the filter location is directly adjacent to the air handler, the TrueFlow Meter will measure the total air handler flow. If the filter is located remotely at a central return, the TrueFlow Meter will measure airflow through the central return. TrueFlow Air Handler Flow Meter Easy and fast to use in the field. The TrueFlow Meter provides direct CFM readings in 2 to 3 minutes without extensive calculations or setup. Designed to measure flow through air handlers rated from 1 to 5 tons. Can be used in a wide range of return plenums and air handler fan configurations. Adjustable sizing to fit standard and custom filter slots. Proven to be more accurate than the single-point temperature rise method and easier than the fan curve method.