Abstract: A system is provided that accurately measures the quantity of liquid that is transferred through a flow meter. The system is composed of a flow meter with an ultrasonic fluid (liquid) sensor mounted therein that operates to sense the presence or absence of liquid flowing through the flow meter so that air flow is not erronecously measured as liquid flow. When there is substantially no liquid flow through the meter, the ultrasonic fluid (liquid) sensor interrupts the transmission of an output signal from a signal-conditioning circuit to a totalizer that operates to process the signal and total the amount of liquid so that any non-liquid material passing through the meter is not included in the total amount of removed liquid by the totalizer. Also provided are methods of using the system to accurately measure the amount of liquid flowing through a flow meter, such as in a grease trap pumping operation.

Abstract: A flow meter is provided that can be used to measure the flow of fluids from a fluid source to a receiving system, and methods of using the flow meter to measure fluid flow. The flow meter is composed of a housing that contains a fluid flow sensing member in the form of a rotatable bladed rotor or turbine in one chamber and a sensor and a signal-conditioning circuit in a second separate chamber. The rotor rotates by fluid flow through the housing chamber. The rotor preferably contains a magnet that passes over a magnetically-operated sensor and triggers it to produce a signal that is processed by the conditioning circuit into a 4-20 mA output signal that indicates a range from no flow to full flow of the liquid through the flow meter.