Abstract: An air flow compensator for use with flow meters which includes a main slide element, a secondary slide element and first and second spring elements. The main slide element includes a magnetic insert in one end thereof and is movable toward a proximity sensor that detects the proximity of the magnetic insert. The first spring element biases both the main slide element and the secondary slide element away from the proximity sensor and the second spring element biases only the secondary slide element away from the proximity sensor. The secondary slide element is both movable together with the first slide element and independently movable with respect to the main slide element.

Abstract: Precalibrated flow meters which include electronic modules that contain, in a storage memory thereof, a plurality of calibration factors that correspond to a plurality of different fluids. The calibration factors can be chosen during field operations using a touch pad on the face of the meters. The precalibrated flow meters monitor current and accumulative totals of fluid volumes. The precalibrated flow meters can be used in conjunction with air flow compensators which sense the flow of air through a fluid flow passage.