Abstract

An apparatus for verifying the calibration of a flow meter contains a flow sensor assembly which has a flow tube defining an axial fluid path through the flow sensor assembly; an upstream temperature sensor in thermal contact with the flow tube; a downstream temperature sensor in thermal contact with the flow tube, the two sensors being operationally connected to a means for producing an output in response to a temperature difference between the first and second sensors; and means for asymmetrically transferring heat to the first and second temperature sensors independently of fluid flow through the flow tube. The calibration of the flow meter's thermal and electronic systems is verified by measuring the flow meter's output in response to a first asymmetric heat transfer to the upstream and downstream temperature sensors when the flow meter is calibrated. The output of the flow meter in response to a second asymmetric transfer to the upstream and downstream sensors is subsequently measured and comparison of the two readings verifies whether the flow meter's thermal and electronic systems remains calibrated.