A new float flowmeter design is presented based on the null method, with electric output signal and either manual or automatic current control in a coil to bring the float back to zero position. The instrument concerned is a constriction‐type device and based on its theory a simple expression can be derived for describing the input–output relationship in quadratic terms. In addition to a description of the device, the static calibration curves using air at 295.16±0.50 K are also provided for volumetric flowrates ranging from 11 to 16 dm3/min and Reynolds numbers between 500 and 800. Typical inaccuracy is 1.8% of flowrate over this range.