Capacitive flow sensor

摘要

An apparatus for measuring the flow rate of a liquid in a line includes a capacitor formed by a pair of electrodes. A charging circuit produces a charging current of constant magnitude. The charging current is used to charge the capacitor to a predetermined voltage. A timing circuit measures the time between the time at which the charging circuit begins to produce the charging current and the time at which the capacitor has been charged to the predetermined voltage. The timing circuit produces a pulse width modulated signal. The magnitude of the pulse width modulated signal is indicative of the time difference.