Drop-detection device

A drop-detection device (11, 11a, 11b) for the detection of drops (TR) escaping from a nozzle of a metering valve (DV), having:

• a signal-generation unit (20), which is configured to produce a carrier signal (TS) with a defined pulse frequency,
• a modulation unit (30, 30a) which is configured to generate a modulated measurement signal due to a physical interaction of the carrier signal (TS) with a drop to be detected (TR),
• an evaluation unit (50), which is configured to determine if a drop (TR) has been dispensed by the metering valve (DV) based on the measurement signal (MS) taking the frequency of the defined pulse into consideration, and
• a demodulation unit (40) that is configured
• to carry out a quadrature demodulation of the measurement signal in order to determine an in-phase component (I) and a quadrature component (Q),
• wherein the evaluation unit (50) comprises a modulation valuation unit (51), which is configured
• based upon the in-phase component (I) and the quadrature component (Q), to determine the amount of amplitude and/or the phase of the modulation signal (MOD) based on the modulated measurement signal (MS),
• to determine amplitude derivative values (dA/dt), comprising the time derivative of the amplitude value and/or phase derivative values (dϕ/dt), comprising the time derivative of the phase of the modulation signal (MOD), and
• to combine at a fixed time interval (IT), a predetermined number of amplitude derivative values (dA/dt) into amplitude comparative values (AM) and/or a predetermined number of phase derivative values (dϕ/dt) into phase comparative values (ϕM).