US 11,920,960 B2
Capacitive measuring system
Torben Zeleny, Wuppertal (DE); Uwe Borgmann, Recklinghausen (DE); and Jan Freiwald, Dortmund (DE)
Assigned to KOSTAL Automobil Elektrik GmbH & Co. KG, Luedenscheid (DE)
Filed by KOSTAL Automobil Elektrik GmbH & Co. KG, Luedenscheid (DE)
Filed on Aug. 3, 2020, as Appl. No. 16/983,330.
Application 16/983,330 is a continuation of application No. PCT/EP2019/052525, filed on Feb. 1, 2019.
Prior Publication US 2020/0361408 A1, Nov. 19, 2020
Int. Cl. G01D 5/24 (2006.01); B60R 21/015 (2006.01); G01R 27/26 (2006.01)
CPC G01D 5/24 (2013.01) [B60R 21/01532 (2014.10); G01R 27/2605 (2013.01)] 6 Claims
OG exemplary drawing
 
1. A capacitive measuring system comprising:
a plurality of capacitive sensors;
an evaluation circuit having a multiplexer, a synchronous rectifier, a sinusoidal signal generator, and a reference voltage divider;
wherein the capacitive sensors are acted on by a mono-frequency voltage signal generated by the sinusoidal signal generator, output signals of the capacitive sensors are transmitted in alternation to the synchronous rectifier via the multiplexer, and signal amplification of output signals of the synchronous rectifier are calibrated as a function of an activatable reference impedance; and
the synchronous rectifier is limited by a MOS semiconductor switch, a source-drain section of the MOS semiconductor switch forms a shunt that is controlled by the mono-frequency voltage signal, and a channel of the multiplexer is provided for transmitting a calibration signal, generated by the reference voltage divider, to the synchronous rectifier alternately with the output signals of the capacitive sensors.