# US 2014/0152327 A1 · Capacitive Proximity Sensor As Well As Method For Capacitive Approximation Detection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0152327 A1 - Document ID: US20140152327A1 - Status: Published application - Kind: A1 - Application number: 13/977,724 - Filed: 2012-01-03 - Published: 2014-06-05 - Earliest claimed: 2011-01-04 - Assignees: Microchip Technology Germany GmbH - Inventors: Holger Erkens - Web page: https://patentgrep.com/patent/US20140152327A1 ## CPC - G01R 27/2605: {Measuring capacitance (capacitive sensors G01D5/24)} - H03K 17/955: using a capacitive detector - H03K 2017/9613: {using two electrodes per touch switch} - H03K 2217/960705: Safety of capacitive touch and proximity switches, e.g. increasing reliability, fail-safe - H03K 2217/96073: Amplitude comparison - H03K 2217/960745: Capacitive differential; e.g. comparison with reference capacitance - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M) ## Abstract A capacitive proximity sensor has a first sensor electrode and a second sensor electrode, a signal generator for providing a first and a second electric alternating signal, a first load element which comprises a first and a second electric load, in which the first alternating signal by the first load can be fed to the first sensor electrode and the second alternating signal by the second load to the second sensor electrode, and wherein the electric loads each together with the capacitive load to be measured at the respective sensor electrode form a lowpass filter, and a signal processing device, which is coupled with the first sensor electrode and with the second sensor electrode, and which is adapted to form a first measurement value from the push-pull portion of a first electric parameter tapped at the first sensor electrode and a second electric parameter tapped at the second sensor electrode. ## Claims ### Claim 1 Capacitive proximity sensor, comprising a first sensor electrode and a second sensor electrode, a signal generator, for providing a first electric alternating signal and a second electric alternating signal, a first load element, which comprises a first electric load and a second electric load, in which the first electric alternating signal by means of the first electric load can be fed to the first sensor electrode and the second electric alternating signal can be fed by means of the second electric load to the second sensor electrode, and wherein the electric loads each time together with the capacitive load to be measured at the respective sensor electrode form a lowpass filter, and a signal processing device which is coupled with the first sensor electrode and with the second sensor electrode, and which is adapted to form a first measurement value from the push-pull portion of a first electric parameter tapped at the first sensor electrode and a second electric parameter tapped at the second sensor electrode. ### Claim 2 (depends on 1) Proximity sensor according to claim 1, wherein the signal processing device comprises a first amplifying circuit which is formed preferably as fully differential amplifier and which selects the push-pull portions of the first electric parameter and of the second electric parameter. ### Claim 3 (depends on 1) Proximity sensor according to claim 1, wherein the signal processing device is adapted to form the first measurement value from the difference between the first electric parameter and the second electric parameter. ### Claim 4 (depends on 1) Proximity sensor according to claim 1, in which the first electric alternating signal preferably has the same amplitude as the second electric alternating signal and/or in which the first electric alternating signal presents a phase shift of preferably 180° from the second electric alternating signal. ### Claim 5 (depends on 1) Proximity sensor according to claim 1, wherein the signal processing device further is adapted to form a second measurement value from the common mode portion of the first electric parameter and second electric parameter tapped at the sensor electrodes. ### Claim 6 (depends on 5) Proximity sensor according to claim 5, wherein the signal processing device for forming the second measurement value comprises a second amplifying circuit, which is formed preferably as an impedance converter, in which the not inverting input of the impedance converter can be fed with the sum of the first electric parameter and the second electric parameter. ### Claim 7 (depends on 1) Proximity sensor according to claim 1, further comprising a field disturbing electrode, which can be fed with a third electric alternating signal. ### Claim 8 (depends on 1) Proximity sensor according to claim 1, further comprising a third amplifying circuit, which comprises the first load element. ### Claim 9 (depends on 1) Proximity sensor according to claim 1, further comprising a second load element, which is coupled with the signal transmitter, wherein the output signals of the second load element can be fed to the signal processing device. ### Claim 10 (depends on 9) Proximity sensor according to claim 9, further comprising a fourth amplifying circuit, which comprises the second load element. ### Claim 11 (depends on 9) Proximity sensor according to claim 9, wherein the sensor electrodes and the exit of the second load element are coupled with the entries of the first amplifying circuit in such a way that the first amplifying circuit at its exits provides the difference between the signals tapped at the sensor electrodes and the output signals of the second load element. ### Claim 12 (depends on 11) Proximity sensor according to claim 11, in which the first sensor electrode is coupled with the inverting exit of the third amplifying circuit, the second sensor electrode is coupled with the not inverting exit of the third amplifying circuit, the first electric alternating signal can be fed to the inverting entries of the third amplifying circuit and the fourth amplifying circuit, the second electric alternating signal can be fed to the not inverting entries of the third amplifying circuit and the fourth amplifying circuit, a first composite signal, which is formed from the electric signal tapped at the first sensor electrode and the signal at the not inverting exit of the fourth amplifying circuit, can be fed to the inverting entry of the first amplifying circuit, and a second composite signal, which is formed from the electric signal tapped at the second sensor electrode and the signal at the inverting exit of the fourth amplifying circuit, can be fed to the not inverting entry of the first amplifying circuit. ### Claim 13 (depends on 11) Proximity sensor according to claim 11, wherein the amplification of the fourth amplifying circuit is adjustable. ### Claim 14 Method for the approximation detection of an object, in which a first sensor electrode is fed with a first electric alternating signal and a second sensor electrode with a second electric alternating signal, wherein the electric alternating signals are fed to the sensor electrodes by means of a first load element, and from the push-pull portion of a first electric parameter, which is tapped at the first sensor electrode, and a second electric parameter, which is tapped at the second sensor electrode, a first measurement value is formed, wherein the first measurement value is indicative for the approach of the object to the sensor electrodes. ### Claim 15 (depends on 14) Method according to claim 14, wherein the electric alternating signals are selected in such a way that the first electric alternating signal preferably presents the same amplitude as the second electric alternating signal and the electric alternating signals are preferably dephased by 180° from each other. ### Claim 16 (depends on 14) Method according to claim 14, in which from the common mode portion of the first electric parameter and the second electric parameter a second measurement value is formed. ### Claim 17 (depends on 14) Method according to claim 14, in which a second load element is fed with the first electric alternating signal and with the second electrical alternating signal, wherein the exits of the first load element and of the second load element are coupled with the entries of a first amplifying circuit in such a way that the first amplifying circuit at its exits provides the difference between the output signals of the first load element and the output signals of the second load element. ### Claim 18 Hand-held device comprising a capacitive proximity sensor, comprising: a first sensor electrode and a second sensor electrode, signal generator, for providing a first electric alternating signal and a second electric alternating signal, a first load element, which comprises a first electric load and a second electric load, in which the first electric alternating signal by means of the first electric load can be fed to the first sensor electrode and the second electric alternating signal can be fed means of the second electric load to the second sensor electrode, and wherein the electric loads each time together with the capacitive load to be measured at the respective sensor electrode form a lowpass filter, and a signal processing device which coupled with the first sensor electrode and with second sensor electrode, and which is adapted to form a first measurement value from the push-pull portion of a first electric parameter tapped at the first sensor electrode and a second electric parameter tapped at the second sensor electrode. ### Claim 19 (depends on 18) Hand-held device according to claim 18, wherein the signal processing device comprises a first amplifying circuit which is formed preferably as fully differential amplifier and which selects the push-pull portions of the first electric parameter and of the second electric parameter. ### Claim 20 (depends on 18) Hand-held according to claim 18, wherein the signal processing device is adapted to form the first measurement value from the difference between the first electric parameter and the second electric parameter.