# US 12,768,813 B2 · Soil moisture sensor based on electrostatic sensing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,768,813 B2 - Document ID: US12768813B2 - Status: Granted - Kind: B2 - Application number: 18/457,143 - Filed: 2023-08-28 - Published: 2025-03-06 - Granted: 2026-10-20 - Earliest claimed: 2023-08-28 - Assignees: STMicroelectronics International N.V. - Applicants: STMicroelectronics International N.V. - Inventors: Marco Maria Branciforte; Fabrizio La Rosa - Web page: https://patentgrep.com/patent/US12768813B2 ## CPC - G01N 27/605: {for determining moisture content, e.g. humidity} - G01N 33/24: Earth materials (G01N33/42 takes precedence) - G01N 33/245: {for agricultural purposes} - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract A soil sensor includes a signal generator, and a transmitter coupled to the signal generator, the transmitter configured to transmit a signal from the signal generator, the signal having a fixed frequency, the transmitter including a transmit electrode embedded within a first dielectric material. The soil sensor includes a receiver, the receiver being configured to electrostatically couple to the transmitter through a channel including soil, the receiver including a charge variation (QVAR) electrode embedded within a second dielectric material. The soil sensor includes a charge variation (QVAR) sensor coupled to the QVAR electrode, the QVAR sensor configured to detect a variation in charge detected at the QVAR electrode in response to the signal from the signal generator and output a digital signal including the charge detected. And the soil sensor further includes a processing circuit coupled to the QVAR sensor and configured to determine a level of moisture in the channel based on the digital signal. ## Claims ### Claim 1 A soil sensor comprising: a signal generator; a transmitter coupled to the signal generator, the transmitter configured to transmit a signal from the signal generator, the signal having a fixed frequency, the transmitter comprising a transmit electrode embedded within a first dielectric material; a receiver, the receiver being configured to electrostatically couple to the transmitter through a channel comprising soil, the receiver comprising a charge variation (QVAR) electrode embedded within a second dielectric material; a charge variation (QVAR) sensor comprising differential inputs, one of the differential inputs being coupled to the QVAR electrode, the QVAR sensor configured to detect a variation in charge between the differential inputs detected at the QVAR electrode in response to the signal from the signal generator polarizing water molecules disposed in the soil and output a digital signal comprising the variation in charge detected; and a processing circuit coupled to the QVAR sensor and configured to determine a level of moisture in the channel based on the digital signal. ### Claim 2 (depends on 1) The soil sensor of claim 1, further comprising a power supply to power the processing circuit. ### Claim 3 (depends on 1) The soil sensor of claim 1, further comprising a transceiver to transmit the determined level of moisture in the channel, and to receive instructions for operation of the signal generator. ### Claim 4 (depends on 1) The soil sensor of claim 1, wherein the processing circuit and the signal generator are disposed within a common water-proof casing. ### Claim 5 (depends on 1) The soil sensor of claim 1, wherein the processing circuit and the signal generator are enclosed in separate water-proof casings and coupled to each other through water-proof cables. ### Claim 6 (depends on 1) The soil sensor of claim 1, wherein the first dielectric material and the second dielectric material comprise the same dielectric material. ### Claim 7 (depends on 6) The soil sensor of claim 6, wherein the first dielectric material and the second dielectric material comprise polytetrafluoroethylene, polyimide, glass, polyester, or metal oxides. ### Claim 8 (depends on 1) The soil sensor of claim 1, wherein the first dielectric material and the second dielectric material provide a water-proof seal around the respective transmit and QVAR electrodes. ### Claim 9 (depends on 1) The soil sensor of claim 1, wherein the QVAR and transmit electrodes comprise regions of metal on a PCB. ### Claim 10 (depends on 1) The soil sensor of claim 1, further comprising a filter to remove noise from the detected signal at the receiver. ### Claim 11 A soil moisture detection method comprising: having a transmitter and a receiver of a soil sensor in a patch of soil; transmitting an output signal from a signal generator through the transmitter; detecting the output signal at the receiver; sensing the detected output signal at a charge variation (QVAR) sensor as a digital signal comprising a variation in charge detected between differential inputs of the QVAR sensor, one of the differential inputs being coupled to the receiver, the digital signal being different from the output signal in response to the output signal polarizing water molecules in the patch of soil; and processing the digital signal from the QVAR sensor to obtain a moisture content of the patch of soil. ### Claim 12 (depends on 11) The soil moisture detection method of claim 11, further comprising filtering the digital signal using a filter. ### Claim 13 (depends on 12) The soil moisture detection method of claim 12, wherein the filtering comprises removing noise generated from transmission of power. ### Claim 14 (depends on 11) The soil moisture detection method of claim 11, further comprising transmitting the moisture content of the patch of soil. ### Claim 15 (depends on 11) The soil moisture detection method of claim 11, wherein the transmitter comprises a transmit electrode embedded within a first dielectric material; and wherein the receiver comprises a charge variation (QVAR) electrode embedded within a second dielectric material. ### Claim 16 (depends on 15) The soil moisture detection method of claim 15, wherein the first dielectric material and the second dielectric material provide a water-proof seal around the respective transmit and QVAR electrodes. ### Claim 17 (depends on 15) The soil moisture detection method of claim 15, wherein the first dielectric material and the second dielectric material comprise polytetrafluoroethylene, polyimide, glass, polyester, or metal oxides. ### Claim 18 A soil sensor calibration method comprising: placing a transmitter and a receiver of a soil sensor in a first patch of soil; generating a first soil moisture measurement using a charge variation (QVAR) sensor of the soil sensor, the QVAR sensor comprising differential inputs coupled to an analog front end (AFE) circuit, and a processing unit, one of the differential inputs being coupled to the receiver, the first soil moisture measurement comprising a first variation in charge between the differential inputs of the QVAR sensor; after generating the first soil moisture measurement, adding a known volume of water to the first patch of soil; after adding the water, generating a second soil moisture measurement using the QVAR sensor of the soil sensor, the second soil moisture measurement comprising a second variation in charge between the differential inputs of the QVAR sensor; and determining a moisture content calibration table for the first patch of soil based on the first and the second soil moisture measurements. ### Claim 19 (depends on 18) The method of claim 18, further comprising: placing the transmitter and the receiver of the soil sensor in a second patch of soil; generating a third soil moisture measurement using the QVAR sensor of the soil sensor, the third soil moisture measurement comprising a third variation in charge between the differential inputs of the QVAR sensor; and determining a moisture content of the second patch of soil based on the third soil moisture measurement and the moisture content calibration table. ### Claim 20 (depends on 19) The method of claim 19, wherein the first patch and the second patch are from a same sample of the soil.