Filtered dielectric sensor apparatus

• US 10,114,054 B1
• Filed: 06/09/2018
• Issued: 10/30/2018
• Est. Priority Date: 05/11/2015
• Status: Active Grant

• Current Assignee: Metin A. Gunsay
• Original Assignee: Metin A. Gunsay
• Inventors: Gunsay, Metin A
• Primary Examiner(s): Gray, Francis C
• Application Number:
  US16/004,379
• Publication Number:
  US 20180292437A1
• Time in Patent Office: 143 Days
• CPC Class Codes: G01F 23/263 by measuring variations in capacitance of capacitors
• CPC Class Codes: G01F 23/266 measuring circuits therefor
• CPC Class Codes: G01R 27/2664 Transmission line, wave guide (closed or open-ended) or strip - or microstrip line arrangements
• CPC Class Codes: G05D 9/12 characterised by the use of electric means

Abstract

A sensor to measure dielectric constant of a medium may have a transmission line acting as a probe, and electronic circuit, and cable filter providing to reduce sensitivity of the sensor to cable parameters and influences. The sensor circuit may use a periodic signal generator to produce a carrier wave, which stimulates the transmission line, through a complex network coupling element. The complex impedance network forms a voltage divider with the transmission line, wherein the output of the voltage divider may be demodulated with an AM demodulator, such as a thermally compensated peak detector. This demodulated signal would be related to the characteristic impedance of the transmission line, and thus to the dielectric constant of the material surrounding the partially inserted transmission line probe. The demodulated signal may be offset, scaled, and linearized with a microcontroller containing signal processing routines, linearizing equations, stored calibration constants and look up tables.

Claims

1. A dielectric sensor apparatus comprising:

a. a sensor assembly further comprising;

i. a voltage signal generator which provides a carrier frequency;

ii. a transmission line probe of one or more segments and being formed of two parallel input lines, where one input line is coupled to a fixed potential, and one input line is coupled to the signal generator through a complex impedance network; and

iii. an AM demodulator coupled to the transmission line probe, providing an output voltage through at least one output data line, whereby the dielectric level of the material may be determined;

b. a microprocessor coupled to the output data line and further coupled to at least one input-output data line which connects to a filter assembly;

c. a power voltage network further comprising a network voltage source, a plurality of power nodes within the dielectric sensor apparatus and a power voltage line connected to the network voltage source;

d. a return voltage network with a plurality of return nodes within the dielectric sensor apparatus and a return voltage line connected to the network voltage source;

e. a cable of wires which includes the power voltage line, the return voltage line and the at least one input-output data line; and

,

f. the filter assembly, located on a sensor side of the cable, further comprising, on each of the at least one input-output data line and the power line of the power voltage network, an inductor in series with the cable and a capacitor, on a sensor side of the inductor and shunted to the return voltage network, and, in the return voltage network, an inductor in series with the cable,

wherein the transmission line probe is inserted into a medium having a dielectric constant and the AM demodulator provides an output voltage signal correlated to the medium'"'"'s dielectric constant and a length of the transmission line probe that is inserted in the medium.

2. The dielectric sensor apparatus of claim 1, the apparatus being utilized as a moisture measuring tool.

3. The dielectric sensor apparatus of claim 2, the moisture measuring tool being selected from the set of moisture content measuring tools consisting of:

a liquid level sensor and a moisture content sensor.

4. The dielectric sensor apparatus of claim 1, further comprising at least one additional data line extending from the sensor to the filter assembly, the at least one additional data line being filtered by an inductor in series with the sensor and cable and the line being shunted to the return voltage network.

5. The dielectric sensor apparatus of claim 1, further comprising at least one additional power line extending from the sensor to the filter assembly, the at least one additional power line being filtered by an inductor in series with the sensor and cable and the line being shunted to the return voltage network.

6. A dielectric sensor apparatus comprising:

a. a sensor assembly further comprising;

i. a voltage signal generator which provides a carrier frequency;

ii. a transmission line probe of one or more segments and being formed of two parallel input lines, where one input line is coupled to a fixed potential, and one input line is coupled to the signal generator through a complex impedance network;

iii. an AM demodulator further comprising a temperature compensated peak detector circuit comprised of two peak detector circuits whose diodes are thermally coupled, with an input of one peak detector coupled to the said transmission line probe through the said complex impedance network and an input of the second peak detector coupled to the said signal generator through a second complex impedance network, and with the outputs of both peak detectors; and

iv. a differential amplifier coupled to outputs of both peak detector circuits, providing an output voltage through at least one output data line, whereby common mode temperature fluctuations are removed and the dielectric level of the material may be determined;

b. a microprocessor coupled to the output data line and further coupled to at least one input-output data line which connects to a filter assembly;

c. a power voltage network further comprising a network voltage source, a plurality of power nodes within the dielectric sensor apparatus and a power voltage line connected to the network voltage source;

d. a return voltage network with a plurality of return nodes within the dielectric sensor apparatus and a return voltage line connected to the network voltage source;

e. a cable of wires which includes the power voltage line, the return voltage line and the at least one input-output data line; and

,

f. the filter assembly, located on a sensor side of the cable, further comprising, on each of the at least one input-output data line and the power line of the power voltage network, an inductor in series with the cable and a capacitor, on a sensor side of the inductor and shunted to the return voltage network, and, in the return voltage network, an inductor in series with the cable

wherein the transmission line probe is inserted into a medium having a dielectric constant and the AM demodulator provides an output voltage signal correlated to the medium'"'"'s dielectric constant and a length of the transmission line probe that is inserted in the medium.

7. The dielectric sensor apparatus of claim 6, the apparatus being utilized as a moisture measuring tool.

8. The dielectric sensor apparatus of claim 7, the moisture measuring tool being selected from the set of moisture content measuring tools consisting of:

a liquid level sensor and a moisture content sensor.

9. The dielectric sensor apparatus of claim 6, further comprising at least one additional data line extending from the sensor to the filter assembly, the at least one additional data line being filtered by an inductor in series with the sensor and cable and the line being shunted to the return voltage network.

10. The dielectric sensor apparatus of claim 6, further comprising at least one additional power line extending from the sensor to the filter assembly, the at least one additional power line being filtered by an inductor in series with the sensor and cable and the line being shunted to the return voltage network.