US 4,399,404 A · Moisture tester with probe

Abstract

The tester has a probe to be inserted into granular or fluid materials for measuring instantly permittivity and temperature. The characteristics of materials are measured according to permittivity, the characteristics of moisture of grains being used as an example in the present embodiment. Features of the tester include: a sensing capacitor within a tip of the probe being an extension of a printed circuit board mounted within a main casing of the probe, an adjustable printed-circuit type capacitor as a reference in cooperation with the sensing capacitor in a balanced input circuit, touch-type switches to which battery is continually supplied to select instantly different calibrations for different characteristic curves without operation of any other switches, and the use of voltage dividers selected by the switches to provide a voltage for zero crossing and another voltage to adjust gain according to the slope of a desired curve, the voltages from a voltage divider for different gains being varied as a function of temperature at the probe.

Claims5

Dependent claims

An electronic tester having a detecting circuit and probe, said probe to be inserted in fluid materials to determine permittivities thereof by capacitive measurements, said probe comprising:

a length of conductive tubing having an end to be inserted into said fluid materials,
a thin substrate of a printed circuit board, an end of said substrate being disposed diametrically within said end of said tubing and extending axially outward beyond said end of said tubing, a first thin layer of conductive material on said substrate, a maximum transverse dimension of said first thin layer of conductive material being substantial but being less than that of said tubing, said thin layer of conductive material and said end of said conductive tubing forming a sensing capacitor having capacitances determined by different permittivities of materials into which said probe is inserted, and
said detecting circuit having an input circuit connected to said sensing capacitor and an output providing signals having intensities according to respective permittivities of said materials into which said probe is inserted.

Dependencies are inferred from the claim text.

Moisture tester with probe

Life of this patent

Moisture tester with probe

Life of this patent

Abstract

Claims5