Grain moisture tester

Claim 2

A grain moisture tester comprising a test cell having a cylindrical container constituting an outer electrode and a cylindrical conductor constituting an inner electrode mounted coaxially within said container and insulated therefrom, an insulator closely surrounding the cylindrical wall of said inner electrode to simulate an air gap, the dielectric constant of said insulator being substantially one, the ratio of thickness of said insulator and the outside radius of said inner electrode being approximately 1:11 and means connected electrically to said electrodes foR measuring permittivity of a sample placed between said electrodes.

Claim 3

A grain moisture tester as claimed in claim 1 in which said insulator is made of closed-cell polystyrene foam.

Claim 4

A grain moisture tester comprising a test cell having a first cylindrical container constituting an outer electrode and a cylindrical conductor constituting an inner electrode mounted within said first container and insulated therefrom, a spring scale having a mounting member, an elongated scale member and a spring, said scale member having an inner end slidably mounted within said mounting member, said spring interconnecting said mounting member and the inner end of said scale member, means for securing said mounting member coaxially within said cylindrical conductor to extend the outer end of said scale member coaxially upwardly from said first container, and electrical circuit means connected to said electrodes for measuring permittivity of a sample placed between said electrodes, said grain moisture tester having a second cylindrical container, said electrical circuit means for measuring permittivity being mounted within said second container, the bottom portion of said first container being mounted within the top portion of said second container, said first container having spaced above its bottom a disk of insulating material as a bottom of that portion of the test cell to hold a sample to be tested, the bottom of said first container having a concentric opening, plug-in connecting means having a portion secured to said disk and connected to said inner electrode and a mating portion secured to said circuit means within said second container, said connecting means extending through the center of said concentric opening to provide conduction from said inner electrode to said circuit means, the spacing between said bottom of said second container and said connecting means being sufficient to prevent significant stray capacitance there-between.

Claim 5

A grain moisture tester comprising a test cell having a first cylindrical container constituting an outer electrode and a cylindrical conductor constituting an inner electrode mounted within said first container and insulated therefrom, a spring scale having a mounting member, an elongated scale member and a spring, said scale member having an inner end slidably mounted within said mounting member, said spring interconnecting said mounting member and the inner end of said scale member, means for securing said mounting member coaxially within said cylindrical conductor to extend the outer end of said scale member coaxially upwardly from said first container, and electrical circuit means connected to said electrodes for measuring permittivity of a sample placed between said electrodes, said grain moisture tester having a second cylindrical container, said electrical circuit means for measuring permittivity being mounted within said second container, the bottom portion of said first container being mounted within the top portion of said second container, said first container having spaced above its bottom a disk of insulating material as a bottom of that portion of the test cell to hold a sample to be tested, the bottom of said first container having a concentric opening, plug-in connecting means having a portion secured to said disk and connected to said inner electrode and a mating portion secured to said circuit means within said second container, said connecting means extending through the center of said concentric opening to provide conduction from said inner electrode to said circuit means, the spacing between said bottom of said second container and said connecting means being sufficient to prevent significant stray capacitance there-between.

Claim 6

A grain moisture tester as claimed in claim 3 wherein said electrical circuit means includes signal generating means and a resistor, said resistor and said test cell being serially connected in the output of said signal generating means, and voltage measuring means connected to said test cell for measuring the voltage developed thereacross.

Claim 7

A grain moisture tester as claimed in claim 4 wherein a temperature-compensating capacitor is connected in parallel with the electrodes of said test cell and mounted within said portion of said test cell to receive a sample.

Claim 8

A grain moisture tester as claimed in claim 4, wherein said voltage measuring means includes a Schmitt trigger circuit having an input responsive to application of alternating-current voltage to cause it to change state for each peak of said applied voltage above a threshold value, alternating-current amplifier means connecting said test cell and the input triggering circuit of said Schmitt trigger, and indicating means connected to the output of said trigger circuit to show the operation thereof.

Claim 9

A grain moisture tester as claimed in claim 4 wherein said electrical measuring means includes a low-voltage disabling circuit, a source of voltage connected to supply power to said electrical measuring means, said voltage measuring means including an indicator circuit, a transistor having an input control circuit and an output circuit, said output circuit being connected through said indicator circuit to said source of voltage, means connected between said test cell and said input control circuit to apply control signal to said input control circuit in response to the voltage developed across said test cell exceeding a predetermined amount, biasing means including a serially connected break-down diode and a resistor connected across said source of voltage, said biasing means also being connected to said input control circuit, said break-down diode normally being conductive to provide the proper bias to said transistor to make it conductive in response to said voltage acrosS said test cell exceeding said predetermined amount, said indicator operating in response to conduction through said transistor, and said break-down diode becoming nonconductive in response to the voltage supplied by said source of voltage dropping below a predetermined desirable amount for operating said electrical measuring means, thereby preventing conduction through said transistor and preventing operation of said indicator.

Claim 10

A grain moisture tester as claimed in claim 7 having an insulator closely surrounding the cylindrical wall of said inner electrode the dielectric constant of said insulator being substantially one and its thickness being sufficient to prevent substantial concentration of electric field near said inner electrode as a result of unavoidable unevenness in the packing of a sample placed between said electrodes, said means connected between said test cell and said input control circuit including a Schmitt trigger circuit having an input responsive to application of alternating-current voltage to cause it to change state for each peak of voltage above a threshold amount.

Claim 11

A grain moisture tester comprising a test cell having a cylindrical container constituting an outer electrode and a cylindrical conductor constituting an inner electrode mounted coaxially within said container and electrically insulated therefrom, circuit means connected to said electrodes for measuring the permittivity of a sample placed between said electrodes, a chassis attached to the bottom of said test cell as a base therefor, said circuit means being mounted within said chassis, and a spring scale permanently fastened to said test cell and calibrated to determine the weight of a sample contained within the cell by weighing said grain moisture tester as a unit, said spring scale comprising a coil spring, an elongated scale member, and a handle, said coil spring and the lower end of said elongated scale member being disposed in said cylindrical conductor, the lower end of said coil spring being fastened to the lower end of said cylindrical conductor, the upper end of said coil spring being connected to the lower end of said elongated scale member, the upper end of said elongated scale member protruding upwardly from the upper end of said cylindrical conductor, and said handle fastened to the upper end of said elongated scale member.

Claim 12

A grain moisture tester comprising a test cell having a cylindrical container constituting an outer electrode and a cylindrical conductor constituting an inner electrode mounted coaxially within said container and electrically insulated therefrom, circuit means connected to said electrodes for measuring the permittivity of a sample placed between said electrodes, a chassis attached to the bottom of said test cell as a base therefor, said circuit means being mounted within said chassis, and a spring scale permanently fastened to said test cell and calibrated to determine the weight of a sample contained within the cell by weighing said grain moisture tester as a unit, said spring scale comprising a coil spring, an elongated scale member, and a handle, said coil spring and the lower end of said elongated scale member being disposed in said cylindrical conductor, the lower end of said coil spring being fastened to the lower end of said cylindrical conductor, the upper end of said coil spring being connected to the lower end of said elongated scale member, the upper end of said elongated scale member protruding upwardly from the upper end of said cylindrical conductor, and said handle fastened to the upper end of said elongated scale member.

Claim 13

A grain moisture tester as claimed in claim 9 in which a swivel is connected in a series with said coil spring between the lower end of said elongated scale member and the upper end of said coil spring.

Claim 14

A grain moisture tester comprising first and second spaced electrodes between which grain is placed to determine its moisture content, a signal generator having its output connected to said electrodes for applying alternating current through the capacitor formed by said electrodes, a transistor having an input control circuit and an output circuit, voltage threshold sensing means having an input connected to said electrodes and an output connected to said input control circuit of said transistor, a source of voltage connected to supply power to said signal generator and to said threshold sensing means, an indicator connected to the output of said transistor, said transistor normally operating between a nonconductive condition and a conductive condition in response to the voltage level across said cell passing through a predetermined level sensed by said voltage threshold sensing means and thereby operating said indicator to show said threshold level, biasing means including a serially connected break-down diode and a resistor connected across said source of voltage, said biasing means also being connected to said input control circuit of said transistor, said break-down diode normally being conductive to apply required bias to said transistor to make it operative in response to the voltage across said cell passing through said predetermined level, and said break-down diode becoming nonconductive in response to the voltage supplied by saId source of voltage dropping below a predetermined desirable amount for operating said signal generator and said threshold sensing means, thereby preventing conduction through said transistor and operation of said indicator.

Claim 15

A grain moisture tester comprising first and second spaced electrodes between which grain is placed to determine its moisture content, a signal generator having its output connected to said electrodes for applying alternating current through the capacitor formed by said electrodes, a transistor having an input control circuit and an output circuit, voltage threshold sensing means having an input connected to said electrodes and an output connected to said input control circuit of said transistor, a source of voltage connected to supply power to said signal generator and to said threshold sensing means, an indicator connected to the output of said transistor, said transistor normally operating between a nonconductive condition and a conductive condition in response to the voltage level across said cell passing through a predetermined level sensed by said voltage threshold sensing means and thereby operating said indicator to show said threshold level, biasing means including a serially connected break-down diode and a resistor connected across said source of voltage, said biasing means also being connected to said input control circuit of said transistor, said break-down diode normally being conductive to apply required bias to said transistor to make it operative in response to the voltage across said cell passing through said predetermined level, and said break-down diode becoming nonconductive in response to the voltage supplied by saId source of voltage dropping below a predetermined desirable amount for operating said signal generator and said threshold sensing means, thereby preventing conduction through said transistor and operation of said indicator.

Claim 16

A grain moisture tester as claimed in claim 11 wherein said threshold sensing means includes an alternating-current amplifier and a Schmitt trigger circuit, said alternating-current amplifier means having an input connected to said electrodes and an output connected to the input control circuit of said Schmitt trigger circuit, the output of said Schmitt trigger circuit being connected to said input control of said transistor, and said trigger circuit being responsive to application of alternating-current voltage from said amplifier means to cause it to change state for each peak of said applied voltage above a threshold amount.

Claim 17

A grain moisture tester as claimed in claim 12 having a resistor in series with said electrodes, the output of said generator being applied through said resistor to said electrodes.