Capacitive moisture measurement

Claim 1

Apparatus for measuring a capacitance-effecting parameter of a certain mass of particulate material, such as the moisture content of grain samples, comprising: a. a supporting frame; b. receptacle means for receiving a sample of particulate material; c. spring means mounting the receptacle means with respect to the supporting frame, said spring means being sufficiently strong as to avoid substantially deflecting and thereby moving the receptacle with respect to the frame when the receptacle is empty, but insufficiently strong to prevent such deflection at the point when the receptacle has received a quantity of particulate material equalling said certain mass; d. means sensitive to movement of the receptacle for indicating when said receptacle has moved due to deflection of said spring means, thereby providing an indication of when the receptacle has received said certain mass of particulate material; e. a capacitance cell including at least two spaced capacitor plates, said cell being disposed to receive said certain mass of particulate material when the latter is dumped from said receptacle; f. means for dumping said certain mass of particulate material from said receptacle into said capacitance cell from a constant height with respect to the capacitance cell whereby the certain mass of particulate material forms a dielectric between the capacitor plates of said cell; g. an oscillatory circuit including said capacitance cell, said capacitance cell being the frequency determining element of said oscillatory circuit; h. temperature sensitive means effectively incorporated in said oscillatory circuit for automatically compensating for any expected oscillation frequency change in said circuit due to deviation of the temperature of the capacitance cell from a preselected standard temperature; i. means for sensing the oscillation frequency of said oscillatory circuit; and j. calibrated means effectively incorporated in said oscillatory circuit for adjusting the oscillation frequency of said circuit, whereby the amount of adjustment needed to restore the oscillation frequency to a preselected value when said cell contains said certain mass of particulate material, can be ascertained as a measure of capacitance-affecting parameters of the certain mass of particulate material.