US 5,708,366 AGranted

Microwave moisture/yield monitor with calibration on-the-go

AssigneeNew Holland North America, Inc.

InventorGeorge F. Nelson

Life of this patent

Estimating the term…

Loading patent…

Abstract

In a grain harvester having apparatus for measuring the moisture content of grain by directing a radio frequency signal along a measurement signal path through the grain and determining the moisture content from the phase shift and attenuation experienced by the measurement signal, calibration apparatus is provided for calibrating the moisture measurement apparatus without interrupting the grain harvesting operation. An attenuator, calibrated to a traceable standard, is selectively inserted into the measurement signal path to produce an expected attenuation of the measurement signal. The actual attenuation resulting from the insertion of the attenuator is compared with the expected attenuation and the difference is used to derive a control voltage for controlling the gain of the measurement signal path.

Claims20

Dependent claims

Apparatus for measuring the moisture content of grain comprising:

a radio frequency signal source for producing a measurement signal;
a measurement signal path including,
a transmit antenna responsive to said signal source for transmitting said measurement signal through the grain,
a gain control means for controlling the magnitude of said measurement signal as said measurement signal moves along said measurement signal path,
a receive antenna responsive to said measurement signal after it has passed through the grain,
and receiver circuit means responsive to said receive antenna for producing signals indicative of the attenuation and phase shift of said measurement signal resulting from the passage of the measurement signal through the grain;
processor means responsive to said signals indicative of the attenuation and phase shift for determining the attenuation of said measurement signal and the moisture content of the grain;
means for electrically introducing into said measurement signal path a resistance having a known attenuation to cause an expected attenuation of said measurement signal;
said processor means including means for determining the difference between an expected and an actual attenuation of said measurement signal as a result of insertion of said resistance into said measurement signal path;
and,
means for adjusting said gain control means according to said difference.

8 more elements

A method of calibrating an apparatus for measuring the moisture content of grain flowing along a grain flow path in a grain harvester, said apparatus having a radio frequency signal source and a measurement signal path including a transmit antenna responsive to said signal source for transmitting a measurement signal through the flowing grain, a receiver antenna responsive to said measurement signal after it has passed through the grain, receiver circuit means responsive to said receiver antenna for producing signals indicative of the attenuation and phase shift of said measurement signal resulting from the passage of the measurement signal through the grain, gain control means for controlling the gain of said measurement signal path, and processor means responsive to said signals indicative of the attenuation and phase shift for determining the attenuation of said measurement signal, said method comprising :

while grain is flowing along said grain flow path, electrically introducing into the measurement signal path an attenuator of known value to cause an expected attenuation of said measurement signal,
determining the difference between the expected attenuation of said measurement signal and the actual attenuation of said measurement signal resulting from the introduction of said attenuator into the measuring signal path, and,
adjusting said gain control means in accordance with said difference.

Dependencies are inferred from the claim text.