| 摘要 |
<p>The harvester has 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.</p> |
