| 摘要 |
Apparatus is disclosed for calibrating a known type of electrical instrument which is used for measuring the amount of moisture in a sample of grain or other particulate material. The instrument operates on the principle that the intensity of an electrostatic field will change in proportion to the moisture content of a material sample of predetermined size placed in the field, i.e., in proportion to the dielectric constant of the sample. The instrument comprises a test cell for receiving the sample and comprises a container having a concentrically disposed electrode therewithin which are part of a resonant electrical circuit; means for establishing a balanced electrostatic field of known intensity in the space between the container wall and electrode; means for measuring the change in field intensity (i.e., an increase in capacitance) effected by the moisture content of the sample and for providing a visual meter readout in the form of a numeric value correlated to the change in field intensity (and thus moisture content); and means for readjusting or recalibrating the instrument to re-establish the desired field intensity in the event of an undesired change therein. The calibration apparatus comprises a dielectric member for slideable insertion between the container wall and the electrode to a predetermined distance to effect a change in field intensity, means for holding the dielectric member in a desired position in the test cell, a pointer detachably connectable to the test cell, and a graduated scale on the dielectric member for cooperation with the pointer to indicate visually a numeric value which corresponds to a numeric value which will appear as the visual meter readout if the instrument is calibrated correctly.
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