Grain sensor using a piezoelectric element

A grain sensor comprising:

• a piezoelectric element, a relatively thin, flat sounding board of substantially greater surface area than said piezoelectric element, mounting means for mounting said piezoelectric element to a first surface of said sounding board whereby forces experienced by said sounding board due to grain particles impinging thereupon are imparted to said piezoelectric element, rigid frame means for surroundingly engaging side edges of said sounding board thereby holding a second surface thereof, opposite said first surface, exposed to impingement by said grain particles, said rigid frame means including inwardly extending flange means for substantially covering a peripheral edge portion of said second surface, wherein at least a portion of said first surface of said sounding board is electrically conductive and wherein said mounting means includes electrically conductive cement means for joining one electrode of said piezoelectric element with said at least one electrically conductive portion of said sounding board first surface, and wherein said first sounding board surface includes at least two electrically separate electrically conductive portions, said one electrode being joined to one of said electrically conductive portions and wherein said mounting means further includes electrically conductive strap means joined to and in electrical contact with an opposite electrode of said piezoelectrical element and with a second of said at least two electrically conductive portions of said sounding board first surface.