Electronic Keyboard Pivot Plate Status Change Detector
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
The Electronic Keyboard Pivot Plate Status Change Detector facilitates the rapid detection of pivot plate status changes while testing keyboards. The circuit derives its value from its ability to compensate for tester fixtures 12, which have different capacitances for each switch matrix pad card connection pair. The circuit permits each fixture matrix connection circuit to have an equivalent capacitive value from 0 pf to 20 pf. This fixture capacitance must be stable during the period in which its associated keybutton position is being tested. The fundamental element of the circuit is a very stable capacitance excited 1 MHz to 1.5 MHz oscillator 10, whose frequency varies approximately 10 KHz for each 2 pf change in input capacitance.