The system includes two conductive sensors to be placed in contact with a body which exhibits voltage changes, such as the leaves of a plant. The sensors are connected to an amplifier having high input impedance and connected with positive feedback and providing good common mode rejection. The amplifier output, in response to voltage changes sensed by the sensors, drives a coil having an iron core, and current flow through the coil is sensed by a utilization device, which, in one arrangement, comprises a magnet secured to the clapper of wind bells.
A corn moisture tester is adapted to measure the moisture content of corn kernels on an ear of corn. The ear of corn may be affixed to the corn stalk. The device includes an ear cradle, a pair of electrode blades and circuit for measuring a moisture-dependent electrical property of the corn kernels. The cradle is adapted for receiving an ear of corn and includes two portions hinged together so they may be opened to receive the ear. When the cradle portions are closed, they form a substantially cylindrical interior cradle surface for engaging the ear of corn. The conductor blades are mounted to one portion of the cradle to pierce the kernels but not the cob when the cradle is closed about an ear under test. The electrical property measuring circuit generates and displays a signal representative of moisture.
A zero capacitance measurement probe to be used to make electrical measurements at a broad range of frequencies without having the probe itself affect the measured values. The probe reduces internal capacitances in the solid state active elements or creates a negative impedance to counteract capacitance external capacitance. Elimination of capacitance is accomplished by adjusting gains and current flow within active elements and by insulating the elements from ground by an additional substrate and metalized layer.
