Operation

Amplitude Measurements

Once the two signals have been separated at each corner, the overall level of the signal must be determined. A change of position is in general manifested in a change of amplitude. The signal's amplitude must therefore be determined in order to calculate its position on the board. There are three methods that are being investigated at this time. The first is phase-sensitive detection. This is the method used by the original system. The input signal is rectified, and then low-pass filtered to produce a DC voltage that is proportional to the amplitude. The second method involves using an RMS to DC converter IC. The chip is designed to output a DC voltage equivalent to the RMS value of the input AC waveform. These chips, while fairly expensive, would take up less space on a circuit board, and simply the circuit significantly. The third method being investigated involves reading the AC waveforms into a PIC, and using the peak values of the waveform read to determine the amplitude of the AC signal. This method would be favorable if it is decided that x, y and z-axis calculations will be done within the control box. This feature is explained below.

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The Radio Drum is a three dimensional motion sensing device. It uses capacitive moments sensing to determine the position of an object moving in a three-dimensional space above a surface. The goal of this project is to redesign the Radio Drum control box for UVATT with the purpose of minimizing cost and size.
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