Low-cost, high-accuracy digitizer signal acquisition apparatus and method
First Claim
1. In a digitizer having one or more conductors disposed across an area and an instrument moved across the area to selected positions to be digitized and producing an analog voltage signal having a DC component related to the position of the instrument, the improvement for producing a digital value from the signal dependent on the position of the instrument on the area comprising:
- (a) voltage to frequency conversion means for receiving the analog voltage signal and for converting it to a pulsed signal at a frequency which is a monotonically increasing or decreasing function of the voltage level of the analog voltage signal; and
,(b) counter means for receiving said pulsed signal from said voltage to frequency conversion means, for counting the pulses of said pulsed signal for an interval, and for producing at an output thereof a digital value proportional to the pulse count whereby said digital value is a monotonically increasing or decreasing function of the voltage level of the analog voltage signal.
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Accused Products
Abstract
An improvement to position digitizing devices wherein sensed response voltages caused by the interaction of a movable instrument relative to conductors beneath a planar surface are converted to digital form and digitally processed to determine instrument position. An integrating voltage to frequency converter is used to produce a frequency with a correspondence to the voltage applied to it. By counting the frequency for a defined length of time, a resultant count is obtained which also corresponds to the applied voltage. By varying the counting period under microprocessor control, acquisition rate and resolution can be varied over several orders of magnitude without changing circuit components. The digitizer includes conductive elements disposed across the digitizing surface and incorporated into an instrument for producing an analog voltage signal having a DC component related to the position of the instrument on the digitizing surface. There is a voltage to frequency converter for receiving the analog voltage signal and for converting it to a pulsed signal at a frequency which is a monotonically increasing or decreasing function of the voltage level of the analog voltage signal. There is a counter for receiving the pulsed signal from the voltage to frequency converter, for counting the pulses of the pulsed signal, and for producing a digital value output proportional to the counted pulses whereby the digital value is similarly related to the voltage level of the analog voltage signal.
23 Citations
27 Claims
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1. In a digitizer having one or more conductors disposed across an area and an instrument moved across the area to selected positions to be digitized and producing an analog voltage signal having a DC component related to the position of the instrument, the improvement for producing a digital value from the signal dependent on the position of the instrument on the area comprising:
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(a) voltage to frequency conversion means for receiving the analog voltage signal and for converting it to a pulsed signal at a frequency which is a monotonically increasing or decreasing function of the voltage level of the analog voltage signal; and
,(b) counter means for receiving said pulsed signal from said voltage to frequency conversion means, for counting the pulses of said pulsed signal for an interval, and for producing at an output thereof a digital value proportional to the pulse count whereby said digital value is a monotonically increasing or decreasing function of the voltage level of the analog voltage signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An improved digitizer for providing a digital value representing the position of a instrument on a digitizing surface comprising:
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(a) means disposed across the digitizing surface and incorporated into the instrument for, in combination, producing an analog voltage signal having a DC component related to the position of the instrument on the digitizing surface; (b) voltage to frequency conversion means for receiving said analog voltage signal and for converting it to a pulsed signal at a frequency which is a monotonically increasing or decreasing function of the voltage level of the analog voltage signal; and
,(c) counter means for receiving said pulsed signal from said voltage to frequency conversion means, for counting the pulses of said pulsed signal over an interval, and for producing at an output thereof a digital value proportional to the counted pulses whereby said digital value is a monotonically increasing or decreasing function of the voltage level of the analog voltage signal. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. In a digitizer having at least one conductor disposed across an area and a instrument moved across the area to selected positions to be digitized and producing an analog voltage signal having a DC component related to the position of the instrument, the improved method for producing a digital value from the signal related to the position of the instrument on the area comprising the steps of:
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(a) receiving the analog voltage signal and converting it to a pulsed signal at a frequency which is a monotonically increasing or decreasing function of the voltage level of the analog voltage signal; and
,(b) receiving the pulsed signal, counting the pulses of the pulsed signal over an interval, and producing a digital value proportional to the counted pulses whereby the digital value is a monotonically increasing or decreasing function of the voltage level of the analog voltage signal. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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Specification