Single channel electrical comparative measuring system
First Claim
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1. Apparatus for processing measured parameters including:
- sensing means for receiving two parameters to be measured and for providing two capacitance measurement values respectively functionally related to the parameters received by said sensing means,a single channel means responsive to such capacitance measurement values for producing output signals with frequencies functionally related to such capacitance measurement values from said sensing means,means for providing a reference voltage, andmeans for alternately coupling said reference voltage and said single channel means to said sensing means for referencing a capacitance measurement value alternately to said voltage reference and applying a capacitance measurement value to said single channel means.
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Abstract
A measuring system based on using a ratio of variable capacitance measurements derived from alternate sampling and referencing of at least two capacitance devices and use of a single channel for the capacitance outputs so that the measurements are basically independent of the circuit components, supply voltage, temperature drift problems. The measurements can be high resolution digital signals.
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Citations
18 Claims
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1. Apparatus for processing measured parameters including:
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sensing means for receiving two parameters to be measured and for providing two capacitance measurement values respectively functionally related to the parameters received by said sensing means, a single channel means responsive to such capacitance measurement values for producing output signals with frequencies functionally related to such capacitance measurement values from said sensing means, means for providing a reference voltage, and means for alternately coupling said reference voltage and said single channel means to said sensing means for referencing a capacitance measurement value alternately to said voltage reference and applying a capacitance measurement value to said single channel means. - View Dependent Claims (2, 3, 4, 5, 6)
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7. Electrical measuring apparatus including:
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sensing means having separate components for respectively receiving a parameter for measurement and for producing measured signals related to said parameters; means for providing a reference signal to said sensing means; single channel means for processing a measured signal and for developing a corresponding pulse width signal; means for alternately coupling said separate components from said sensing means to said single channel means and said means for providing a reference signal so that, in one alternate coupling, one of said separate components from said one sensing means is coupled to said reference signal and a second one of said separate components from said sensing means is coupled to said single channel and, in the other alternate coupling, the first one of said separate components from said one sensing means is coupled to said single channel means and the second one of said separate components from said sensing means is coupled to said reference signal. - View Dependent Claims (8, 9, 10)
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11. Apparatus for use in measuring differential pressures as a ratio including:
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functionally interrelated first and second capacitor means for sensing the pressure in at least two pressure conduits where said capacitor means are electrically chargeable at a rate proportion to pressure; comparator means responsive to a capacitor means for producing an alternating signal having a time period related to the rate of charging for the capacitor means; a source of reference voltage;
an insulated-gate metal oxide semi-conductor means coupled between said capacitor means and said comparator means for selectively coupling, in a first condition, one of said first or second capacitor means to said comparator means and for coupling said reference voltage to the other of said first or second capacitor means and for coupling, in a second condition, the said other of said first or second capacitor means to said comparator means and for coupling said reference voltage to the said one of said first or second capacitor means. - View Dependent Claims (12)
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13. Apparatus for use in measuring the magnitude values of a capacitance means where such magnitudes are functionally related to measured parameters, said apparatus being a subcombination comprised of:
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comparator means responsive to alternately occurring first and second magnitude values derived from capacitance means for producing an alternating signal where half cycles of said alternating signal have time periods related to the magnitude of said first and second magnitude values, an insulated-gate metal oxide semi-conductor means for receiving such first and second magnitude values at first and second inputs and for receiving a reference voltage from a reference voltage source, said semi-conductor means in a first condition, coupling one of said capacitance magnitude values to said comparator means and coupling such reference voltage to one of said first and second inputs, and in a second condition, coupling the other of said capacitance magnitude values to said comparator means and coupling such reference voltage to the other of said first and second inputs; and means responsive to said alternating signal coupling said semi-conductor means to the output of said comparator means for switching said semi-conductor means between said first and second conditions, thereby alternately coupling such first and second magnitude values to said comparator means. - View Dependent Claims (14, 15)
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16. A method for measuring physical parameters using a common detecting channel and including the steps of:
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applying at least one such physical parameter to a first capacitance sensing means which initially is at a reference voltage level for developing a capacitance value as a function of the magnitude of the applied parameter; electrically clamping a second capacitance sensing means to such reference voltage while such first capacitance sensing means develops a capacitance value; applying the capacitance value of such first capacitance sensing means to a common electrical channel means and producing a first pulse width signal as a function of the capacitance value developed by such first capacitance sensing means; switching such reference voltage to the first capacitance sensing means to electrically clamp such first capacitance sensing means to such reference voltage while applying to such second capacitance sensing means another physical parameter for developing a capacitance value as a function of the magnitude of such another applied parameter; and
applying the capacitance value developed by such second capacitance sensing means to such common electrical channel means for producing a second pulse width signal as a function of the magnitude of such another applied parameter. - View Dependent Claims (17)
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18. A method for measuring parameters including the steps of:
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applying at least two measurement parameters to capacitance sensing means for developing respective capacitance values as a function of the applied parameters; electrically clamping a first capacitance sensing means to a reference voltage while connecting a second capacitance sensing means to a single channel capacitance responsive circuit means; obtaining a first pulse width signal from said circuit means, said pulse width signal being functionally related to the capacitance value of said second capacitance sensing means; and obtaining a second pulse width signal for the other parameter by electrically clamping the second capacitance sensing means to the reference voltage while connecting the first capacitance sensing means to such circuit means.
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Specification