High precision, high frequency current sensing and analog signal decoding network
First Claim
1. A network employing current sensing and analog signal decoding to measure a desired parameter, said network comprising:
- first means for sensing the desired parameter and outputting a first current signal related to a unit measure of the desired parameter, said first means including a first sensor for producing a first sensor signal, a second sensor for producing a second sensor signal, and drive means for providing said first sensor with a first drive signal having a predetermined carrier frequency and said second sensor with a second drive signal having said predetermined carrier frequency; and
second means, responsive to said first current signal, for demodulating said first current signal to obtain a demodulated signal having a component that reflects the unit measure of the desired parameter, said second means including feedback means for generating an offset signal having a component proportional to said component of said demodulated signal and combining said offset signal with said first current signal to provide a resultant signal having a component that reflects the unit measure of changes in the desired parameter.
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Abstract
An apparatus and method are provided for performing parametric measurements using sensor transducer devices to recover frequency variant, amplitude modulated information from encoded sensory signals. A unique network is employed to achieve low-impedance current sensing in conjunction with analog signal decoding. More particularly, the network includes a circuit for current sensing the desired parameter and providing an analog sensor output signal related to the unit measure (i.e., relative value) of the desired parameter. The network also includes a circuit for receiving the demodulating the sensor output signal to obtain a signal representing the electrical equivalence of the measured parameter. The circuit for demodulating employs synchronous sampling techniques and includes a subcircuit, closed-loop through which the demodulated output is fed for generating an offset or error correcting signal. The offset signal is combined with the sensor output signal to generate a resultant signal reflecting static and dynamic changes in the parameter of interest.
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Citations
27 Claims
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1. A network employing current sensing and analog signal decoding to measure a desired parameter, said network comprising:
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first means for sensing the desired parameter and outputting a first current signal related to a unit measure of the desired parameter, said first means including a first sensor for producing a first sensor signal, a second sensor for producing a second sensor signal, and drive means for providing said first sensor with a first drive signal having a predetermined carrier frequency and said second sensor with a second drive signal having said predetermined carrier frequency; and second means, responsive to said first current signal, for demodulating said first current signal to obtain a demodulated signal having a component that reflects the unit measure of the desired parameter, said second means including feedback means for generating an offset signal having a component proportional to said component of said demodulated signal and combining said offset signal with said first current signal to provide a resultant signal having a component that reflects the unit measure of changes in the desired parameter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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10. A network employing current sensing and analog signal decoding to measure a desired parameter associated with an object, said network comprising:
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a first reflected impedance transducer (RIT) for producing a first RIT signal and a second RIT sensor for producing a second RIT signal, wherein said first RIT and said second RIT are each driven at a predetermined carrier frequency to establish proper magnetization coupling with the object; establishing means, operatively communicating with said first and second RIT sensors for providing said first RIT sensor with a first drive signal having said predetermined carrier frequency and said second RIT sensor with a second drive signal having said predetermined carrier frequency and substantially 180°
out of phase with said first drive signal; andcombining means for combining said first RIT signal with said second RIT signal to produce a first current signal, wherein the portions of said first sensor signal and said second sensor signal at said predetermined carrier frequency are substantially eliminated from said first current signal; demodulating means, responsive to said first current signal, for demodulating said first current signal to obtain a demodulated signal having a component that reflects the unit measure of the desired parameter; wherein said demodulating means includes; feedback means for generating a second current signal having a component proportional to said component of said demodulated signal and combining said second current signal with said first current signal to provide a resultant current signal having a component that reflects the unit measure of changes in the desired parameter, wherein said feedback means has a substantially linear transfer function; converting means for converting said resultant current signal to a corresponding resultant voltage signal; sampling means for sampling said resultant voltage signal to generate a sampled signal, wherein said sampling means includes a capacitor that operates in a substantially net zero volt mode; synchronizing means for synchronizing operation of said sampling mans with said establishing means wherein said resultant voltage signal is sampled at predetermined intervals such that phase correlation demodulation is achieved; and integrating means, responsive to said sampled signal, for integrating said sampled signal to provide said demodulated output signal.
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11. A method for measuring desired parameters by employing low impedance current sensing and analog signal decoding, said method comprising the steps of:
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providing sensing means for sensing the desired parameter and producing a current signal relating to the desired parameter; sensing the desired parameter and producing said current signal related to the desired parameter; and wherein said sensing means includes a first sensor for providing a first sensor signal and a second sensor for providing a second sensor signal; transmitting a first drive signal having a predetermined frequency to said first sensor; and transmitting a second drive signal that has substantially said predetermined frequency and is phase shifted by approximately 180°
relative to said first drive signal to said second sensor;demodulating said current signal to obtain a demodulated signal having a component that reflects a unit measure of the desired parameter, wherein said step of demodulating includes; generating an offset signal proportional to said component of said demodulated output signal; combining said offset signal with said current signal to provide a resultant alternating signal having a component that reflects changes in the unit measure of the desired parameter; sampling said resultant alternating signal to produce a sampled signal. - View Dependent Claims (27)
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Specification