Measuring and testing – Fluid pressure gauge – Combined
Reexamination Certificate
2006-05-09
2008-03-25
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Fluid pressure gauge
Combined
Reexamination Certificate
active
07347098
ABSTRACT:
A circuit produces an output that is proportional to the molar density of gas in a chamber. The circuit employs an operational amplifier which measures the temperature using a RTD or other element that changes resistance with temperature. The RTD is placed such that it produces a decreasing current draw at the inverting input of the operational amplifier as the temperature increases. This decreasing current draw in turn produces a decreasing voltage at the output of the operational amplifier. By changing the ratio of resistors connected to the non-inverting terminal of the operational amplifier one changes the offset of the output voltage. By changing the feedback resistor connected from the output of the operational amplifier to the inverting terminal and connecting the output of the inverting terminal to a voltage divider including the RTD device, one can change the gain with temperature. Thus the output voltage of the operational amplifier is carefully controlled to be proportional to 1/T for many different temperature scales and ranges. The output of the amplifier serves as the biasing voltage for a pressure transducer.
REFERENCES:
patent: 4395915 (1983-08-01), Singh
patent: 4766763 (1988-08-01), Kurtz
patent: 5428985 (1995-07-01), Kurtz et al.
DeWeert Joseph Van
Kurtz Anthony D.
Jenkins Jermaine
Kulite Semiconductor Products Inc.
Lefkowitz Edward
Plevy, Esq. Arthur L.
The Plevy Law Firm
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