Process gas distribution system and method with automatic transducer zero calibration
First Claim
1. In or for a process gas distribution control unit which handles hazardous gases, said control unit having at least one gas pressure measurement transducer for measuring the pressure of gas handled by said control unit and outputting a measured output correlated to the pressure wherein there is an ideal output for each value of pressure,a system for correcting the measured output to approximate the ideal output at corresponding values of pressure, comprising:
- means for subjecting said transducer to a known value of pressure to cause said transducer to output a measured output, there being a known ideal output for said known value of pressure,means for reading the measured output of said transducer at said known value of pressure,means for developing an offset correlated to the difference between said measured output and said known ideal output at said known value of pressure,memory means for storing data corresponding to said offset value, andcorrection means utilizing the stored data corresponding to said offset value for correcting all subsequent measured outputs of said transducer by adding or subtracting said offset value to said subsequent measurements of said transducer.
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Accused Products
Abstract
A system including a plurality of gas flow control units in cabinets which are connected to distribute process gas, on demand, to a plurality of utilization locations known as "tool" locations in a semi-conductor manufacturing plant. Transducers are used in the system to measure pressures and other control parameters. Zero calibration of the transducers is provided by automatically subjecting each transducer to a reference computer routine to compute the difference between the standard value and the transducer output, and store the difference as an "offset" to correct the output of the transducer. Thus, re-calibration is performed simply and quickly, at a relatively low labor cost and with relatively little downtime for the system.
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Citations
17 Claims
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1. In or for a process gas distribution control unit which handles hazardous gases, said control unit having at least one gas pressure measurement transducer for measuring the pressure of gas handled by said control unit and outputting a measured output correlated to the pressure wherein there is an ideal output for each value of pressure,
a system for correcting the measured output to approximate the ideal output at corresponding values of pressure, comprising: -
means for subjecting said transducer to a known value of pressure to cause said transducer to output a measured output, there being a known ideal output for said known value of pressure, means for reading the measured output of said transducer at said known value of pressure, means for developing an offset correlated to the difference between said measured output and said known ideal output at said known value of pressure, memory means for storing data corresponding to said offset value, and correction means utilizing the stored data corresponding to said offset value for correcting all subsequent measured outputs of said transducer by adding or subtracting said offset value to said subsequent measurements of said transducer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 14)
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9. In or for a process gas distribution control unit which handles hazardous process gases, said control unit having at least one gas pressure measurement transducer for measuring the pressure of gas handled by said control unit and outputting a measured output correlated to the pressure, wherein there is an ideal output for each value of pressure,
a method for correcting the measured output of said pressure transducer to approximate the ideal output at a corresponding value of pressure, comprising the steps of: -
subjecting said transducer to a known value of pressure to cause said transducer to output a measured output, there being a known ideal output for said know value of pressure, reading the measured output of said transducer at said known value of pressure, developing an offset value correlated to the difference between said measured output and said known ideal output at said known value of pressure, storing data corresponding to said offset value in memory means, and correcting all subsequent measured outputs of said transducer by adding or subtracting said data corresponding to said offset value to said subsequent measurements by said transducer. - View Dependent Claims (10, 11, 12, 13, 15, 16, 17)
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Specification