The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 10, 2003
Filed:
Jul. 09, 1999
Dwight S. Larsen, Allen, TX (US);
Tamas I. Pattantyus, Dallas, TX (US);
Mykrolis Corporation, Bedford, MA (US);
Abstract
An improved mass flow sensor interface (“MFSI”) circuit and method are disclosed for sensing and measuring mass flow rate of a gas and provide an output voltage proportional to the mass flow rate in a mass flow controller. The improved MFSI circuit of the present invention includes upstream and downstream mass flow sense elements a precision current source to drive the circuit. The circuit further includes an operational amplifier to sum the voltage upstream of the upstream sense element with the voltage downstream of the downstream sense element. A reference voltage is electrically connected to the positive node of the operational amplifier. An upstream shunting resistor and a downstream shunting resistor share a common junction at the negative node of the operational amplifier and are electrically connected in parallel to the upstream and downstream mass flow sense elements. The MFSI circuit of this invention further includes a reference resistor connected between the reference voltage source and the positive node of the operational amplifier and a feedback resistor connected between the positive node and the output of the operational amplifier. The operational amplifier of the MFSI circuit provides an output signal proportional to the resistance change across the upstream and downstream sense elements, and therefore proportional to the gas mass flow rate.