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:
May. 31, 1994
Filed:
Jul. 01, 1991
Jonathan Castle, Los Angeles, CA (US);
Moore Industries International Inc., Sepulveda, CA (US);
Abstract
A microprocessor-controlled remote resistance measurement system is disclosed wherein the connection leads to the three- or four-wire resistance temperature devices (RTDs) are multiplexed via a four-channel analog multiplexer at the input of the unit. A separate two-channel multiplexer is also used to multiplex a fifth input for measurement of a reference resistor. The output of the multiplexer is coupled to a voltage-to-frequency converter, wherein the frequency output is utilized as an input to the microprocessor-based controller. The microcontroller can check for broken wires by addressing the multiplexers to individually isolate any of the connecting wires to the remote RTD sensors. The output of the multiplexer is monitored in a Test Mode by connecting a known impedance to the multiplexer output to determine if any RTD connections are defective. If one of the voltage sensing wires is faulty, the known impedance will cause an erroneous frequency reading into the microcontroller, which will then provide an indication on the display for determining exactly which RTD wire is broken. Only two address lines are used to control the five multiplexer channels through the use of a function selector circuit and a two-stage measurement cycle.