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:
Jul. 19, 1988
Filed:
Aug. 28, 1986
John M Fruhwald, Pittsburgh, PA (US);
Bacharach, Inc., Pittsburgh, PA (US);
Abstract
A transmitter circuit adapted to be connected to a sensor and generate a 4-20 milliampere signal proportional to the output of the sensor includes a first amplifier which is connected to the sensor and has an output voltage proportional to the sensor output voltage. A predetermined reference voltage is supplied to a reference input of the first amplifier. A second amplifier housing an output voltage responsive to a difference between its input voltages, has its output connected to the gate of an output transistor, preferably a fluid offset transistor. An output resistor is connected between the positive power supply and the source of the output transistor. The output of the first amplifier is supplied to the positive input of the second amplifier and the voltage at the source of the output transistor is supplied to the negative input of the second amplifier. The output current for the transmitter is generated at the drain of the output transistor. If any of the positive power supply wire, the current output wire or the common potential wire should break, the output current of this transmitter circuit drops to zero.