Intelligent field interface device for fluid storage facility
First Claim
1. In a system for monitoring tank parameters at a control location in a fluid storage faciity including at least one tank including a parameter transducer associated therewith for providing a transducer output signal in response to a physical parameter of said tank including a field supply of electric power;
- a controller means at said control location for providing an interrogation signala duplex communication link connecting said control location and a field interface means at said tank for providing to said duplex communication link a parameter reading signal corresponding to said transducer output signal in response to each occurrence of said interrogation signal on said duplex communication link;
said field interface means including a transmitter/receiver including an input line and an output line;
an improved arrangement for connecting said field interface means to said duplex communication link comprising in combination;
converter means connected to said field supply of electric power for providing an FID power supply pair for providing a source of electric power to said field interface means at a constant voltage which is magnetically isolated from said field supply of electric power;
first optocoupler means connecting said input line to said duplex communication link comprising a light emitting source powered from said field supply of electric power and a light responsive switching device connected to said input line and being optically coupled to said light emitting device and powered from said FID power supply pair;
a second optocoupler means connecting said output line to said duplex communication link comprising a light emitting source powered from said FID power supply pair and a light responsive switching device connected to said duplex communication link and being optically coupled to said light emitting device and powered from said field supply of electric power; and
surge protection means shunting said field supply of electric power and earth ground.
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Accused Products
Abstract
An intelligent field interface device for use in a fluid storage facility is disclosed. A bidirectional standard serial communication bus (20) provides communication between a plurality of the interface devices (17) and a central location (18). Surge and lightning protection (50, 51) as well as a high degree of electrical and magnetic isolation (45) are provided between the power supplies of the system. Each device includes a local one chip microcomputer (35) which has a field set address (56) and communicates through optoisolation (27) with the bus through a UART (28). Analog multiplexing (40) of RTD outputs (176-179) or outputs of other transducers (162) is provided to a local to analog to digital converter (36) so that all measured tank parameters may be transmitted digitally back to the control location. An arrangement for both testing and operating a motor operated valve (110) through a two-wire circuit (141, 132) including a limit switch (119) is also shown.
95 Citations
5 Claims
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1. In a system for monitoring tank parameters at a control location in a fluid storage faciity including at least one tank including a parameter transducer associated therewith for providing a transducer output signal in response to a physical parameter of said tank including a field supply of electric power;
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a controller means at said control location for providing an interrogation signal a duplex communication link connecting said control location and a field interface means at said tank for providing to said duplex communication link a parameter reading signal corresponding to said transducer output signal in response to each occurrence of said interrogation signal on said duplex communication link; said field interface means including a transmitter/receiver including an input line and an output line;
an improved arrangement for connecting said field interface means to said duplex communication link comprising in combination;converter means connected to said field supply of electric power for providing an FID power supply pair for providing a source of electric power to said field interface means at a constant voltage which is magnetically isolated from said field supply of electric power; first optocoupler means connecting said input line to said duplex communication link comprising a light emitting source powered from said field supply of electric power and a light responsive switching device connected to said input line and being optically coupled to said light emitting device and powered from said FID power supply pair; a second optocoupler means connecting said output line to said duplex communication link comprising a light emitting source powered from said FID power supply pair and a light responsive switching device connected to said duplex communication link and being optically coupled to said light emitting device and powered from said field supply of electric power; and surge protection means shunting said field supply of electric power and earth ground. - View Dependent Claims (2, 3, 4, 5)
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Specification