Intrinsic safety module interface

• US 4,954,923 A
• Filed: 08/19/1988
• Issued: 09/04/1990
• Est. Priority Date: 08/19/1988
• Status: Expired due to Fees

• Current Assignee: Varco International Inc. (NOV, Inc.)
• Original Assignee: Cooper Industries, Inc. (Eaton Corporation PLC.)
• Inventors: Curry, David W., Hoeflich, John C.
• Primary Examiner(s): SALATA, ANTHONY J
• Assistant Examiner(s): Wysocki, A. Jonathan
• Application Number:
  US07/234,037
• Time in Patent Office: 746 Days
• Field of Search: 361/54, 361/56, 361/87, 361/88, 361/91, 361/111, 361/117-119, 379/98, 379/443, 379/451, 379/437, 73/23, 367/81, 367/86, 367/13, 367/147, 367/901
• US Class Current: 361/111
• CPC Class Codes: H02H 9/008 Intrinsically safe circuits

Abstract

An interface system interconnects a common power supply and plural data communications paths located in a safe environment to a plurality of load devices located in a flammable atmosphere. A module power attenuator attenuates the electrical power output level of the common power supply to a first predetermined level for application to the load devices. A digital signal attenuator attenuates the electrical power level between data communications paths to a second predetermined level for application to the load devices. Coupling devices are utilized to maintain electrical segregation but allow communication to and from the safe environment.

Claims

1. An interface system interconnecting a common power source and a plurality of data communications paths located in a safe environment to a plurality of load devices located in a flammable atmosphere which share said common power source, said interface system comprising first attenuating means in said flammable atmosphere for attenuating the electrical power supplied by said power source to said plurality of load devices to a first predetermined power level, second attenuating means in said flammable atmosphere for attenuating the electrical power delivered by said data communications paths to said plurality of load devices to a second predetermined power level, said first and second attenuating means increasing the total electrical power transferred from said common power supply to said load devices such that the sum of storage capacities of said load devices is greater than an allowable storage capacity for a single load device consisting of any of said load devices, and coupling means for segregating said power source from said data communications paths to and from said safe environment.

2. The interface system of claim 1, wherein said first attenuating means includes an electrical resistance of preselected value in series with said power source to limit the current therefrom to a respective one of said plurality of load devices, and a plurality of zener diodes connected in parallel with one another between the serially connected power source and resistance and the said respective one of the load devices, to limit the voltage supplied to said respective one of the load devices.

3. The interface system of claim 2, wherein said plurality of zener diodes consists of three zener diodes.

4. The interface system of claim 2, wherein said plurality of zener diodes consists of three zener diodes connected in parallel with one another.

5. The interface system of claim 2, wherein said second attenuating means consists solely of an electrical resistance of preselected value to limit the current of the load device associated therewith to a predetermined level.

6. The interface system of claim 1, wherein said coupling means comprises at least one opto-coupler.

7. The interface system of claim 2, wherein said coupling means comprises a plurality of opto-couplers, one in each of said data communications paths.

8. The interface system of claim 7, further including logic means for conditioning the output of the respective opto-coupler for application to a respective one of said load devices.

9. The interface system of claim 4, wherein said coupling means comprises a plurality of opto-couplers, one in each of said data communication paths, and logic means in circuit with said opto-couplers for conditioning the outputs thereof to said load devices.

10. In an electronic data acquisition and display system for monitoring and controlling equipment in flammable atmospheres, using electrical circuitry partly installed in a safe non-flammable atmosphere, the combination comprising a power supply installed in said safe atmosphere and having an intrinsically safe output circuit, a plurality of load devices disposed in said flammable atmosphere and sharing said power supply via said electrical circuitry, said load devices adapted to store electrical energy, a plurality of data communications paths disposed in said safe area, barrier means connected to said electrical circuitry and to said data communications paths for coupling said paths to said load devices while limiting the transfer of electrical energy from said paths to said devices;

said electrical circuitry including attenuating means for reducing the level of electrical energy delivered to said load devices from said power supply, and further including electrical isolation means for decoupling said data communications paths from said power supply.

11. In a system of intrinsically safe electrical circuits for installation in a flammable atmosphere for interaction with interconnected energy storage devices therein, and wherein a portion of the electrical circuits is to be installed in a safe non-flammable atmosphere, the combination comprising a power supply common to all of said energy storage devices;

a plurality of data communications circuits, one for each energy storage device;

power attenuating means connected between said power supply and said energy storage devices for increasing the total allowable energy storage capacity of the energy storage devices; and

isolating means for segregating said interconnected energy storage devices while allowing them to share power and communications from said common power supply and said plurality of data communications circuits.

12. In a system of intrinsically safe electrical circuits for installation in a flammable atmosphere for interaction with interconnected energy storage devices therein, and wherein a portion of the electrical circuits is to be installed in a safe non-flammable atmosphere, the combination comprising a power supply common to all of said energy storage devices;

a plurality of data communications circuits, one for each energy storage device; and

means for increasing the total power transferred from said common power supply to said plurality of energy storage devices, such that the sum of the storage capacities of said plurality of energy storage devices is greater than the allowable storage capacity for a single intrinsically safe device consisting of any of said plurality of energy storage devices.