Intrinsically safe photoelectric sensing

Claim 2

An intrinsically safe sensing system comprising: a photoelectric sensing means including a photoelectric transmitter and a photoelectric receiver; circuitry means for operatively interconnecting said photoelectric sensing means to a power source, said circuitry means including electrical barrier means for limiting the energy to said sensing means to a safe level; electrical cable interconnecting means extending between said photoelectric sensing means and said circuitry means, said interconnecting means being long enough to provide for positioning of said sensing means in a hazardous area, and positioning of said circuitry means in a safe area; and wherein said circuitry means is provided in a single module located in a safe area.

Claim 3

An intrinsically safe sensing system comprising: a photoelectric sensing means including a photoelectric transmitter and a photoelectric receiver; circuitry means for operatively interconnecting said photoelectric sensing means to a power source, said circuitry means including electrical barrier means for limiting the energy to said sensing means to a safe level; electrical cable interconnecting means extending between said photoelectric sensing means and said circuitry means, said interconnecting means being long enough to provide for positioning of said sensing means in a hazardous area, and positioning of said circuitry means in a safe area; and wherein said circuitry means comprises a transmitting circuit with barrier means, and a receiving circuit with barrier means; said transmitting circuit including a transistor electrically interconnected between said cable interconnecting means and said transmitting circuit barrier means; and said receiving circuit including a preamplifier electrically interconnected between said cable interconnecting means and said receiver circuit barrier means, so that a signal from said photoelectric receiver will pass through said barrier means withous significant degradation.

Claim 4

An intrinsically safe sensing system comprising: a photoelectric sensing means including a photoelectric transmitter and a photoelectric receiver; circuitry means for operatively interconnecting said photoelectric sensing means to a power source, said circuitry means including electrical barrier means for limiting the energy to said sensing means to a safe level; electrical cable interconnecting means extending between said photoelectric sensing means and said circuitry means, said interconnecting means being long enough to provide for positioning of said sensing means in a hazardous area, and positioning of said circuitry means in a safe area; and wherein said circuitry means comprises a transmitting circuit with barrier means, and a receiving circuit with barrier means; said transmitting circuit including a transistor electrically interconnected between said cable interconnecting means and said transmitting circuit barrier means; and said receiving circuit including a preamplifier electrically interconnected between said cable interconnecting means and said receiver circuit barrier means, so that a signal from said photoelectric receiver will pass through said barrier means withous significant degradation.

Claim 5

An intrinsically safe sensing system comprising: a photoelectric sensing means including a photoelectric transmitter and a photoelectric receiver; circuitry means for operatively interconnecting said photoelectric sensing means to a power source, said circuitry means including electrical barrier means for limiting the energy to said sensing means to a safe level; electrical cable interconnecting means extending between said photoelectric sensing means and said circuitry means, said interconnecting means being long enough to provide for positioning of said sensing means in a hazardous area, and positioning of said circuitry means in a safe area; and wherein said circuitry means comprises means for supplying a low frequency ac current to said photoelectric transmitter and for receiving low frequency ac current from said photoelectric receiver, said photoelectric transmitter and receiver being ac coupled.

Claim 6

An intrinsically safe sensing system comprising: a photoelectric sensing means including a photoelectric transmitter and a photoelectric receiver; circuitry means for operatively interconnecting said photoelectric sensing means to a power source, said circuitry means including electrical barrier means for limiting the energy to said sensing means to a safe level; electrical cable interconnecting means extending between said photoelectric sensing means and said circuitry means, said interconnecting means being long enough to provide for positioning of said sensing means in a hazardous area, and positioning of said circuitry means in a safe area; and wherein said circuitry means comprises means for supplying a low frequency ac current to said photoelectric transmitter and for receiving low frequency ac current from said photoelectric receiver, said photoelectric transmitter and receiver being ac coupled.

Claim 7

An intrinsically safe sensing system comprising: a sensing means; circuitry means for operatively interconnecting said sensing means to a power source; said circuitry means comprising: a transmitting circuit, with electrical barrier means for limiting the energy from said sensing means to a safe level; and a receiving circuit, with electrical barrier means for limiting the energy to said sensing means to a safe level; electrical cable interconnecting means extending between said sensing means and said circuitry means, said interconnecting means being long enough to provide for positioning of said sensing means in a hazardous area, and positioning of said circuitry means in a safe area; said transmitting circuit including a transistor electrically interconnected between said cable interconnecting means and said transmitting circuit barrier means; said receiving circuit including a preamplifier electrically interconnected between said cable interconnecting means and said receiver circuit barrier means so that a signal from said sensing means will pass through said barrier means without significant degradation; and said circuitry means being provided on a single module located in a safe area.

Claim 8

An intrinsically safe sensing system comprising: a sensing means; circuitry means for operatively interconnecting said sensing means to a power source; said circuitry means comprising: a transmitting circuit, with electrical barrier means for limiting the energy from said sensing means to a safe level; and a receiving circuit, with electrical barrier means for limiting the energy to said sensing means to a safe level; electrical cable interconnecting means extending between said sensing means and said circuitry means, said interconnecting means being long enough to provide for positioning of said sensing means in a hazardous area, and positioning of said circuitry means in a safe area; said transmitting circuit including a transistor electrically interconnected between said cable interconnecting means and said transmitting circuit barrier means; said receiving circuit including a preamplifier electrically interconnected between said cable interconnecting means and said receiver circuit barrier means so that a signal from said sensing means will pass through said barrier means without significant degradation; and said circuitry means being provided on a single module located in a safe area.

Claim 9

A single module for use in a safe area as part of an intrinsically safe sensing system, said module comprising: a base of electrically insulating sheet material, having a safe area end and a hazardous area end; a first set of terminals on said safe area end of said base; a second set of terminals on said hazardous area end of said base; a transmitting circuit mounted on said base, operatively electrically connected to said first and second terminal sets, and including: electrical barrier means for limiting the energy from said first set of terminals to said second set of terminals to a safe level; and a transistor, said transistor electrically connected between said barrier means and said second set of terminals; a receiving circuit mounted on said base, operatively electrically connected to said first and second terminal sets, and including: electrical barrier means for limiting the energy to said first set of terminals from said second set of terminals to a safe level; and a preamplifier, said preamplifier electrically connected between said barrier means and said second set of terminals; and means for encapsulating said transmitting and receiving circuits to prevent access thereto, while allowing testing of said circuits.

Claim 10

A single module for use in a safe area as part of an intrinsically safe sensing system, said module comprising: a base of electrically insulating sheet material, having a safe area end and a hazardous area end; a first set of terminals on said safe area end of said base; a second set of terminals on said hazardous area end of said base; a transmitting circuit mounted on said base, operatively electrically connected to said first and second terminal sets, and including: electrical barrier means for limiting the energy from said first set of terminals to said second set of terminals to a safe level; and a transistor, said transistor electrically connected between said barrier means and said second set of terminals; a receiving circuit mounted on said base, operatively electrically connected to said first and second terminal sets, and including: electrical barrier means for limiting the energy to said first set of terminals from said second set of terminals to a safe level; and a preamplifier, said preamplifier electrically connected between said barrier means and said second set of terminals; and means for encapsulating said transmitting and receiving circuits to prevent access thereto, while allowing testing of said circuits.

Claim 12

A system as recited in claim 3 wherein said circuitry means further comprises a signal processing circuit, said circuitry means mounted on a single module located in the safe area.

Claim 13

A system as recited in claim 1 wherein said circuitry means comprises a transmitting circuit with barrier means, and a receiving circuit with barrier means, and wherein said transmitting and receiving circuits are each encapsulated on said module to prevent access thereto.

Claim 14

A system as recited in claim 8 wherein said transmitting circuit includes a transistor electrically interconnected between said cable interconnecting means and said transmitting circuit barrier means, and wherein said receiving circuit includes a preamplifier electrically interconnected between said cable interconnecting means and said receiver circuit barrier means, so that a signal from said photoelectric receiver will pass through said barrier means without significant degradation.

Claim 15

A system as recited in claim 5 wherein said base has a cutout formed therein disposed generally between said transmitting and receiving circuits; and wherein each of said transmitting and receiving circuits includes a plurality of Zener diodes; and an electrically conductive material bar dispose on said base on the opposite side thereof as said transmitting and receiving circuits and accessible through said cutout in said base; said Zener diodes electrically connected at one end thereof to said bar.

Claim 18

A module as recited in claim 5 further comprising a signal processing circuit mounted on said base between said transmitting circuit and said receiving circuit, and said second set of terminals, and operatively electrically connected between said first set of terminals and said transmitting and receiving circuits.

Claim 19

A system as recited in claim 4 wherein said sensing means comprises photoelectric sensing means.