High, low and thermocouple burn-out alarm system

Claim 2

An alarm system for a temperature sensitive transducer subject to an open circuit condition, including in combination: a. alarm signal translating circuitry connected between said transducer and an alarm energizing means for providing a signal path for hot and cold alarm signals at said transducer, which signals in turn alter the conductive state of said alarm energizing means and thereby provide electrical control of visual or audible alarm indicators, b. said signal translating circuitry including a current steering gate connected to said alarm energizing means and responsive to hot, cold and burn-out alarm signals from said temperature sensitive transducer to alter the conductive state of said alarm energizing means, and c. an electroresponsive current switch connected between said current steering gate and a selected node in the signal path of said signal translating circuitry, said current switch responsive to a predetermined voltage change at said selected node to thereby provide a corresponding change in current flowing through said alarm energizing means and an indication of an alarm condition at said transducer.

Claim 3

The alarm system defined in claim 1 wherein said current steering gate includes first and second emitter coupled transistors connected to said current switch, one of said first and second emitter coupled transistors connectable to receive hot and cold alarm signals from said signal translating circuitry and the other of said first and second emitter coupled transistors connected to a reference potential, whereby the connections of said first and second emitter coupled transistors to receive said hot and cold alarm signals and said reference potential, respectively, are interchangeable for the hot and cold alarm operations of said system.

Claim 4

The alarm system defined in claim 2 wherein said signal translating circuitry includes a differential amplifier means connected to said temperature sensitive transducer and further connected to said selected node to generate said predetermined voltage change at said selected node necessary to drive said burnout control switch means nonconducting upon the occurrence of an open circuit condition at said transducer, said differential amplifier means operative to amplify both increasing and decreasing cold and hot alarm signals, respectiVely, for controlling the conductive state of said steering gate without affecting the conductive state of said burnout control switch means in the absence of an open circuit condition at said transducer.

Claim 5

The alarm circuitry defined in claim 3 wherein said signal translating circuitry further includes step function generating means interconnected between said differential amplifier means and said current steering gate, said step function generating means connected to receive a set point reference voltage in addition to hot and cold alarm signals from said differential amplifier means for generating predetermined step functions to drive said current steering gate to predetermined states of conduction and to thereby control said alarm energizing means in response to both hot and cold alarm signals amplified in said signal translating circuitry.

Claim 6

Alarm condition responsive circuitry, including in combination: a. amplifier means responsive to an open circuit or burnout alarm condition to provide a predetermined voltage change at the output terminal thereof, b. current switch means including a transistor connected to both said output terminal of said amplifier means and to an alarm energizing means and responsive to said predetermined voltage change for altering the electrical signal condition at said alarm energizing means, thereby providing an alarm indication of said open circuit or burnout alarm condition, whereby said transistor serves as a source of substantially constant current for said alarm energizing means during normal non-alarm operation of said circuitry and interrupts current flowing through said alarm energizing means in response to said predetermined voltage change at the output of said amplifier means.

Claim 7

Alarm condition responsive circuitry, including in combination: a. amplifier means responsive to an open circuit or burnout alarm condition to provide a predetermined voltage change at the output terminal thereof, b. current switch means including a transistor connected to both said output terminal of said amplifier means and to an alarm energizing means and responsive to said predetermined voltage change for altering the electrical signal condition at said alarm energizing means, thereby providing an alarm indication of said open circuit or burnout alarm condition, whereby said transistor serves as a source of substantially constant current for said alarm energizing means during normal non-alarm operation of said circuitry and interrupts current flowing through said alarm energizing means in response to said predetermined voltage change at the output of said amplifier means.

Claim 8

Circuitry defined in claim 5 wherein: a. said amplifier means includes a differential amplifier connected to a thermocouple and responsive to both normal temperature induced voltage changes at said thermocouple and burnout or open circuit conditions at said thermocouple to provide an output alarm signal voltage at the output terminal thereof, and b. a current steering gate coupled to said differential amplifier and further connected between said current switch means and said alarm energizing means, said current steering gate conducting current through said alarm energizing means during the nonalarm operation of said circuitry and interrupting current flowing through said alarm energizing means during alarm conditions to thereby provide electrical control of alarm indicators controlled by said alarm energizing means.

Claim 9

Circuitry defined in claim 6 wherein: a. said alarm energizing means is a relay, said circuitry further including b. a Schmitt trigger interconnected between said current steering gate and the output of said differential amplifier and responsive to signal voltage changes thereat for controlling the conductive state of said current steering gate, and thereby controlling the energization of said relay, and c. means for applying predetermined reference voltages to both said current steering gate and to said Schmitt trigger to establish the level of switching therein in accordance with the set point temperature control of said alarm circuitry.

Claim 10

An alarm system having high, low and thermocouple burnout alarm capability, including in combination: a. alarm signal translating circuitry connected between a temperature sensitive transducer and an alarm energizing means for providing a signal path for hot and cold alarm signals at said transducer, said signals being operative to alter the conductive state of said alarm energizing means and providing electrical control of visual or audible alarm indicators, said signal translating circuitry including amplifying means providing an output signal changing in a first direction in response to a temperature alarm condition at said transducer and changing in a second direction in response to a burn-out or open circuit condition at said Transducer, and b. a bypass signal path connected in parallel with a portion of said translating circuitry and between an output node of said amplifying means and the current path for said alarm energizing means, said bypass signal path including a current switch in said current path of said alarm energizing means and responsive to said signal change in a second direction for interrupting the current flow through said alarm energizing means, whereby signal changes in both said first and second directions at said output node of said amplifying means are operable to alter the conductive state of said alarm energizing means and provide alarm indications for both temperature and open circuit alarm conditions at said transducer.

Claim 11

An alarm system having high, low and thermocouple burnout alarm capability, including in combination: a. alarm signal translating circuitry connected between a temperature sensitive transducer and an alarm energizing means for providing a signal path for hot and cold alarm signals at said transducer, said signals being operative to alter the conductive state of said alarm energizing means and providing electrical control of visual or audible alarm indicators, said signal translating circuitry including amplifying means providing an output signal changing in a first direction in response to a temperature alarm condition at said transducer and changing in a second direction in response to a burn-out or open circuit condition at said Transducer, and b. a bypass signal path connected in parallel with a portion of said translating circuitry and between an output node of said amplifying means and the current path for said alarm energizing means, said bypass signal path including a current switch in said current path of said alarm energizing means and responsive to said signal change in a second direction for interrupting the current flow through said alarm energizing means, whereby signal changes in both said first and second directions at said output node of said amplifying means are operable to alter the conductive state of said alarm energizing means and provide alarm indications for both temperature and open circuit alarm conditions at said transducer.