Apparatus for detecting probe dislodgement
First Claim
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1. Apparatus for indicating the dislodgement of an article from a body, said apparatus comprising:
- a temperature responsive element having a characteristic which varies as a function of its temperature, said element adapted for contact with a body for sensing the proximity of said element to said body;
means for periodically heating said temperature responsive element and for developing a control signal which varies in accordance with said characteristic of said element and is representative of the heating of said element and the heat dissipated from said element, said control signal changing in level during the period of heating of said element at a rate dependent upon the dissipation of heat from said element during said period of heating;
and means responsive to said control signal for developing during said period of heating of said temperature responsive element an indication of said proximity of said element to said body.
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Abstract
A loose probe alarm in which a temperature responsive element (14) arranged for attachment to a body is periodically heated (20, 22, 26) and the effects of self-heating of the temperature responsive element are monitored (32, 36, 38) to determine whether the temperature responsive element has been dislodged from the body. The alarm is arranged to sense during the heating period of the temperature responsive element the difference in the amount of heat dissipated by the temperature responsive element when it remains in contact with the body to which it has been attached and when it has been dislodged from this body.
47 Citations
13 Claims
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1. Apparatus for indicating the dislodgement of an article from a body, said apparatus comprising:
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a temperature responsive element having a characteristic which varies as a function of its temperature, said element adapted for contact with a body for sensing the proximity of said element to said body; means for periodically heating said temperature responsive element and for developing a control signal which varies in accordance with said characteristic of said element and is representative of the heating of said element and the heat dissipated from said element, said control signal changing in level during the period of heating of said element at a rate dependent upon the dissipation of heat from said element during said period of heating; and means responsive to said control signal for developing during said period of heating of said temperature responsive element an indication of said proximity of said element to said body. - View Dependent Claims (2, 3, 4, 5)
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6. Apparatus for sensing body temperature comprising:
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a probe housing having a contact surface adapted for contact with a body; a thermistor having an electrical resistance which varies as a function of its temperature, said thermistor positioned within said contact surface of said probe housing for sensing the temperature of said body and for sensing the proximity of said thermistor to said body; a source of fixed voltage; means for coupling said fixed voltage source to said thermistor to develop across said thermistor a first signal component representative of said temperature of said body; a source of pulse signals; means for coupling said pulse signal source to said thermistor to periodically heat said thermistor and to develop across said thermistor a second signal component which varies in accordance with said electrical resistance of said thermistor and is representative of the heating of said thermistor and the heat dissipated from said thermistor, said second signal component changing in level during the period of heating of said thermistor at a rate dependent upon the dissipation of heat from said thermistor during said period of heating; means coupled to said thermistor for separating said first and said second signal components; means coupled to said separating means and responsive to said first signal component for developing an indication of said temperature of said body; and means coupled to said separating means and responsive to said second signal component for developing during said period of heating of said thermistor an indication of said proximity of said thermistor to said body. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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13. Apparatus for sensing body temperature comprising:
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a probe housing having a contact surface adapted for contact with a body; a thermistor having an electrical resistance which varies as a function of its temperature, said thermistor positioned within said contact surface of said probe housing for sensing the temperature of said body and for sensing the proximity of said thermistor of said body; a source of fixed voltage; means for coupling said fixed voltage source to said thermistor to develop across said thermistor a first signal component representative of said temperature of said body; a source of pulse signals; means for coupling said pulse signals source to said thermistor to periodically heat said thermistor and to develop across said thermistor a second signal component which varies in accordance with said electrical resistance of said thermistor and is representative of the heating of said thermistor and the heat dissipated from said thermistor, said second signal component changing in level during the period of heating of said thermistor at a rate dependent upon the dissipation of heat from said thermistor during said period of heating; means responsive to said first signal component for developing an indication of said temperature of said body; and means responsive to said second signal component for developing during said period of heating of said thermistor an indication of said proximity of said thermistor to said body.
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Specification