Temperature monitoring systems

A temperature monitoring system, comprising:

• a housing defining a linear array of spaced sight tubes, and a passage intersecting each sight tube;
• an elongated member movably mounted in the passage in the housing to intersect each sight tube within the housing, the member defining a plurality of openings one for each of said sight tubes whereby upon movement of the member in relation to the housing, the member may act as a shutter to open and close each sight tube;
• a pyroelectric sensor coupled to each sight tube on one side of the shutter;
• a support means for supporting an object whose temperature is to be monitored, located on the other side of the shutter;
• drive means coupled to the shutter member for moving the shutter member to alternately expose each sensor to the shutter itself and to the monitored object;
• and
• circuit means coupled to each sensor for processing the output from each sensor to provide an output signal representative of the temperature of the object being monitored, the circuit means comprising:
• a differentiating of each sensor, and
• sampling means coupled to the output of the differentiating circuit for sampling the initial level of the differentiated output and responsive thereto to produce said output signal.

Heating apparatus for heating a sheet plastics member which is displaced along a path through the plant in discrete steps, said apparatus comprising:

• a heating array which has a plurality of individually controllable heating elements and is arranged for heating successive lengths of the sheet member,
• a temperature monitoring system located immediately downstream of the heating array, and
• control means responsive to the output signal produced by the monitoring system during each displacement of the sheet plastics pattern on the subsequent length of the sheet plastics member, the temperature monitoring system comprising:
• a housing defining a linear array of spaced sight tubes, and a passage intersecting each sight tube;
• an elongated member movably mounted in the passage in the housing to intersect each sight tube within the housing, the member defining a plurality of openings one for each of said sight tubes whereby upon movement of the member in relation to the housing, the member may act as a shutter to open and close each sight tube;
• a pyroelectric sensor coupled to each sight tube on one side of the shutter;
• a support means for supporting an object whose temperature is to be monitored, located on the other side of the shutter;
• drive means coupled to the shutter member for moving the shutter member to alternately expose each sensor to the shutter itself and to the monitored object;
• and
• circuit means coupled to each sensor for processing the output from each sensor to provide an output signal representative of the temperature of the object being monitored.