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Thermistors
AGC Thermistor detector elements have the same mounts as the hot-wires.
The Thermistor is a thermally sensitive resistor that has a high negative co-efficient of resistance. They are manufactured from a mixture of the oxides of Manganese, Nickel and Cobalt. They are sintered in an oxidising atmosphere in the form of small beads (0.012" dia.). A covering of glass is then placed over the bead to protect it from further oxidation and reduction.
After several days of ageing in an accurately controlled atmosphere, the beads are welded to the support mount. The next step involves matching the thermistors in Helium or another gas atmosphere and they have a specific resistances at 25 o C. By applying current, the resistance of the bead is lowered.
The characteristic of thermistors is such that they can be operated at relatively low operating temperatures, They have high sensitivity at low temperatures and are suitable for applications at sub-ambient temperatures.
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