Optical Pyrometer

 This item, which strictly speaking is a "Radiation Pyrometer", was made by Cambridge and Paul around 1920 and is a Fery's Thermo-Couple Pyrometer, patented in 1905.This one carries the serial number 43385.

Stored in a wooden box, the equipment consists of three parts, a sensing module, a moving coil meter calibrated from 600 to 1400 degrees Centigrade and an armoured interconnecting cable.





 The principle of the equipment is based on the fact that a bi-metal element, made of specific metals, when heated, will develop a voltage across its ends which can be used to pass current though a moving coil meter. Inside the black cylinder is such a bi-metal element, and as can be seen in the last picture, the cylinder carries a concave mirror. Essentially we have a reflecting telescope which is focused on the bi-metal element. There's an eyepiece at the end of the cylinder for aiming the device fitted with an optional red filter to protect the eye.

There are several applications for such an equipment, including checking the temperature of a furnace or heated steel that's being treated for tempering.

Not bad for a fiver?
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