Foster Instrument Co Ltd
Optical instrument which looks like a microscope in a black finish with a brown leather satchel case with strap.
This device was used to confirm readings from thermocouple pyrometers installed in kilns in Stein's refractory works at Castlecary. It works by sighting at the heat source; the adjusting knob is turned until the electrical element "disappears"; that is when the colour of the element is identical to that the heat source. Th scale is then read from the optical pyrometer.
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Dimensions:case:H 19cm (H 7 1/2")
Dimensions:case:W 14cm (W 5 1/2")