I hold this pyrometer of Jean-Marc LIÉGE who pleasantly gave it to me in 1988 when I left the SOFRAMIR company of Vienne (38 Isère - France). One day, Jean-Marc asked me about what was this apparatus. There was an optical pyrometer chapter in my technology book of class of 1st, and I am certainly the only one that had read it. Like I knew the answer of the difficult question, Jean-Marc remained very astonished about it. Knowing my passion for this kind of old-fashioned thing, he gave it to me.

Download Enlarge !

Download Enlarge !

The optical pyrometer makes it possible to measure the temperature of an incandescent object, by simple optical aiming. Measurement consists in comparing, in red monochromatic light, the brightness of the object with that of the pyrometer lamp filament.

The pyrometer is directed on the incandescent object. It then gives an image on which the filament is detached. This one appears darker or more clearly, according to whether its brightness is lower or higher than that of the object.

The pyrometer has a rheostat which makes possible to change the intensity in the filament of its lamp standard. Measurement is obtained with the disappearance of the filament whose colour merges with that of the incandescent object, giving the very clear impression of a cut filament.

Then the intensity in the filament gives the temperature measurement. This measurement is obtained by direct reading on the luminous dial in the eyepiece of the pyrometer.

Measurement procedure :

• Hold the apparatus of the left hand. Approximately place the rheostat at mid scale. Lower the levers of the black filter and the red filter. Switch on the master switch. The indicator lamp shines.
• Regulate the eyepiece to obtain a quite clear vision of the filament.
• Direct the pyrometer on the incandescent object and regulate with the objective.
• The images of the incandescent object and the filament must be quite clear.
• Raise the black filter. Turn the rheostat to make disappear the filament.
• See directly on the right scale and multiply by 100.
• For measurements below 900°C, the red filter is not useful. See results on the left scale.