The Pyrometer Series Metis MY51 with pyroelectrical detector operates in a narrow band around 5.14 µm, where glass above 1 mm thickness is completely opaque. Merchantable uncoated soda lime glasses are also a poor reflector at this waveband, therefore they offer nearly “Black Body” conditions for infrared temperature measurement with Metis MY51 Series.
It is the ideal choice for all kind of applications like forming, bending, tempering, annealing, sealing and hardening of glass in float, construction, automotive and lamp manufacturing processes. For temperature measurement of glass below 100°C we recommend using Metis MY80 and for temperatures below 50°C Metis MY81. Optical and electronic parts are housed in a rugged IP65, extruded aluminium casting to operate in harsh industrial environments.
Each temperature range of MY51 is available as well with different fast exposition times of 10, 40, or 100 ms. Slower models offer better optical resolution (smaller spot size). To achieve effectively the best optical resolution of 200:1, the 100 ms version can be supplied with fixed focus lenses only.
The infrared energy radiated by the target is centered via focusable or fixed focus lenses directly on the detector. The focussing feature allows control of the cone of vision and offers the possibility to measure either a small spot (focused) or the average of a bigger spot (out of focus). Fixed focus lenses with larger diameter collect more infrared energy and therefore result in smaller spot sizes. The lenses are made of calcium fluoride CaF2 which is highly transparent in visible and infrared regions up to 10 µm. If additional windows are necessary they must offer similar optical characteristics.
The detector is sensitive to infrared radiation in an area called the cone of vision. For the spot size diameter Ø of the cone of vision at shortest, medium and widest focal distances, please see Chart 2. For full scale temperatures up to 1300°C the cone of vision diameter in front of the lens is about 16mm and about 9 mm for full scale temperatures above. This area has to be kept free from any intervening objects. The spot size diameter for distances not given in the chart can be calculated by interpolation.