A third conductor
starting from the top of the tube passes down through it, and comes out at
the face of the metal plug. The tube is inserted in the medium whose
temperature is to be found, and the electric resistance of the coil is
measured by a differential voltameter. From this it is easy to deduce the
temperature to which the platinum has been raised. This pyrometer is
probably the most widely used at the present time.
Tremeschini's pyrometer is based on a different principle, viz., on the
expansion of a thin plate of platinum, which is heated by a mass of metal
previously raised to the temperature of the medium. The exact arrangements
are difficult to describe without the aid of drawings, but the result is
to measure the difference of temperature between the medium to be tested
and the atmosphere at the position of the instrument. The whole apparatus
is simple, compact, and easy to manage, and its indications appear to be
correct at least up to 800 deg.C.
The Trampler pyrometer is based upon the difference in the coefficients of
dilatation for iron and graphite, that of the latter being about
two-thirds that of the former. There is an iron tube containing a stick of
hard graphite.
Pages:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25