Siemens 7MC3040-..., Operating Manual, Page: 62 / 116

s
Operating manual PA
54
Most burning, annealing and hardening furnaces emit a radiation of near-
ly '1' which corresponds to the conditions of a black body if the aperture
through which the measurement is made is relatively small.
16.3 Measurements of Real Radiators
Real radiation sources are characterized by the relation of the emitted
radiation to the radiation of a black body with the same temperature.
Measurements outside a furnace - which applies to all other self-
contained targets - always show a reading which is too low. Considera-
ble errors can occur at targets with reflecting, polished or bright surfaces,
e.g. molten steel and metal without oxide layer and ceramic materials.
Exact results can only be obtained when the emissivity coefficient is cor-
rectly adjusted on the PA pyrometer.
The spectral emissivity coefficient of a body does not represent an exact
material constant, but is also largely dependent on the surface proper-
ties. For different materials the spectral emissivity coefficient
e
for the
spectral ranges

= 8 - 14

m (PA 10),

= 1.1
– 1.7

m (PA 20) and

=
0.8 - 1.1

m (PA 30) is shown in the following tables: