4 Glass-lined temperature
probes
4.1 Probe types
Pfaudler offers two different types of
probes for temperature measurement
which operate according to different
physical measuring principles.
These probe types are:
n Temperature probe type T
With this probe, a thermocouple per-
forms the sensing function. Thermo-
couples are based on the physical
effect of a charge shift in an electrical
conductor (wire) along a temperature
gradient. The free electrons move
from the hot end of the wire to the
cold end of the wire.
n Temperature probe type TW
This probe is equipped with a resist-
ance thermometer as the sensor.
Resistance thermometers are based
on the physical effect that the elec-
trical resistance of conductors and
semiconductors changes subject to
the temperature.
4.2 Joint features and properties
Both probe types have a sensor that is
fused into the glass. Thus, the sensor
is excellently protected against aggres-
sive media, and its placed directly in the
product. This arrangement offers users
the following advantages:
n The probes have very short response
times. The response behavior of the
measuring probes type T and TW
is shown in Fig. 1 in comparison to
probes with plugged-in sensors.
n The sensors of the probes have not
been simply screwed-in, producing
error-prone sealing surfaces in the
product.
n Due to the quick and precise tem-
perature measurement, the produc-
tion process can be controlled safely
and economically. In many cases, the
product quality is also improved.
n The sensors are not subject to ageing
because they are made of extremely
pure and highly resistant noble met-
als and have been fused into the glass
layer in a chemically inert process.
Glass is absolutely diffusion-tight,
therefore, reaction with hydrogen is
also excluded.
0 10 20 30 40 50 [s]
E T/TW Ta
100
50
t [%]
Fig. 1 Time response
MT_05_00001
Measured in inside the reactor (100 l) with water at 120 rpm
T/TW measuring probe type T/TW on
thermometer well, D = 40 mm
Ta thermocouple with tantalum sensor in
thermometer well, D = 40 mm
E Reference measurement with unprotected
pallaplat element (cannot be used in glass-lined reactor)
© Pfaudler GmbH ·
OI 302-8 e
3
Temperature probes type T/TW
© Pfaudler GmbH 3
Temperature probes type T/TW
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