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Product Information
Motor and machine protection
Temperature monitoring with PTC-thermistors
Technical base data
Typical resistance-temperature characteristic
The advantage of PTC-thermistors is demonstrated by the
very steep curve as shown in the graph. This graph shows
the relationship between temperature and resistance. The
characteristic of the curve demonstrates the accuracy of
the PTC‘s. The increase in the resistance from the switching
point onwards is exponential. The DIN-standards relevant
to these products cover the temperature range from
+60°C to +180°C and are DIN 44081 and 44082.
Resistance values (according to DIN 44081 and DIN
44082)
The resistance temperature characteristic of PTC- thermistors
for the thermic protection of machines is defined by
the following formula:
Temperature
range
PTC-resistance
RKL
Measuring DC voltage U
(test voltage)
TKL
-20°C to TROT RKL ≤ 250 Ω U ≤ 2,5V
-20K
at TROT -5K RKL ≤ 550 Ω U ≤ 2,5V
at TROT +5K RKL ≥ 1330 Ω U ≤ 2,5V
at TROT +15K RKL ≥ 4000 Ω U ≤ 7,5V
Load must not be applied to the thermistors as this creates
a self-heating effect.
At ambient temperature the resistance value of thermistors
is normally between 50 Ω and 100 Ω. It can also
be between 30 and 250 Ω. At ambient temperature the
resistance values have no relevance to the serviceability
(functionality) at the ROT (rated operating temperature).
The ROT of PTC-thermistors in the range of +60°C to
+180°C progresses normally in steps of 10 K.
REISSMANN Sensortechnik GmbH · Schollenäcker 3 (unterm Wasserturm) · D-74538 Rosengarten-Uttenhofen
Telefon +49 (0)791 950 15-0 · Telefax +49 (0)791 950 15-29 · E-Mail info@reissmann.com · Internet http://www.reissmann.com
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