6
Functional description
6.1
General functions for measuring temperatures with thermocou-
ples
6.1.1
Principle of temperature measurements
Fig.6-1:
Temperature measurement
The thermocouple supplies (active) a voltage U
θ
, which depends on the tem-
perature difference between the measuring point (w) and the comparison point
(u, terminal). k is the temperature coefficient of the thermocouple. It is de-
pendent on the material and the temperature. Therefore a change in the
thermo-voltage is not proportional to the temperature change. The software
executes the linearization.
To enable evaluation of the temperature at the measuring point, the tempera-
ture of the comparison point must be known. The latter is measured by a
terminal temperature sensor that is integrated into the module.
6.1.2
Temperature data sampling
Fig.6-2:
Block diagram
1
... Counters and logic
The thermo voltage at the input terminals is amplified and converted into a
proportional frequency in the voltage-to-frequency converter. The measure-
ment period lasts 100 ms.
Due to the integrating measurement procedure used, any interference that oc-
curs at the AC line frequency (50 Hz, 60 Hz) is filtered out.
Functional description
TM 240/A, TE 220/A for KeStudio U3
© KEBA 2011
Project engineering manual V1.10
18
Summary of Contents for Kemro TM 240/A
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