Hardware Manual COMBILOG 1020
48
Temperature Measurement with Thermocouple
Thermocouples consist of two “thermoelectric wires” made of dif-
ferent materials (e.g. platinum and platinum rhodium) that are
welded to eachother at one end. If the contact and the other ends
of the thermoelectric wires have different temperatures, a “ther-
moelectric voltage” U
th
appears at the contact of both thermoelec-
tric wires. This voltage is largely proportional to the temperature
difference. It can be measured and used for temperature meas-
urement purposes. With datalogger COMBILOG 1020 the ther-
moelectric voltage is measured differentially.
Since thermocouples can only measure a temperature difference
(difference between temperature to be measured and tempera-
ture at the connecting terminals on the sensor module), a termi-
nal temperature (internal cold junction compensation, TC
int
) or a
known temperature reference (external cold junction compensa-
tion, TC
ext
) also have to be determined.
With measurement of temperature with internal cold junction
compensation an additional temperature sensor is necessary to
measure the temperature
ϑ
k
at the “cold” terminal. A special cold
junction terminal is available, where a Pt100 temperature sensor
is integrated directly in the terminal block. The temperature of the
test point is determined on basis of linearisation trace to
ϑ
x
=
Lin(U
x
+Lin
-1
ϑ
k
).
Summary of Contents for COMBILOG 1020
Page 1: ...COMBILOG 1020 Datalogger Hardware Manual Version 3 09...
Page 2: ...Hardware Manual COMBILOG 1020 2 Issue 03 11 2005 Technical data are subject to change...
Page 4: ...Hardware Manual COMBILOG 1020 4...
Page 6: ...Hardware Manual COMBILOG 1020 6...
Page 12: ...Hardware Manual COMBILOG 1020 12...
Page 86: ...Hardware Manual COMBILOG 1020 86 Bild 8 1 Example Master Slave System...
Page 169: ...Hardware Manual COMBILOG 1020 169...
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