Datasheet

DATA SHEET
Technical changes reserved
0141 0316-115 07/2009
Thermocouple module
with digital I²C-Interface - THMOD-I²C
Scaling of thermo voltage
Temp. mV -300 -800 -1360
-200 -5,891 6609 3305 2203
-100 -3,554 8946 4473 2982
-50 -1,889 10611 5306 3537
0 0 12500 6250 4167
50 2,023 14523 7262 4841
100 4,096 16596 8298 5532
200 8,138 20638 10319 6879
300 12,209 24709 12355 8236
400 16,397 28897 14449 9632
500 20,644 - 16572 11048
600 24,905 - 18703 12468
700 29,129 - 20815 13876
800 33,275 - 22888 15258
900 37,327 - 24913 16609
1000 41,276 - 26888 17925
1100 45,119 - 28810 19206
1200 48,838 - 30669 20446
1300 52,410 - 32455 21637
1370 54,819 - - 22440
The thermoelectric effect
The temperature measurement with thermocouples is based on the
Seebeck-Effect: At the junction point of two different metals, a tempe-
rature dependent contact voltage originates.
Therefore, a thermocouple or thermopair consists of two point shaped
wires of different metals or metal alloys joined together. If this junction
point is heated up, a voltage can be measured at the ends.
However, in practice, now it is not possible to have only one thermopair
in a current circuit. There must be at least one more point at which the
ends are brought together or another metal, e.g. a modied copper
spool of moving coil instruments. It contains further thermopairs from
which the individual thermo voltages are added in the current circuit.
In the end, the sum is the total of all thermo voltages at the instrument.
Now, if one takes care that transfer at copper of the measuring system
is done at a point, for which the temperature is known, the basis of
temperature of „connection point“ and thermo voltage at the tempera-
ture of the thermocouple can be determined.
In laboratory applications, the connection point can be created in ice
water. In this case, the measured thermovoltage corresponds to the
Seebeck-voltage of the used thermocouples.
Usually the temperature connection point is determined by means of
an absolute measurement method, for example with a PT 1000. Then,
it is possible to mathematically compensate the temperature of the
connection point.
In practice, the connection of thermocouples is done over uniform
leads, which are either of the same material or with expensive inert
metal elements or from an alloy which has the same thermal data.
Then the extension is normally up to the connection point, where the
temperature is again compensated over an absolute temperature mea-
surement.
As per DIN IEC 584-1 (DIN EN 60 584-1), the following thermopairs
are standardised.
Identication
letter
Symbol Measuring
range in °C
Thermovoltage
in µV
E NiCr-CuNi -200...+1000 -8825...+76373
J Fe-CuNi -210...+1200 -8095...+69553
K NiCr-Ni -200...+1372 -5891...+54886
N NiCrSi-NiSi -200...+1300 -3990...+47513
T Cu-CuNi -200...+400 -5603...+20872
Without inert metal thermocouple
Identication
letter
Symbol Measuring
range in °C
Thermovoltage
in µV
S Pt10 %RH-Pt -50...+1768 -235...+18694
R Pt13 %RH-Pt -50...+1768 -226...+21103
B Pt30 %RH
-Pt6 %RH
+250...+1820 -291...+13820
Inert metal thermocouple
B+B Thermo-Technik GmbH | Heinrich-Hertz-Straße 4 | D-78166 Donaueschingen
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