418 Properties of the Modules
imc CANSAS Users Manual - Doc. Version 1.9 - 05.12.2014© 2014 imc Meßsysteme GmbH
6.20.4 Temperature measurement
The amplifier channels are designed for direct measurement with thermocouples and Pt100-sensors.
Any combinations of the two sensor types can be connected.
6.20.4.1 Thermocouple measurement
The cold junction compensation necessary for thermocouple measurement is built-in. For this purpose,
UNI8 comes with the appropriate Pt1000 resistors for measuring the junction temperature. Note,
however, that these resistors are not installed in the plugs themselves but on the housing, so that they
are actually at some distance from the real contact point. This point's exact location is where the thermo-
wires meet the electric contacts in the plug, basically where they are soldered or crimped. Since the
temperature sensor Pt1000 and the contact point are separated in space, their temperatures can also
diverge. This temperature difference can also lead to measurement errors. However, situations do exist
where the measurement results are valid; for example, inside a switch cabinet where the temperature
processes are stabilized, the internal cold junction compensation is in practice adequate.
With CANSAS-SL-UNI8-L having LEMO terminals, thermocouple measurement requires a specially
designed cable from imc equipped with a built-in Pt100 temperature sensor. The connection is then
made in the same way as with the model without a Pt100 inside of the connector.
However, if the temperature processes in CANSAS' environment are not stable, a Pt100 in the connector
is absolutely necessary. This is certainly the case if there is a draught, if the module is used on-board a
vehicle, if cables with terminals of different temperature are connected, if the ambient temperature is
fluctuating or, when in doubt, whenever reliable and precise measurement is required.
The following circuit diagrams reflect each of the varieties with and without Pt100 in the connector.
We strongly recommend using a Pt100 in the connector for all thermocouple measurements.
All common thermocouple types with their characteristic curves are supported. However, it is only
possible to measure with multiple thermocouples at the same time if they are all of the same type. Thus,
all channels set to Type K will work, but not 1 channel Type K and one channel Type J won't. A
combination of thermocouple measurement and Pt100 measurement, by contrast, is possible.
For connection with ITT VEAM plugs, the module comes with the appropriate Pt1000 resistors for
measuring the junction temperature. Note, however, that these resistors are not installed in the plugs
themselves but on the housing, so that they are actually at some distance from the real contact point.
This point's exact location is where the thermo-wires meet the electric contacts in the plug, basically
where they are soldered or crimped. Since the temperature sensor Pt1000 and the contact point are
separated in space, their temperatures can also diverge. This temperature difference can also lead to
measurement errors. However, situations do exist where the measurement results are valid; for
example, inside a switch cabinet where the temperature processes are stabilized, the internal cold
junction compensation is in practice adequate.
Using a LEMO connector the thermocouple measurement can only be measured with an external Pt100
in the connector, for example the TH-LEM-150.
However, if the temperature processes in the device’s environment are not stable, a Pt100 in the
connector is absolutely necessary. This is certainly the case if:
there is a draught
if the module is used on-board a vehicle
if cables with terminals of different temperature are connected
if the ambient temperature is fluctuating
whenever reliable and precise measurement is required.
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