UNI8: universal 419
imc CANSAS Users Manual - Doc. Version 1.9 - 05.12.2014© 2014 imc Meßsysteme GmbH
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.
A description of the available thermocouples .
6.20.4.1.1 Thermocouple mounted with ground reference
The thermocouple is mounted in such a way that it already is in electrical contact with the device
ground / chassis.
This is ensured by attaching the thermocouple to a grounded metal body, for instance. The thermocouple
is connected for differential measurement. Since the unit is grounded itself, the necessary ground
reference exists.
In the CANSAS operating software, select the measurement mode "Thermocouple (mounted with
ground reference)".
Thermocouple measurement with ground
reference
It is not a problem if the ground potential at the thermocouple differs from that of the device units by a
few volts. However, the maximum allowed common mode voltage may not be exceeded.
The negative signal input -IN may not be connected to amplifier ground point -VB(D). Connecting them
would cause a ground loop through which interference could be coupled in.
If you accidentally select the operating mode "Thermocouple (mounted without ground reference)",
there is a danger that a large compensation current will flow through the thermocouple's (thin) line
and the connector plug. This can even lead to the destruction of the amplifier. Compensation currents
are a danger with every single end measurement. For that reason, single end measurement is really
only allowed -and only then really necessary- if the thermocouple has no ground reference of its own.
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