266 Properties of the Modules
imc CANSAS Users Manual - Doc. Version 1.9 - 05.12.2014© 2014 imc Meßsysteme GmbH
With imc CANSAS-C12 (with or without divider plugs), the reference potential discrepancies (-IN)
between different sensors can be no greater than ±40 V without causing damage. Up to a discrepancy of
±5 V, there is no loss of system precision (but typically not even up to ±40V).
When measuring relatively large voltages with the divider-plugs, it may be necessary to note the polarity
of the "differential inputs"!
+40 V differential voltages can result by combining respective absolute potentials of
-IN1 = +20 V and IN2 = 20 V in relation to an arbitrary reference potential (e.g. "GRND").
This means: If a range of ±20 V (or, respectively, ±2,5 V) referring to a common (though "arbitrary")
reference point is ensured for every measurement input, this conforms to allowable limits.
Measurement with Pt100-units represents a special case:
All of a plug's connected Pt100 sensors are fed by a common reference current supply, so that there is
no potential isolation between the individual channels.
The cancellation of the potential isolation even affects both input plugs:
The Pt100-channels of the one plug (Plug1) cyclically assume the potential of the channels at Plug 2!
Also, the entire cabling for the Pt100 channels amounts to a dynamic capacitive load at Plug 2's
inputs.
For this reason, mixed operation consisting of Pt100-measurements on one plug and current/voltage
measurement on the other is not advised.
Voltages in ranges >2 V are connected at the so-called Divider plug (CAN/DSUB-U6D).
For current measurements, a plug with shunt resistors is available (CAN/DSUB-I6).
For temperature measurement, the special Thermo-plug (CAN/DSUB-T6) is available. It comes with built-
in cold junction compensation.
A specially Pt100 plug is also available (CAN/DSUB-Pt100), which enables the direct connection of Pt100
resistors in 4-wire configuration and which comes with a built-in reference circuit.
6.3.1 Connector plugs C12
For the pin assignment of the DSUB-15 plugs see here .
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