IMC CANSAS - CI8 Isolated Voltage Channels with Current and Temperature Mode

C8 voltage, temperature, current 275
imc CANSAS Users Manual - Doc. Version 1.9 - 05.12.2014© 2014 imc Meßsysteme GmbH
6.5 CI8 isolated voltage channels with current and temperature mode
8 differential, analog inputs
Parameter
Value (typ. / max.)
Remarks
Inputs
8
2 x DSUB-15 / 4 channels
Measurement modes (DSUB)
voltage
temperature, RTD (Pt100)
current
resistor
with shunt connector (ACC/DSUB-I4)
Measurement modes
(LEMO and ITT Veam)
voltage
current
RTD (Pt100)
resistance
with internal shunt
Measurement mode (2T)
temperature type-K
Each of the module CI8's isolated voltage channels has its own isolated amplifier, operated in the voltage
mode. Along with voltage measurement, current measurement (with DSUB via a shunt plug), resistor
and temperature measurement are all provided for.
The CI8 module supports TEDS to read and write sensor information.
Beside working with CAN-bus per default, the CI8 is also configurable as CANopen module.
The analog bandwidth (without low-pass filtering) of the isolated voltage channels is 440 Hz(-3dB).
Technical data CI8.
General remarks on isolated channels:
When using an isolated channel (with or without supply), one should make sure the common mode
potential is "defined", one way or another: Using an isolated channel on an isolated signal source usually
does not make sense. The very high common mode input impedance of this isolated configuration (>
1G ) will easily pick up enormous common mode noise as well as possibly letting the common mode
potential drift to high DC-level. These high levels of common-mode noise will not be completely rejected
by the amplifier's common-mode (isolation-mode) rejection.
So, as a general rule: isolated amps should be used in environments where the common-mode level is
high but "well defined" in terms of a low (DC-) impedance towards (non-isolated) system ground
(CHASSIS).
In other words: isolated amps are used in environments where the common mode levels and noise are
already inherent in the process and not just accidental results of the equipment's isolation.
If, in turn, the signal source itself is isolated, it can be forced to a common-mode potential, which is the
potential of the measurement equipment. This is the case with a microphone: the non-isolated power
supply will force the common mode potential of the microphone and amp-input to system ground
instead of leaving it floating, which would make it susceptible to all kinds of noise and disturbance.
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