Cs-4108-Fd, Cl-4124-Fd - IMC C SERIES User Manual

96 Device description

5.6 CS-4108-FD, CL-4124-FD

CS-4108-FD and CL-4124-FD are 8- and 24-channel universal measurement devices, respectively, with
sampling rates of up to 50 kHz per channel. They are specially designed for measurement tasks in
environments with unclear voltage fields such as test rigs or large-scale machinery. The input channels
are electrically isolated, differential and equipped with per-channel signal conditioning including filters.
The isolated voltage channels have their own isolated amplifier, operated in the voltage mode.
Along with voltage measurement, current measurement via a shunt plug and temperature measurement
via temperature plug ACC/DSUBM-T4 can be performed. The use of the
possible, however it cancels the insulation.
Technical details: CS-4108-FD, CL-4124-FD analog inputs
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 (>1 GΩ) 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).
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.
© 2018 imc Test & Measurement GmbH
Reference
139
General remarks on isolated channels
ICP-extension plug
52
imc C-SERIES - Manual, Version 4 R 3 - 2018-10-19
is also