IMC C SERIES User Manual page 123

5.8.4.3 Probe-breakage recognition
The amplifier comes with the ability of probe-breakage recognition.
Thermocouple: If at least one of the thermocouple's two lines breaks, then within a short time (only a
few samples), the measurement signal generated by the amplifier approaches the bottom of the input
range in a defined pattern. The actual value reached depends on the particular thermocouple. In the case
of Type K thermocouples, this is around -270°C. If the system is monitoring a cutoff level with a certain
tolerance, e.g. Is the measured value <-265°C, then it's possible to conclude that the probe is broken,
unless such temperatures could really occur at the measurement location.
The probe-breakage recognition is also triggered if a channel is parameterized for "Thermocouple" and
measurement starts without any thermocouple being connected. If a thermocouple is later connected
after all, it would take the period of a few measurement samples for transients in the module's filter to
subside and the correct temperature to be indicated. Note also in this context that any thermocouple
cable's connector which is recently plugged into the amplifier is unlikely to be at the same temperature
as the module. Once the connection is made, the temperatures begin to assimilate. Within this phase,
the Pt100 built into the connector may not be able to indicate the real junction temperature exactly. This
usually takes some minutes to happen.
RTD/Pt100: If the leads to the Pt100 are broken, then within a short time (only a few samples), the
measurement signal generated by the amplifier approaches the bottom of the input range, to about
200°C, in a defined pattern. If the system is monitoring a cutoff level with a certain tolerance, e.g. Is the
measured value <-195°C, then it's possible to conclude that the probe is broken, unless such
temperatures could really occur at the measurement location. In case of a short-circuit, the nominal
value returned is also that low.
In this context, note that in a 4-wire measurement a large variety of combinations of broken and shorted
leads are possible. Many of these combinations, especially ones with a broken Sense lead, will not return
the default value stated.
5.8.5 Current fed sensors
Measurement of current-fed sensors, e.g. ICPs is possible with the DSUB-15 imc plugs. Therefore the
special connector ACC/DSUB-ICP2 is required.
For measurement of current-fed sensors, the special connector
For the supply of the special connector, the module provides a 5 V (Vcc) voltage at PIN17. This voltage is
short-circuit proof and independent of the voltage supply module.
For the description of the measurement with current feed sensors, see here
·
With the former Cx-70 this mode is not possible, if a channel has been set to thermocouple
measurement.
·
The ACC/DSUB-ICP2 plug cannot be used together with triaxials.
© 2018 imc Test & Measurement GmbH
ACC/DSUB-ICP2
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Note
imc C-SERIES - Manual, Version 4 R 3 - 2018-10-19
CS-7008-FD, CL-7016-FD
is required.
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