West Control Solutions KS 800 Operating Instructions - Manual (Page 14)

Multi-Temperature-Controller KS 800
The controller inputs are not galvanically isolated. Therefore, measurement errors may occur with
thermocouple measurements above approx. 700
°
C and unsuitable thermocouples. This effect is due
to a decrease of the insulation value between protective tube and thermocouple to values of
a few kOhm from these temperatures dependent of construction type and insulation material.
Additionally, potential differences between the individual thermocouples due to hot gas ionization
may cause measurement errors or troubles due to compensating currents.
For the same reason, there may be problems when using grounded and isolated thermocouples in
mixed applications. The potential differences between thermocouples must not exceed 7Vss.
We urgently recommend avoiding mixed operation.
If using grounded and isolated thermocouples in an installation should be indispensable for
other reasons, the negative arm of the isolated thermocouple must be grounded at KS 800.
Already grounded thermocouples must not be grounded for a second time!
When replacing isolated thermocouples by non-isolated ones, removal of the negative arm
grounding at KS 800 is indispensable.
5.1.2 Cold-junction temperature compensation
There are four possibilities of temperature compensation:
1. The temperature compensation is ineffective (for PT 100 or mV inputs)
2. Internal temperature compensation. Compensating lead must be used up to KS 800.
3. External temperature compensation. Compensating lead must be used only up to the
cold-junction reference, leads between reference and KS 800 can be of copper.
4. Remote measurement of a cold-junction reference. Input IN8 can be configured so that it
functions as input of the temperature sensor of a remote cold-junction reference.
The thermocouples of each individual measuring point are connected to a common cold-
junction reference by means of compensating lead. The leads between cold-junction refe-
rence and KS 800 can be of copper. The 8th input is used for measuring the temperature of
this cold-junction reference and correcting the input voltage accordingly. For maintaining the
specified accuracy, the sensor should be a resistance thermometer. When using this tempe-
rature compensation method in an installation containing several KS 800 controllers, this
method must be used with each individual unit.
5.2 DC voltage (<100mV) IN1+/IN1- ... In8+/IN8-
DC voltages up to 100 mV instead of thermocouples can also be connected. Scaling of these valu-
es is possible via software adjustments.
The input resistance is approx. 100 k
Ω
.
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