Emotron EMX-D, Instruction Manual

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Emotron AB 01-5016-01r0 Control Connections 17
4.4.4 Current signals ((0)4-20 mA)
A current signal like (0)4-20 mA is less sensitive to distur-
bances than a 0-10 V signal, because it is connected to an
input which has a lower impedance (250

) than a voltage
signal (20 k

). It is therefore strongly advised to use current
control signals if the cables are longer than a few metres.
4.4.5 Twisted cables
Analogue and digital signals are less sensitive to interference
if the cables carrying them are “twisted”. This is certainly to
be recommended if screening cannot be used. By twisting
the wires the exposed areas are minimised. This means that
in the current circuit for any possible High Frequency (HF)
interference fields, no voltage can be induced.
4.4.6 Manual control using 10 k

potentiometer
The drive system can easily be controlled manually with the
help of a 10 k

potentiometer which is connected in the
following manner:
Fig. 13 10 k

potentiometer
4.4.7 Switching off
When it is desired to switch off the heat exchanger, for
example at night, this can be done using a relay connected in
series with the control signal. This relay interrupts the signal
to control signal terminal number 2. In this way, no alarm
about interruption of power supply is given. The control sig-
nal can of course also be reduced to its minimum value, in
order to achieve the same result. If the control signal is low
or absent the drive system switches to purging mode.
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