Despatch P1400+ Temperature Controller - Manual (Page 17)

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CAUTION:
The only wires that should run together are those of the same category.
If any wires need to run parallel with any other lines, maintain a minimum space of 150mm between
them.
If wires MUST cross each other, ensure they do so at 90 degrees to minimise interference.
4.4 Use of Shielded Cable
All analogue signals must use shielded cable. This will help eliminate electrical noise induction on
the wires. Connection lead length must be kept as short as possible keeping the wires protected by
the shielding. The shield should be grounded at one end only. The preferred grounding location is at
the sensor, transmitter or transducer.
4.5 Noise Suppression at Source
Usually when good wiring practices are followed, no further noise protection is necessary.
Sometimes in severe electrical environments, the amount of noise is so great that it has to be
suppressed at source. Many manufacturers of relays, contactors etc supply 'surge suppressors'
which mount on the noise source. For those devices that do not have surge suppressors supplied,
Resistance-Capacitance (RC) networks and/or Metal Oxide Varistors (MOV) may be added.
Inductive coils:- MOVs are recommended for transient suppression in inductive coils, connected in
parallel and as close as possible to the coil. Additional protection may be provided by adding an RC
network across the MOV.
Figure 7. Transient suppression with inductive coils