How To Choose Instrumentation Signal Cables?

The diversity of instruments now used in process plants, their growing susceptibility to electrical interference, and the need for more precise information regarding the process parameters have complicated the choice of cables for process instrumentation.

Length of Cable Run

The choice of conductor size is heavily determined by the volt dip that the circuit can tolerate.

Electrical Interference

Any erroneous voltage or current is considered electrical interference. Originating from other sources and appearing in the signal transmission system. When this voltage reaches an excessive level.

When the signal-to-noise ratio is too high, errors occur. Circuit for measuring and control. There are three categories into which electrical interference sources can be divided:

? Magnetic coupling from AC fields, like those in power connections and motors.

? Electrical connection with neighboring circuits (capacitive)

? Direct connection, such as standard return leads for several circuits or earth current loops involving two or more earth points

Magnetic fusion

• Utilization of twisted pair or triad cores
• Measurement cables should be routed away from AC fields and vice versa.?
• Take out the interference's primary cause.
• Measurement cables should be installed in appropriately seared steel conduits or covered trays.

Electrical coupling (capacitive)

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Direct connection

• use XLPE or another high-quality insulation.
• Minimize the chance of moisture getting into cables.
• Earth appears on screen once.
• Use only one pair or triode per circuit, i.e., refrain from "sharing" leads across courses.

Environmental Conditions Identification

? Optimum operating circumstances

? The presence of moisture or chemicals

? Cut through or abrasion of resistance

? Fire resistance

? The installation method, such as conduit, direct burying, tray, etc.

Storage

Drums should always be stored with their flanges touching and in a vertical position next to one another. The complex and well-drained surface should be used for storage. To stop moisture from entering the drum after a length of cable has been severed from it, the end of the drum should be sealed once more with an end cap.

Installation

As far as SANS 10198 applies to instrumentation signal cable and control cables, all cables must be installed in compliance with that standard. The product guarantee from CBI Telecom Cables will be void if you don't do this.