Evaluation of the Shielding Properties of Cable Trays for Use in an Industrial Environment

The proper shielding of control cables in an industrial control system is an important part of the system's design. With the advent of direct digital and analog process control in large industrial facilities such as steel mills and power plants, the minimumization of interference induced in the communication link between the in-plant transducers and analog or digital controller becomes an important problem. The communication link may be very short, or run for several miles, depending upon the installation. In most cases, this link is a pair of electrical conductors. It is often necessary to shield these control and instrumentation cables. This paper describes a series of tests that were developed to determine the shielding efficiency of cable trays made of various types of material. Tests are described for both electromagnetic and electrostatic fields. As in most engineering decisions, the final choice of material must be the result of a compromise.