A measuring system; determination of shielding effectiveness for instrumentation cables

Instrumentation cables are used in the transmission of both analog and digital signals at low voltage transmission lines. These cables have a wide application field. Factories, refineries, petrochemical plants, power plants, combined cycle natural gas and filling plants constitute the some application areas of this cable. For these production oriented areas, cables are expected to be robust. External effects can be physical or electromagnetic because of rising electronic devices. Therefore, especially in industry, it is anticipated that data cables carry signal with minimal losses. A cable which is shielded against interference, there are some ways to protect conductor; an aluminium tape (thickness between 20 to 100 µ (micron)), solid or stranded, bare or tinned copper determined in accordance with international or regional standards and solid, bare, tinned copper or galvanized steel braiding construction. Shielding elements may be used singly or in a combined structure. Each structure has a distinctive electromagnetic permeability. Maximum shielding effectiveness earned with the appropriate rate structures. Overlaps of aluminum tape, cross sectional area of copper or steel wire, type of copper, coverage of braiding play a decisive role. In this thesis, test setups in accordance with international, European and Turkish standards has been established for measuring different shielding structures. Shielding effectiveness of cables was observed on specified frequency band range . The obtained results are compared between each other and optimum shielding structure was found. It is known that coaxial and CCTV cables shielding effectiveness laid down by standards. Studies of these cable types were investigated in the literature. The main objective of this study; measure the transfer impedance and the shielding effectiveness of chosen instrumentation cables with test setups specified in standards. Measurements was repeated and compared with each other. This study is an example for other data cables whose test metods are determined but not published. Measurements of the shielding effectiveness on these cables has never been done before. So obtained result is the first for instrumentation cables.