Braided copper/wire

Note how the electrical conductors are insulated from the parts that are handled. A metal-bodied kettle must have separate insulation wherever mains-connected parts are attached however plastic is an electrical insulator. Figure 1.1 shows the mains power connections in the base. The coloured insulation (live, neutral and earth) of the braided copper wires is plasticised PVC. 

In more demanding applications, the electrode lead wires should be shielded, preferably by purchasing the type that has a fine coaxial braided copper wire around the central signal-carrying lead. The shield should be connected to the amplifier reference but not connected to the electrode signal wire itself since this would abrogate its shielding effect. 

Steel wire armour as opposed to steel wire braid has lower electrical impedance for a given length of cable. This is an important benefit in networks that are solidly earthed at their power source. Some special applications that require as low an impedance as is practical to achieve in the cable have some of the armour wires replaced by copper wires. Hence the parallel circuit consisting of the steel and copper wires has a lower total impedance than the steel wires on their own. The impedance of the armouring, with or without the copper wires, is predominantly resistive and so the inductive reactance at the power frequency can therefore be ignored. 

In order to minimise the possible damage to a cable, and to provide a safe path for electrical earth return currents, it is necessary to specify a metallic armouring. There are several types of metallic armouring used in the oil industry, i.e. galvanised steel wires (GSWA), aluminium wires (AWA), tinned copper wire braid (TCUWB), phosphor bronze wire braid (PBWB). 

Before the Second World War, the standard insulation for wire used in telecommunications in the UK was waxed acetylated cotton, the conductor being tinned copper wire, while for tropical use the conductors were oleo-resinous enamelled copper wire. Jumper wire had braided wool insulation. 

Over the next two decades extruded PVC with a lacquered, lapped rayon secondary coating for protection against soldering temperatures and for identification was the standard wire insulation. The jumper wire over this period was PVC-coated tinned copper wire with a cellulose lacquered rayon braid secondary coating containing a nonflammability additive. 

Figure 9-13. (a) Cross-section of coaxial cable housing, (b) and (c) Schematic of silver-plated copper wire used in braid that shields coaxial cable, (b) is resistant to cracking during flexing, while the tarnished wire (c) is easily cracked. 

Note Wherever a cable lead connecting the above devices (such as for RTDs) has to pass through a magnetic field, it may be screened with tinned copper-braided wires to nullify the effect of stray fields. The field may distort the readings. 

Where can we find thick copper braids Well, I tend to use regular solder wick lying around the lab. I am fairly convinced by now that if I partially soak some solder into it, it works great as a high-frequency shunt. I won t be caught ordering Litz wire just yet. 

Fig. 3.4 (c) Penn State design tip exchange setup ffor an FIM or a pulsed-laser atom-probe with a vacuum lock. The tip can be heated by passing a current through the wire loop. The tip is mounted on an internal gimbal and is cooled through a copper braid by a refrigerator. 

You can make your own tab and bus wire. Copper foil is available in thicknesses from. 002 to. 021 from McMaster-Carr or another supplier. It can be cut into thin strips to your particular specifications. You can also use flat grounding braid for bus ribbon, as it is made for heavier current carrying capacity. Grounding braid comes in a variety of thicknesses and widths and is usually tinned. Make sure to use Tinnit to tin the tab and bus if you make your own - it also helps to minimize oxidation. You can use round wire, either solid or stranded, for bus connections as well as cell connects, if you desire, but the flat ribbon is probably easier to work with. Square mils... 

In making gilt wire, a bar of silver, alloyed with copper, approximately 2 inches in diameter is plated with gold and drawn down to wire in the usual way. It is then used for weaving into gold braid and embroideries such as one sees on uniforms, clerical and masonic vestments, etc. 

Tin is also used as a coating for copper armour wires or armour braiding where rubber compounds are used in the inner or outer sheathing. 

It is a practical alternative to tinned copper braid in many applications where steel wire should... 

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