Twisted pair

The communication between the units is performed through a local ring network, based on twisted pair wire as shown in the figure below. 

Twin-fluid atomizer Twisted pair cable Twitchell splitting Twitchell s reagents Two-film theory... 

Data Communication Wires. Electronic cables such as data communication wires employ three basic designs coaxial, twisted pair, and fiber optics (3,4) (Eig. 1). Coaxial cables are so named because the axis of curvature of its outer conductor is concentric to its inner central wire. The metal braiding wrapped around the insulated center wire acts as the return current conductor in addition to shielding the wire from various interferences. 

Eig. 1. Cable designs (a) coaxial cable (b) twisted pair cable can be unshielded, as in regular telephone wiring, or shielded (as shown here) with braiding or... 

The twists of twisted pair cable act as a shield against radio frequency interference (REI), and electromagnetic interference (EMI), and against the cross talk interference that a wire exerts on nearby wires the more twist the less interference. Telephone wires can use large numbers of pairs. In most cases the pairs are not shielded with braiding or foil, as shown in Eigure lb for data communication wire. Data communication wires work at very high... 

Signal Transmission and Conditioning. A wide variety of physical and chemical phenomena are used to measure the many process variables required to characteri2e the state of a process. Because most processes are operated from a control house, these values must be available there. Hence, the measurements are usually transduced to an electronic form, most often 4 to 20 m A, and then transmitted to the control house or to a remote terminal unit and then to the control house (see Fig. 6). Wherever transmission of these signals takes place in twisted pairs, it is especially important that proper care is taken so that these measurement signals are not cormpted owing to ground currents, interference from other electrical equipment and... 

Temperature Measurement shift. Measurement not representative of process. Indicator reading varies second to second. Ambient temperature change. Fast changing process temperature. Electrical power wires near thermocouple extension wires. Increase immersion length. Insulate surface. Use quick response or low thermal time constant device. Use shielded, twisted pair thermocouple extension wire, and/or install in conduit. 

The first teehnique that enhanees eoupling between windings is twisted pair winding. This oeeurs when two or more wires are twisted together and then... 

The matrix can be taken away by HN03 except at the ends of the wire, to allow easy soldering. Below IK, the electrical contact can be done also by squeezing the wires to be connected inside a thin A1 tube (see, for example, Section 12.4). For low-level signals, shielded twisted pairs or cryogenic coaxial cables are used. When thousands of wires are necessary, as in large experiments, Kapton strips with deposited conductors [3] or woven wires [4] are used. 

Fig. 10.2. Twisted pair suppresses magnetically coupled interference because it tends to null out the effects of...

Twin-wire paper formers, 18 120 Twisted nematic LCDs, 15 113 characteristics of, 15 114 Twisted pair wire cable, 7 714 Twisted yarn, 11 178... 

The speed of information transfer can be increased by switching from twisted pair cables to coaxial or fiber optics, however, these types of cables add to the installation costs. In the future, communications between sensors and multiplex boxes and the rest of the system may use a combination of technologies including traditional means such as twisted wire and coaxial and non-traditional methods such as infrared or radio wave. 

Plugs for graphite bridge initiators are made by molding the plastic about a twisted pair of enameled wires, and thea grinding the surface clean, bis ieaves a plastic surface with two metal islands separated by twice the thickness of the enamel. A droplet of colloidal suspension of graphite in water is applied over the point of closest approach of these islands to dry. Since both resistance... 

Clearly, such interference can be reduced by increasing the distance between the source and the measurement circuit—mutual inductance and capacitance both being inversely proportional to the distance. Inductive coupling can also be much reduced by the use of twisted pair cable (Fig. 6.65). If adjacent loops in the circuit have the same area (e.g. loops 1 and 2) and are coupled with the same magnetic field, then the induced voltages between points A and B and between B and C will cancel each other out, and this will be repeated along the whole section of twisted pairs. 

Fig. 6.65. The twisted-pairs technique for reducing inductive coupling...

The physical wiring typically used is the plant standard twisted-pair wiring Tor 4- to 20-mA instrumentation. Because of the networking capability of the bus, more than one device can be supported on a single pair of wires, and thus wiring requirements are reduced. Compared to a host level bus such as Ethernet, field buses exhibit slower communication rates, have longer transmission distance capability (1 to 2 km), use standard two-wire installation, are capable of multidrop busing, can support bus-powered devices, do not have redundant modes of bus operation, and are available for intrinsically safe installations. Devices on the field bus network may be either powered by the bus itself or powered separately. 

Another countermeasure is to transmit signals on twisted pairs of wires by using differential amplifiers. If magnetical coupling exists, the induced voltage would be of the same size and would thus be cancelled at the receiver. Furthermore, as the level of the induced voltage increases with the area of a loop a twisted pair of wires insures that induced voltages are kept low. 

Presently possible transfer media in LANs simple twisted-pair wires, coaxial cable, and fiber optic cables, are characterized in Table I more in detail. 

Twisted-pair cable Coaxial cable Fiberoptic... 

Twisted-pair wire is the cheapest transfer medium, but is sensible to noise from the environment, and is normally (depending on the distances) limited to lower transmission speeds. Therefore this type of cabling is used mainly for asyn-... 

Coaxial cable is less sensitive to noise and is suited for higher transmission speeds than twisted-pair cable. Baseband techniques (serial bit-by-bit transmission) as well as (frequency modulated) broadband techniques are possible. Types of possible communication techniques in coaxial cables are listed in Table 9.2. 

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