Generic Features of Potentiometers Benefits to the User

• Absolute measurement •No loss of position upon power down•Lower system design costs - no need for extra signal conditioning•Lower cost electronics•Able to operate in electrically noisy environments•Classed as simple apparatus - able to operate inhazardous areas without specific approvals - lower system design costs•Lower installation costs • Simple electronics • Low current • Good EMC • Intrinsically safe • Quick and easy installation

Features of the Hybrid Potentiometer Benefits to the user

• Conductive plastic on wire element •No metal to metal contact increases the operational track life, reduces maintenance and service costs•No degradation in performance - better system accuracy over a longer period•No output drift during service life of the potentiometer - no drift in process control or requirement to re-calibrate- therefore lower service cost•Very small movements can be sensed•Better system accuracy. Eases design for customer•Increased reliability, longer operating life, lower service costs•Improved system accuracy reduces design costs•Improved system accuracy reduces design costs•Reduced system cost over working life. • Self compensating for track wear • Linearity, temperature, humidity stability • Virtually infinite resolution • Low hysteresis • Self cleaning, long life contact design • Low electrical contact noise • Zero width current taps • Competitive price The Penny+Giles hybrid track potentiometer was developed to combine the advantages of both conductive plastic andwirewound potentiometers and provide optimum sensor performance. The principle advantages are: • Infinite resolution and long life, provided by the conductive plastic track • Stability under extremes of temperature and humidity, provided by the wirewound element.Linearity and resistance values are typically those of the wirewound element to which zero width taps, capable of carrying full rated element current, may be attached.The hybrid track consists of a conventional precision wirewound potentiometer element upon which has been mechanically andelectrically bonded a thin film of high resistivity conductive polymer track. The polymer track comprises a plastic matrix in which carbon particles are suspended; the density of the carbon controlling the resistivity of the polymer. The polymer track is 'wiped' by a precious metal contact, giving a virtually infinite resolution with considerable resistance towear (since the majority of the current still flows in the wire, the carbon content of the conductive plastic film is low, and thefilm is therefore very hard). The advantages of wirewound technology remain - linearity as-wound is good (i.e. without resorting to corrective techniquesafter initial manufacture), temperature coefficient of resistance is low and predictable, and resistance stability with change ofhumidity is good. It is essential however, that unlike wirewound potentiometers, hybrid track potentiometers are only used as potential dividers, with a high wiper circuit impedance (at least one hundred times track resistance). As with purely conductive plastic film potentiometers, hybrid track potentiometers cannot be used as variable resistors. The operating principle The sheet resistivity of the polymer is chosen to give a track resistance at least three orders higher than the wirewound elementupon which it is deposited. This causes most of the potentiometer element current to be carried in the wire, with only a very small proportion in the parallel polymer track.

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