Vega VEGAFLEX 67 Operating Instructions Manual

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Vega VEGAFLEX 67 Operating Instructions Manual Manual pdf 16 page image

5 Connecting to power supply5.1 Preparing the connectionAlways keep in mind the following safety instructions:l Connect only in the complete absence of line voltagel If voltage surges are expected, overvoltage arresters should beinstalled according to Profibus specificationsTip:We recommend VEGA overvoltage arrester B63-32.In hazardous areas you must take note of the respective regulations,conformity and type approval certificates of the sensors and powersupply units.Power is supplied via a Profibus DP/PA segment coupler or aVEGALOG 571 EP input card. The power supply range can differdepending on the instrument version.The data for power supply are specified in chapter "Technical data".Connection is made with screened cable according to the Profibusspecification. Power supply and digital bus signal are carried over thesame two-wire connection cable.Use cable with round cross-section. A cable outer diameter of 5 … 9 mm(0.2 … 0.35 in) ensures the seal effect of the cable gland. If you areusing cable with a different diameter or cross-section, exchange theseal or use a suitable cable gland.Please make sure that your installation is carried out according to theProfibus specification. In particular, make sure that the termination ofthe bus is done with appropriate terminating resistors.On the instrument with cable entry ½ NPT and plastic housing there isa metallic ½" threaded insert moulded into the plastic housing.Caution:No grease should be used when screwing the NPT cable gland orsteel tube into the threaded insert. Standard grease can containadditives that corrode the connection between threaded insert andhousing. This would influence the stability of the connection and thetightness of the housing.With systems with potential equalisation, connect the cable screendirectly to ground potential at the power supply unit, in the connectionbox and at the sensor. The screen in the sensor must be connecteddirectly to the internal ground terminal. The ground terminal outside onthe housing must be connected to the potential equalisation (lowimpedance).Safety instructionsVoltage supplyConnection cableCable gland ½ NPTCable screening andgrounding16 VEGAFLEX 67 • Profibus PA5 Connecting to power supply32313-EN-120329