Vega VEGAPULS 68 Operating Instructions Manual

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Vega VEGAPULS 68 Operating Instructions Manual Manual pdf 26 page image

265 Connecting to power supplyVEGAPULS 68 • 4 … 20 mA/HART - four-wire29262-EN-1607075 Connecting to power supply5.1 Preparing the connectionAlways keep in mind the following safety instructions:Warning:Connect only in the complete absence of line voltage.• The electrical connection must only be carried out by trainedpersonnel authorised by the plant operator.• If overvoltage surges are expected, overvoltage arresters shouldbe installed.Supply voltage and current output are carried on separate two-wireconnection cables if reliable separation is required. The supply volt-age range can differ depending on the instrument version.The data for power supply are specified in chapter "Technical data".The standard version can be operated with an earth-connected cur-rent output, the Exd version must be operated with a floating output.This instrument is designed in protection class I. To maintain thisprotection class, it is absolutely necessary that the ground conductorbe connected to the internal ground terminal. Take note of the generalinstallation regulations.Always connect the instrument to vessel ground (potential equalisa-tion) or in case of plastic vessels to the next ground potential. Forthis purpose there is a ground terminal on the side of the instrumenthousing.For power supply, an approved installation cable with PE conductor isrequired.The 4 … 20 mA current output is connected with standard two-wirecable without screen. If electromagnetic interference is expectedwhich is above the test values of EN 61326 for industrial areas,screened cable should be used.Use cable with round cross section for instruments with housing andcable gland. To ensure the seal effect of the cable gland (IP protectionrating), find out which cable outer diameter the cable gland is suitablefor.Use a cable gland fitting the cable diameter.If screened cable is required, we recommend connecting the cablescreen on both ends to ground potential. In the sensor, the screenmust be connected directly to the internal ground terminal. Theground terminal on the outside of the housing must be connected tothe ground potential (low impedance).In Ex systems, the grounding is carried out according to the installa-tion regulations.With the Exd version, the minus side of the signal output is galvani-cally connected to ground via protective diodes. When connecting theinstrument to a grounded PLC, equalising currents can flow in caseSafety instructionsVoltage supplyConnection cableCable screening andgrounding