Vega VEGABAR 55 Operating Instructions Manual

Vega VEGABAR 55 Operating Instructions Manual Manual pdf 16 page image

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.We generally recommend the use of screened cable for HARTmultidrop mode.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.If screened cable is necessary, connect the cable screen on both endsto ground potential. In the sensor, the screen must be connecteddirectly to the internal ground terminal. The ground terminal on theoutside of the housing must be connected to the potential equalisation(low impedance).If potential equalisation currents are expected, the connection on theprocessing side must be made via a ceramic capacitor (e. g. 1 nF,1500 V). The low frequency potential equalisation currents are thussuppressed, but the protective effect against high frequency interfer-ence signals remains.Take note of the corresponding installation regulations for Exapplications. In particular, make sure that no potential equalisationcurrents flow over the cable screen. In case of grounding on both sidesthis can be achieved by the use of a capacitor or a separate potentialequalisation.5.2 Connection procedureProceed as follows:1 Unscrew the housing cover2 If an indicating and adjustment module is installed, remove it byturning it slightly to the left.3 Loosen compression nut of the cable entry4 Remove approx. 10 cm of the cable mantle, strip approx. 1 cminsulation from the individual wires5 Insert the cable through the cable gland into the sensor6 Lift the opening levers of the terminals with a screwdriver (seefollowing illustration)Cable gland ½ NPTCable screening andgroundingSingle/Double chamberhousing16 VEGABAR 55 • 4 … 20 mA5 Connecting to power supply36733-EN-091008