Instruction ManualNivuMaster Ultrasonic Sensors®NivuMaster Ultrasonic Sensors - Rev. 06 as of 29.07.2011 Page 25Please note:- we recommend to route the sensor line directly to the NivuMaster withoutusing additional clamps within the switching cabinet.- Do not lay several sensor lines in a multi-core cable. Each sensor cableshall be laid separately.- Lay sensor cables isolated from power lines and frequency-controlled motorlines.- It is possible to extend the sensor cable up to 800 m. Please always keep inmind that in case of voltage drops there is a minimum voltage of 18 V DCleft for sensor supply.The resistance of single wires shall not exceed 30 Ohm.6.3 Overvoltage Protection PrecautionsFor efficient sensor protection it is necessary to use overvoltage protection unitson both sides if required.NIVUS recommends for sensor as well as for transmitter side overvoltage pro-tection units Type SonicPro.Fig. 6-13 Lines without overvoltage protectionFig. 6-14 Overvoltage protection on transmitter side