Analog Signal Protection Protecting analog signals (4-20 mA current loop) with the PLUGTRAB PT 1X2… and PT 2X2… TRABTECH Application Note 2554A 1 © PHOENIX CONTACT - 02/2009 Description Analog signals, such as 4-20 mA current loops, can be protected with the PLUGTRAB PT 1X2… or PT 2X2… series. These modules provide protection for one (PT 1X2…) or two (PT 2X2…) pairs of signal circuits. The PLUGTRAB is installed in one of two base elements: the PT…+F-BE base provides isolation between the shield and ground while the PT…-BE base bonds the shield to ground. The bond in the PT…-BE base provides a drain for noise collected on the shield. Using the PT…+F-BE base prevents unwanted ground loops by isolating the shield and ground. Pair 1 Signal 12 10 Field Devices 11 9 11 9 5 7 3 1 6 4 8 2 OUT 12 10 5 3 7 1 Shield IN 6 8 4 2 OUT IN PT 1X2+F-BE base Control Panel PT 1X2-BE base Figure 1. Typical Base Wiring for PT 1X2 Pair 1 Pair 2 Pair 1 Signal 12 10 Field Devices Pair 1 Pair 2 Pair 2 11 9 11 9 5 7 3 1 6 4 8 2 OUT IN PT 2X2+F-BE base Figure 2. Typical Base Wiring for PT 2X2 12 10 5 3 7 1 Shield 6 8 4 2 OUT IN PT 2X2-BE base Control Panel Analog Signal Protection 1.1 Proper Grounding The PLUGTRAB prevents surge energy from reaching the control equipment by diverting this energy to the ground circuit. Figure 3 shows a grounding block attached to the DIN rail. A ground wire should be connected from the grounding block to the AC power ground. The wire should be: During a surge event, energy can come from several signal cables. If multiple PLUGTRABs are used to protect different signal lines, they will all divert the surge energy to the ground, via the DIN rail, requiring a large diameter wire. −− the same diameter/gauge as the power ground wire. −− not placed next to or near a signal wire. Unprotected IN Protected OUT Protection of Control Equipment Controller Input/Output Analog IN IN OUT Analog OUT To Common Ground Figure 3. Proper grounding with the PT…X2-BE 90 52 66 45 Figure 4. Dimensions 2 Phoenix Contact 2554A Analog Signal Protection 2 Products Description of analog one circuit protection Type PLUGTRAB plug, 5 V DC PT 1X2-5DC-ST 2856016 PLUGTRAB plug, 12 V DC PT 1X2-12DC-ST 2856029 PLUGTRAB plug, 24 V DC PT 1X2-24DC-ST 2856032 PLUGTRAB plug, 12 V AC PT 1X2-12AC-ST 2856045 PLUGTRAB plug, 24 V AC PT 1X2-24AC-ST 2856058 PLUGTRAB base element, accepts PT 1X2 plugs PT 1X2-BE 2856113 PLUGTRAB base element, includes integrated gas discharge tube, accepts PT 1X2 plugs PT 1X2+F-BE 2856126 Description of analog two circuit protection Type PLUGTRAB plug, 5 V DC PT 2X2-5DC-ST 2838241 PLUGTRAB plug, 12 V DC PT 2X2-12DC-ST 2838254 PLUGTRAB plug, 24 V DC PT 2X2-24DC-ST 2838228 PLUGTRAB plug, 12 V AC PT 2X2-12AC-ST 2838270 PLUGTRAB plug, 24 V AC PT 2X2-24AC-ST 2838283 PLUGTRAB base element, accepts PT 2X2 plugs PT 2X2-BE 2839208 PLUGTRAB base element, includes integrated gas discharge tube, accepts PT 2X2 plugs PT 2X2+F-BE 2839224 3 Order No. Order No. Accessories Description Type Tester, for checking the functions of TRABTECH protective devices, includes adapter for PLUGTRAB devices CHECKMASTER 2838924 Test Adapter, for PLUGTRAB CM-PA-PT/A 2816933 2554A Phoenix Contact • P.O. Box 4100 • Harrisburg, PA 17111-0100 • USA Sales: 1-800-888-7388 • Technical Service: 1-800-888-7388 www.phoenixcontact.com Order No. 3