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Tablets & Capsules May/June 2021 33 The impact of noise on a metal detector is illustrated by the real-time polar graph shown in Figure 3. Because elec- trical noise has a distinct irregular shape (the red squiggly line) the metal detector (Eriez Xtreme) can quickly iden- tify the interference, drastically reducing troubleshooting and downtime. Vibration. The impact of vibration on a metal detector is two-fold. First, at adequate levels, the vibration can trip the detector. Second, it can fatigue the solder joints on the detector's circuit boards. Like electrical noise, vibration has a distinct signature, as shown in red in Figure 4. Vibration presents itself at 0 degrees to the metal detector and is easily identified in the real-time polar graph. As the figure shows, the vibration signature penetrated the green boundary, causing a false trip. If vibration is present, consider dampening devices. by powering the metal detector from a "clean" lighting or instrument circuit. The circuit must be free of inductive loads such as motors, solenoids, and motor starters. If you must power the metal detector using a less-than-favorable source, you can use a constant-voltage transformer with harmonic neutralization to eliminate or reduce false trip- ping from line noise. This transformer should be mounted within 3 to 5 feet (1 to 1.5 meters) of the metal detector. Further, the metal detector's power source must con- tain a reliable ground connection. It must be connected to the metal detector's protective earth terminal. The metal detector should be grounded at one point through the power supply ground wire. No other ground connections are permitted, including mounting hardware and conduit. Inductive loads sharing the same power circuit usually create noise. While metal detectors are equipped with electronic filter circuits to reduce incoming electrical noise, there is a limit to what a detector can withstand without false tripping. Figure 3 Real-time polar graph showing electrical noise Electrical noise Figure 4 Real-time polar graph showing vibration Vibration signature 20_0313_AD_O Tab and Cap Mag.pdf 1 3/13/20 1:50 PM