RFID corrects for gate misalignment

. Machine guards are often treated with considerable abuse, ending up bent and warped, but continue to serve their purpose as long as they can be latched shut and remain protected by machine interlocks. The Guardmaster “SensaGuard” family of inductive switches, from Rockwell’s Allen-Bradley division, use RFID coded targets that will still latch the switches when they are up to 15mm away – in the case of 18mm targets – and 25mm away in the case of 30mm targets. Paul Davies, local business leader for safety components, says: “It is very difficult to defeat these switches.” He explained that they cannot be defeated with magnets, bits of wire or screwdrivers – though admitted they could be overcome either by removing the targets and taping them to the switches, or shorting out the relay output wires. However, they fulfil the requirements of Category 4 (EN954)/SIL 3 (IEC61508). They are TUV approved and environmentally protected to IP69K (1,200 psi washdown). Minimum working gap is 4mm, because of side lobes. Each batch series has an individual code. A flat pack version with a magnetic hold feature is to be introduced in Q2 2007. According to Davies, prices are £50-80 each.