Model 214D-1 Batch Controller - Hoffer Flow Controls - #51

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Installation43 HP289 should be as short as possible and connected to the grounding lug onthe side of the case.In order to comply with the requirements for ElectromagneticCompatibility as per EMC-Directive 89/336/EEC of the Council of European Community, this wiring practice is mandatory.Although it is also possible to connect shields to the signal ground(terminal 2) this practice is not in accordance with EMC directives. RC Networks for Interference Suppression When driving highly inductive loads with the control relays, it isrecommended that RC suppression networks (often called "Snubbers") are used for two reasons: To limit the amount of electrical noise caused by arcing acrossthe relay contacts which may, in extreme cases, cause the microprocessor to act erratically. To protect the relay contacts against premature wear throughpitting.RC suppression networks consist of a capacitor and series resistor andare commonly available in the electrical industry. The values of R andC are dependant entirely on the load. However, if the user is unsure of the type of snubber to use, values of 0.25µF and 100 ohms will usually suffice. Note that only AC voltage approved RC suppression networks should be used.The basic principle of operation is that the capacitor prevents a series ofsparks from arcing across the contact as the contact breaks. The series resistor limits the current through the contact when the contact first makes