Metal Finishing Guide Book


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The Interface To keep the equipment as standard as possible, the popular choices for interfaces are the RS-232 and RS-422. Each requires only a pair of shielded, twisted wires to transmit information. This significantly reduces the number of wires needed for a multiple-rectifier system, as the twisted pair simply connects from the interface controller to each rectifier in a sequential fashion. In other words, the same pair of wires goes to the first rectifier to the second to the third, and so on. This eliminates the many wires that are commonly found connecting remotely located control panels to rectifiers. The Software The software should consist of standard control packages modified to meet the user's specific requirements. A language such as Quick Basic, used on the host computer, will provide the necessary operating speed for the host, along with the ability to modify or upgrade the program easily at any point. Faster languages, such as assembly code, may be required for a microcomputer located on the rectifier to control output waveforms adequately. A Main Frame A link between a main frame and the host computer is always a possibility, increasing the overall capability of the system. Such a link might be the first step toward complete factory automation. Use of a main frame provides a means for data from all parts of the finishing operation to be accumulated, correlated, and disseminated to various departments. For many smaller and middle-sized operations, computer automation is becoming financially feasible. Benefits include reductions in rework and reject rates, in downtime, and in chemical costs. Additional savings could be realized by the reduced power usage of a computer-controlled operation. In the near future computer automation may very well be the key factor in whether certain metal-finishing operations are profitable. RECOMMENDED TEST EQUIPMENT Aside from the usual hand tools usually found in a well-equipped industrial tool box, the following are recommended tools for power supply troubleshooting: 1. A clamp-on AC ammeter 2. A digital volt-ohm meter (DVM) 3. A battery-operated oscilloscope There are several options to consider when purchasing these instruments for testing in an industrial environment. The clamp-on ammeter should be an AC device, as it will be used at currents up to 1,000 A AC. All exposed metal parts must be sufficiently insulated to ensure safe use around 600 V AC equipment. An analog-type clamp-on ammeter is preferred over most digital ammeter types, unless the digital unit is sufficiently filtered to prevent display jitter when measuring incoming line AC. When buying a digital ammeter, one should test the instrument on an operating power supply before making the final purchase decision. The digital volt-ohm meter best suited for power-supply testing is battery operated and durably packaged so that it will stand up in an industrial environment. A heavy-duty rubber-covered case is best. To be the most useful, the 746

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