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USE OF THE COATING THICKNESS MONITOR IN CONJUNCTION WITH A STORED PROGRAM COMPUTER

Advantages from building an RTM based system usually include lower cos than a stored program computer for a fixed small task, and faster operation than a computer because of specialization to the task. The CTM is a good example of how a system can be hardwired to give very high performance. Another benefit of hardwiring is involved in interfacing, because a computer usually has to be specialized to meet interface constraints. On the other hand the RTM system once hardwired, is relatively inflexible for month to month changes, and large algorithms are not particularly suited to the structure because of limited control and processing structures. The analysis algorithm implemented in the CTM is getting to the complexity limit that one might wish to hardwire.

By using a computer with an RTM system one might combine the advantages of both high performance processing, and flexibility in the analysis and control algorithms. The time-consuming functions in this problem are the reading of the beta gages and storing them in memory, and the averaging and distribution analysis. Accepting switch inputs, converting them from decimal, and displaying results happen infrequently compared to the constant stock movement.

PROBLEM STATEMENT

Assume an RTM system is attached to a small computer to provide the CTM functions, and design a system to provide the functions of the original monitor. You may use any of the small computers described in Chapter 6. The input information about the material, Kj, the number of samples to be taken in the computation of the averages, the allocation of memory for results, and the various analysis functions would all be specified as parameters to the RTM system. Also, the RTM system might check for out of tolerance limits. Note, the RTM system would use the small computer's memory on a shared basis to store results.

DESIGN CONSIDERATIONS

It is important in this design not to give up any of the computer's flexibility. Doing too much automatically will often lead to a system that cannot be changed in the future, hence a large amount of automation is undesirable. Another problem which will arise is that constant use of the computer's memory by the hardwired portion of the system will cause its processor to stop, hence the design should allow some computation (say 50%) while the memory is being utilized. The gross structure of such a system is shown in Figure CTM-3.

There are several types of designs that might be examined. One would be similar to the alarm scanner (see Chapter 6) which performs one instruction at a


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