W

W We make no effort to cover all measurements and hardware here. We have selected, however, a number of items we think are important, or are worth emphasizing, or have not been covered adequately elsewhere. A glaring omission is that of flow metering. We are very suspicious of the accuracy of most inplant flow meters because only rarely do plants have facilities for their calibration, but we have nothing new or unique to offer for improvement. Considerable emphasis, on the other hand, has been placed on temperature-measurement dynamics since this subject seems to be widely misunderstood or inadequately understood. And we have devoted some space to control-valve sizing and selection since the new (1974) ISA equations for calculating the operating Cv and for predicting the flow regime are not yet widely used.

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