Measurement and Control

Honey, D. W.

doi: 10.1177/002029406900200904pmid: N/A

Roots, William K.; Shridhar, Malayappan

doi: 10.1177/002029406900200903pmid: N/A

The common distributed parameter thermal processes that can be modelled by the cascade of a time constant and a transit delay (ie: boilers without superheaters, furnaces, ovens, vats, torches, fluidised beds, etc) are discussed. These are often multiposition controlled by solenoid valves, tapped transformers and similar discontinuous control elements. It is well known that if controller sensitivity, process gain, process parameters, and transducer locatons are arbitrarily combined these processes can exhibit instability. Over the years empirical design rules have been developed to determine such critical parameters as process gain, controller sensitivity, transducer type and location and the like. This paper uses a describing function approach to establish a facile technique for determining the stability criteria of such processes in terms of the controller parameters. This is then developed into a graphical display that gratly simplifies the design procedures associated with thermal processes and their control and instrumentation.

Clarke, D. W.

doi: 10.1177/002029406900200906pmid: N/A

The operation of a digital computer in a control laboratory imposes stringent requirements for a suitable language. Such a machine is used as part of a hybrid computer, to control and test pilot-scale plant, to analyse pre-recorded data, and to process relevant off-line programs. To achieve this degree of flexibility a high-level language with the facility for employing machine-language subroutines is essential. For on-line systems, input and output of data involves a straight-forward extension to normal practise; the main difficulty lies in the programming for the servicing of interrupts. This paper discusses the use of Fortran as the basis language of an on-line system and compares this with possible Algol-based systems.

Blackwell, G. J.

doi: 10.1177/002029406900200905pmid: N/A

Wilson, H. S.; Wylupek, W. J.

doi: 10.1177/002029406900200901pmid: N/A

Jones, D. W.; Pearson, J. E.

doi: 10.1177/002029406900200902pmid: N/A

Diode matrices are given for an inexpensive decoder to deal with an output in Watts reflected code from a Hilger and Watts digitizer in an analogue-to-digital converter. One application is to the output of a broad-line nuclear magnetic resonance spectrometer.