The ideal On-line measuring element is a device which is cheap, reliable, accurate, noise free and needs little or no maintenance. Very few of the available transducers live up to these requirements and many currently being used in the sugar process can only be considered second best. The information which is collected from these devices has to be fully understood and allowance must be made for all the possible sources of error.
There are still many process parameters which cannot be measured1 at all. The On-line detection of moisture content of both sugar and dry pulp being a good example. Other measurements which still cause considerable trouble are those of continuous band weighing, humidity measurements, batch counting, high temperatures and various flow applications.
Whenever a new control system is required, the initial study is almost always centred around the measurement involved. There is ample equipment to carry out the control function once an accurate and reliable is available. Although more and more transducers are being made generally available to process industries, they often fail to fulfil their purpose in the sugar industry for one reason or another. Difficulties arise from several sources. The transducer may not measure the actual parameter under control, the sample measured may not be a good average value and the transducer may itself be unstable and its calibration unreliable. These units are sometimes delicate devices and some of the conditions in which they operate can be very arduous.
All these factors place a severe limitation upon the application of transducers however, if their characteristics are repeatable and sensible precautions are taken to protect them from damage it is often surprising how much useful information can be obtained1.
Proceedings: CITS 1971
pdf download: CITS1971-121-151.pdf