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| Simple, Sophisticated, Smart |
Designed to be different |
Engineered to be the best |
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The Next Generation in on-line Measurement of POROSITY
MultiPerm
NT.2002
On-line POROSITY Measurement from VALUE SYSTEMS
Fig. 1.0 -
Filter Paper – L/m²/sec. @ 200 Pa. The measurement principle used by the MultiPerm on-line porosity measurement system was invented by Value Systems in 1993 and supersedes technology used on analogue systems. This principle recognises the importance of change in pressure that occurs during measurement and that varies from grade to grade and from one product type to another. The MultiPerm system provides innovative ‘sheet sensor contacting technology’ also invented by Value Systems. This technology ensures the integrity of the air bearing between the surface of the sheet and the face of the sensor eliminating the possibility of extraneous airflow from affecting porosity measurement in turn preventing upsets to closed loop control, e.g. refining.
Analogue systems rely on continuous and perfect contact with the sheet at all times to provide good correlation with the QC Lab. This contact varies with any sheet imperfection such as sheet flap, creasing, piping, holes, machine or sheet vibration, etc. and when any of these occur extraneous air is introduced resulting in calibration drift and measurement error. Under these conditions it is very unwise to use the porosity output signal for maintaining closed loop control of say refining!
The MultiPerm system monitors the contact between the sheet and the surface of the sensor every one centimetre in the machine direction; equivalent to 2000 Hertz on a machine operating at 1200 metres per minute or 120,000 iterations of the measurement per minute thus providing the fastest most analytical on-line porosity measurement platform available today.
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