Measuring and testing – Moisture content or absorption characteristic of material
Patent
1997-04-03
1998-10-27
Williams, Hezron E.
Measuring and testing
Moisture content or absorption characteristic of material
73 2901, 324634, 324636, 324640, G01R 2726, B29C 7104, G01N 502, H05B 906
Patent
active
058264582
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a moisture detection meter particularly but not exclusively suited for use in the forming section, or `wet end` of a Fourdrinier or other papermaking machine.
At the wet end of a Fourdrinier machine a water/fibre stock is applied to the surface of a moving drainage fabric at an upstream end of a forming section of the machine. Water is removed and a drained fibre layer is delivered for further processing and drying at a downstream end of the section.
It is desirable to be able to monitor the drainage efficiency along the forming section and therefore it is known to use microwave detection meters in a sensing head placed beneath the drainage fabric which detect the quantity of moisture by measuring the frequency of resonance of microwaves which are directed into the fabric and stock. In such an arrangement, it is usual to have more than one microwave cavity in order that a fixed frequency reference can be compared to a sensed frequency of resonance and the difference therebetween can be determined. The determined difference is indicative of the moisture content of the stock.
A problem arises due to the necessity to use more than one cavity in the sensing head insofar as a minimum limit is placed on the dimensions of the head which can restrict the position in the machine at which the sensor can be placed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a moisture detection meter in which the dimensions of the sensing head can be substantially reduced thereby increasing the possibilities for location of the meter in the machine.
According to the present invention therefore there is provided a moisture detection meter comprising a sensing head having a single chamber which is open upwardly, a dielectric resonator member in said chamber and field generation means to generate an oscillating electric field in said chamber, said resonator member and said field interacting to produce at least one field component which is directed out of said open top of said chamber to interact with stock passing over the sensing head, detection means to detect the frequency of resonance of said field component after interaction with said stock and an indicator device operable to provide an output indicative of the moisture content of said stock.
With this arrangement it is possible to provide a moisture meter which has a sensing head of substantially reduced dimensions.
Preferably said dielectric resonator has a relatively high dielectric constant at the frequency of operation and may be substantially equal to 80.
Preferably said open top of said chamber is covered with at least one layer of a material having a low permittivity thereby permitting the field component to exit the chamber and interact with the stock without significant perturbation or attenuation. The material may conveniently be polytetrafluoroethylene (PTFE) which is a low loss, low permittivity material.
Preferably the frequency of the oscillating field generated by the field generating means is substantially 1 GHz and most preferably in the range 0.6 to 0.75 GHz.
Preferably the field generating means is connected to a voltage controlled oscillator which is tunable so as to be capable of providing an oscillating signal to the field generating means over a predetermined frequency range. Preferably the field generating means comprises an electrical coupling mounted adjacent to said resonator member along a transverse axis thereof. With such an arrangement, perturbation of the electric field provided by the generating means by the dielectric resonator material, produces one field component of sufficient strength to exit the chamber through the open top, whilst minimising the strength of other field components.
Preferably the detection means includes peak detection means and/or means for tracking a peak across a frequency range to detect a peak signal which occurs at resonance. Preferably both peak detection means and means for tracking a peak are used and the latter may be embodie
REFERENCES:
patent: 3586971 (1971-06-01), Bosisio
patent: 3597566 (1971-08-01), Johnson
patent: 3883798 (1975-05-01), Free
patent: 4042879 (1977-08-01), Ho et al.
patent: 4381485 (1983-04-01), Steinbrecher
patent: 4829233 (1989-05-01), Flemming et al.
patent: 4904928 (1990-02-01), Lewis
patent: 5046356 (1991-09-01), Osaki et al.
patent: 5333493 (1994-08-01), Cutmore
patent: 5334941 (1994-08-01), King
patent: 5554935 (1996-09-01), Kraszewski et al.
patent: 5621330 (1997-04-01), Greenwald et al.
patent: 5648038 (1997-07-01), Faithi et al.
patent: 5666061 (1997-09-01), Assenheim
patent: 5686841 (1997-11-01), Stolarczyk et al.
Scapa Group PLC
Wiggins J. David
Williams Hezron E.
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