A New Microwave Thickness Gauge<sup>*</sup>

Soga, Hiromu

doi:10.1080/00222739.1973.11688884

Cited by 5 publications

(1 citation statement)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The usual quantity to be measured is the wetness and the vast majority o the sensors are based on transmission or reflection. Some sensors are resonant, but they are normally not made for measuring through layers of considerable thickness [3,4,5,6]. In this case transmission measurement is impossible because of the steel band.…”

mentioning

confidence: 98%

Sensor for Measuring the Mass Per Unit Area of a Dielectric Layer

Nyfors¹,

Vainikainen²

1984

14th European Microwave Conference, 1984

View full text Add to dashboard Cite

A sensor for non-contact measurements of the thickness or mass per unit area of a dielectric layer has been developed. It has been constructed for measuring a cake of wooden particles on a steel band in the particle board industry. The sensor is suspended at a distance above the layer of particles to form a strip line resonator together with the steel band. The resonant frequency and the quality factor are measured. The resonant frequency correlates well with the mass per unit area and the quality factor can be used to deduce the mean wetness in the layer. The sensor is insensitive to moderate variations in the distance between the sensor and the steel band. I NTRODUCTI ONIn the particle board factory the wooden particles are spread out to form a uniform cake on a steel band before the pressing phase. For the automatic control of the process, it is essential to be able to measure the mean and the spatial distribution of the mass per unit area of the ca-ke. The mean mass is usually measured also by other methods, but the distribution is checked only visually and by sampling the product once in the beginning of each shift. Continuous monitoring of the distribution leads to a more uniform quality and savings in the consumption of raw materials, as even the weakest parts of the board will be strong enough with a smaller mean mass per area than without control. Continuous measurements are also important to give an alarm in the case of sudden disturbances in the spreading machine. Pressing of a defective cake can cause the press to break down causing expensive pauses in the production. A sensor has been developed for this purpose. It is suspended above the cake for non-contact measurement of the mass per unit area at the site of the sensor. To get the spatial distribution the sensor can be mechanically scanned over the cake, or many sensors can be mounted in a row. THE SENSORMany different kinds of sensors using radio waves for measuring various properties of dielectric materials have been developed [1,21. The usual quantity to be measured is the wetness and the vast majority o the sensors are based on transmission or reflection. Some sensors are resonant, but they are normally not made for measuring through layers of considerable thickness [3,4,5,6]. In this case transmission measurement is impossible because of the steel band. Measurement of reflection was tested, but because of the low attenuation in the particle layer, this proved impractical. Small changes in distance and pointing angle, caused by the movement of the sensor and/or the steel band, did also cause errors. Therefore a resonant sensor that measures through the layer was developed.

show abstract

mentioning

confidence: 98%