DD143114A1 - METHOD AND DEVICE FOR MOISTURE MEASUREMENT OF DIELECTRIC MATERIALS - Google Patents

Abstract

The process allows for capacitive and non-destructive Moisture measurement in dielectric materials, especially in construction and Natural and agricultural products. The procedure is characterized by the use of a stray field that the Moisture determination in the substance to be investigated up to a Penetration depth of 150 mm allows.

Description

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applicant:

Poppei, Prof. Dr habil _β, Gerhard Krauss, Dr.-Ing., Albrecht Seifert, Dipl _o ~ Phys., Klaus-Dieter Seifert, Axel

Registered Agent:

Engineering College 7 / ismar

- Office for the New Movement and Property Rights

Title of the invention

Method and device for moisture measurement of dielectric substances

Field of application of the invention

The proposed method and the moisture meter developed for moisture measurement in water-absorbing substances. They are suitable for monitoring wetting and drying processes.

General field of application is the rapid determination of the moisture content in dielectric substances of organic and inorganic nature,

The main field of application is the determination of moisture in building constructions, in construction and earth materials as well as in agricultural products.

Characteristics of the Known Technical Solutions There are known moisture measuring methods in which the electrical resistance change, electrostatic charge, dielectric constant change, magnetic energy generated by friction, generation of electromagnetic fields by electrostatic field discharge, centrifugal separation, and weighing methods are used as the conversion method. Dielectric processes are among the most advanced moisture management processes.

This method is represented by the DK-Feutemesser, which in the "Bauzeitung" Issue 3, 1978, p. 156/157 by Prof. dr. habil. G. Poppei and Dipl _e- Phys. Seifert was introduced. , '

Other methods for nondestructive moisture measurement after

15 Patent No .: 2508601 (BRD patent); Utilization of oil friction on film surfaces for electrostatic charging and their display. The patent no.: 2030377 (FRG patent) describes a method for measuring the humidity of moving dielectric materials, The measured value is the performance of the

2O electromagnetic field caused by the discharge of electrostatic fields used. The previous methods have the following disadvantages:

- High expenditure on equipment technology

- cumbersome and time-consuming handling by necessary fulfillment of process conditions such as movement, vibration, friction u. a.

- large mass and extensive spatial dimensions

- Suitability limited to specific material forms (foils, surfaces)

30- missing depth effect

- lack of localization of humidity centers - high acquisition costs.

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Object of the invention,.

The aim of the invention is a measuring method and a device for instantaneous measurement of the moisture content of dielectric substances up to a penetration depth of 150 mm. This achieves the following 5 advantages:

- Immediate detection of the mean value of moisture in a volume of several cubic decimeters

- Immediate detection of the spatial distribution of moisture in extended structures

10- Localization of cash register sources, such as B, hidden pipe breaks

- tracking of moisture and desiccation processes,

Explanation of the essence of the invention

The object of the invention is a measuring arrangement, the

The change in the dielectric constant of substances under the influence of moisture compares _β. The measuring method should be variably adaptable for various such measuring tasks. The relative dielectric constant for the substance to be investigated is highly dependent on the influence of moisture. moisture

Increase in increase leads to an increase, moisture reduction to a lowering of the dielectric constant. The dielectric constant of most electrically non-conductive solids is 2 to 6, that of the distilled water is 80. A stray field capacitor consisting of two juxtaposed

251iegenden parallel electrodes, without coupling to the DUT has its own basic capacity C _Q. This basic capacity depends on the plate size and the plate material. Air acts as a dielectic with the constant E = 1, but if another substance with a higher dielectric

30trizitätskonstante immediately before the stray field plates, so the capacity of the stray field capacitor increases. The capacity increase is displayed and represents the moisture-dependent variable to be evaluated. The measurement is carried out up to a penetration depth of approx. 150 mm.

The measuring device consists of the following modules (FIG. 1):

- Power supply 1

- Oscillator level 2

- driver and amplifier stage 3

5 measuring and inverting circuit 4.

Measuring capacitor 5 · - display 6

The conventionally designed HF generator consists of a quartz-controlled oscillator stage, which produces an extremely narrow

Loubility allows, and the driver stage, the repercussions of the output stage on the oscillator suppressed ₀ The coupling of the individual stages'ist adjustable and thus the effective at the capacitive voltage divider RF voltage. The two-stage Pi ~ filter ensures an optimal upper

15-wave suppression «The capacitively adapted measuring circuit consists of two matching capacitors C. and C ^ and one equalizing capacitor CL and the stray field capacitor C. This arrangement represents a capacitive voltage divider, from which via the rectifier diode D. and the potentiometer

2OIL the C-dependent current change is displayed (Figure 2).

Embodiment.

The moisture meters manufactured according to this principle can be made in different sizes according to the field of application, whereby the base area of the stray field capacitor

Sators can limit up to 250 cm, without the penetration depth is significantly reduced.

The oscillator operates at a frequency of 27 »12 MHz, the entire electronic structure is in a shielded

Housing housing, wherein the housing must not have an electrical connection to the stray field plates. The indication of the capacitance change-humidity change, which is caused by the moisture of the pores of the relevant material, can be carried out analogously, quasi-digitally or also digitally.

35gen.

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Analog display: Ammeter 100 UA

Quasi-digital display: Dial-up circuit designed for this application for 10 rows of light-emitting diodes which are combined to form a continuous light band.

This type of display is particularly suitable for the construction of humidity testers.

The sensitivity of the moisture meter can be switched by means of a measuring range switch located on the front panel. Measurement range I: Corresponds to the maximum sensitivity of the

Device (approximately O .., 30% relative humidity over the entire scale width) Measuring range II: Corresponds to the sensitivity to detect the relative humidity change from O ... 100 % .

The moisture meters are equipped with a calibration button, which allows to simulate a relative humidity of 100% in order to balance the device. The adjustment is done with an adjustment knob located on the front panel,

Claims (2)

invention claim Method and device for measuring the humidity of dielectric substances, characterized in that the change of the relative dielectric constant "E _r " of the substances, which changes with the moisture of the substance, by means of the principle of the stray field capacitor whose stray field generates a high-frequency generator , is displayed via a capacitive voltage divider, wherein. the following dependencies are optimized, the higher the frequency, the smaller the plate electrodes of the stray field capacitor, thereby a better adaptation to the surface of the substance to be examined and thus a greater penetration depth of the stray field. 2, method and apparatus according to item 1, characterized in that preferably a frequency range of the stray field is selected from 1 to 100 Mz. For this 1 page drawings