DD221549A1 - DISCONTINUOUS CAPACITIVE LIMIT-LAYER MEASURING METHOD WITH FREQUENCY-DEPENDENT RETURN-COUPLED OSCILLATOR - Google Patents

Abstract

The invention relates to a circuit arrangement for capacitive boundary layer measurement with a frequency-dependent feedback oscillator for the entire field of MCR technology, where fill level registrations are required. The aim of the invention is that without much effort in terms of voltage and temperature stabilization, a circuit arrangement has been developed, which is arbitrarily applicable and can be arranged arbitrarily. The advantages are also: - smallest construction costs - low material complexity - susceptible to disturbance - low acquisition costs

Description

a) Title of the invention

Discontinuous capacitive boundary layer measuring method with frequency-dependent feedback oscillator

b) Application of the invention

The invention relates to a circuit arrangement for discontinuous capacitive boundary layer measurement with a frequency-dependent feedback oscillator between media having different relative dielectric constants and a difference in relative dielectric constants

c) Characteristic of the known technical solutions

So far, in V / P 151 356 a circuit arrangement is known, which causes on the principle of capacitive detuning a tearing of the oscillator oscillation. As oscillator circuit brought by capacitive feedback to vibrate transistors are used. The relatively complex stabilization measures with respect to the ambient temperature and the supply voltage are in stark contrast to the relatively simple and uncomplicated circuit arrangement. These necessary stabilization measures have a cost-intensive effect. In addition, the arrangement switches according to ΥΠ? 151 356 only with an increase in the relative dielectric constant at the probe.

d) Object of the invention

The aim of the invention is a circuit arrangement for a discontinuous capacitive Grenzschichtmeßverfahren with frequency-dependent feedback oscillator without complex stabilization measures for supply voltage and ambient temperature.

Usable for all types of electrical, conductive and insulating liquid and granular substances with different relative dielectric constant and a difference in relative dielectric constant £> 1.

e) Presenting the essence of the invention

- Technical task

The invention is based on the object, a-circuit. to develop arrangement for a discontinuous capacitive Grenzschichtmeßverfahren that allows to guarantee the smallest size, high registration sensitivity, low cost of materials and reduced susceptibility to interference and thus eliminates the known deficiency of the prior art.

Features of the invention

The object is achieved in that an integrated initiator circuit is made with a suitable circuit to a frequency-dependent switching system.

Especially when using the available in the DDR initiator circuits omitted due to the internal stabilization of the operating voltage of the oscillator system, additional stabilization measures. The puncture principle of the frequency-dependent switch is shown in Appendix 1.

The oscillation frequency fo of the oscillator system is determined by the input resonant circuit C ^ GgLg. The feedback of the oscillator system is realized via the filter system F 1. On the pass frequency of PiItersystems F ^ the frequency of the input resonant circuit fo with C ^ is exactly matched. This results in the condition f = f. for the oscillatory ability of the oscillator. If the capacitance of the capacitor C3 ", which is designed as a measuring probe, is changed by immersing the probe in a substance with a changed relative dielectric constant ε _r , the oscillatory

frequency f. '

As a result, the condition f = f. no longer satisfied and the oscillation of the oscillator stops. By the subsequent stages of the circuit arrangement (demodulator, switching amplifier), the suspension of the oscillator is registered and converted into a usable output signal Q ^. The sensitivity of the system depends mainly on the bandwidth of the pi system P.

f) embodiment

The circuit can, depending on the design of the probe oil ·, the probe in the already known form z. B. can be performed as a rod or rope probe, are used for the realization of boundary layer detectors between any media with a difference in the relative dielectric constant.

In the Ti'gur 2, the circuit arrangement is shown as an exemplary embodiment.

In the + ~> ~ Qur 3 is the probe body in which the circuit arrangement is accommodated, as an exemplary embodiment.

The probe body consists of a terminal housing 2, which contains the entire electronic circuit. The threaded piece 3 is used to seal the installation point (flameproof versions are possible) and as a support for the measuring capacitor designed as a rod probe first

Claims (1)

g) claim for invention A discontinuous capacitive boundary layer measuring method with a frequency-dependent feedback oscillator suitable for registering the boundary layer marks between substances with a difference in relative dielectric constant λ £ γ> 1, characterized in that a band filter system is located in the feedback branch of the oscillator system, which ensures the oscillation capability of the oscillator system in a frequency-dependent manner and responds to both increase and decrease in the relative dielectric constant of the medium present at the probe. Berzu_3_Seiten drawings