DE1473209A1 - Measuring probe with counter electrode and specially protected insulation sections - Google Patents

Description

Measuring probe with counter electrode and specially protected insulation sections Electronic level measuring devices work with a capacitive or galvanic measuring principle with measuring sensors, which essentially consist of a mostly metallic mounting flange, a certain arrangement of insulating bodies for the realization of an insulated bushing, and a Le which is electrically isolated from the flange by the insulating body and represents the actual active measuring part. Depending on the type of measurement method, the Part of the maBactive conductor opposite the medium in which it is probe-bound immersed, uninsulated or with insulation that is closed on all sides, which lies inside the container.

'L ", -, uninsulated probe difficulties arise in practical operation regarding the maintenance of the insulation resistance between the probe and the flange which are conditioned by the type and influence of the medium to be measured. Hence are especially wetting of the insulator with conductive uild in the sol, its occurring Encrustations of considerable disadvantage and cause disturbances and work.

In the case of isolated probes, difficulties arise in the manufacture of a pressure-tight joint between the insulating material surrounding the probe and the Flange or the parts belonging to the flange or the probe, because in particular physical properties of insulating materials to be used advantageously a seal that is stable over a long period of time; complicate or exclude. As soon however, the medium to be measured penetrates through the mentioned joint to the probe body, the probe becomes unusable for measuring purposes, albeit because of other things Precautions the medium to be measured does not yet need to escape from the container.

The aforementioned difficulties make it seem straightforward, the medium in advancing to the critical points on the measuring sensor, namely the isolator of the uninsulated sensor or the sealing joint in the case of insulated measuring sensors to prevent.

This intention is achieved according to the invention by an air cushion, which encloses the mentioned critical points and so shedliche effects of the Excludes medium at the named locations.

The subject matter of the invention is closer to an exemplary embodiment Figure 1 explains the basic arrangement of a sensor.

The flange 2 is inserted into the container wall 1. The active one The probe 4 is fastened directly in the flange 2 by means of the insulator 5 and razt into the Medium 7 in. The pipe 6 is attached to the flange 2 by means of a seal 3 and is effected with rising medium 7 the formation of an air cushion 8, so that finally two different liquid levels 9, 10 arise. When the tank is depressurized, it is at rest on the enclosed volume 8, the pressure or the liquid column from the difference of the two liquid levels 9t 10. If the container is under pressure, then the In principle, the same principle of operation, but the enclosed volume is still additionally under tank pressure.

As a result, the insulator 5 cannot be affected by the rising liquid) el 10 can be used.

Basically the same mode of operation occurs with isolated sensors on, in which then the probe body within the container completely from the insulating material is enclosed.

In principle, the critical point is then to be found in point 11 and again protected by the air cushion 8.

By suitably shaping the tube 6, the insulator 5 and the probe 4 can be adapted to the particularities of a particular measurement problem, e.g. B. Viscosity, conductivity or dielectric constant.

The use of the tube 6 as a concentric counter electrode is particular In the case of smaller containers with plastic walls, this is a prerequisite for reliable function the level control, at the same time parasitic effects can be eliminated and the effect of a change in conductance caused by the medium between the probe rod and the counter electrode can be increased to a maximum.

Claims (2)

Patent claims 1. Sensor for level display according to capacitive or galvanic measuring method, characterized in that the protruding into the container Toile of the sensor as a whole have a shape such that a consentric one Arrangement of a measuring active probe and a counter electrode lying at ground potential arises, with the air insulation distances between the measuring probe rod and relative to the concentric counter-electrode lying at the potential of the pool are small compared to the creepage distances along the insulating body and the rising medium the measure-active center electrode at the same or later Time reached than the concetrical one connected to the flange Counter electrode. 2. Sensor according to claim 1, characterized in that at one preferably vertical installation of the sensor is the ascending and samit into the cavity between the measuring probe rod and the concentric counter electrode penetrating medium through an overlying air cushion on the complete Wetting of the insulator u, -id thus to the reduction of the insulation resistance is prevented, with the container pressure and the pressure of the liquid column acting on the air cushion out of difference between the liquid. level in the container and the liquid level acts in the container and the cavity formed by the probe.