DE2210297C2 - Continuous level meter for electrically conductive liquids - Google Patents

Description

10

15th

the coil produces a very precise linear signal, which only needs to be corrected for the effects of temperature fluctuations. By Using austenitic steel as the core of the probe, the temperature influence is already reduced, however, a further electronic correction of the measurement signals is advantageous. In the following it becomes a Circuit described, with the help of which influences of different temperatures can be compensated.

Since the display has a different slope and also has no common output potential, the compensation is expediently done in such a way that that an auxiliary voltage is entered, which the display in the unwetted state at low temperature corresponds, so that the voltage present in this case is suppressed to zero. Then the Resistance of the receiver changed so that a common starting potential for the display at different Temperatures is reached. In order to obtain a uniform slope measure, the signal changes, those by the level, and those ^ the caused by the temperature, multiplied together The addition of this product and the receiver voltage at low temperature gives the voltage that is used for display, where a linear relationship between level and voltage independent of the liquid temperature given is. Another advantage of the level meter according to the invention is that it can be replaced can without having to open the container containing the liquid to be monitored. It can also be limited through the length of the cladding tube, the measuring length can be changed by adding a shorter or longer one Level meter is used. An embodiment of the invention is shown in the drawing, and although show

Fig.i the level meter according to the invention in Longitudinal axial section and

F i g. 2 and 3 circuits, as they are advantageous to compensate for the temperature change during operation of the level meter occurs over a larger temperature range

The Fi g. 1 shows a container 1 which has an electrical Contains conductive liquid 2 In the wall of the container 1, a cladding tube 3 is welded as a blind tube Cladding tube 3 is a hollow core 4 made of an austenitic steel, which on its outside after Kind of a two-start screw is provided with grooves 5, and to dampen the eddy currents occurring in it has a longitudinal slot 6 In the grooves 5 are a primary 7 and a secondary coil 8 made of metal sheathed Mineralisoüertem wire arranged The return lines of the coils 7 and 8 are inside the Kerns 4 out to a display device, not shown, and are expediently held in the middle by brackets 9, for example made of ceramic.

The F i g. 2 and 3 show, in the known symbols of electrical engineering, circuits through which a compensation the temperature response of the display is made possible.

In Fig. 2 Part I is the mains supply, Part II the transmitter part, Part III the receiver part, Part IV the level meter probe and Part V the cabling. The total receiver voltage present at terminals 9 and 10 is decoupled via Ce , filtered and peak-equalized free of thresholds. With Pv

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suppression voltage. A constant current is impressed via Rks, which records the change in resistance of the level meter in the form of a DC voltage at R _K \ ur.d R _K 2 The change in resistance of Re is recorded in such a way that with Rk3 zero voltage is present at low temperature 11 a voltage signal analogous to the temperature is generated.As already described, this voltage signal is added to the total voltage at V2 and amplified together. The signal obtained is multiplied by the temperature signal and the value obtained is added to the output from V2 at V3 the receiver feed line is compared with Rk 3 . The in F i g. The circuit shown in FIG . 2 has the disadvantage that the ohmic line resistance of the receiver lead must be balanced with Rk3. The circuit in Fig. 3 avoids this disadvantage. However, this requires two additional lines to the probe, and a separately reliable constant current source Vl is required, which impresses the current for monitoring the temperature curve. Since only the difference is evaluated at V , the line resistance is negligibly small.

For this purpose 3 sheets of drawings

Claims (1)

1 2 Winding the bobbins next to or on top of each other is conditional Claim: an increased amount of wire, since the individual Windings are laid next to one another without any spacing Inductive measuring transducer for continuous the need to, by soldering together the metal level measurement, electrically conductive liquid 5 coat the necessary exact spacing of the turns th with a measuring transformer, its primary and ensure. Secondary coil on a common, cylindric- From GB-PS 12 51 347 a level meter is loaded see, austenitic core are arranged coaxially, knows, in which four concentric coils a measuring | ^; characterized by the combination of forming a bridge, which is a temperature compensating, from following features: OK level-dependent signal supplies The coils are with of different diameters wound one on top of the other a) The core (4) has two, like a two-kelt and the entire structure is relatively complex,
common screw arranged grooves (5) from Aus der De-AS 12 43 891 is a level meter the same slope and the same slope, which gets by with two concentric coils, § was standing; ί5 which, however, have very different diameters. b) in one of the slots (5) is the winding of the primary coil (7) monofilar inlaid; sen is between the inner and the outer coil c) in the other groove (5) is the winding of the hand, so that this level meter has a secondary coil (8) Monofilar inlaid tiv has a large outer diameter 20 Furthermore, from DE-OS 19 59041 and the US-PS 33 24 722 thermal level meter known, where catchy, helical grooves for Recording an outer coil are present. These thermal level meters are for measuring in The present invention relates to a continuous very hot liquid not readily suitable level meters based on the induction principle for and cannot be used in a pre-aggressive accommodate electrically conductive liquids, e.g. for liquid-protecting cladding tubes, sigmetall, the object of the present invention induced in a secondary coil being a continuous Voltage is monitored. Such level meters ierlicher level meters based on the induction principle are used to protect against corrosive liquids - 30 for electrically conductive liquids with linear filling mostly arranged in a closed jacket tube, which is easy to assemble, during loading Füllstandsnicsser of this type are known per se In drive interchangeable and against fluctuations in the the report by H. W. Sloco. .b: Liquid metal level display as a result of changing temperatures of the excess Measurement (Sodium) - ■ State of the Art Study, No waking fluid is insensitive about it NAA-SR-MEMO-12582 of '5.11.67 of the Liquid 35 is also to be a series production, i. H. a standard Metal Engineering Center, on pages 10 to 16, the useful signals are sated and the an overview of the known devices for these calibration data on probes of any length is possible Kind given. It is also known from DE-PS 12 10 998. Knows, two flat, rectangularly formed, in a.
a distance from one another in the liquid. A measuring transformer, whose primary and chend with their flat sides facing one another, is assigned to a secondary coil on a common, cylindrical. Such an arrangement requires that austenitic cores are arranged coaxially as filling cladding tubes, which are used at a certain distance from one another. In order to maintain liquid with longer ducts, the grooves arranged in a two-start screw are spaced apart even at changing temperatures of the same slope and spacing, fixed connections between the ducts are required , in which there is experience monofilar inserted, while in the other groove the slightly impurities are inserted when winding the secondary spool monofilar. Liquid metals, for example their oxides and the 50 As a result of the even distance, no direct level meter is adversely affected. Transmission between the primary and the secondary coil also requires the arrangement in two cladding tubes, since there is an increased effort in the center of the secondary coil. From GB-PS 11 01 058 forming wire in opposite directions, the two legs device is known, which, among other things, also affect the adjacent wires of the primary coil. However, filling level measurement of electrically conductive liquids arises over the length of the coils one of several th should be usable. Here it is proposed to have a composite field on fields, which in Benetein core made of stainless steel from one or two adriation with an electrically conductive liquid is dampened by the eddy currents that arise in this often mineral-insulated and metal-sheathed cable, a primary and a secondary coil in a helical manner has the fact that the windings are to be wound in grooves, the coils either being sunk next to one another 60 or having a particularly beneficial effect or being wound one above the other. How the filling · on the form of the resulting electromagnetic level measurement should take place in detail is fields, so that a particularly good useful signal is not specified; nor is it taken into account that one will. Furthermore, the grooves ensure that the winding is Wickbifilare ungeeignt "for the effects trainees lungs in an exact distance below geringstmöglischalten, the brass at the beginning and end of the measurement range 65 material costs can be inserted. From this it can be seen that the length of the flushing capability is unbalanced by a standardization of the useful signals and on the longitudinal axis of the core, so that the calibration data can also be transferred to Son and the generated field is also irregular. That reaches the arbitrary length The special arrangement