SU1143981A2 - Inductive analog level indicator for molten metals - Google Patents

Abstract

INDUCTIVE ANALOG LEVEL TERMINAL FOR HIGH METALS by auth. No. 624117, about tl and h a rant and with the fact that, in order to increase the sensitivity and linearity of the conversion and reduce the temperature error, between the beginning (end) of the supply winding and the end (beginning) of the signal winding, a compensating capacitance is turned on, the value of which is half of the total parasitic capacitance between the windings of the converter. CLI 4ik nb SS CO 00 Es Hh iH.-II.

Description

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The invention relates to instrumentation and measurement technology and can be used to convert the position of the interface between two media, one of which is electrically conductive, into an electrical signal.

According to the main auth. No. 624117 is well known for a level gauge containing an inductive transducer, made in the form of an air transformer, a no-JO cable placed in a protective cover, a low-frequency generator and a measuring transducer. In order to eliminate additional temperature errors resulting from changes in the properties of the protective cover and the measured medium, the signal winding of the inductive converter is bridged by resistance, the magnitude of which is in a certain COOTHO with the parameters of the sensor. In a number of cases between the windings of inductive converters, in addition to inductive coupling, there is a parasite on the capacitive power. The presence of such a connection leads to the distribution of the excitation current between the supply and signal windings, i.e. Part of the excitation current flows through the signal winding and, therefore, causes a voltage drop across it. As a result of this distribution of currents, the output signal of the converter contains, in addition to the useful signal carrying information about the position of the interface between two media, a parasitic component that depends on the magnitude of the parasitic connection, which leads to a decrease in the sensitivity of the conversion; the dependence of the parasitic component on the resistance of the supply and signal windings leads to an additional temperature error; the nonlinearity of the current in the winding in bumps leads to the nonlinearity of the transient response of the converter. The purpose of the invention is to increase the sensitivity and linearity of the transform, reducing the temperature error of the inductive transducers caused by parasitic capacitive coupling between the transducer windings. The goal is achieved by the fact that in an inductive level gauge containing an inductive transducer, made in the form of

power supply and signal windings, and a measuring transducer, including a low-frequency generator and a device for processing an inductive signal converter, between opposite power lines of the power supply and signal windings (the beginning of the signal winding and the end of the supply winding, or between the start of the power end of the signal winding). includes a compensating capacitor, the value of which is equal to half of the total parasitic capacitance between the windings of the converter. Fig. 1 is a schematic diagram of an inductive converter; Fig. 2 is a graph showing the distribution of currents in the supply and signal windings; FIG. 3 shows the option of switching on the compensation capacitance and the measuring transducer. The level gauge contains the supply 1 and signal 2 windings, the distributed capacitance 3 between the windings of the converter. In Figures 2 and 3, the labels are accepted; 4 - current distribution in the supply winding, 5 - current distribution in the signal winding, 6 - current distribution in the signal winding with a compensating capacitance connected, „- transducer length, compensating capacitance 7 and measuring transducer 8. Parasitic capacitive coupling between the windings the converter causes the CHT0 portion of the excitation current 1 | to branch from the supply winding to the signal winding (Fig. 1). This portion of current 1 causes a voltage drop across the signal winding, which significantly reduces the sensitivity of the converter. Due to the fact that the capacitive coupling is distributed along the length of the converter, currents of different magnitude 4 will flow in different parts of the supply winding (Fig. 2), and this leads to a nonlinearity of the transient characteristic of the converter. The connection of the compensating capacitance in this way is caused by the redistribution of currents in the windings of the converter. In different parts of the signal winding, the currents will have different phases 6 (figure 2). Analysis of the physical processes occurring in the inductive transducer shows that, in order to fully compensate for the parasitic component, the compensating capacitance should be equal to :.

g - Hl.

  2

. where. Spz - total parasitic capacitance between the windings of the converter.

The use of the invention makes it possible to reduce the temperature errors of measurement of inductive converters caused by parasitic capacitive coupling between the windings of the converter and to increase the sensitivity and linearity of the transducer.

Claims (1)

INDUCTIVE ANALOGUE LEVEL METER FOR LIQUID METALS according to ed. No. 624117, with the fact that, in order to increase the sensitivity and linearity of the conversion and reduce the temperature error, between the beginning (end) of the supply winding and the end (beginning) of the signal winding is included compensating capacity, which is equal to half the total stray capacitance between the transformer windings. Figure 1 about 1143981 ²