CS232012B1 - Connection of measuring inductive or capacity bridge - Google Patents

Description

The invention relates to the connection of a measuring inductive or capacitive bridge powered by alternating current. These are bridges whose all four branches are composed of either inductance inductive bridges or capacitance - capacitive bridges. These bridges may be either balanced or unbalanced.

Bridge methods are often used in measuring practice both in laboratory measuring devices and in evaluation circuits of various sensors for industrial use, for their advantageous properties. Many different measuring bridges are known from the literature for measuring resistance, inductance and capacitance, or other quantities derived therefrom. Each measuring bridge has its advantages and is practically suited for a particular application where its advantages stand out. The invention relates to either an inductive or capacitance measuring bridge, where the change in the inductance or capacitance of one or more branches is evaluated. A disadvantage of known bridges for measuring small changes in inductance or capacitance is low sensitivity. If the sinusoidal supply voltage is not observed precisely, the jumper cannot be reset.

These disadvantages are minimized by the connection of the measuring inductive or capacitive bridge according to the invention, which consists in that the first capacitor is connected in parallel to the inductive bridge on the supply side and the second capacitor on the output side. inductance, on the output side a second inductance, wherein both the inductive bridge and the capacitive bridge are in resonance and supply frequency.

232 012

By connecting the bridge to the resonance with the input supply frequency, it is possible to avoid reactive current flowing into the circuit and thus the AC voltage source can be dimensioned for significantly lower power. Furthermore, the resonant circuit improves the sine wave of the supply voltage, which contributes to perfect bridge balancing. For less demanding applications, it is even possible to use a rectangular waveform of the supply voltage and supply the bridge via a decoupling resistor. The resonant circuit draws only a sinusoidal signal from the rectangular waveform. The progress achieved by the invention further consists in increasing the measurement accuracy of the various quantities converted to inductance or capacitance change. In particular, the wiring is suitable for small changes in inductance or capacitance where other methods are no longer satisfactory, for example for the measurement of various non-electric quantities where major changes in inductance or capacitance cannot be achieved.

In the accompanying drawing, two examples of connection of the measuring bridges according to the invention are schematically shown, in which Fig. 1 shows the connection of a measuring induction bridge and Fig. 2 shows the connection of a measuring capacitive bridge.

The induction bridge 1 - Fig. 1 consists of four inductors, one of which is measured. The supply and output sides of the bridge are indicated by arrows. The capacity bridge 4 is similar - Fig. 2.

On the supply side of the measuring inductive bridge 1, a first capacitor 2 is connected in parallel and on the output side a second capacitor 2 at capacitance values such that a resonance of the bridge relative to the supply frequency is achieved along with the inductance of the bridge. On the supply side of the measuring capacitance bridge 1, a first inductance 2 is connected, and on the output side a second inductance 6 with inductance values such that resonance with respect to the supply frequency is achieved along with the bridge capacitance.

The principle of the operation of the measuring inductive bridge is that the measuring inductive bridge 1 operates in a resonance state and the operation of the capacitive bridge 4 is analogous, with the resonance resulting in low current consumption from the power supply and increased sensitivity of the inductive bridge 1. .

Claims (1)

SUBJECT OF THE INVENTION 232 012 Connection of the measuring inductive or capacitive bridge, characterized in that the first capacitor (2) is connected in parallel to the inductive bridge (1) and the second capacitor (3) is connected on the output side, while the capacitive bridge (4) is on the supply side connected the first inductor (5) and the second inductor (6) on the output side, both inductive bridge (1) and capacitive bridge (4) being in resonance · 1 drawing 232 012 The measuring bridge according to the invention has been successfully tested in the measurement of residual magnetic fractions in the waste water of OKR coal treatment plants. The bridge was composed of four inductances, one of which was measuring, whose inductance changed very little by the presence of measured magnetic fractions. fully proved. The invention can be advantageously applied in all areas of industry, in particular in the chemical and ore industries