Electronic field device with a sensor unit for capacitive level measurement in a container

Abstract

The invention relates to an electronic field device with a sensor unit (2), for capacitive level measurement in a container (3), whereby the electronic field device is connected to the sensor unit (2) by corresponding signal paths. The electronic field device generates a voltage signal for operation of the sensor unit (2) and receives and analyses a measuring current from the sensor unit (2). According to the invention, an analogue / digital converter (8), for digitising the analogue measuring current, a microprocessor (1) and a memory unit (7) are provided, whereby the microprocessor carries out the generation of the voltage signal, the analysis of the measuring current, a compensation for interference and a determination of the recorded parameters for the sensor / container arrangement, according to given programme sequences and the corresponding programmes are stored in the memory unit (7).

Description

technical field [0001] The invention relates to an electronic field device according to the preamble of claim 1 having a sensor unit for capacitive fill level measurement in a container. Background technique [0002] Field devices for capacitive level measurement have been known for many years. In these devices, a probe extending into the vessel forms a capacitor with the vessel wall. The capacitance of the capacitor thus created depends on the fill level as well as on the dielectric constant of the medium to be measured. [0003] One possibility for measuring this capacitance is the so-called apparent current measurement method. In it, a conventional rectification circuit is used to measure, for a given frequency and voltage, the amount of alternating current flowing through a capacitor formed by the probe, the medium and the vessel wall. However, the fact that the apparent current depends not only on the capacitance, but also on the conductivity of the medium to be meas...

AI Technical Summary

Problems solved by technology

However, this method has disadvantages such as difficulties due to the fact that the reactive current essentially disappears in media with a small dielectric field number and high conductivity, where it is possible to use the apparent current to measure

Additionally, such existing synchronous rectification circuits have been shown to be sensitive to electromagnetic interference

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