Calibration- and/or monitoring method for FMCW radar fill level measuring devices

摘要

A method is based on measuring a distance to a reference reflector arranged at a known distance, in order to calibrate and/or monitor a coherent frequency modulation, continuous wave radar, fill-level measuring device, wherein the reference reflector can be reliably identified. To this end, a reference reflector executing oscillations toward the fill-level measuring device with an oscillation frequency is used, which is inserted in the beam path of periodically linearly frequency modulated transmission signals transmitted from the fill-level measuring device. The fill-level measuring device receives fractions of the transmission signals reflected back on reflectors in the container and records based on these received signals and their time correlation relative to the respectively associated transmission signal for each received signal an echo function, which shows the amplitudes of the received signal as a function of the associated position of the associated reflector. Based on the time change of a plurality of sequentially recorded echo functions and the oscillation frequency of the reference reflector, the position of the reference reflector in the echo functions is identified and its reference reflector position determined.

主权项

1. A method for calibrating and/or monitoring a coherent frequency modulation, continuous wave radar, fill-level measuring device for measuring a fill level of a fill substance in a container, comprising the steps of:
sending toward the fill substance, with a predetermined repetition frequency, transmission signals linearly frequency modulated by means of a predetermined modulation, and receiving as received signals their fractions reflected on reflectors located in the beam path of the transmission signals back to the fill-level measuring device; a reference reflector executing oscillations toward the fill-level measuring device with an oscillation frequency amounting to less than half the repetition frequency is inserted above the fill substance at a known distance from the fill level measuring devices in the beam path of the transmission signals; for each received signal, an echo function, which is based on the received signals and their time correlation relative to the respectively associated transmission signal is recorded, which echo function shows the amplitudes of the received signal as a function of its frequency difference relative to an instantaneous transmission frequency of the transmission signal present at its receipt, a signal travel time associated with the frequency difference by way of the time dependence of the modulation or a distance to the respective reflector corresponding to the signal travel time; based on the time change of a plurality of sequentially recorded echo functions and the oscillation frequency of the reference reflector, a frequency difference, signal travel time or distance to be assigned to the refernce reflector is identified and determined as associated reference reflector position; and the calibrating and/or monitoring of the fill-level measuring device occurs based on the reference reflector position and the known distance of the reference reflector from the fill-level measuring device.