Signal generator for a measuring apparatus and measuring apparatus for automation technology

Patent metadata

Field	Value
Publication number	US-2016147251-A1
Application number	US-201414901163-A
Country	US
Kind code	A1
Filing date	Jun 2, 2014
Priority date	Jul 5, 2013
Publication date	May 26, 2016
Grant date	—

Abstract

The invention relates to a signal generator for producing periodic signals for a measuring apparatus ( 1 ) of automation technology, wherein the signals have sequential, discrete signal frequencies, which lie within a predetermined frequency range, a control- and/or computing unit ( 4 ), a clock signal producer ( 6 ), wherein the clock signal producer ( 6 ) provides a constant sampling frequency, which is greater than the maximum discrete signal frequency in the predetermined frequency range, a memory unit ( 7 ), in which for each of the discrete signal frequencies the amplitude values of the corresponding periodic signals are stored or storable as a function of the sampling frequency, wherein the control- and/or computing unit ( 4 ) reads out the stored or storable amplitude values of the discrete frequencies successively with the sampling frequency of the clock ( 6 ) from the memory unit ( 7 ) and produces the periodic signals or forwards for producing, and a static filter unit ( 12 ) with a limit frequency, which lies above the maximum signal frequency and which removes frequency fractions caused by the sampling.

First claim

1 . Signal generator for producing periodic signals for a capacitive measuring apparatus ( 1 ), wherein the signals have sequential, discrete signal frequencies, which lie within a predetermined frequency range, comprising: a control- and/or computing unit ( 4 ), a clock signal producer ( 6 ), wherein the clock signal producer ( 6 ) provides a constant sampling frequency, which is greater than the maximum discrete signal frequency in the predetermined frequency range, a memory unit ( 7 ), in which for each of the discrete signal frequencies the amplitude values of the corresponding periodic signals are stored or storable as a function of the sampling frequency, wherein the control- and/or computing unit ( 4 ) reads out the stored or storable amplitude values of the discrete signal frequencies successively with the sampling frequency of the clock ( 6 ) from the memory unit ( 7 ) and produces the periodic signals or forwards for producing and a static filter unit ( 12 ) with a limit frequency, which lies above the maximum signal frequency and which removes frequency fractions caused by the sampling.

2 . Signal generator as claimed in claim 1 , wherein in the memory unit ( 7 ) for each of the discrete signal frequencies the amplitude values of the corresponding periodic signal are stored or storable as a function of the sampling frequency in the form of at least one search table ( 8 ; 9 ), a so-called lookup table (LUT).

3 . Signal generator as claimed in claim 1 , wherein the memory unit ( 7 ) uses an integer delta implementation, in the case of which the amplitude values of each periodic signal for one period are stored at equidistant intervals.

4 . Signal generator as claimed in one or more of claim 1 , wherein the control- and/or computing unit ( 4 ) dynamically produces with the assistance an algorithm ( 18 ) a look-up table ( 8 , 9 ) for each of the discrete signal frequencies.

5 . Signal generator as claimed in claim 4 , wherein the algorithm ( 18 ) is preferably an iterative or a recursive algorithm.

6 . Signal generator as claimed in claim 1 , wherein at least two search tables ( 8 , 9 ) are provided, wherein via the first search table ( 8 ) the output of a first discrete signal frequency occurs, while in the second search table ( 9 ) the calculating and storing of the sampling points for a second discrete signal frequency occur in parallel.

7 . Signal generator as claimed in claim 1 , wherein the frequency range lies preferably between 50 kHz and 5 MHz.

8 . Signal generator as claimed in claim 1 , wherein the sampling frequency lies preferably at 20 MHz.

9 . Signal generator as claimed in claim 1 , wherein the control/computing unit ( 4 ) varies or sets the amplitude values of the periodic output signal produced by the signal generator ( 5 ) by adapting the algorithm ( 18 ) and/or wherein the control unit- and/or computing unit ( 4 ) varies or sets the stored amplitude values in their size by a binary shifting operation of an output register ( 20 ).

10 . Signal generator ( 5 ) as claimed in claim 1 , wherein the control- and/or computing unit ( 4 ) corrects the amplitude values of the periodic output signal produced by the signal generator ( 5 ) in such a manner that amplitude changes as a result of a frequency dependent attenuation are at least approximately compensated by the static filter unit ( 12 ) or by other disturbance effects.

11 . Apparatus for capacitive determining and/or monitoring of fill level or limit level of a medium ( 17 ) in a container ( 16 ) comprising a probe unit ( 2 ) having at least one probe electrode ( 14 ) and an electronics unit ( 3 ), which supplies the at least one probe electrode ( 14 ) with an electrical measurement signal and receives and evaluates an electrical response signal from the probe unit ( 14 ), wherein the electronics unit ( 3 ) supplies the at least one probe electrode ( 14 ) at least at times with a measurement signal, which has a number of sequential, discrete signal frequencies lying within a predeterminable frequency range, wherein the discrete signal frequencies are produced by a signal generator ( 5 ) associated with the electronics unit ( 3 ) and claimed in claim 1 , wherein the electronics unit ( 3 ) ascertains based on the sequential, discrete signal frequencies a signal frequency optimal for current application parameters, and wherein the electronics unit ( 3 ) determines based on the response signal belonging to the optimal signal frequency the fill level or the limit-level of the medium ( 17 ) in the container ( 16 ) or another physical process variable.

12 . Apparatus as claimed in claim 11 , wherein the electronics unit ( 3 ) is implemented at least partially in an FPGA ( 10 ).

13 . Apparatus as claimed in claim 11 , wherein components for producing the at least one search table ( 8 ; 9 ) are implemented in the FPGA ( 10 ).

14 . Apparatus for determining or monitoring a predetermined fill level, a phase boundary or density of a medium in a container, comprising an oscillatable unit, wherein the oscillatable unit is placed at the height of the predetermined fill level, wherein a control- and/or computing unit is provided, which excites the oscillatable unit by means of a frequency sweep within a predeterminable frequency range in the working range of the oscillatable unit successively with sequential, discrete signal frequencies to execute oscillations, wherein the corresponding oscillations of the oscillatable unit are received in the form of received signals, wherein via the frequency sweep that signal frequency is ascertained, in the case of which the oscillatable unit oscillates with an oscillation frequency, which has a predetermined phase shift between the transmission signal and the received signal, and wherein a transmitting/receiving unit excites the oscillatable unit with the ascertained signal frequency to execute oscillations or wherein the following frequency sweep is started.

Assignees

• Endress & Hauser Gmbh & Co Kg

Inventors

• Rummele-Werner Stefan
• Fruhauf Dietmar
• Wernet Armin
• Uppenkamp Kaj
• Bechtel Gerd

Classifications

• G06F1/08 Primary

  Clock generators with changeable or programmable clock frequency · CPC title

• G06F1/0321

  Waveform generators, i.e. devices for generating periodical functions of time, e.g. direct digital synthesizers (G06F1/0314, G06F1/035 take precedence) · CPC title

• G06F1/0328

  in which the phase increment is adjustable, e.g. by using an adder-accumulator · CPC title

• G01F23/266 Primary

  measuring circuits therefor · CPC title