WO2009068364A1 - Procédé pour faire fonctionner un appareil de mesure, et appareil de mesure - Google Patents

Procédé pour faire fonctionner un appareil de mesure, et appareil de mesure Download PDF

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Publication number
WO2009068364A1
WO2009068364A1 PCT/EP2008/063813 EP2008063813W WO2009068364A1 WO 2009068364 A1 WO2009068364 A1 WO 2009068364A1 EP 2008063813 W EP2008063813 W EP 2008063813W WO 2009068364 A1 WO2009068364 A1 WO 2009068364A1
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WIPO (PCT)
Prior art keywords
frequency
measuring device
measuring
operating
frequencies
Prior art date
Application number
PCT/EP2008/063813
Other languages
German (de)
English (en)
Inventor
Peter Wolf
Andreas Braun
Uwe Skultety-Betz
Joerg Stierle
Bjoern Haase
Kai Renz
Original Assignee
Robert Bosch Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
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Application filed by Robert Bosch Gmbh filed Critical Robert Bosch Gmbh
Publication of WO2009068364A1 publication Critical patent/WO2009068364A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G01S17/36—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated with phase comparison between the received signal and the contemporaneously transmitted signal
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G01S17/34—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V8/00—Prospecting or detecting by optical means
    • G01V8/10—Detecting, e.g. by using light barriers
    • G01V8/12—Detecting, e.g. by using light barriers using one transmitter and one receiver

Definitions

  • the invention is based on a method for operating a measuring device, for example a distance measuring device or a locating device, in which internally high-frequency operating signals are used, which in principle represents a potential source of radio interference at the relevant operating frequencies.
  • Measuring devices which, in order to measure a distance to a measuring object, modulate a light source in its amplitude with a measuring frequency. This measuring signal is received again by the measuring device after reflection on the measuring object and processed to determine the distance between the measuring device and the measuring object
  • Near field sensors which generate electric fields in the vicinity of sensor electrodes at a plurality of measuring frequencies and on the basis of the determined at these measurement frequencies electrical coupling between the sensor electrodes, in particular the phase position of the capacitive coupling, on the presence and the distance (or in this case Depth) of a dielectric object.
  • the appropriate operating frequencies of such measuring devices are above a few MHz, for example in the range of 300 MHz to 1 GHz or even 2 GHz to 3 GHz. With insufficient shielding these devices are thus potential radio interferers. In the process, interference radiation is potentially generated not only at the operating frequency itself. Rather, all signal frequencies used internally in the device for the function represent potential interferers.
  • the said devices have in common that they are flexible in carrying out the measurement with respect to the operating frequency within wide limits.
  • the operating frequency can be flexibly selected, for example, by using a voltage-controlled oscillator (VCO) and a phase locked loop (PLL) in multiples of a fundamental frequency.
  • VCO voltage-controlled oscillator
  • PLL phase locked loop
  • a typical characteristic of the measuring devices relevant for this invention further consists in that the measured variable detected in the measuring instrument is superimposed with distorting interference signals, for example noise, and a certain minimum measuring duration is required to determine a disturbance-free measured variable.
  • This minimum measurement time is required in order to be able to perform a sufficiently long averaging of the measured quantities or to achieve a sufficiently frequency-sensitive band-pass filtering with the aim of reducing the noise bandwidth.
  • the duration of the measurement process can not be shortened technically.
  • the electrical signals causing the potential radio interference must therefore be actively switched for a certain minimum duration for proper functioning of the measuring device.
  • error signals The relevant for the minimum measurement duration noise (such as noise voltages), which adversely affect the measurement result of the device, will be referred to in the following as error signals, so there is no risk of confusion with radio interference, in the sense of this application. with those signals in which the meter itself is independent of display errors e.g. disturbs the radio reception.
  • the invention is based on a method for operating a measuring device or of a measuring device, in particular a distance measuring device or locating device, wel
  • a measuring device or of a measuring device in particular a distance measuring device or locating device, wel
  • An essence of the invention is the recognition that the noise potential of the meter can be greatly reduced by choosing a multi-frequency mode of operation which massively increases the number of frequencies, with the aim of drastically shortening the operating time at a single operating frequency. It is therefore proposed that the electronic circuit of the device is designed or controlled so that the operating time of the measuring unit is deliberately minimized at a selected operating frequency, with the aim of the radiated due to the use of the internal working signal in the vicinity of the working frequency electrical Minimize interference energy. In this case, the electronic circuit for generating and processing the operating frequencies is optimized in accordance with the invention to the normalized measuring method used for the evaluation of the legal authorization capability of the interference potential of such measuring devices.
  • the inventive method for measuring a measured variable L in particular a method for determining a distance L of a target object to a measuring device or for determining an inclusion depth L of an object in a medium leads to determine the measured variable L during a total measuring time T several measurements L n of
  • the total measuring duration T for determining the measured variable L is subdivided into a plurality n of individual measurements L n at operating frequencies f n with individual operating times T n .
  • the respective individual operating time T n for a measurement at the frequency f n is minimized according to the invention such that a temporally integrated interference signal level which the measurement signal of the frequency f n generates in a frequency interval f S t or ⁇ 1 x ⁇ F B p does not exceed the specifiable limit value.
  • the inventive method is as far as possible to a minimum reduced operating time of the circuit at each of the individual operating frequencies.
  • the number of measurement frequencies is massively increased, for example, to a number in the order of 50. Since the measurement inaccuracy is essentially determined by the total measurement period T for determining the measurement variable L, the individual measurement durations T n at the respective measurement frequencies - significantly reduced. The residence time within a measurement at a single frequency f n is then only two milliseconds for a total measurement duration of 100 ms. In the resulting evaluation of the measurement signal at the frequency f n as a short-term disturbance then significantly higher emission noise levels are allowed.
  • a control loop is then settled when the control voltage of the VCO has reached its final value.
  • the required control voltage is measured for each of the frequencies used.
  • a microprocessor can then tabulate this voltage. If this table is available for all frequencies, the microprocessor can feed in a frequency change, the resulting after settling control voltage by means of, for example, a converter and a summing amplifier directly into the VCO. With this method, the settling time of the system can be greatly reduced.
  • the suppression of the interference during the transient phase of the frequency synthesis for generating the operating frequencies is particularly effective when the frequency synthesis, in particular the involved phase locked loop and the voltage controlled oscillator are monolithically integrated on an integrated circuit. Dividers or switching means can then effectively prevent potentially problematic frequency signals from leaving the integrated circuit.
  • the interference field level which is relevant for the approval capability of a measuring device and which the measuring device generates in certain frequency bands can advantageously be further reduced, in particular by two measures. Both of the methods listed below can be used individually as well as in combination, in order to reduce the interference potential of the measuring device.
  • the generated individual frequencies f n have a relative distance ⁇ f nm to one another, which is greater than a predetermined frequency window ⁇ F B p, which typically has a size in the range of 150 kHz, and for example by a Broadcasting standard for electrical measuring devices according to bandpass filter corresponds.
  • a predetermined frequency window ⁇ F B p typically has a size in the range of 150 kHz, and for example by a Broadcasting standard for electrical measuring devices according to bandpass filter corresponds.
  • the frequency synthesis clock By activating the frequency synthesis clock for only a short time in order to generate the operating frequencies, or deliberately detuning the frequency at times when the frequency synthesis is not carried out, it is possible to reduce the duration of the interference emission to the time used for the measurement and to reduce or completely suppress radiation, in particular during switching to a new measuring frequency.
  • the output signal of a phase-locked loop of the frequency-generating electronics can be activated or deactivated by means of a switching means.
  • corresponding means may be provided which allow the operating frequencies f n of the measuring electronics to be shifted by means of a frequency divider into a lower frequency range in order thus to reduce the interference potential in the predetermined frequency window.
  • Correction signal is directly influenced to produce a corresponding frequency modulation.
  • the output frequency of the phase locked loop of the measuring electronics can be periodically modulated by means of this correction signal over a period of time T M.
  • the operating time T n is selected at the operating frequency f n equal to the period T M or an integral multiple (zx T M ) this period.
  • the requirements for electrical shielding for radio interference suppression of the meter can be reduced.
  • the installation space which would normally be occupied by metallic shielding cages could be used differently.
  • 1 shows the standard measurement method used for the evaluation of the authorization capability of the interference potential of a device
  • 2 shows an embodiment of a distance measuring device according to the invention in an electrical schematic diagram
  • Fig. 3 shows an embodiment of the flowchart of the invention
  • FIG. 1 deals with the normalized measuring sequences relevant for the evaluation of the interference potential of a measuring device.
  • the object of the invention is to reduce the electrical interference potential of a measuring device with unchanged measurement performance. To understand the invention, it is therefore necessary in a first step to know how the evaluation of the permissibility of an interference potential of any electrical device is carried out in the relevant standards.
  • a measuring antenna is located at a standard predetermined distance (for example 10 m).
  • the tapped voltages at the measuring antenna allow to close back on the interference field strengths located at the location of the measuring antenna.
  • the voltage level that can be tapped on the measuring antenna located in the measuring chamber is not directly decisive. That is, not the electric field strength determined at the measuring antenna is decisive. Rather, the tapped off at the measuring antenna voltages of a signal supplied to the processing chain. Only the signals obtained at the end of this processing chain are used for evaluating the permissibility of the interference level of the device under test and for this purpose compared with maximum amplitudes, which are specified in a standard for the respective frequency bands.
  • FIG. 1 schematically shows the measurement sequence for determining the interference potential of an electrical device in the frequency range f 0 in accordance with the customary radio interference suppression standards, such as, for example, EN 55022.
  • the signal levels picked up at the measuring antenna are first fed to a bandpass filter 102, which has a bandwidth ⁇ F B p of, for example, 100 kHz.
  • the signal resulting at the output of this filter 102 is fed in the next step to a so-called "quasi-peak” detector 103, which consists of a rectifying element and an averaging RC network The task of this "quasi-peak"
  • Detector is to evaluate the noise potential of at the frequencies f 0 ⁇ 1 Zi x .DELTA.F B p only briefly existing noise levels as noise, which are present during a longer period in the vicinity of the frequency f 0 . This is done by the capacitor is charged from the equivalent circuit of the quasi-peak detector 103 due to the series resistor Ri at a voltage applied only briefly to the input only to a lower voltage level, as in a permanently applied AC voltage corresponding to a permanent noise.
  • the measurement signal resulting at the output of this quasi-peak detector is forwarded to a display rating stage 104, which simulates the inertia of a conventional moving coil display instrument.
  • the inertia of such a measuring device can be taken into account by the voltage level resulting at the output of an RLC filter. Therefore, in Figure 1, the display rating stage 104 is characterized as such an RLC filter.
  • the display rating level 104 Only at the output of the display rating level 104 resulting voltage level, which is referred to as quasi-peak radio noise level, forms the basis for the evaluation of the noise level and thus for the permissibility of the emission of an electrical device to be tested. That is, the tapped at the output of the stage 104 voltages are determined and compared in an evaluation stage 105 with a maximum value permitted by the standard. If the voltage picked up at the output of the display evaluation stage 105 falls below the standard permissible value at all frequencies specified in the standard f 0 , the tested electrical device may be placed on the market with regard to the radio interference suppression regulations.
  • standard test procedure is to take into account by the measurement specification (ie in particular by the introduction of a quasi-peak detector and a sluggish display rating level) that the interference potential, eg the interference potential for radio or television reception , is much lower, if the present at the frequency f 0 interference only temporarily, that is available for short times.
  • the core of the invention consists in constructing the measuring device according to the invention so that (despite the minimum measuring time necessary due to the error signals) the operating time at a single operating frequency can be reduced so much that the interference potential due to the emission of electric fields due to the short operating time this frequency is low enough to prevent radio interference from other devices.
  • FIG. 2 shows a block diagram of an embodiment of a measuring device according to the invention.
  • the measuring device according to the invention is a device for determining the distance of the measuring device to a measurement object located at an unknown distance, that is to say a distance measuring device, in particular an electro-optical rangefinder.
  • the measuring device contains a light source, for example a laser diode
  • the optical power of the laser diode is amplitude modulated at a high frequency f.
  • the photodetector e.g. a photodiode (213).
  • the optical signal received by the detector (213) is first measured phase-resolved in an evaluation circuit for this purpose.
  • a sense amplifier (214) and an analog-to-digital converter (215) may be used for this purpose.
  • the measuring device is expediently controlled by a digital logic (200), for example by a microprocessor or a logic circuit, which is connected to the remaining circuit blocks by means of digital data signals.
  • a digital logic for example by a microprocessor or a logic circuit, which is connected to the remaining circuit blocks by means of digital data signals.
  • the processor (200) first controls a frequency synthesis circuit which i.a. to generate the modulation frequencies for the light emitter (212).
  • This frequency synthesis circuit includes a phase locked loop, which at its
  • Output frequency bisector (206) generates a multiple N of a provided base frequency f r ⁇ f .
  • This phase-locked loop expediently consists of a symmetrizing frequency bisector (206), at whose output the result signal of the frequency synthesis can be tapped, a voltage controlled oscillator (205), a frequency (207), a phase comparator (202) and a loop filter (203).
  • the level of the analog signal applied to the output of the loop filter controls the frequency of the oscillator (205).
  • the processor (200) can thereby modify the divisor value N of the frequency divider (207) via digital control signals and in this way control the value of the synthesis frequency.
  • the microprocessor (200) has the possibility of measuring the control signal of the VCO (205) required for a divisor value N by means of an analog-to-digital converter (ADC) (216).
  • ADC analog-to-digital converter
  • DAC digital-to-analogue converter
  • the synthesized frequency signal can be forwarded to a further controllable frequency divider (209) with divisor M.
  • the output signal of this frequency divider (209) is used as a trigger signal to enable edge-synchronous conversion of the analog signal present at the output of the measuring amplifier (214).
  • the output signal of the frequency divider (209) is also fed to a further frequency divider (210) which reduces the frequency by a factor of 4 and with its output signal drives a driver stage (211) which generates the modulation signal of the laser diode.
  • the frequency of the modulation signal generated by the drive stage (211) is referred to below as the modulation frequency.
  • the modulated drive generates a time-modulated intensity of the light emitted by the laser (212).
  • the intensity of the light received at the photodetector (213) is then composed of a certain fraction of the modulated laser light, a constant component I 0 and a noise component R (t) and, as a function of time t, has the following time course
  • I (t) Im cos (2 ⁇ ft + ⁇ ) + I 0 + R (t)
  • the phase shift ⁇ is thereby changed by the transit time of the light to the target.
  • the optically received intensity is processed in an amplifier (214) and fed to the analog-to-digital converter (215).
  • the converter (215) is operated in the receive path with four times the modulation frequency of the emitter, it is possible, by means of digital signal processing, from the 4 individual, converted per modulation period signal values on the phase angle ⁇ of the incident on the photoreceiver (213) Close light back and to determine the distance L between the meter and target object (216) in a next step to a constant location component X.
  • the constant position offset component X is generated, for example, by phase shifts, as in practice caused by the drive circuit (211) or the laser diode.
  • X can be determined, for example, by using a mechanical deflection unit and a device-internal reference path of the measuring device in a calibration measurement before the actual measurement.
  • the light within the measuring device can be deflected by means of the deflection unit directly onto the photodetector (213) without the light reaching the target object (216). Since the distance L ref traveled by the light via the reference deflection unit is known, a measurement of the phase ⁇ ref using the reference deflection unit can be carried out and the unknown position offset X based on the relationship ⁇ f)
  • phase uncertainty ⁇ is directly proportional to the uncertainty ⁇ in the determination of the phase angle.
  • the phase uncertainty ⁇ can be reduced by increasing the modulation frequency f. For this reason, preferably frequencies greater than 200 MHz are used as the modulation frequency.
  • phase error ⁇ can only be reduced in practice by a sufficiently long averaging over a large number of measuring periods.
  • Invention essential point is that in order to achieve a given or predetermined angular error ⁇ (corresponding to a spatial error .DELTA.L), the operation of the measuring device for a given minimum measurement period T, for example, 100 ms is required.
  • the Total measurement time T is therefore subject to the restriction with regard to the desired measurement accuracy or measurement uncertainty and can not be shortened arbitrarily.
  • the measuring device can radiate potentially unacceptably high interference levels during measuring operation.
  • lower modulation frequencies ie for example 10 MHz, have a significantly reduced interference potential since the board length then represents only a small fraction of the wavelength of the interference radiation.
  • the output signals of the VCO (205), the output divider (206) and the signals processed in the circuit blocks (210, 211, 212, 215) and (214) are to be regarded as a potential source of interference, because high-frequency signals are generated or processed in these circuit blocks.
  • the radiation of the noise levels can be reduced, for example, by miniaturizing substantial parts of the circuit containing high frequencies, e.g. by being grouped in an integrated circuit. However, this succeeds only limited. Thus, e.g. the laser diode (212) or the ADC (215) not, or can be integrated with great effort on an IC.
  • the dominant noise emission can then be mediated by the supply of the modulation signal between driver circuit (211) and photoemitter (212) or the clock supply of the ADC (215).
  • the measuring devices known from the prior art use a plurality of modulation frequencies f n , which is typically in the typical order of magnitude of 5. This results in a plurality of distance values L n , which result during operation or during measurement with the respective frequency f n .
  • this minimum measurement time can be distributed in approximately equal proportions, that is, each of 20 ms, 5 individual frequencies f n at a total required minimum measurement period of for example 100 ms.
  • the average interference power is reduced at a single measurement frequency by dividing the operating time into a plurality of discrete individual frequencies, the operating time for the individual frequency is still far greater than for the evaluation as a short-pulse interferer, or for the so-called quasi Peak determination, relevant time scale of typically 1 ms.
  • a temporary operation with a duration of considerably more than 1 ms is still regarded by the relevant test standards effectively as a permanent disturbance, so that correspondingly reduced transmission powers at the frequencies used are necessary.
  • the core of the invention is the recognition that the interference potential of the measuring device can be greatly reduced for a given total measurement time by selecting a multi-frequency operating mode which massively increases the number of measurement frequencies, with the aim of increasing the service life of a single Drastically reduce the modulation frequency.
  • the number of measuring frequencies of the measuring device is massively increased, for example to a number of 50, the one whole order of magnitude above the known from the prior art number of measurement frequencies.
  • the residence time or individual measurement duration T n at a single frequency f n is then in the example described above for a total measurement duration of 100 ms only two milliseconds. With the resulting classification as a short-term fault, considerably higher emission noise levels are then permissible for the measuring device.
  • the relative distance of the respective individual frequencies that are used is greater than the predetermined by the radiation standard-bandpass filter (102) frequency window. Typical minimum distances are for example 150 kHz.
  • the frequency synthesizer used to generate the modulation frequency must have a high degree of precision.
  • This frequency precision requires a minimum required settling time of the phase-locked loop, which can typically be between 100 ⁇ s and 5 ms. After a frequency change, therefore, it is necessary to wait until the start of the measurement with a new frequency until the voltage-controlled oscillator VCO (205) operates at its nominal frequency.
  • the circuit potentially generates the interference to be avoided.
  • the switching means (208) open to prevent the propagation of interference-related frequency signals, for example, to the leads to the laser diode.
  • the modulation frequency in a low-frequency band for example 10 MHz, are laid, in which the radiation potential is low.
  • the suppression of the interference radiation during the transient phase of the frequency synthesis is particularly effective if the frequency synthesis, in particular the phase-locked loop (206, 207, 202, 204) and the voltage-controlled oscillator (205) are monolithically integrated on an integrated circuit. Dividers (209) or switching means (208) can then effectively prevent potentially problematic frequency signals from leaving the integrated circuit.
  • the summing amplifier (204) and the converters (217,216) can be used.
  • the control loop is then settled when the control voltage of the VCO (205) has reached its final value.
  • the converter (216) can be used to pre-measure the required control voltage for each of the frequencies used.
  • a microprocessor can then tabulate this voltage. If this table is available for all frequencies, the microprocessor can now, with a frequency change within a measurement, feed the control voltage resulting after the settling directly into the VCO (205) with the aid of the converter (217) and the summing amplifier (204).
  • the loop filter (203) then has only the task of making detailed adjustment of the control voltage. With this method, the settling time of the system can then be greatly reduced.
  • DAC digital to analog converter
  • a triangular ramp would be used here.
  • At the output of the frequency divider then results in a triangular ramp corresponding frequency modulation, ie a variable over time frequency.
  • the output frequency then varies by a frequency center value set by means of the divider N (207). If the amplitude of this modulation is suitably selected, then only a lower signal power results for interference signals at the output of the bandpass filter (102) according to the radio emission standard.
  • the frequency deviation predetermined by the deliberately selected modulation must be greater than the bandwidth of the bandpass filter (102).
  • a frequency modulation of + / ⁇ 120 kHz and a bandwidth of the bandpass filter (102) results in + / ⁇
  • the meter performs initialization measurements that precede the actual measurement process and that serve to prepare the instrument.
  • the initialization measurements include a sequence in which first the switching means (208) is opened, so that no high-frequency signals reach the other circuit parts, and therefore no interference signals are emitted.
  • the output of the DAC (217) is then set to a defined rest potential and initially left constant.
  • the transient process of the phase locked loop of the frequency synthesis can be accelerated for the following measurements by directly specifying the known control voltage of the VCO by means of the DAC (217) after a frequency change.
  • FIG. 3 An embodiment of the method for dividing the measuring time to the individual measurement frequencies is shown in Fig. 3.
  • the switch 208 is opened to suppress spurious radiation during frequency switching.
  • the frequency synthesis is set to a new operating frequency.
  • the divisor N (207) is set and the DAC (217) is set to the already tabulated setpoints.
  • the DAC (217) is configured to generate, for example, 1 kHz low amplitude triangular signal based on the tabulated setpoint for the given center frequency. That is, the tabulated value serves as a DC offset superimposed on a 1 kHz triangle signal.
  • This triangular signal causes an associated time course at the output frequency (232) of the phase-locked loop, ie the output frequency is no longer constant in time, but a variation .DELTA.f is subjected to the center frequency f n . If this variation .DELTA.f is greater than the width of the frequency filter (102) which is relevant in accordance with the standard, the standard determination of the interference level inevitably leads to a lower value.
  • the synthesis frequency is now passed on to the other circuit parts.
  • the ADC (215) acquires measured values which are used to determine the phase of the signal at the frequency f n become.
  • the switch (208) is opened again.
  • the microprocessor On the basis of the converter values of the ADC (215), the microprocessor then calculates the averaged phase values ⁇ n and local values L n at the given measurement frequency f n .
  • the mean value f n can be used for the calculation of the position values, since the averaging time of, for example, 2 ms advantageously amounts to an integer multiple of the modulation period of the triangular signal (231).
  • the frequency-index-dependent averaging coefficients A n take into account, for example, that the uncertainty of a position determination L n at a modulation frequency f n , can be higher than a position determination L m at a different modulation frequency f m . This is usually the case when the modulation frequency f n is lower than the modulation frequency f m . If the phase error is the same, this is due to the conversion coefficient
  • phase value and distance value then a larger location error.
  • the mean value L can then be displayed as a final result, for example on a display of a range finder, or passed on by means of a data transmission to a data evaluation unit.
  • the frequency modulation of the operating frequency reduces the dwell time of the device in the frequency window of about 150 kHz which is relevant for the radio interference suppression standard.
  • the duration of the interference emission can be reduced to the time used for the measurement.
  • Both methods can be used both individually and in combination to reduce the noise potential of the meter.
  • the method according to the invention or a measuring device operating according to this method is not limited to the embodiments described so far. So there is one
  • Invention can thus also be used in circuits which deviate from the embodiment shown in FIG.
  • the demand on the speed of the converter (215) can be reduced by adding an intermediate frequency
  • the use of an intermediate frequency conversion is particularly advantageous when the photodetector (213) has a non-linear characteristic, as is the case, for example, with avalanche effect photodiodes.
  • the described method can also be used with or without the use of conscious frequency modulation, i. with or without application of a triangular ramp or other modulation of the control signal of the VCO (205).
  • VCO voltage controlled oscillator
  • PLL phase locked loop
  • Alternative frequency synthesis circuits such as delay-locked loops or ring oscillators, may also be used.
  • the method according to the invention is not limited to the use of measuring times T n of the same length. By using measuring times of different lengths at different measuring frequencies f n , a further reduction of the noise level of the measuring device can be produced.
  • the method according to the invention is not limited to use in distance measuring devices. It is also possible, for example, to successfully use the measuring method for multi-frequency near-field sensors for locating which, based on the phase position of, for example, capacitive coupling of sensor electrodes at different frequencies, are based on the depth of a detected dielectric object. shut down. The measured variable L in this case would then be the inclusion depth of the detected object in a medium under investigation.

Abstract

L'invention concerne un procédé pour faire fonctionner un appareil de mesure, en particulier un télémètre ou un appareil de localisation, comprenant une électronique de mesure qui est exploitée à différentes fréquences de fonctionnement dans la plage des hautes fréquences. Selon l'invention, afin de réduire les émissions radio parasites, l'ensemble de la durée de fonctionnement pendant un processus de mesure de l'appareil de mesure est répartie sur un grand nombre de fréquences de mesure, le temps de fonctionnement à une fréquence individuelle étant réduit au minimum, et les valeurs de mesure individuelles obtenues aux fréquences individuelles étant regroupées en une valeur de mesure globale afin de réduire l'incertitude de mesure.
PCT/EP2008/063813 2007-11-30 2008-10-15 Procédé pour faire fonctionner un appareil de mesure, et appareil de mesure WO2009068364A1 (fr)

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DE102007057701A DE102007057701A1 (de) 2007-11-30 2007-11-30 Verfahren zum Betreiben eines Messgerätes sowie Messgerät
DE102007057701.1 2007-11-30

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Citations (4)

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