Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/103—Measuring devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
  • A61B5/107—Measuring physical dimensions, e.g. size of the entire body or parts thereof
  • A61B5/1072—Measuring physical dimensions, e.g. size of the entire body or parts thereof measuring distances on the body, e.g. measuring length, height or thickness
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
  • A61B5/7235—Details of waveform analysis
  • A61B5/7253—Details of waveform analysis characterised by using transforms
  • A61B5/7257—Details of waveform analysis characterised by using transforms using Fourier transforms
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B17/00—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B5/00—Measuring arrangements characterised by the use of mechanical techniques
  • G01B5/02—Measuring arrangements characterised by the use of mechanical techniques for measuring length, width or thickness
  • G01B5/06—Measuring arrangements characterised by the use of mechanical techniques for measuring length, width or thickness for measuring thickness
  • G01B5/061—Measuring arrangements characterised by the use of mechanical techniques for measuring length, width or thickness for measuring thickness height gauges
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B2560/00—Constructional details of operational features of apparatus; Accessories for medical measuring apparatus
  • A61B2560/02—Operational features
  • A61B2560/0223—Operational features of calibration, e.g. protocols for calibrating sensors
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
  • A61B2562/02—Details of sensors specially adapted for in-vivo measurements
  • A61B2562/0204—Acoustic sensors

Definitions

• the present invention relates to a length measuring device with egg ⁇ nem caliper, a linear guide in the form of a hollow profile on which the caliper is mounted externally displaceable to bring him into contact with an object to be measured with respect to its length, an inner slider, the is mounted displaceably in the interior of the hollow profile, a Mag ⁇ netan extract, the caliper and inner slide magnetically coupled, so that the inner slide every movement of the Mess ⁇ slide along the hollow profile follows, a measuring device for measuring the position of the inner slide along the hollow profile and a visible in the outer space of the hollow profile display of the determined by the measuring device length in accordance with the measured position of the inner slider.
• the invention is particularly directed to linear encoders for Mes ⁇ sung the body size of individuals.
• Such length ⁇ gauges are also referred to as Stadiometer.
• a typi ⁇ cal such length measuring device has a dipstick, which is designed as a vertical linear guide for a caliper (head slider).
• the measuring rod is vertically ⁇ aligned and mounted on a wall or mounted on a platform. To measure the height, the person steps in front of the measuring rod, whereafter the head slider is pushed down on the measuring rod until it comes into contact with the head of the person to be measured.
• a measuring scale is provided with graduation scales ⁇ scale.
• the caliper in turn, is provided a reading unit, the re ⁇ gistriert the scale Paging ⁇ strokes while moving the caliper to the dipstick and thus detects the incremental change in position of the measurement slider.
• the absolute height of a graduated scale stroke ko ⁇ diert may be, so that with the reading unit, the height of the head Slider can be determined, which is then displayed on a display on the calliper.
• Another type of body length meter includes an elbow held by a person measuring the body length.
• One leg of the elbow is held in contact with the head of the person to be measured. From this leg in support on the head, a second leg is perpendicular from, wherein the elbow is held so that the second leg is directed vertically to the ground.
• a terminator is level measurement device provided with an ultrasonic transducer that from the transit time of a transmitted ultrasonic signal reflected on the ground and runs back to the ultrasonic transducer, the height of the first to the person located in support on the top of the ⁇ measuring leg via the soil and thus determines the body size and displays.
• a disadvantage of the ⁇ ses type of length measuring device is that Messungenau- CANDIES may occur in that the measuring person performing holds not exactly aligned so the angle piece, that the second leg is directed exactly vertically on the floor.
• a further disadvantage is that changing Conversely ⁇ environmental conditions (for example, dust or other impurities in the air) or lying on the ground objects can falsify the measurement.
• Another type of length measuring device has a platform on which the person to be measured occurs, and a vertically above ⁇ half of the persons to be measured firmly suspended horizontal carrier.
• a distance measuring device based on ultrasonic wave time is attached, which is directed to the head of standing on the platform to be measured person.
• the person to be measured wears a cap to ensure a well-defined reflection of the ultrasonic waves from the top of the head.
• From the distance of the upper Side of the head of the person to the vertically above the person to be measured permanently installed distance measuring device can be derived from the difference of the suspension height of the distance ⁇ measuring device and the measured distance to the top of the head, the body length of the person to be measured.
• This length measuring device is prone to errors, since the measurement can be falsified by changing environmental conditions and disturbing influences in the open measuring path between the ultrasonic transducer and the top of the head of the person to be measured.
• the length measuring device has a linear guide in the form of a hollow housing, on which the caliper is mounted on the outside displaceable. Inside the housing, an inner slider is slidably mounted therein. A magnet assembly magnetically couples the caliper and the inner slider so that the inner slider follows any movement of the caliper along the guide. The inner slider is in sliding contact with a linear potentiometer to provide a voltage signal that is proportional to a position of the inner slider.
• the position of the inner slider and thus of the thus coupled measuring ⁇ slider is derived along the linear guide.
• certain interfering factors such as smoke or dust that do not penetrate into the housing are reduced in their influence on the measurement accuracy.
• the potentiometer has sliding contacts that generate abrasion and wear out over time. To counteract this, high-quality materials must be used, which of course increases the production costs. But even under these conditions Wear can lead to a deterioration of the measuring accuracy.
• the hollow profile at least Wenig ⁇ is provided one end with an end wall. Furthermore, the inner slider covers the cross section of the hollow profile in wesent ⁇ union, so that in the interior of the hollow profile between the end wall and the inner slide a closed cavity is formed, which can serve as an acoustic resonator.
• the measuring device has a loudspeaker and a microphone inside the acoustic resonator between the end wall and the inner slider.
• Means coupled to the microphone and the speaker control and evaluation unit is directed to a ⁇ , to cause the speaker to output an acoustic pulse and then receive the impulse response of the acoustic resonator with the microphone.
• the control and evaluation unit is further configured to determine from the im ⁇ pulse response of the acoustic resonator whose fundamental frequency and to determine from the fundamental frequency, the length of the resonator and thus the position of the inner slide along the hollow profile.
• the lowest natural frequency is here meant according to a standing wave whose wavelength is twice as long as the acoustic Re ⁇ sonator.
• the inner slider substantially covers the cross section to effectively reflect incident sound waves, but may also have a small aperture, for example to allow air to pass through as it moves.
• control and evaluation unit is adapted to transform the received Impulsant ⁇ word of the acoustic resonator through a Fourier transformation into a frequency spectrum and the frequency spectrum of the fundamental frequency at certain.
• the Fourier transformation is preferably carried out in the form of a discrete Fourier transformation (DFT) or a fast Fourier transformation (FFT).
• control and evaluation unit is adapted to determine the distance of two consecutive maxima in the determination of the basic ⁇ frequency in the frequency spectrum.
• the distance can be used to determine to each maximum in the frequency spectrum how many harmonics it is.
• ⁇ ser information can then from any maximum a fundamental frequency are determined, and these are then averaged to a fundamental frequency are telt. It can be averaged several distances aufnismfol ⁇ gender maxima to determine the fundamental frequency.
• control and evaluation unit is to be ⁇ directed to choose the bandwidth of the acoustically ⁇ tables pulse generated through the microphone so that the smallest wavelength given is greater than twice the diameter of the hollow section ⁇ fils.
• the hollow profile is also provided at the other end with a second end wall to form a second acoustic resonator in the interior of the hollow profile between the second end wall and the inner slider.
• a second loudspeaker and a second microphone are arranged in this second acoustic resonator.
• the control and evaluation unit is further configured to cause the second loudspeaker to emit an acoustic impulse to record with the second microphone the impulse response of the two ⁇ th acoustic resonator, to determine therefrom the Grundfre ⁇ frequency of the second acoustic resonator and from the fundamental frequency to determine the length of the second resonator and thus the position of the inner slider along the hollow profile.
• control and evaluation unit can then advantageously be further added, by using the specific lengths of the akusti ⁇ rule resonator, the second acoustic resonator be ⁇ known length of the hollow profile between the end wall and the second end wall and the known axial Length of the inner slider to carry out a calibration of the length determinations.
• the magnet arrangement has at least one permanent magnet on the caliper and a permanent magnet on the inner slider which are ordered that opposite poles of the two Perma ⁇ nentmagnete are aligned facing each other to each other.
• the magnet arrangement in each case four permanent magnets are arranged on the inner slider and on the caliper to each other so that in each case a pair of permanent magnets on the caliper and on the inner slider with opposite poles facing each other is aligned with each other.
• the magnet arrangement only one permanent magnet on one of the measuring slide and the inner slide, whereby then contains the other component of the measuring slide and the inner slide ferromagnetic or paramagnetic material, so that measurement ⁇ slide and inner slider are magnetically coupled.
• the outer dimensions of the inner slider are vorzugswei ⁇ se adapted to the inner dimensions of the hollow profile, so that the inner slider sitting as possible clearance, but slidably in the hollow profile. Accordingly, the inner dimen ⁇ measurements of the caliper gauge are adapted to the external dimensions of the hollow profile, that the caliper with possible ge ⁇ ringem game, but is mounted slidably on the outside of the hollow profile.
• 1 shows a schematic view of a length measuring device
• Fig. 3 is a cross sectional view of the length measuring device in Be, shows ⁇ rich of inner slide and caliper wherein the Slider components themselves are not shown, but le ⁇ diglich arranged in them permanent magnets,
• FIG. 5 shows the temporal amplitude curve of a signal stimulating the loudspeaker to emit an acoustic pulse as a function of time
• Fig. 6 shows the recorded microphone signal of the impulse response of the acoustic resonator in the hollow profile
• FIG. 7 shows the impulse response of the acoustic resonator of FIG. 6 transformed into a frequency spectrum
• Fig. 8 shows a schematic view of the hollow profile in the longitudinal ⁇ section of another embodiment for a Hadnmessvor- direction shows.
• Fig. 1 shows a side view of a length measuring device, which may for example be attached to a wall.
• the length measuring device has a hollow profile 2 as a linear guide, on the outside of which a caliper 4 is mounted, which carries a head plate 3.
• the caliper 4 is lowered so far to ⁇ until the top plate 3 rests on top of the head of the person to be measured.
• an inner slide 6 is slidably mounted (see Figure 2).
• the inner slide 6 is disc-shaped in cross section or, as shown here, provided with a closed lower end wall, so that the inner slide 6 covers the cross section of the hollow profile 2.
• the outer dimensions of the inner slider 6 are connected to the inner adapted dimensions of the hollow profile 2, so that the inner ⁇ re slide 6 with the least possible play, but slidably in the interior of the hollow section 2 sits.
• the inherent ⁇ ren dimensions of the measuring slide 4 are adapted to the external dimensions of the hollow section 2, so that the measuring slide 4 with little play as possible, but is slidably supported on the outer circumference of the hollow profile. 2
• Fig. 3 shows a cross section through the hollow section 2 in Be ⁇ rich the caliper and the inner slider, the caliper and the inner slider component itself are not shown, but only the magnet assembly of a plurality of permanent magnets, in the inner slide and caliper are introduced.
• the inner slide 6 four permanent magnets 7 are distributed around the circumference introduced, which are distributed at a distance of 90 ° to each other around the circumference.
• four permanent magnets 5 are also placed in the caliper 4, which are distributed in corresponding Abstän ⁇ the 90 ° around the outer caliper.
• the arrangement of the permanent magnets is such that opposing permanent magnets 5 and 7 of the Mess ⁇ slide 4 and the inner slider 6 are aligned with opposite poles to each other.
• this is achieved in that the per ⁇ manentmagnete 7 of the inner slider are aligned with a magnetic pole, in this example with the north pole, to the outside, while the permanent magnets 5 also with this magnetic pole, here the north pole, to the outside are arranged so that in each case a pair of permanent magnets 5 and 7 facing opposite poles facing each other.
• the caliper 4 and the inner slider 6 are magnetically coupled together.
• the inner slider 6 follows every movement of the caliper 4 along the hollow profile 2. In FIG. 2, only one of the permanent magnets 5 and 7 is shown in each case.
• more or less than four permanent magnets per slider component may be provided, for example, only one permanent magnet in the caliper 4 and the inner slide 6. It is even possible that even a magnet either in the inner slide 6 or in the caliper 4 is provided and the other slider component without own magnet contains ferro- or paramagnetic material, so that a magnetic attraction between the inner ren slide 6 and the caliper 4 is effected.
• the magnet or magnets of the magnet assembly are preferably permanent magnets ⁇ but electromagnets can be used in principle.
• Fig. 4 shows a schematic longitudinal sectional view of a hollow ⁇ profile 2 of a length measuring device.
• the inner slider 6 is simply disk-shaped and covers the cross section of the hollow section 2 from.
• the hollow profile 2 is provided at the lower end with a closed end wall 40, so that between the end wall 40 and the inner slide 6, a closed space is formed in the hollow profile, which can be considered as an acoustic resonator.
• the measuring device for determining the position of the inner slide 6 along the longitudinal direction of the hollow profile 2 includes a loudspeaker 22 and a microphone 20, which are arranged in the interior of the acoustic resonator 30.
• the loudspeaker ⁇ 22 and the microphone 20 are connected to a control and evaluation unit 9, which is shown here arranged in the outer space of the hollow profile, but which can also be accommodated in the interior of the hollow profile.
• the control and evaluation ⁇ unit 9 is a programmable karseinrich ⁇ device, which is adapted to the speaker 22 for Abga ⁇ be an acoustic pulse to stimulate and record the resulting impulse response of the acoustic resonator 30 by recording the signal of the microphone 20.
• the tax and teech 9 is further adapted to determine from the acoustic impulse response, the fundamental frequency f 0 of the resonator.
• This fundamental frequency f 0 has a wavelength ⁇ 0 equal to twice the length of the acoustic resonator (the simplest standing wave in the acoustic resonator 30 is a half-wave each having a velocity node on the end wall 40 and on the reflective wall of the inner slider 6).
• the length of the resonator can thus be determined:
• Fig. 5 shows the time dependence of a signal generated by the control and evaluation unit 9 excitation signal for the loudspeaker ⁇ cher 22 for emitting an acoustic pulse.
• This signal preferably consists of a positive and negative half ⁇ wave with a substantially rectangular shape.
• the excitation signal does not have an ideal rectangular shape (which in principle would have an unlimited frequency spectrum) because the bandwidth of the pulse is limited.
• the bandwidth of the pulse should be chosen so that the smallest wavelength given RESIZE ⁇ SSER than twice the diameter of the hollow profile is. This ensures, as already mentioned above, that the sound propagates in the hollow profile as a plane wave.
• the time length of a half-wave of the excitation signal should be greater as the period of the signal with the lowest frequency to be evaluated.
• FIG. 6 shows the time profile of the impulse response of the acoustic resonator recorded with the microphone 20.
• the transformation into a frequency spectrum is carried out by a Fourier transformation. Possible methods of digital signal processing for Fourier transformation are, for example, the discrete Fourier transformation (DFT) or the fast Fourier transformation (FFT), for the execution of which the control and evaluation unit 9 can be set up.
• DFT discrete Fourier transformation
• FFT fast Fourier transformation
• Fig. 7 now shows a section of the frequency spectrum of the impulse response. This includes local maxima, caused by being excited ⁇ eigenmodes clearly visible. These occur at integer multiples of the fundamental frequency f 0 .
• the fundamental frequency can thus also be determined via the distances of adjacent modes in the frequency spectrum.
• This procedure has the advantage that the lower limit frequency of the ver ⁇ applied speaker can be selected to be greater than the egg ⁇ gentliche to be determined fundamental frequency f 0 of the acoustic Reso ⁇ nators.
• the lower limit frequency of a loudspeaker is determined inter alia by the size of its membrane. The larger this is, the lower the cutoff frequency can be. Since the speaker is placed inside the hollow profile, the smallest possible membrane diameter is sought.
• the simplest standing wave in the acoustic resonator can not be easily observed with the present method, since the loudspeaker can not adequately generate the large wavelength required for this purpose.
• This effect can also be seen in FIG. 7, from which indicates that the fundamental frequency is slightly more than 300 Hz (intervals of successive maxima). At a little more than 300 Hz, however, in the frequency spectrum shown in FIG. 7, no usable maximum can be recognized at the fundamental frequency of slightly more than 300 Hz for the reason given.
• FIG. 8 shows a further embodiment with which the accuracy of the measurement of the measuring device can be improved.
• a schematic view of the hollow profile is shown in longitudinal section of the length measuring device.
• an acoustic resonator 30 is formed in the hollow profile 2, in which a loudspeaker 22 and a microphone 20 are located (the control and evaluation unit connected thereto is omitted here for the sake of simplicity of illustration).
• a second acoustic resonator 32 is formed in the hollow profile between the opposite second end wall 42 of the hollow profile and the inner slider 6.
• a second speaker 26 and a second microphone 24 are also verbun ⁇ with the control and evaluation.
• the length measurement can be calibrated, since the length of the hollow profile between the end Walls 40 and 42 and the axial length of the inner slider 6 are known.
• the sound speed can be determined by the following equations:
• the thus determined speed of sound can then be used, for example, to determine the length of the one acoustic resonator 30: Reference sign list

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• Biomedical Technology (AREA)
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• 2012
  • 2012-11-09 DE DE102012220468.7A patent/DE102012220468B3/de not_active Expired - Fee Related
• 2013
  • 2013-08-14 EP EP13750048.4A patent/EP2916733B1/de active Active
  • 2013-08-14 CN CN201380057386.3A patent/CN104755028B/zh active Active
  • 2013-08-14 JP JP2015541041A patent/JP6139692B2/ja active Active
  • 2013-08-14 US US14/441,802 patent/US10143402B2/en active Active
  • 2013-08-14 BR BR112015010615A patent/BR112015010615A2/pt not_active IP Right Cessation
  • 2013-08-14 WO PCT/EP2013/067022 patent/WO2014072089A1/de not_active Ceased
  • 2013-08-14 ES ES13750048.4T patent/ES2610403T3/es active Active

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