Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
  • G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
  • G01V3/10—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils
  • G01V3/101—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils by measuring the impedance of the search coil; by measuring features of a resonant circuit comprising the search coil
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
  • G01V3/15—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for use during transport, e.g. by a person, vehicle or boat

Definitions

• the present invention relates to a metal detector according to the preamble of claim 1.
• Metal detection devices of this type are primarily used for localizing metal parts laid under a surface, such as reinforcing iron in reinforced concrete or lines and other construction elements in building parts.
• Such known metal detection devices prove to be disadvantageous with regard to their accuracy and ease of use, because when the surface is scanned with the Measuring part, the position of the object sought is determined by the maximum of the deflection, which results in a relatively flat signal curve as a function of the scanning path. This means that the surface has to be painted over several times and the determination of the maximum remains relatively imprecise due to its blurring. In addition, it is tiring for the user to look at the pointer of the instrument and at the same time to assess the position and movement of the measuring part.
• FIG. 1 is a perspective view of a metal detector according to the invention on a concrete surface
• FIG. 2 is a perspective view of the measuring part of such a metal detector
• FIG. 3 shows a schematic illustration of a double coil and a marking device in a sectional view
• Fig. 4 shows the block diagram of an inventive
• FIG. 5 shows a diagram of the signal curve as a function of the scanning path according to a further embodiment of the invention.
• the 1 comprises an evaluation part 1 with an image output device 2 and one with keys and / or switch-provided field 3.
• the device 2 can have a cathode ray tube, a liquid crystal dot matrix or other display means.
• the evaluation part 1 is connected via cables 4 and 5 to a measuring path device 6, 7, 8 or to a probe 9.
• the device 6, 7, 8, which together with the probe 9 forms the actual measuring part, consists of a part 6, a rotatable guide device 7 and a flexible traction means 8, the part 6 having an unwinding device on the inside.
• the metal detector according to FIG. 1 is used, for example, to locate reinforcing bars 10, 10 ', 10 "in a concrete wall 11 and functions as follows:
• the probe 9 emits an alternating magnetic field of, for example, 1500 Hz and also serves as a sensor which detects the reactions caused by the reinforcing bars 10, 10 ', 10 "by interactions with the mentioned alternating magnetic field.
• the traction means 8 can, for example, be a plastic thread that is only slightly stretchable with the probe 9.
• the unwinding device in the interior of part 6 is connected to a clock disk, from which the distance a between the unwinding part 6 and the probe 9 results from counting the pulses.
• the guide device 7 is connected to an angle encoder or a timing disk in order to determine the angle ⁇ C between a reference direction and the direction of the traction means.
• the measurement signal along the scanning path 12 is digitized and stored in connection with the rectangular coordinates calculated from the values of ⁇ and a.
• the measurement signal is displayed directly in the form of brightness and / or color patterns on the display device, or only the points are displayed which each correspond to an associated extreme value of the measurement signal, that is to say the position of a reinforcing iron.
• the display device 2 can also be used to indicate numerical values which correspond, for example, to the degree of coverage at the point of a reinforcing bar indicated by the position of the probe on the screen.
• Printer / plotter can be connected to get the image on any scale.
• FIG. 2 shows a measuring part 21 with the omission of part of the upper cover, which contains a marking device.
• the measuring part 21 has two wheels 22, 22 ', which are coupled via a common axis 23, in order to effect a guidance in a straight direction when rolling off, wherein a rail could also be provided for guidance along a straight line for the same purpose.
• the wheels have a non-slip surface and a well-defined radius, for example in that the wheel is made of hard material and the rolling surface of the wheel contains a groove in which a soft and non-slip rubber ring is inserted.
• the measuring part 21 is provided with a displacement measuring device consisting of a clock disc 24 driven by the axis 23 and a double fork light barrier 25 and with a coil 26 serving as a sensor, which represents the actual metal detector.
• the measuring part 21 connected to an evaluation part via a connecting cable 27 serves to locate a reinforcing bar 29 in a concrete wall 28.
• the front side of the measuring part 21 is provided with switches and / or keys 19 and, if appropriate, with light-emitting diodes 18.
• the displacement measuring device functions in such a way that, when the axis 23 rotates, the double fork light barrier 25 generates two signals, for example 90 ° out of phase, by interaction with the clock disk 24, from which the scanning path traversed can be determined in order to determine the position of the metal part determine.
• the metal detector has an auxiliary device which is based on the continuous storage of values of at least one physical quantity in order to subsequently determine the positions which correspond to the extreme values of the measurement signal, the physical quantity being an electrical analog or digital signal or a mechanical-geometric position.
• an adjustment is carried out automatically by pressing a button on the suspended evaluation part and when the measuring part is further away from metallic objects.
• the measuring part 21 is then placed on the surface to be examined and one of the keys 19 prepares for the start of a measurement. Now the measuring part 21 is moved by hand with slight pressure on the surface in a first direction, for example from from left to right.
• the rigidly coupled wheels 22 and 22 "result in a straight guidance of the movement.
• the measuring signal that is created is automatically electronically stored point by point and in function of the scanning path that is traversed.
• the electronic circuit recognizes this and during a After a short waiting time, the positions of those values along the scanning path where there is a signal maximum or minimum are calculated from the point-by-point stored measurement curve.
• the position of the reinforcing iron is then indicated at these points by a light-emitting diode
• Several positions, under which a reinforcement bar is located, can be specified in a short time and with high accuracy. Additional information about the diameter of the reinforcement bar and the depth below the surface are indicated at the corresponding locations on the display of the evaluation part and if necessary printed out on a paper strip.
• the double coil of a measuring part 21 has a ferrite shell core 31 with an inner winding 32 and / or an unconventional outer winding 33.
• An optional marking device comprises a solution 34 with a fiber pen 35 with a dye-soaked writing tip 36.
• the fiber pen 35 is pressed in the non-activated state by a spiral spring 37 against a stop of the socket 34.
• the socket 34 can, for example, be mounted on the measuring part and can preferably be unscrewed for removal when not in use.
• all other elements of the double coil and the marking device are preferably made of non-metallic and non-magnetic material.
• the double coil allows a switchover from the inner winding 32 to the outer coil 33 in order to obtain additional information from the two magnetic fields which differ in the course of the field lines, which allows not only the depth but also the diameter of the reinforcement rod to calculate.
• the felt pen 35 is pressed down when the measuring part or the probe 21 (FIG. 2) is exactly over a reinforcing bar in order to conveniently mark the surface of the concrete slab 28 there, under which a piece of metal is located.
• the exact position of the reinforcing iron 29 is calculated according to the invention from the stored measurement values and at the backward movement of the measuring part 21 is displayed, for example, by means of a light-emitting diode 18.
• the measuring part 21, which is preferably provided with a double coil according to FIG. 3, could also be implemented with one or more coils with or without core material.
• a solution with a ferrite rod would have the advantage that additional information could be obtained by an axial movement of the probe.
• the recording could be carried out on a film spread out on the concrete surface 39 or on an adhesive tape rolled out of the measuring part in the matrix or thermal printing process.
• the marking could also be done with the aid of adhesive dots from a supply roll in the measuring part.
• the marking could also contain additional information, for example about the depth and / or the diameter of the metal piece.
• the metal detector according to FIG. 4 has a measuring part 41 and an evaluation part 42.
• the measuring part 41 comprises a displacement transducer 43, which supplies two signals J1 and J2 which are phase-shifted by 90 ° in order to distinguish the forward and the backward movement, as well as two coils 44, 45 which 3, an input unit 47 with a first key for switching the coils and a second key for establishing readiness for a measurement, and a display unit 48 with light-emitting diodes, lamps or LCDs.
• the evaluation part 42 has a high-impedance oscillator 49 which is connected to a capacitor circuit 50 which forms a resonant circuit with the coil 44 or 45 which has just been activated.
• the output of the circuit 50 is connected via the series circuit of a rectifier circuit 51 and a low-pass filter 52 to the first input of a differential amplifier 53, the second input of which is supplied with the output signal of a digital-to-analog converter 54 used for automatic drift compensation.
• the output signal of the differential amplifier 53 is added to the data bus of a microprocessor 58 via the series connection of a multiplier 55, a non-linear amplifier 56 and an analog-digital converter 57.
• the evaluation part 42 comprises a forward-backward detector 59, which is acted upon by the signals J1 and J2, the pulse output of which is connected to the counter input of a counter 60, which together with a Read-write memory (RAM) 61, a read memory (ROM) 62 and an input and output circuit 63 is connected to the microprocessor 58, both the counter 60 and the circuit 63 having been won by the detector 59 ⁇ Nnen forward-backward signal, which indicates the direction of movement.
• the circuit 63 supplies the digital signals for the digital-to-analog converter 54, for the display unit 48 and for a further display unit 64, and the calibration signal for the multiplier 55.
• the circuit 63, to which a further input unit 65 is connected, is connected to the input unit 47 via further connections.
• the oscillating circuit formed by the capacitor circuit 50 and the coil 44 or 45 just connected is excited by the oscillator 49, the properties of the signal at the output of the circuit 50 being changed when metal is present in the vicinity of the coil.
• the change in amplitude is preferably evaluated.
• additional information is obtained which allows not only the depth but also the diameter of a metal To determine the rod.
• the switchover can be carried out manually or automatically by the microprocessor 58 via the circuit 63 and the unit 47.
• the output signal of the circuit 50 is fed through the described path to the signal input of the microprocessor 58, wherein the elements 53 to 56 can also be omitted if, for example, an analog-digital converter 57 with a high resolution of e.g. 12 bit is used, but it is expensive and / or slow. In contrast, the converters 54 and 57 in FIG. 4 would be provided for 8 bits.
• the microprocessor calculates the amplitude or another selected parameter of the input signal, stores the corresponding value and carries out all operations which have been described in connection with the method explained with reference to FIG. 2.
• the main signal is multiplied by the multiplier 55 with a digital calibration signal supplied by the circuit 63, the value of the digital signal being a function of the selected rod diameter.
• the nonlinear amplifier 56 for example a logarithmizer, is provided in order to reduce the demands on the downstream converter 57 which result from the fact that The input signal of the same strongly depends on the depth of the reinforcing iron in the concrete.
• the memory 61 (RAM) serves to store the measured values and as working memory of the microprocessor.
• the memory 62 (ROM) contains the evaluation program and function tables. Of course, other more convenient memories can also be used.
• Display unit 64 can be an alphanumeric display of the values of the bar depth or the overlap of the input or 'calculated Stab pen ⁇ diameter, the constants expected Mess Market ⁇ , the Materialkon ⁇ , zwi ⁇ chen the lateral Di ⁇ tanz the last two maxima or minima etc. enable.
• the input unit 65 has buttons and switches for selecting a desired type of use, for example for determining the rod depth for a given rod diameter, for triggering the automatic adjustment of the drift in order to emit a signal when there is no metal nearby simultaneous determination of the rod depth and the rod diameter, for entering parameters relating to the diameter, the material constant or the metal type, etc.
• the unit 48 can have a plurality of lamps or light-emitting diodes, one for indicating that the displacement speed the measuring part or the probe has come close to the greatest permissible speed, another to indicate that there is no malfunction, and a third to indicate that a reinforcing iron was run over during a new measurement during the first direction of movement of the probe, and also to display the calculated position of the reinforcing bars during the movement in the second direction.
• the measuring part 21 (FIG. 2) can have a single axis and a third point sliding on the surface, for example made of PTFE or sapphire.
• the auxiliary device can have a simple coil and means, for example similar to photo lenses, in order to move the coil into a second position which is raised by a defined amount over the concrete surface.
• a scanning process can be carried out by moving the measuring part 9 without elements 6, 7, 8 (FIG. 1) in the forward or backward direction.
• the diagram shows the course of the signal strength S as a function of the scanning path X, For example, according to line 12 in FIG. 1, the metal parts sought being located below the signal maxima. If the measuring part passes over the points A, B, C,..., The electronics only recognizes a maximum (or a minimum) as such if the last stored largest signal value, for example S 1, around a certain amount S M - - S. was undercut. In this position (point D), for example, a green LED 18 lights up, which thus indicates to the user of the device that a maximum (or minimum) has been exceeded.
• the marking device itself can also be used in combination with any metal detection device according to the prior art.
• the invention also includes the combination of measurement and evaluation part in one and the same unit.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Remote Sensing (AREA)
• Physics & Mathematics (AREA)
• Environmental & Geological Engineering (AREA)
• Geology (AREA)
• General Life Sciences & Earth Sciences (AREA)
• General Physics & Mathematics (AREA)
• Geophysics (AREA)
• Electromagnetism (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

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• 1988
  • 1988-02-12 CH CH53088A patent/CH676051A5/de not_active IP Right Cessation
• 1989
  • 1989-02-09 EP EP19890901835 patent/EP0360845A1/de not_active Withdrawn
  • 1989-02-09 WO PCT/CH1989/000022 patent/WO1989007775A1/de not_active Ceased

Non-Patent Citations (1)

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