EP0165256A4 - Detecteur d'objets. - Google Patents

Detecteur d'objets.

Info

Publication number
EP0165256A4
EP0165256A4 EP19840904069 EP84904069A EP0165256A4 EP 0165256 A4 EP0165256 A4 EP 0165256A4 EP 19840904069 EP19840904069 EP 19840904069 EP 84904069 A EP84904069 A EP 84904069A EP 0165256 A4 EP0165256 A4 EP 0165256A4
Authority
EP
European Patent Office
Prior art keywords
output
state
input
capacitance
object detector
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP19840904069
Other languages
German (de)
English (en)
Other versions
EP0165256A1 (fr
Inventor
Iain Godfrey Saul
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CONSOLIDATED TECHNOLOGY (AUST) PTY Ltd
CONS TECHNOLOGY AUST Pty Ltd
Original Assignee
CONSOLIDATED TECHNOLOGY (AUST) PTY Ltd
CONS TECHNOLOGY AUST Pty Ltd
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
Publication date
Application filed by CONSOLIDATED TECHNOLOGY (AUST) PTY Ltd, CONS TECHNOLOGY AUST Pty Ltd filed Critical CONSOLIDATED TECHNOLOGY (AUST) PTY Ltd
Publication of EP0165256A1 publication Critical patent/EP0165256A1/fr
Publication of EP0165256A4 publication Critical patent/EP0165256A4/fr
Withdrawn legal-status Critical Current

Links

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
    • G01V3/088—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 operating with electric fields

Definitions

  • Embodiments of the invention may for example be adapted particularly but not exclusively to provide a means for detecting the positions of studs or other supporting structures within walls.
  • United States patent specification 4,099,188 describes an object detector comprising an electronic switching device the output of which is. in use cyclically switchable between at least two different states, said switching device having a capacitance which is in use of the detector cyclically charged and discharged under conditions whereby the rate of charge and/or discharge of the capacitance determines the time interval, for each cycle of the output of said device, for which said output is in one of said states, the rate of charge and/or discharge of said capacitance being influenced, in the presence of an object in the vicinity of the object detector whereby to effect variation of the length of said time interval.
  • the capacitance is defined at least in part by a flat plate and direct variation of that capacitance, occurring in the presence of said object is utilized to effect variation of the length of the time interval.
  • OMPI _ ⁇ need to form the capacitance as including a plate imposes manufacturing constraints which may not be desired. For example it is not always convenient to form the detector with a flat plate of substantial area.
  • An object of the invention is to provide an object detector which permits more flexibility in the manner of formation of the capacitance.
  • the invention in one form is characterised by the provision of second means in use providing an electric field therearound, said second means being arranged whereby in use of the detector said electric field is at least partially discharged in the presence of a said object in the vicinity of said second means to effect said influencing of the rate of change and/or discharge of said capacitance.
  • the switching device is formed as a free running multivibrator, the output of which comprises said output of the switching device and which output is switched alternatingly between two states, such as on and off states, and wherein the rate of charge or discharge of the said capacitance effects said variation is the length of said time interval by determining the length of time for which the output is in at least a particular said state during each cycle, such as by determining the length of the on and/or off parts of each cycle of output of the multivibrator.
  • Such a free running multivibrator may include a Schmitt gate device, the output of which comprises said output of the switching device, said Schmitt gate device being of a kind in which the output is conditioned to a first state when the input thereof is at one state and whereupon on traverse of the state of the input from said one state to another state the output is switched to a second state on said input reaching said second state, said output being connected to said input via a feed-back network coupled whereby in use to revert said input to said one state when said output is conditioned to said second state.
  • the Schmitt gate device is a Schmitt inverter gate in which case said one state and said second state are low states and said another state and said first state are high states.
  • Said capacitance may provide a connection between said input and one side of an electric supply for said detector and an impedance may be provided between the -other side of said supply and said input.
  • the placing of said input in said one state may act to discharge said capacitance and said capacitance may be caused to remain in its uncharged state until the output is next placed in said first state pursuant to operation of the Schmitt gate device, whereafter said capacitance is charged through said impedance from said supply to cause said input to be conditioned progressively towards said another state until said another state is reached, whereafter the output is again conditioned to said second state for initiation of another cycle of operation, whereby the parts of each cycle of the output device for which the output of said Schmitt gate device is in its second state are dependent on the rate of charge of said capacitance.
  • the said second means is coupled to the input of said Schmitt gate device and operates to effect partial diversion of charging of said capacitance to an extent dependent on whether or not
  • the second means may comprise an electrode.
  • the feedback network may for example include a diode arranged to permit conduction from said input to said output in parallel to said Schmitt gate device under the condition that the input is in said another state and the output is in said second state, but to preclude such conduction when the output is in said first state.
  • a resistance or other impedance may be provided in series with said diode.
  • a reference device which may be otherwise similar to the detector above described is provided arranged whereby in use to provide an output which can at least be adjusted so as in the absence of an object in the vicinity of said second means to be substantially in phase with said output of said free running multivibrator but arranged whereby introduction of the object to the vicinity of said second means differentially effects the free running multivibrator and said reference device .
  • the free running multivibrator for the free running multivibrator, the length of the said time interval during at 'least one cycle of the output thereof is varied as compared to the length of the corresponding time interval for the output of the reference device, whereby the presence of said object can be detected by detecting the condition where the outputs of the free running multivibrator and reference device are not momentarily in the same state.
  • the free running multivibrator and reference device are " preferably interconnected so as to synchronise the time of beginning of each cycle of the outputs thereof.
  • the reference device is provided with third means similar to said second means for varying a said time interval for the output thereof, corresponding to the said time interval, the length of which is varied by influencing the rate of change and/or discharge of said capacitance.
  • the invention may also be implemented using a comparator arranged to switch the output state thereof when the signal on one input thereof exceeds a reference level applied to the other input, said one input being connected to said capacitance, said capacitance being arranged to permit progressive charging thereof when the output of the comparator is in one state during each cycle thereof, and to effect discharging thereof when the output of the comparator is subsequently in another state during each cycle of operation thereof, whereby the time period between said one input of the comparator reaching said reference level and the effecting of discharge of said capacitance is dependent on the rate of charging of said capacitance, said time interval being the time on each said cycle for which said output of said comparator is in said one or said another state.
  • the output of the comparator changes state for a said interval on each cycle of the comparator output.
  • the second means may in this case be connected to said one input to effect variation of said time interval when an object is near thereto.
  • Embodiments of this kind may be provided with a reference comparator otherwise operating in a similar way to the first mentioned comparator.
  • Figure 1 is a circuit diagram of an object detector constructed in accordance with the invention
  • Figure 2 is a timing diagram showing wave forms in use generated in the detector of figure 1;
  • FIG. 3 is a circuit diagram of an alternative form of detector constructed in accordance with the invention.
  • Figures 4 and 5 are timing diagrams illustrating wave forms appearing in the circuit of figure 3 under two different conditions of operation thereof;
  • Figure 6 is a circuit diagram of a further detector constructed in accordance with the invention.
  • Figure 7 is a timing diagram showing wave forms appearing in the circuit of figure 6 under one operating condition thereof;
  • Figures 8 and 9 are circuit diagrams ' of two further alternative forms of detector constructed in • accordance with the invention.
  • Figure 10 is a diagram showing a possible form of electrodes for incorporation into the detector of figure 6.
  • the object detector 10 for which the circuit is shown in figure 1 includes a Schmitt inverter gate Gl having its input connected via a resistor Rl to a positive supply line 12.
  • the output of the gate Gl is connected to the input via a feedback network com ⁇ prising a resistor R2 and a diode Dl connected in series.
  • the diode Dl has its anode connected to the input of gate Gl.
  • a sensing electrode 14 is connected to the input to the gate Gl.
  • the Schmitt inverter gate Gl is characterised in that when the input signal thereto exceeds a prede ⁇ termined level, the output level changes from a pre-existing high level to a low level. Similarly, when the input signal magnitude drops below the predetermined level the output rises to a high level.
  • the output signal waveform is otherwise independent of the input signal waveform.
  • the detector 10 is dependent for its operation on the existence of stray capacitance between terminals of the gate Gl. Although the interaction of these stray capacitances with other integers of the circuit may be complex, the mode of operation of the circuit of the detector 10 can be understood by considering only the stray capacitance CI as existing between the input to the gate Gl and the negative supply line 16. Assuming firstly that the capacitor CI is discharged and that the voltage conditions of the diode Dl are such as to preclude conduction thereof, the capacitor CI will charge via the resistor Rl so that the voltage on the input to the gate Gl will rise from a low value progressively with time to a high value.
  • the diode Dl was rendered non-conductive because the output from the gate Gl was at a high state the fall in the gate output to its low state has the effect that the diode has its anode, at the input to the gate Gl, at a higher potential than the cathode, so that the diode becomes conductive whereby the capacitor CI is dis ⁇ charged quickly through the diode Dl and resistor R2 to the output of the gate Gl. Thereafter, after a time interval t., from discharge, the output of the gate Gl is again placed in a high state and a new cycle of operation begins with a fresh charging of the capacitor CI.
  • the time interval t 2 after reaching the threshold 19 and before discharge of capacitor CI begins is due to internal delays within the gate .Gl which cause the switching of the output to occur at a later time than the alteration of the input state which causes that output switching.
  • the time interval t., after the output reaches the low state and before the high state is regained after discharge of the capacitor CI is due to internal delays in the gate which hold the output in the low state for a short time notwithstanding that the input state is- low pursuant to discharge of the capacitor CI.
  • the input to the gate Gl is held low for the time period t., as shown at 25 in the input signal waveform.
  • the device 10 thus comprises in essence a free running astable multi-vibrator, the input and output waveforms of which comprise repetitive cycles as are represented at 27 and 29 respectively in the waveforms at "a" and "b” in figure 2.
  • the gate output exhibits a negative going pulse 29a of interval approximately equal to t-,.
  • the electrode 14 is arranged in any convenient • form such as in the form of a conductive wire or plate arranged to generate an electric field therearound pursuant to application of signal thereto during charging of the capacitor CI in each cycle of the input signal, so that when an object such as a non-conducting object is brought into proximity to the electrode the charge on the electrode tends to be dissipated.
  • the rate of charge of the capacitor CI during the charging period of each cycle is relatively decreased so that the time interval t. is increased as compared with the static condition where no object is nearby.
  • the extent to which this effect occurs is dependent upon various factors such as the overall impedance levels prevailing in the circuit, particularly the values of Rl and CI and the repetition rate of the oscillator represented by the gate circuit. Generally, frequencies of the order of 2 MHz may be employed. Resistance Rl may be chosen to be of large value, such as 2 M ⁇ with commercially available devices Gl such as type 74C14.
  • FIG. 3 shows a detector 31, being a modifi ⁇ cation of the arrangement of figure 1.
  • Schmitt inverter gates Al and A2 Gate Al has its input connected via a resistor R3 to a positive supply line 22 whilst gate A2 has its input connected via a resistor R4 to the moving contact of a potentiometer VR5, the latter being connected between two further resistors R6, R7 in a series network across the positive supply line 22 and negative supply line 24.
  • the inputs of the two gates Al and A2 are connected to the outputs via respective feedback loops which include a common resistor R8.
  • the feedback loop for gate Al includes a diode D2 having its anode connected to the input to the gate Al and its cathode connected to one end of resistor R3.
  • the other end of resistor R8 is connected to the output of gate Al via a further diode D3.
  • the feedback loop for gate A2 includes a diode D4 having its anode connected to the gate input.
  • the cathode of the diode D4 is connected to the same end of resistor R8 as diode D2.
  • the other end of resistor R8 is connected to the output of gate A2 via a diode D5.
  • Diodes D3, D5 have their anodes connected to resistor R8 and their cathodes connected to the outputs of the respective gates Al, A2.
  • the outputs of the two gates Al and A2 are also connected via respective resistors R9, RIO to the collector and base respectively of a transistor TRl, the emitter of the transistor TRl being connected to the negative supply line 24. Output from the circuit is taken via an output line 28 connected to the collector of transistor TRl.
  • Transistor TRl is NPN type such as type 2N3904.
  • An electrode 30 similar to the electrode 14 previously described is connected to the input to gate Al.
  • OMPl . 30 is not near an object, or can be made the same by adjustment of potentiometer VR5.
  • the threshold voltages will also be similar so that the input waveforms for both, as indicated at “a” and “c” in figure 4, will be the same and of the same duration, whilst the output waveforms will likewise be of the same with similar durations of the respective on and off intervals as shown at “b” and “d” in figure 4.
  • Discharge of the capacitances C2, C3 associated with the respective gates Al, A2 occurs in this instance through respective diodes D2 and D4, as well as through the common resistor D8 and a respective one of the diodes D3 and D5 when the respective gate outputs are in low conditions.
  • Figure 5 shows input and output voltages for the two gates Al and A2 for the condition where gate Al reaches its threshold voltage before gate A2.
  • the input signals for the gates Al and A2 are shown respectively at “a” and “c” in figure 5, whilst the output voltages are shown respectively at “b” and “d”
  • the part 17 of the waveform of the input voltage Vin to gate Al is relatively of greater slope than that of the corresponding part 17 of the input voltage Vin to the gate A2.
  • the time interval t' being the interval between initiation of charging of capacitor C2, and the reaching of the threshold voltage denoted by line 19 is relatively less than the corresponding interval t- for the other gate.
  • the capacitance C2 does not begin immediately charging after such reversion to the high state of the output of gate Al because that input is maintained in a low state for a further time interval for the reason now described. More particularly, referring to the output voltage waveform of gate A2 at "d" in figure 5, it will be seen that because the threshold voltage for the gate A2 is not reached until the time interval t. which is greater than the time interval t 1 , the output of gate A2 is not conditioned to its low state until a somewhat later time than the corresponding condi ⁇ tioning of the output of gate Al to the low condition.
  • the transistor TRl operates to detect a condition where there is phase alteration between the parts of each cycle of the outputs of the two gates for which the outputs are negative. More particularly, the transistor TRl is operable to provide a high output only under the condition where the output from gate A l is high and output from gate A2 is low. In other conditions of outputs from Al and A2, the output frcm transistor TRl is low. Thus, during normal operation, the outputs Al and A2 will be in phase so that the collector and base voltages of transistor VR1 will always be the same as each other and no output will result from transistor TRl. When there is a phase displacement between the output signals, there will still be a substantial period of time during each cycle of operation of the device where the outputs likewise are the same, either high or low.
  • the electrode 30 is connected to the input of gate Al and thus, by the mechanism previously described, the charging rate of the capacitance C2 associated with gate Al will be altered in accordance with whether or not discharge of the electric charge on the electrode 30 occurs so in turn being influenced by whether or not an object is in the vicinity of the electrode 30.
  • the potentiometer VR5 is first adjusted, when no object is in the vicinity of electrode 30, so that the output and input voltages of the two gates Al and A2 are as represented in figure 3, that is to say so that the outputs are in phase whereby no output is derived from transistor TRl. Then, when an object is moved into into the vicinity of the electrode 30 the charging rate of the capacitance C2 associated with gate Al is slowed so that gate Al reaches its input threshold on each cycle of operation at a later stage than gate A2 so giving rise to an output pulse train from tran ⁇ sistor TRl.
  • the pulse train from the output of transistor TRl may be passed to a suitable detecting circuit.
  • such a circuit may comprise an integrating circuit operable to integrate pulses when present on output line 28 and trigger a suitable relay or other switching device for operating a warning device such as a lamp.
  • Figure 6 shows the circuit of a further detector 41.
  • Schmitt inverter gates A3, A4 similar to the gates Al and A2 previously mentioned.
  • Gate Al has its input connected via a resistor Rll to a positive supply line 32 whilst gate A4 has its input connected via a resistor R12 to _. the movable contact of a variable resistor VR13.
  • Variable resistor VR13 is connected at one end to a resistor VR14 and at the other to a resistor VR15.
  • This series circuit comprised of resistors R14, R15 and variable resistor VR13 is connected across posi ⁇ tive supply line 32 and a negative supply line 34.
  • the inputs of gates A3 and A4 are connected via respective feedback loops, including a common resistor R16, to the outputs thereof. More particularly the input of gate A3 is connected to the anode of a diode D6, the cathode of the diode D6 being connected to one end of a resistor R16. The other end of the resistor R16 is coupled to the cathode of a diode D7, the anode of that diode being connected to the output of the gate A3.
  • the input of gate A4 is connected to the anode of a diode D8, the cathode of that diode being connected to the same end of resistor R16 as diode D6.
  • the output of the gate A4 is connected to the anode of a further diode D9, the cathode of which is connected to the same end of resistor R16 as is diode D7.
  • the junction between diodes D7-, D9 " and resistor R16 is connected to negative supply 34 via a resistor R17.
  • the outputs from the gates A3 and R4 are connected via respective resistors R18, R19 to the collector and base respectively of a transistor TR2, the emitter of which is connected to the negative supply line 34 and the collector of which is also connected to an output line 42.
  • the stray capacitances from inputs to negative supply are shown at C4, C5 for the respective gates Al, A2.
  • each electrode 44, 46 is coupled to the inputs to the gates A3 and A4 respec ⁇ tively.
  • the resistors Rll, R12 and R16 and R17 are selected so that under the condition of the outputs of the gates A3, A4 being high, there is insufficient current flow through diodes D6, D8 and resistors R16, R17 to prevent charging of the stray capacitances C4, C5 associated with the two gates.
  • the capacitors C4, C5 may charge to the threshold values of the two gates, at least under a condition of appropriate setting of the potentiometer VR13.
  • the voltage to which the capacitors are so discharged may be made arbitrarily low. This may be accomplished, for example, by making the values of Rll and of the equivalent resistive network between positive supply 32 and the input to gate A2 much greater than the sum the values of resistors R16 and R17.
  • the value of R17 must in this event also be chosen to be sufficiently large as compared with the effective impedance between the positive supply line 32 and the outputs of the gates A3, A4, when these are in the high condition, to permit maintenance of the reverse bias of the diodes D6, D8 in the high condition of output from a gate A3 or A4.
  • FIG 7 shows, at "a" and ⁇ c" input waveforms for gates A3, A4 respectively for the condition where the input of the gate A4 reaches the threshold- level of that gate before the input level of the gate A3 reaches the threshold level of gate A3.
  • the reaching of the threshold level for gate A4 is shown as occurring at the time interval t", after the beginning of an input waveform cycle.
  • the output of that gate A4 is then placed in a low condition after the following time interval t ⁇ as before.
  • this does not result in immediate discharging of the capacitor C5 because of the aforedescribed holding of the junction between resistors R16 and R17 at a high condition whilst the output of gate A3 remains in a high condition.
  • FIG. 8 shows further detector 61 in accordance with the invention.
  • the detector 61 includes an oscillator
  • a resistor R20 is connected from one input of amplifier
  • the output from the oscillator 49 is connected via separate diodes D10, Dll to respective inverting inputs of two comparators A5, A6 constituted by operational ampli- bombs.
  • the inverting input of comparator A5 is connected to positive supply via a resistor R22 and to an electrode 52.
  • the non-inverting input, of the comparator is connected via a resistor R23 to positive supply and to negative supply via a resistor R24.
  • the resistors R23, R24 thus Constitute a voltage divider operable to tie the non-inverting input to a fixed reference potential.
  • the stray capacitance from the inverting input of comparator A5 to negative supply is shown as a capacitance C7.
  • the non-inverting input of comparator A6 is connected to positive supply via a resistor R25 whilst the inverting input is connected to positive supply via a resistor R26 connected to the movable contact of a potentiometer VR27 itself connected between positive and negative supply.
  • the non-inverting input of comparator A6 is connected to negative supply via a resistor R28.
  • Resistors R25 and R28 constitute a potential divider operable to main ⁇ tain the non-inverting input of comparator A6 at a reference potential which is fixed and which may be selected to be the same as the potential to which the non-inverting input of comparator A5 is held.
  • the stray capacitance from the inverting input of comparator A6 to negative supply is indicated by reference C8.
  • U-mEmTi 21 are connected via respective resistors R29, R30 to the collector and base respectively of a transistor TR3 having its emitter connected to negative supply.
  • the output from the transistor TR2 is taken from the
  • the oscillator 49 constituted by operational amplifier 50 and associated components generates a cyclic output during cycles of which the output is for one part maintained low and
  • the comparators operate to condition the outputs thereof to a low state as opposed to a high state prevailing before such a voltage is reached.
  • the capacitors C7 and C8 charge at the same
  • capacitors C7 and C8 can discharge through the respec ⁇ tive diodes D10 and Dll to negative supply.
  • the voltage on the capacitors C7 drops abruptly whereupon the outputs of the two comparators are reverted to high states. Thereafter, a subsequent cycle of
  • the voltage on the- non-inverting input of one of comparators A5 or A6 will reach the reference level before that of the other so that its output will be conditioned to a high state for a relatively longer period of time before subsequently being reverted to a low state pursuant to discharging of the capacitors C7 and C8, which discharging in any event occurs substan ⁇ tially simultaneously under control of the oscillator.
  • the transistor TR3 is responsive to a condition where the output of comparator A5 is high and that of comparator A6 is low to generate an output on line 54 therefrom.
  • FIG. 9 shows a still further detector, wherein an oscillator 58 is constituted by a Schmitt gate G3 having its output connected to its input by a resistor R31 and having its input connected to negative supply via a capacitor C9.
  • the output from the oscillator 58 is connected via diodes D12, D13 to inputs of respec ⁇ tive Schmitt inverter gates A7, A8.
  • the input of gate A7 is connected to positive supply via a resistor R32.
  • Gate A8 has its input connected via a resistor R33 to the movable contact of a potentiometer VR34 having one end connected to negative supply and the other end connected to positive supply. •
  • the input to gate A7 is connected to an electrode 60.
  • a transistor TR4 has its collector connected via a resistor R35 to the output of gate A7 and its base connected via a resistor R36 to the output of gate A8. Output from the transistor TR4 is taken on an output line 62.
  • the operation of the arrangement of figure 9 is similar to that of figure 8.
  • the oscillator 58 produces repetitive cycles of output, for one part of which the output of the oscillator is high and for another part of which the output is low.
  • potentiometer VR34 If potentiometer VR34 is adjusted so that both gates A7, A8 operate in synchronism, the two capacitances CIO, Cll charge via, on the one hand, the resistor R32 and, on the other hand, via the potentiometer VR34 and the resistors R33 until the threshold voltages of the gates A7, A8 are reached whereafter the outputs thereof are switched from formerly prevailing high states to low states.
  • the timing of the high and low parts of each cycle of operation of the oscillator are arranged so that after the outputs are so placed in low states the capacitances CIO, Cll are discharged by placing of the oscillator output in a low state, the discharge occurring through diodes D12 and D13 whereafter the output of the gates A7, A8 are again reverted to a high state.
  • the associated gate will have its output placed in a low state first and will thus be caused to remain in that low state for a longer period until discharge of the capacitances CIO and Cll occurs than would be the case for the other gate.
  • the detectors shown in any one of figures 1, 3, 6, 8 or 9 may be encompassed in a suitable casing together with a suitable power supply, as well as switch and alarm circuitry including for example a warning light as previously described.
  • the electrode or electrodes may be positioned adjacent one surface of the casing and the casing adapted to be hand held and moved over surfaces such as over the surface of a wall.
  • the extent to which charge is discharged from the elec ⁇ trodes 14 during such movement will be dependent upon physical parameters associated with the material defining the surface over which the device is moved.
  • the detector is suitable for sensing the presence of wooden studs behind plaster walls and for detecting other objects such as metal objects in walls.
  • electrodes 14, 30, 44, 46, 52 and 60 may be formed as wire coils, although other forms may also be used.
  • figure 10 shows the electrodes 44, 46 of the detector of figure 6 as being so constituted by elongated wire coils LI, L2 respec- tively. Coil Ll is connected at one end to the input to gate A3 and at the other end to negative supply line 34 via a capacitor C12.
  • Coil L2 is connected at one end to the input of gate A4 and- t the other end to negative supply line 34 via capacitor C13.
  • the coils Ll, L2 are preferably arranged coaxially with coil Ll being within coil L2.
  • Ll may be formed of about 50 turns of wire of thickness suffi ⁇ cient to maintain rigidity so as to form a helix of about 2cm diameter.
  • Coil 46 may for example be formed of similar wire, defining a helix of about 3cm diameter and comprised of about ten turns.
  • the tran ⁇ sistors TRl, TR2, TR3 and TR4 are NPN types, these transistors could alternatively be replaced by suit ⁇ able PNP types such as type 2N3906.

Abstract

Détecteur d'objets permettant de détecter des montants à l'intérieur de parois, muni d'un oscillateur (G1, R1, R2, D1, C1) avec un condensateur (C1) qui est chargé et déchargé de manière cyclique. Une électrode (14) est couplée à l'oscillateur et agencée pour produire un champ électrique tout autour. Ce champ est partiellement déchargé lorsqu'un objet se trouve à proximité de l'électrode pour faire varier le signal de sortie de l'oscillateur afin de permettre la détection de l'objet. Un mode spécifique de réalisation comprend deux oscillateurs, dont les signaux de sortie sont influencés de manière variable par l'introduction de l'objet à proximité de l'électrode.
EP19840904069 1983-11-09 1984-11-08 Detecteur d'objets. Withdrawn EP0165256A4 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AU2303/83 1983-11-09
AUPG230383 1983-11-09

Publications (2)

Publication Number Publication Date
EP0165256A1 EP0165256A1 (fr) 1985-12-27
EP0165256A4 true EP0165256A4 (fr) 1986-09-24

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EP19840904069 Withdrawn EP0165256A4 (fr) 1983-11-09 1984-11-08 Detecteur d'objets.

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EP (1) EP0165256A4 (fr)
JP (1) JPS61500379A (fr)
CA (1) CA1229673A (fr)
GB (1) GB2160661B (fr)

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Publication number Priority date Publication date Assignee Title
FR2853058B1 (fr) * 2003-03-27 2005-05-13 Valeo Securite Habitacle Detection de presence par capteur capacitif

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US4099118A (en) * 1977-07-25 1978-07-04 Franklin Robert C Electronic wall stud sensor

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DE2027408C3 (de) * 1970-06-04 1974-12-12 8728 Hassfurt Voll Christl Metallsuchgerät in einem handlichen, tragbaren Gehäuse zur Auffindung von verdeckten metallischen Einschlüssen
SU748319A1 (ru) * 1978-06-02 1980-07-15 Предприятие П/Я Р-6303 Импульсный вихретоковый металлоискатель

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US4099118A (en) * 1977-07-25 1978-07-04 Franklin Robert C Electronic wall stud sensor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of WO8502268A1 *

Also Published As

Publication number Publication date
GB2160661A (en) 1985-12-24
EP0165256A1 (fr) 1985-12-27
CA1229673A (fr) 1987-11-24
GB2160661B (en) 1987-02-11
JPS61500379A (ja) 1986-03-06
GB8515989D0 (en) 1985-07-31

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