FIELD OF THE INVENTION:
[0001] The present invention relates to a system and method for a proximity detector.
More particularly, the present invention relates to a system and method for proximity metal
detection using inductive technology and intelligent feedback temperature control.

BACKGROUND OF THE INVENTION:
[0002] Proximity metal detector may be a device used for detection of ferrous and non-
ferrous metals that may not be readily apparent. Metal detectors may find their applicability in a
vast range of industries, varying from food industry to automobile industries and like. These
metal detectors generally use an oscillator to detect any metal in the close proximity of the metal
detector. The oscillator may be configured to produce an alternating current, which may then be
allowed to pass through a coil producing the alternating magnetic field. The magnetic field
produced by the coil may thus induce eddy current within the metal lying in close proximity of
the metal detector, which may in turn lead the metal to produce its own magnetic field. This
change in the magnetic field produced by the metal lying in the close vicinity of the metal
detector may be sensed using another coil. The above principle used for the proximity metal
detection stands true for both ferrous and non-ferrous metals.
[0003] In conventional technology, the metal detectors used in industries may employ
different principles of electronics, such as capacitive, inductive, photo electric, hall-effect and
like. An inductive type proximity sensor works on the principle of eddy current losses, as the
object comes in vicinity of sensing, eddy current losses are generated in the target and amplitude
of oscillation may be reduced. This change is amplitude may than be detected and monitored.
Inductive type metal detectors used in the conventional technology may employ oscillator
circuits that may be critical to build and complex to operate. Using such oscillator in the metal
detectors may lead to reduced efficiency of the device The metal detector disclosed in the
conventional technology so far show eddy current losses in the coil. The eddy current losses in
the coil may lead to reduced efficiency of the device. Further, with such type of oscillators it
may be difficult to design current source and balance oscillator circuit with respect to the eddy
current losses in the coil. Such metal detectors fail to respond, where a wide range of 3

temperature compensation may be required. That means such metal detectors may find
applicability in industries where the temperature range may be a small and limited.
[0004] Thus there exists a need of a metal detection assembly including in circuitry an
effective and easy to operate oscillator. Also, there exists a need of a system with built in
temperature compensation for suitable output in wide ranges. Further the technology may
demand for customized sensor output as per the customer requirement.

SUMMARY OF THE INVENTION:
[0005] In an aspect, the present invention relates to a proximity detector. The proximity
detector comprises a sensing unit, wherein the sensing unit further comprises an oscillator unit
configured to detect a target in proximity via oscillatory electric signals. The sensing unit is
further composed of a temperature compensation feedback unit, wherein the temperature
compensation feedback unit is configured to detect operating temperature for the detecting unit.
The proximity detector further comprising an intelligent logic control unit configured to adjust
detection threshold of the sensing unit according to operating temperature.
[0006] In another aspect, the sensing unit is inductive type.
[0007] In yet another aspect, the intelligent logic control unit is configured to take
feedback from the temperature compensation feedback unit in order to adjust detection threshold.
[0008] In still another aspect, the sensing unit gives stable output in wild temperature
range.
[0009] In yet another aspect, the detecting unit is less sensitive to noise environment.

OBJECTS OF THE INVENTION:
[0010] The main object, of the present invention is to provide a proximity metal detector
using an oscillator that is easy to build and operate. 4

[0011] Another main object, of the present invention is to provide a proximity metal
detector with an output that is easily diagnosed as per the requirement.
[0012] Yet another object, of the present invention is to provide a stable operation of the
proximity metal detector upto a range of 125 C of temperature using intelligent feedback.
[0013] Still another object, of the present invention is to provide a proximity metal
detector that is less sensitive to noise environment.

BRIEF DESCRIPTION OF DRAWINGS:
[0014] The features of the present invention are set forth with particularity in the
appended claims. The invention itself, together with further features and attended advantages,
will become apparent from consideration of the following detailed description, taken in
conjunction with the accompanying drawings. One or more embodiments of the present
invention are now described, by way of example only, with reference to the accompanied
drawings wherein like reference numerals represent like elements and in which:
[0015] Fig. 1 illustrates a proximity metal detector by way of a block diagram, according
to various embodiments.
[0016] Fig. 2a illustrates sensing unit and feedback mechanism for a proximity metal
detector by way of a block diagram, according to various embodiments.
[0017] Fig. 2b illustrates a constant frequency waveform graph for the proximity metal
detector with damped and un-damped oscillations, according to various embodiments.
[0018] Fig 2c illustrates a camp circuit for the proximity metal detector, according to
various embodiments.
[0019] Fig 2d illustrates a constant frequency waveform graph for the proximity metal
detector with negative half clamped over positive half, according to various embodiments.
[0020] Fig. 3 illustrates oscillator unit in combination with a temperature compensation
unit, according to various embodiments. 5

[0021] Fig. 4 illustrates inductive proximity sensor and temperature sensing circuitry
connected to the controller, according to various embodiments.

DETAILED DESCRIPTION:
[0022] While the invention is susceptible to various modifications and alternative forms,
specific embodiment thereof has been shown by way of example in the drawings and will be
described in detail below. It should be understood, however that it is not intended to limit the
invention to the particular forms disclosed, but on the contrary, the invention is to cover all
modifications, equivalents, and alternative falling within the spirit and the scope of the invention
as defined by the appended claims.
[0023] Before describing in detail embodiments it may be observed that the novelty and
inventive step that are in accordance with the present invention reside in the proximity metal
detector accordingly, the drawings are showing only those specific details that are pertinent to
understanding the embodiments of the present invention so as not to obscure the disclosure with
details that will be readily apparent to those of ordinary skill in the art having benefit of the
description herein.

[0024] The terms “comprises”, “comprising”, or any other variations thereof, are
intended to cover a non-exclusive inclusion, such that a setup, device that comprises a list of
components does not include only those components but may include other components not
expressly listed or inherent to such setup or device. In other words, one or more elements in a
system or apparatus proceeded by “comprises… a” does not, without more constraints, preclude
the existence of other elements or additional elements in the system or apparatus.

[0025] Figure 1 illustrates a proximity metal detector 100 by way of a block diagram.
The proximity metal detector 100 comprises an oscillator unit 102, wherein the oscillator unit
102 may be configured to detect a target 114 lying in close proximity. The oscillator unit 102
may detect the target 114 via change of amplitude of oscillatory electric signals generated in
response to the target 114 detected. The output of the oscillator unit 102 may be fed to an
amplitude shifting unit 104. The amplitude shifting unit 104 may be configured to shift the 6

amplitude of the output signal of the oscillator unit 102. The metal detector 100 may further
include a diode 106 configured to transfer output signal of the amplitude shifting unit 104 to an
intelligent control unit 110. The diode 106 may be a fixed biased for constant current using the
current source. The output from the diode 106 may be fed to an intelligent control unit 110,
wherein the intelligent control unit 110 may be configured to adjust detection threshold of a
sensing unit 116 according to the operating temperature of the metal detector 100. In an
embodiment, the sensing unit 116 may include a combination of the oscillator unit 102 and a
temperature compensation feedback unit 108. The temperature compensation feedback unit 108
may be configured to detect operating temperature for the metal detector 100. Finally, the output
of the metal detector 100 may be examined through the output stage 112 attached to the
intelligent control unit 110.
[0026] The sensing unit 116 of the metal detector 100 may be of inductive type, wherein
the principle of operation of the inductive type sensors may be based on eddy current losses. In
an embodiment, the oscillator unit 102 of the sensing unit 116 may comprise an inductor-
capacitor circuit as shown in figure 1. In an example, the inductor-capacitor circuit of oscillator
unit 102 may also be defined as frequency tuning circuit of oscillator unit 102. Specifically in an
embodiment, the inductor-capacitor circuit, of the oscillator unit 102 may be configured to
generate eddy current losses in the target 114 whenever the target 114 comes in close vicinity to
the metal detector 100. On the introduction of eddy current losses in the target 114, the
amplitude of oscillating electric signals from the oscillating unit 102 may get damped. The
damped oscillating signals from the oscillator unit 102 may than be passed to the amplitude
shifting unit 104, than through the diode 106 and finally to the intelligent control unit 110. The
damping of oscillating electric signals from the oscillator unit 102 may result in fall of output
voltage below threshold. The intelligent control unit 110 may than be configured to compare the
change in voltage level with respect to set threshold to trigger the change in output.
[0027] The sensing unit 116 of the metal detector 100 further comprises the temperature
compensation feedback unit 108. The temperature compensation feedback unit 108 may be
configured to detect operating temperature of the metal detector 100. In one way, the
temperature compensation feedback unit 108 may be configured to compensate for the deviation
in operating temperature of the metal detector 100. In another way the temperature 7

compensation feedback unit 108 may provide a feedback voltage to the intelligent control unit
110. The intelligent control unit 110 may thus adjust its target 114 detection threshold with the
help of software algorithm. The metal detector 100 being a closed loop system which may avoid
temperature errors during target detection. Specifically in an embodiment the oscillating unit
102 of the metal detector 100 may be configured to send un-damped oscillating electric signals
ahead to amplitude shift unit 104 and so on in case when no metal is detected.
[0028] Figure 2a discloses a sensing and control assembly 200 for a metal detector. The
sensing and control assembly 200 may include a power supply unit 202. Power supply unit 202
may be configured to power the metal detector 100 as shown in figure 100, with a constant
voltage, irrespective of the variations in the supply voltage. The metal detector 100 may be
supplied with a constant voltage in order to protect against voltage fluctuations, further it may be
configured to provide stable and error free signal for analog to digital conversion. In an
embodiment, the power supply unit 202 may be configured to supply power to the sensing unit
204. Specifically in an embodiment, the sensing unit 206 may be powered with a constant
voltage of 12 V. The sensing unit 204 may be configured to include a temperature compensation
feedback unit 206 and an oscillator unit 208. The oscillator unit 208 may be colpitts oscillator,
the said oscillator unit 208 may generate continuous self-oscillations. The oscillation frequency
of the oscillator 208 may be tuned by a frequency tuning circuitry (not shown in the figure)
consisting of capacitor network maintain constant inductance. The frequency of oscillations in
such an oscillator 208 may be derived by way of general equation;
F=1/2√LC
The amplitude of oscillations may be defined by the supply voltage. In an example, the use of
constant voltage may be recommended in order to ensure error free signal conditioning
irrespective of the battery voltage variation.
[0029] The sensing unit 204 may further include the temperature feedback control unit
206, wherein the temperature feedback control unit 206 may be connected to the oscillator unit
208. The temperature feedback control unit 206 may be connected to the oscillator unit 208 in
order to detect the operating temperature of the metal detector 100. The oscillator unit 208 may
be configured to generate oscillating signals of constant frequency as shown in figure 2 (b). 8

Figure 2(b) clearly indicates that the oscillating signals generated by the oscillator unit 208 are
sinusoidal signals of constant frequency. To increase the sensing voltage potential level of the
sensing unit 204, a clamping circuit 214 as represented in figure 2(c) may be utilized. The
clamping circuit 214 may be a combination of a capacitor 216 connected to a diode 218, wherein
the diode 218 may conduct electric current in only one direction and prevents the signal
exceeding the reference value and the capacitor 216 so attached may provide a DC offset from
the stored charge. The clamping circuit 214 may clamps the negative half cycle of the waveform
to the positive half cycle, and the resultant may be a waveform as depicted in figure 2(d), with
increase sensing voltage potential level.
[0030] The assembly 200 further includes an intelligent control unit 210. The intelligent
control unit 210 may be connected to oscillator unit 208 and temperature compensation feedback
unit 206, further the intelligent control unit 210 may be supplied with a constant 12 V voltage
supply from the power source 202. An output stage 212 may be in connection with the
intelligent control unit 210, wherein the output 212 may be provided with rigid electrical
protections as per automation and industrial standards, compatible with both push and pull type
loads.
[0031] Figure 3 illustrates an assembly 300 comprising an oscillator unit 302 and a
temperature compensation unit 310. In an embodiment the assembly 300 may represent sensing
unit 300. The temperature compensation unit 310 may be connected to the oscillator unit 302,
wherein the oscillator unit 302 may be configured to act as proximity sensor. The temperature
compensation unit 310 may comprise a diode 306, wherein the diode 306 may act as temperature
sensor. The diode 306 may be connected to a current source 304 used for biasing the diode 306
and an ADC 308 in order to monitor the diodes forward voltage at varying temperature.
[0032] Figure 4 illustrates an assembly 400 comprising an inductive proximity sensor
402, a temperature sensing circuitry 410 and a controller unit 404. The controller unit 404 may
further include a comparator 406 and a control unit 408. The comparator 406 may be configured
to receive a sensor signal from the inductive proximity sensor 402 at one end, wherein adjusted
threshold signal at the other end. The comparator 406 compares the two signals and sends the
resultant signal to the control unit 408, wherein the output of the control unit represents the
desired output. 9

[0033] Although the present invention has been described in considerable detail with
reference to figures and certain preferred embodiments thereof, other versions are possible.
Therefore, the spirit and scope of the present invention should not be limited to the description of
the preferred versions contained herein.

















10

WE CLAIM:
1. A proximity detector comprising:
a sensing unit, the sensing unit comprising:
an oscillator unit configured to detect a target in proximity via oscillatory
electric signals,
a temperature compensation feedback unit configured to detect operating
temperature for the detector; and
an intelligent control unit configured to adjust detection threshold of the sensing
unit according to operating temperature.
2. The proximity detector as claimed in claim 1, wherein the sensing unit is inductive type.
3. The proximity detector as claimed in claim 1, wherein the intelligent logic control unit is
configured to take feedback from the temperature compensation feedback unit in order to
adjust detection threshold.
4. The proximity detector as claimed in claim 1, wherein the sensing unit gives stable output
in wide temperature range.
5. The proximity detector of claim 1 is less sensitive to noise environment.