Inertia Sensor Detecting Materials using Electromagnetic Signals

ERIETTA VASILAKI

Department of Electronics Engineering

Hellenic Mediterranean University

Chania, GREECE

IRAKLIS RIGAKIS

Department of Electrical and

Electronics Engineering

University of West Attica

Atghens, GREECE

THEODORE PAPADOULIS

Department of Electronic Engineering

Hellenic Mediterranean University

Chania, GREECE

ALEXIOS STARIDAS

Department of Electrical and Computer

Engineering

Hellenic Mediterranean University

Heraklion, GREECE

ANTONIA PSAROUDAKI

Depa rtment of Nutrition and Dietetics

Sciences

Hellenic Mediterranean University

Sitia, GREECE

LAMBROS FRANTZESKAKIS

Department of Electronic Engineering

Hellenic Mediterranean University

Chania, GREECE

ZISIS MAKRIS

Department of Electronics Engineering

Hellenic Mediterranean University

Chania, GREECE

DIAMANTO LAZARI

Department of Pharmacognosy-

Pharmacology

Aristotle University of Thessaloniki,

Thessaloniki, GREECE

EMMANUEL ANTONIDAKIS

Electronics Engineering

Hellenic Mediterranean University

Chania, GREECE

Abstract: There are many commercial sensors that use inertia systems and others that use electromagnetic systems. Until now, none of the

existing sensors combines a circular inertia movement with the simultaneous transmission of electromagnetic radiation in the band of very

low (VLF) and ultra low (ULF) frequencies. The aim of this paper is to show the design of such a sensor, that contains an electromagnetic

signal generator and to observe and monitor its movement on a free rotating inclined platform. An accurate positioning and monitoring

system is used in order to measure the velocity and acceleration at every position on its movement. It is a novel system that is already in use

in material identification and localization. It is indubitably working and exports excellent results, although we are not still familiar with the

laws of physics that determine the specific phenomenon. Until this point the sensor is used to identify only a limited number of materials.

In the future it would be ideal to use it for more materials, find their frequencies and create a library that contains many materials and

different kind of substances.

Keywords: electromagnetic field, sensor, frequency, time, acceleration, gray code, inertia system

Received: June 9, 2021. Revised: June 12, 2022. Accepted: July 15, 2022. Published: August 3, 2022.

1. Introduction

We live in a world that almost everything is controlled

and sensed by sensors. The importance of the sensors for

mankind is obvious. The first sensors appeared with the

existence of the living creatures and they are their organs.

Eyes and ears are typical examples. The first detect

electromagnetic radiation, while the second detect sound.

Later, man realized that he needed measuring instruments in

order to solve everyday life problems, so he started creating

sensors. The first sensors were mechanical, such as a

thermometer. The rise of electricity led to the construction of

electrical sensors. The evolution of semiconductors had as

result the creation of new advanced sensors and digital

measuring devices.

A sensor is a devise that detects a physical quantity and

produces a countable signal. Usually modern sensors are

devices that detect an external signal and respond to it with

an electrical signal and they ensure that measurement data

are transmitted faster and more accurate.

One of the classifications of sensors, is active-passive.

The next classification is based on the kind of the materials

the sensor detects, for example Electric, Biological,

Chemical, Radioactive, etc. Another type of sensors are

Analog and Digital Sensors. The final classification is based

on the phenomenon that occurs, i.e. Photoelectric,

Thermoelectric, Electrochemical, Electromagnetic, etc.

Some types of sensors are accelerometer, IR sensor,

temperature sensor, pressure sensor, frequency sensor,

gyroscope and many others. There are inertia sensors, such

as gyroscope, and there are electromagnetic sensors such as

accelerometer.

A unique sensor that combines the movement of an

inertia system with the transmission of very low (VLF) and

ultra low (ULF) electromagnetic frequencies is described

below.[1], [2].

2. System and Circumferential

(Apparatus)

An inertia system [3], [4] is on a circular motion path.

The inertia system has a telescopic antenna and circuitry to

bring signal to the antenna. Under some circumstances a

force is exerted on the antenna of the inertia system that

alters its expected motion. It has been observed that this

force appears when specific material is located towards the

direction pointed by the antenna. The antenna has emitted

appropriate signal for the specific material.

This paper shows how the inertia system is designed and

how it is operated. Then the Electronic Circuitry that is

generating the signals on the antenna will be analyzed. Also,

the circuitry on the inertia system, used to detect the force

that is exerted on the inertia system at the presence of the

material, is described. The method how the appropriate

signals are found for each specific material is presented.

Some parameters that affect the force will be analyzed

WSEAS TRANSACTIONS on SYSTEMS

DOI: 10.37394/23202.2022.21.15

Erietta Vasilaki, Iraklis Rigakis,

Theodore Papadoulis, Alexios Staridas,

Antonia Psaroudaki, Lambros Frantzeskakis,

Zisis Makris, Diamanto Lazari, Emmanuel Antonidakis

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2.1. Inertia System Design and Operation

An inertia systems on circular motion is designed and

operated that consists of four Units: (1) An Electronic Box

containing: (a) a Signal Generator System, producing

electromagnetic signals, and (b) a force detection circuitry,

(2) a Telescopic Antenna where the signals are emitted from,

(3) a perpendicular Axial fixed underneath the generator box

around which the circular motion will take place and (4) a

Base through which the inertia system is able to rotate

around its Axial. Fig.1 (a), (b) shows the System. By “x” is

marked the Center of Mass of Units 1&2.

Fig.1 (a) The inertia system with its four units: Electronic Box, Telescopic

Antenna, Perpendicular Axial and Base[5]

Fig.1 (b) The outline figure of the inertia system

The inertia system consists of 2 pieces: Piece 1 is the

Electronics box with the antenna attached on it, and the

perpendicular axial fixed underneath the generator box.

Piece 2 is the cylindrical base with can hold the generator

and antenna. Pieces 1 and 2 of the inertia systems can be

viewed in Fig.2.

Fig.2[5]

The Base is tilted from vertical position. The system

resting position is as shown on Fig.3.

Fig.3 Resting position of the system

An initial position is given to the system. Then the

system will start its movement. In the following Fig.4, the

series of frames from 1-11 show the movement followed by

the inertia system. Frame 1 shows the original position which

is the initial condition of the system. The System is brought

to initial position, Frame 1, and it is released to start its

motion. Frames 1-11 show one oscillation.

Fig.4

The weight W of Units 1&2, of Piece 1, is causing a

torque that makes the inertia system to rotate on a damped

oscillation around its axial. The Weight component on the

direction of movement is Wt(t). Another force when the

movement starts, is the friction Tf. The Inertia system

follows a movement based on the application of these forces.

The motion is described by angular velocity ω(t).

Fig. 5 Diagram that shows the forces on the system

On the antenna of the inertia system a signal is applied by

the Generator Circuitry. Different signals may be applied on

the antenna according to the type of material that will need to

be detected and will be affecting the movement. When a

material is located in a direction headed by the antenna, only

then an extra force F is excreted on the antenna of the inertia

system. This force F is opposing the movement. Fig. 5 shows

the forces on the system.

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Erietta Vasilaki, Iraklis Rigakis,

Theodore Papadoulis, Alexios Staridas,

Antonia Psaroudaki, Lambros Frantzeskakis,

Zisis Makris, Diamanto Lazari, Emmanuel Antonidakis

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Then, total torque is calculated by the following

equation:

 () = 1 

󰇛󰇜 2 

󰇛󰇜 3 ()

Fig.6 shows the forces exerted on the inertia system that

affect its motion and the angular velocity ω(t) that the system

is rotating around the axial. If ω(t) becomes zero before the

end of the expected motion (frame 11) then this suggests the

presence of an extra force exerted on the inertia system. The

angular velocity ω(t) cannot become zero when the system

starts its motion on the downward path (Frame 1-6). This is

because the friction is small and the force F(t) is small too,

compared to the weight.

Fig.6

On the other hand, on the upwards path (Frame 7-11), all

the forces act in the same direction opposing the movement

ω(t), as shown in Fig.7. If the system stops before Frame 11

this suggests the presence of an extra force. The larger the

force F the sooner the movement will stop. The following

video shows the movement of the inertia system.

https://youtu.be/tcGJNDHG6AI

Fig.7

2.2 Electronic Circuitry

In this section, the electronics in the box of the inertia

system are analyzed. The signal generator and the force

detection circuitry have the electronics schematic diagram in

the Fig.8 bellow.

2.2.1 The Signal Generator circuitry

The Micro Computer Unit MCU1 processor receives

commands from the user through a keyboard while the user

can see and select from the display. In the MCU1 memory,

information is stored about the signals that need to be

produced for the different materials to be detected. The

frequencies of the signals are from 1-100KHz. The signal

amplitude is from 1-30V pp. A 3.3V lithium battery of 2700

mAh is used and powers up the system for about 10 hours.

The system display remains powered on only while the user

is changing the settings through the keyboard, so no

considerable amount of power is consumed on the display.

After MCU1 receives command from the user for the type of

material to be searched, the MCU1 gives commands to the

DDS to produce the signal for the selected material, with

great accuracy of 0.001Hz. The output of the DDS is

amplified and then put on the antenna. The user can select

the amplitude of the output signal.

2.2.2 The Force detection circuitry

A vertical-axis accelerometer is used as a vibration sensor. It

has been observed that: when the Force F is exerted on the

system, as a result of the presence of material in the direction

headed by the antenna, the inertia system mechanically

vibrates with characteristic frequency. The signal of the

accelerometer is conditioned and then entered into MCU2 to

be processed. In the MCU2 an FFT algorithm is running to

calculate the vibration frequencies.

MCU 1

DDS

POWER

SUPPLY

Verical -AXIS

ACCELERATION

SENSOR

ELECTRONIC

COMPASS

SIGNAL

CONDITIONER

OUTPUT

AMPLIFIER

LCD

DISPLAY

KEYBOARD

MCU 2

+3.3V

+5V

+12V

-12V

GND

BATTERY

BUZZER

LED INDICATOR

Fig.8 Electronics schematic diagram for the signal generator and the force

detection circuitry

Also, not shown in the diagram of Fig.8, a wireless

communication module can be included in the System. The

wireless module transmits the angle of heading to a nearby

computer.

Fig.9 is a picture taken from an oscilloscope. On the

upper part the signal of the accelerometer in time is showing.

On the right side of the signal, it can be seen signal with

higher amplitude. This is when the antenna heading passes

in-front of the direction of the material.

On the bottom part of Fig. 9, the FFT (Fast Fourier

Transform) of the above signal is showing the mechanical

vibration frequencies of the antenna, and the amplitude of

every frequency. The scale is 2Hz (1/500ms) per division of

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Erietta Vasilaki, Iraklis Rigakis,

Theodore Papadoulis, Alexios Staridas,

Antonia Psaroudaki, Lambros Frantzeskakis,

Zisis Makris, Diamanto Lazari, Emmanuel Antonidakis

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the oscilloscope. We notice the higher peak is at the 6th

division on the screen of the oscilloscope, which represents

12Hz. This is the characteristic mechanical vibration

frequency of the inertia system when the force F is applied.

This designates the presence of the material.

Fig.9 Picture taken from an oscilloscope [5]

2.3. Angular Positioning System

The angle of the sensor is calculated by using Gray code

[7]–[11] (reflected binary code). The Gray code is a binary

enumerating system that consecutive numbers differ by just

one bit.

An example is shown below.

Decimal

Value

Binary

Code

Gray

Code

0000

0001

0010

0011

0010

0100

0110

0101

0111

0110

0101

0111

0100

1000

1100

Table 1. Examples of Binary and Gray code [6]

A 9-bit Gray code is used in order to have 29=512

combinations.

A cycle is 360°, so the accuracy of each step in the code

is:

360°/512 = 0,703125° ≈ 0,7°

That means that the minimum difference of the calculated

angles is about 0,7°.

The disk that has the Gray code printed on it, is attached

to an electronic reader communicating with a raspberry-pi

computer board, that sends the readings of the angles

wireless to a computer.

Fig.10 Vertical representation of the 9-bit Gray code

Fig.11 Electronic reader

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Erietta Vasilaki, Iraklis Rigakis,

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Zisis Makris, Diamanto Lazari, Emmanuel Antonidakis

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Fig.12 Disk of Gray code attached to raspberry computer and wireless

connection with laptop.

Fig.13 Complete inertia system with sensor, gray code and connection with

raspberry and laptop.

3. Experimental procedure

The experimental procedure is described below.

The electromagnetic sensor that is described in section II

and a chemical substance, such as phenol, will be used for

this paper.

The sensor is placed in a fixed position where it can

move freely around its axis in a circular movement. The

angle of the rotation of the sensor begins at 50° and stops at

about 300°. Phenol is placed in a prearranged position

opposite sensor. The distance between the sensor and the

phenol is 5m. The quantity of the phenol in use is 1 kg and it

is placed at 184.3°

Phenol, also called carbolic acid, is an aromatic organic

substance with the chemical formula C6H5OH [12]–[16]. It is

a very simple compound that responds to the frequency of

3696,8 Hz. Its formula is shown below:

The frequency of the phenol is adjusted to the sensor.

The sensor is activated and starts its movement. When the

antenna of the sensor is aligned with the phenol, a

deceleration on the sensor can be observed. This deceleration

is recorded by a raspberry-pi computer board and it is sent to

a laptop. A diagram of deceleration versus angle is made

(Fig.13).

This diagram shows the force that is applied on the

antenna of the sensor, in the form of deceleration. The sensor

receives decelerations that vary in intensity throughout its

total movement. When the antenna of the sensor passes in

front of the material in use, a force is applied on the antenna

and the deceleration increases significantly.

4. Conclusion

Every substance has a certain frequency that is the

corresponding frequency for each material. When the sensor

emits this frequency, the material interacts with the sensor

and applies a force on the antenna of the sensor.

According to Fig.13 it is shown that when the sensor

points at the direction of the phenol, while transmitting its

corresponding frequency, a deceleration on the antenna is

observed. More specific the deceleration is maximum among

the other decelerations that are being recorded. The

decelerations that appear in the angles that do not contain

any substance, could be considered as noise. That means that

these decelerations are just random due to mechanical factors

of the movement.

It has been observed that when the sensor transmits the

frequency of a substance and gets aligned with the certain

substance, the recorded deceleration is always the maximum.

So, if such a diagram is available then we can say by

certainty that in the angle where the maximum deceleration

is observed there is the material in study.

This method is already in use for identification of

substances. If the frequency of a substance is known, then

when the sensor emits the certain frequency it can identify

every material that contains the certain substance. Also, it

can find the place where the substance is as long as it is

placed in a distance less than 5m.

The sensor could be used as a new method of detection of

substances. A library can be created with the frequencies of

substances. Then this could be a novel method for

identification of substances with a short-range non-contact

sensor [17]-[21]. It is a fast, relatively cheap method that

does not deform the samples in study. It is easy in use and

very precise. It can identify a part of a molecular structure, or

the whole chemical substance, as well as the material in

general.

More research needs to be done on the physics about the

force applied on the antenna. Also, more work needs to be

WSEAS TRANSACTIONS on SYSTEMS

DOI: 10.37394/23202.2022.21.15

Erietta Vasilaki, Iraklis Rigakis,

Theodore Papadoulis, Alexios Staridas,

Antonia Psaroudaki, Lambros Frantzeskakis,

Zisis Makris, Diamanto Lazari, Emmanuel Antonidakis

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Fig.13 Graph of acceleration versus angle for Phenol

done correlating the detection frequency with the molecular

structure.

Summarizing the main points of the paper:

 Every material reacts to a certain frequency, its

corresponding frequency

 When the sensor emits the corresponding

frequency of a material near it, a force is applied

on the antenna of the sensor and a deceleration

is recorded.

 This deceleration is maximum when the antenna

passes in front of the material.

 It is a novel method of identification of

substances and materials.

 It could be used in localization of materials.

 This method doesn’t affect the substances in

use. It doesn’t destroy them and in most of the

cases it is not necessary for the substances to be

taken out of their packages in order to be

studied.

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Erietta Vasilaki, Iraklis Rigakis,

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Antonia Psaroudaki, Lambros Frantzeskakis,

Zisis Makris, Diamanto Lazari, Emmanuel Antonidakis

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DOI: 10.37394/23202.2022.21.15

Erietta Vasilaki, Iraklis Rigakis,

Theodore Papadoulis, Alexios Staridas,

Antonia Psaroudaki, Lambros Frantzeskakis,

Zisis Makris, Diamanto Lazari, Emmanuel Antonidakis

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