Yarmouk University

Hijjawi Faculty For Engineering Technology

Electronics Engineering Department

Comatic Jordan Company

Al-Ameer Rashid Bin AL Hassan

Hospital

Prepared By:

Emad Mohammad Adnan Otoum

(2010972101)

Supervised By:

Eng. Ma'mon Al-Tantawi

2014

Acknowledgements I would give my thanks for everyone who assisted me in preparing my field training report.

I am greatly indebted to Eng. Ma'mon Al-Tantawi for his continues supervision, and guidance during training duration.

Also deep of thanks for technical staff in Prince Rashed Bin AL-Hassan hospital and Comatec Jo. for their collaboration and patience to give me their experiences especially in device maintenance. To my parents , who stood beside me throughout my life , and to whom I will be indebted forever, also to my brothers and sisters for their understanding , patience and encouragement that have been given to me.

Abstract

This report was prepared for the graduation requirement of our engineering

faculty. Each student has a practical training period for about six month in one

of the relied institution from our college. The period training is the most

important period in our studying plan, it forms the character of the engineer so

we must improve our skills and knowledge in field training.

My first training period in extends from 15/1 to 1/4/2014 in comatec Jordan in

amman and my second training period in extends from 2/4 to 2/8/2014 in

Prince Rashid Bin Al-Hassan Military hospital.

About Comatec

Comatec Group is one of the leading companies in Telecom deployment and

Civil works that started 1989 in Jordan. Today the company operate in 6

countries (Jordan, Lebanon, Cyprus, Egypt, KSA and Malta). Comatec have

two different Telecom segments; namely Telecom Civil work deployment and

Telecom operation. It have more than 300 Telecom professionals with

extensive hands-on Telecom and IT experience in mutli-technologies.

About Princess Rashid Bin Al hassan

Hospital

Figure 1: princess Rashid Ben Al-Hassan Hospital.

Prince Rashid Bin Al-Hassan Hospital (1966) with a capacity of 259 beds, is a

general hospital located in Irbid in the north of Jordan.

It is a teaching hospital for the University of Science and Technology Medical

and Nursing students.

It is a very busy hospital with an occupancy rate of 85%, 22 thousand annual

admissions and almost 6000 operations a year.

Table Of Contents

Table of figure Acknowledgements Abstract About Chapter one: Background Information ....................................................................................... 1

1.1 Introduction ................................................................................................................... 1

1.2 GSM Architecture Overview ........................................................................................... 1

1.2.1 The GSM Mobile Station(MS): .................................................................................... 2

1.2.2 The Basic Station Subsustem ................................................................................... 3

1.2.3 The Network Switching System (NSS) ....................................................................... 5

Chapter Two: Medical Devices And Equipments……………………………………………9

2.1 Basic Type Of Medical Device: .......................................................................................10

2.2 Radiology Or Imaging Group: .........................................................................................11

2.2.1 X-ray Machine ...........................................................................................................12

2.3 MRI (Magnetic Resonance Imaging) ..................................................................................15

2.3.1 The Major Components Of MRI ....................................................................................16

2.4 ICU Equipments ..................................................................................................................18

2.4.1 Patient Monitor ..........................................................................................................18

2.4.2 Blood Pressure .........................................................................................................19

2.4.3 Electrocardiogram (ECG) ..........................................................................................20

2.4.4 Pulse Oximetry (SPO2).............................................................................................21

2.5 Neuro-Electrophysiology Department ..................................................................................24

2.5.1 EEG (Electroncephalogram) .....................................................................................24

2.5.2 ECG (Electrocardiogram) ..........................................................................................18

Chapter Three: Work Shop ............................................................................................................. 34

3.1 Types of Maintenance: ........................................................................................................27

3.1.1 How To Test Some Electroparts ................................................................................28

Conclusion References

Table of figure

Fig 1 : GSM Architecture………………………………………………………………….….………..1

Fig 2: BSS comprises………………………………………………………………………….…….....4

Fig 3: Key elements of the NSS…………………………………………………………….………...6

Figure 4: functional components for instrumentation system……………………….……….11

Figure 5: Radiology or Imaging Example..……………………………………………….……….12

Figure 6: a- X-Ray device…………………………………………………………………………….13

Figure 7: x-ray tube components………………………………………………………..………….14

Figure 8: x-ray tube housing……………………………………………………………..………….16

Figure 9: MRI Scanner with components …………………………………………………..…….18

Figure 10: Block diagram of a patient monitor. ………………………………………………….19

Figure 11: Block diagram of a blood-pressure system…………………………………………21

Figure 12: Block diagram of an ECG system. ……………………………………………………22

Figure 13: Block diagram for pulse oximetry system……………………………………..……23

Figure 14: patients monitor display……………………………………………………………..…26

Figure 15: ECG signal. ………………………………………………………………………….…....29

Figure 16: Color code…………………………………………………………………………………29

Figure 17: capacitor. ……………………………………………………………………………….…30

Figure 18 :Voltage Regulator……………………………………………………………………..…31

Figure 19: Relays…………………………………………………………………………………...….32

1

Chapter one

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1.1 Introduction:

The aim of a GSM (Global system for mobile communication) system is to make best use of the available frequencies to provide:

• Coverage: getting a usable radio signal to all areas in the network

• Capacity: handling the call traffic generated by the subscribers

• Quality: low interference, few calls dropped etc

1.2 GSM Architecture Overview:

Fig 1 : GSM Architecture

A GSM network is made up of three subsystems:

• The Mobile Station (MS).

2

• The Base Station Sub-system (BSS): comprising a BSC and several BTSs.

• The Network and Switching Sub-system (NSS): comprising an MSC and

Associated Registers.

There is several interfaces are defined between different parts of the

system:

• 'A' interface between MSC and BSC.

• 'Abis' interface between BSC and BTS.

• 'Um' air interface between the BTS (antenna) and the MS.

1.2.1 The GSM Mobile Station (MS):

The mobile station consists of:

• Mobile equipment (ME).

• Subscriber identity module (SIM).

The SIM stores permanent and temporary data about the mobile, the

subscriber and the network, is including:

• The International Mobile Subscribers Identity (IMSI).

• MS ISDN number of subscriber.

3

• Authentication key (Ki) and algorithms for authentication check.

The two parts of the mobile station allow a distinction between the actual

equipment and the subscriber who is using it. The IMSI identifies the

subscriber within the GSM network while the MS ISDN is the actual telephone

number a caller (possibly in another network) uses to reach that person.

Security is provided by the use of an authentication key and by the

transmission of a temporary subscriber identity (TMSI) across the radio

interface where possible to avoid using the permanent IMSI identity.

The IMEI may be used to block certain types of equipment from accessing the

network if they are unsuitable and also to check for stolen equipment.

1.2.2 The Base Station Subsystem (BSS) :

The BSS comprises:

• Base Transceiver Station (BTS).

• One or more Base Station Controllers (BSC).

4

Fig 2: BSS comprises

The purpose of the BTS is to provide radio access to the mobile stations and

manage the radio access aspects of the system .The BTS contains of Radio

Transmitter/ Receiver (TRX), Signal processing and control equipment, And

Antennas and feeder cables.

The BSC allocates a channel for the duration of a call and maintains the call;

this includes monitoring quality, controlling the power transmitted by the BTS

or MS, and generating a handover to another cell when required.

The effect of gains and losses in the BTS equipment on the signal power sent

to the antenna is an important consideration for link budget calculations.

Planning BTS

5

positions requires a software tool such as Asset. Acquiring sites and

implementing the plan involves a combination of surveying, engineering and

legal work.

Handover in GSM is always ‘hard’ that is the mobile only ever has a

communication link (traffic channel) open with one base station at one time.

This is true of any system with multiple frequencies, since the mobile must

retune at the handover. Single frequency systems (such as CDMA) may use

soft handover.

The quality and power level of the radio link compared with that available from

neighboring cells are important inputs to the handover decision made by the

BSC.

Base stations are linked to the parent BSC in one of several standard network

topologies. The actual physical link may be microwave, optical fiber or cable.

Planning of these links may be done using a tool such as Connect.

1.2.3 The Network Switching System (NSS):

Key elements of the NSS:

• Mobile Switching Centre (MSC) with Visitor Location Register (VLR).

• Home Location Register (HLR) with Authentication Centre (AuC).

6

• Equipment Identity Register (EIR).

• Gateway MSC (GMSC).

Fig 3: Key elements of the NSS

1.2.3.1 Mobile Switching Centre (MSC):

The functions of the MSC is Switching calls, controlling calls and logging calls

, Interface with PSTN, ISDN, PSPDN , Mobility management over the radio

network and other networks , Radio Resource management - handovers

between BSCs , and Billing Information .

Visitor Location Register (VLR):

Each MSC has a VLR and the VLR stores data temporarily for mobiles served

by the

MSC,

the Information stored includes:

• IMSI

• Mobile Station ISDN Number

7

• Mobile Station Roaming Number

• Temporary Mobile Station Identity

• Local Mobile Station Identity

• The location area where the mobile station has been registered

• Supplementary service parameters

Notice that the VLR stores the current Location Area of the subscriber, while

the HLR stores the MSC/VLR they are currently under. This information is

used to page the subscriber when they have an incoming call.

1.2.3.2 Home Location Register (HLR):

The HLR Stores details of all subscribers in the network, such as:

• Subscription information.

• Location information: mobile station roaming number, VLR, MSC.

• International Mobile Subscriber Identity (IMSI).

• MS ISDN number.

• Tele-service and bearer service subscription information.

• Service restrictions.

• Supplementary services.

8

Together with the AuC, the HLR checks the validity and service profile of

subscribers.

HLR Implementation:

There is one HLR in a network, May be split regionally, And he Stores details

of several thousand subscribers, he Stand alone computer - no switching

capabilities, and May be located anywhere on the SS7 network, and he

Combined with AuC.

1.2.3.3 Equipment Identity Register (EIR)

The EIR is a database that stores a unique International Mobile Equipment

Identity (IMEI) number for each item of mobile equipment. And controls

access to the network by returning the status of a mobile in response to an

IMEI query.

The Possible status levels are:

• White-listed: The terminal is allowed to connect to the network.

• Grey-listed: The terminal is under observation by the network for possible

Problems.

• Black-listed: The terminal has either been reported stolen, or is not a type

Approved for a GSM network. The terminal is not allowed to connect to the

9

Network.

The EIR may optionally be used by the operator to control access to the

network by certain types of equipment or to monitor lost or stolen handsets.

1.2.3.4 Gateway Mobile Switching Centre (GMSC):

A Gateway Mobile Switching Centre (GMSC) is a device which routes traffic

entering a mobile network to the correct destination. And he accesses the

network’s HLR to find the location of the required mobile subscriber, and the

particular MSC can be assigned to act as a GMSC , The operator may decide

to assign more than one GMSC.

10

Chapter Two

2 Medical Devices and

equipments

A medical device is “any item promoted for a medical purpose

that does not rely on chemical action to achieve its intended effect” [Medical Device Amendments (Public law 94-295)]

2.1 There are several basic types of medical

devices: There are several basic categories of medical equipment, and medical

equipment suppliers will often manufacture or provide only one category or a

small range of highly specialized equipment and therapies.

Diagnostic equipment includes medical imaging machines, used to aid

in diagnosis. Examples of these are ultrasound and MRI machines,

PET and CT scanners, and x-ray machines.

Therapeutic equipment includes infusion pumps, medical lasers and

LASIK surgical machines.

Life support equipment is used to maintain a patient's bodily function.

This includes medical ventilators, anaesthetic machines, heart-lung

machines, ECMO, and dialysis machines.

11

2.2 Radiology or imaging group

Figure 4: Radiology or Imaging Example.

Radiology is the branch or specialty of medicine that deals with the study and

application of imaging technology like x-ray and radiation to diagnosing or

treating

This group deals with equipments used for radiology, imaging and image

processing such as:

X-ray machine

CT scanners

ultrasound

MRI machine

For an example I will talk briefly about some of these equipments:

12

Figure 5: a- X-Ray device.

2.2.1 X-ray machine

X-rays are electromagnetic radiation (photon) observed when a beam

of electrons strikes a target with wavelengths, 10pm< <10nm.these photons

travel with the speed of light, c=3*10^8m/s.

The X-ray tube contains anode and cathode, the cathode is connected to

a high voltage generator, this cause the cathode to emit electrons with high

speed and energy, this electrons hits the anode causing it to generate X-rays,

the X-rays generated from the tube are restricted by the aperture in the

collimator, the Al filter removes low-energy X-rays that would not penetrate

the body, scattered secondary radiation is trapped by the grid whereas

primary radiation strikes the screen phosphor, the resulting light exposes the

film, the electron beam current is controlled by adjusting the filament current,

with compensation of filament current for variations of anode current

2.2.2 X-Ray Imaging System Components

The x-ray machine is divided into four major components.

13

• The Tube

Figure 6: x-ray tube components

The X-ray tube contains either a filament or cathode emitter that expels

accelerated electrons and leads them to a metal anode, where current is now

flowing. The electrons that have been emitted toward the anode make up an

electron beam. The beam hits a focal point in the anode, where a small

percentage is converted into X-ray photons. The photons are discharged in all

directions, and once the control unit is put to use, the adjusted currents and

voltage result in a beam of X-rays that is projected onto a visible substance.

An X-ray machine essentially acts as a camera, but without the visible light.

Instead, it uses the X-rays that were produced to expose the film. X-rays use

electromagnetic waves that can break through several layers due to the

energy held inside of them. If the body is being X-rayed, the skin tissue will

not absorb the waves coming from the X-ray but the dense parts of the body

will, which is why bones, tendons and ligaments are able to be examined.

14

Figure 7: x-ray tube housing

2.2.3 X-Ray Tube Housing Purposes Decreases leakage radiation to maximum level of 100 mR/hour at a

distance of 1 meter.

Minimizes exposure dose to patient and radiographer.

Provides mechanical support for x-ray tube .

Oil circulates around x-ray tube

Insulator protecting from electric shock

Dissipates heat

Cooling fan

The Operating Console

The operating console is the control unit, which works to manage the currents,

voltage and timer. The current control has a display that allows adjustment of

the tube current to vary radiation intensity. The voltage control also has a

display, allowing adjustments in the anode to change the energy of radiation.

The timer control determines the duration of the exposure; once the time

stops, no more radiation is being produced.

• The High Voltage Section

The high-voltage power supply uses a transformer to accurately alternate

between the voltage of currents being sent to the emitter or to the anode. The

emitter requires a small voltage supply to produce small currents, while the

anode needs a large voltage supply to keep the speed of the electrons up.

The energy of radiation that is produced is dependent on the high speed of

the electrons.

15

2.2.4 Types of X-Ray Equipment Two types:

Diagnostic

therapeutic

The most problems of x-ray machine in general as follow:

Action Cause Problem

1-check cable connection. 2-inspect with DMM.

1-cable is hewn. 2-there is s/c or o.c.

Hand switches doesn’t give exposure.

Check/replace relay/microswitch

Relay /microswitch Table motions

Calibrate shatters by move potentiometer in a proper position.

Shatters Collimator doesn’t give a proper size.

Replace x-ray tube with a new one

x-ray tube defective x-ray tube

Table 1: The most problems of X-Ray machine.

Note: x-ray is dangerous, it cause cancer diseases and it convert H2O to H2 and OH , OH may be link

with another OH to give H2O2 which is acid and this acid may enter in DNA composition. So in

conventional x-ray there is banking system which consist of three champers (right , left , and middle) e.g

if you want to take image for chest, choose right and left champers, but you cann’t choose middle for

spanned column.

2.3 MRI (Magnetic Resonance Imaging): The MRI scan uses magnetic and radio waves, meaning that there is no

exposure to X-rays or any other damaging forms of radiation.

Magnetic Resonance Imaging (MRI) is primarily a medical imaging technique

most commonly used in radiology to visualize detailed internal structure and

limited function of the body. MRI provides much greater contrast between the

different soft tissues of the body than computed tomography (CT) does,

making it especially useful in brain, heart, muscles, and cancer imaging.

Unlike CT, it uses no ionizing radiation, but uses a powerful magnetic field to

align the nuclear magnetization of (usually) hydrogen atoms in water in the

body.

16

Figure 8: MRI Scanner with components

2.3.1 The Major Components of MRI:

gantry:

Magnet: it is a super conductor, for cooling using Helium (He).

Shim: using it for homogenous magnetic field inside the cylinder.

Radio frequency coil.

Gradient coil (for directions x, y, z) : X: left to right, Y: for deep,

Z: foot to head.

Consol.

Couch.

Room cabinet.

17

2.3.2 How does it work: The patient lies inside a large, cylinder-shaped magnet. Radio waves 10,000

to 30,000 times stronger than the magnetic field of the earth are then sent

through the body. This affects the body's atoms, forcing the nuclei into a

different position. As they move back into place they send out radio waves of

their own. The scanner picks up these signals and a computer turns them into

a picture. These pictures are based on the location and strength of the

incoming signals. Our body consists mainly of water, and water contains

hydrogen atoms. For this reason, the nucleus of the hydrogen atom is often

used to create an MRI scan in the manner described above.

2.3.3 What does an MRI scan show:

Using an MRI scanner, it is possible to make pictures of almost all the tissue

in the body. The tissue that has the least hydrogen atoms (such as bones)

turns out dark, while the tissue that has many hydrogen atoms (such as fatty

tissue) looks much brighter. By changing the timing of the radio wave pulses it

is possible to gain information about the different types of tissues that are

present.

An MRI scan is also able to provide clear pictures of parts of the body that are

surrounded by bone tissue, so the technique is useful when examining the

brain and spinal cord. Because the MRI scan gives very detailed pictures it is

the best technique when it comes to finding tumours (benign or malignant

abnormal growths) in the brain. If a tumour is present the scan can also be

used to find out if it has spread into nearby brain tissue.

The technique also allows us to focus on other details in the brain. For

example, it makes it possible to see the strands of abnormal tissue that occur

if someone has multiple sclerosis and it

is possible to see changes occurring when there is bleeding in the brain, or

find out if the brain tissue has suffered lack of oxygen after a stroke.

The MRI scan is also able to show both the heart and the large blood vessels

in the surrounding tissue. This makes it possible to detect heart defects that

have been building up since birth, as well as changes in the thickness of the

muscles around the heart following a heart attack.

18

2.4 ICU equipments The Intensive Care unit (ICU) department has several types of equipment

that can do some work for of the patients that they have serious cases as an

example for this equipments (Patient Monitor, Defibrillator, Infusion Pump,

Syringe Pump and other equipment).

2.4.1 Patient Monitor It’s a medical device that displays a major body functions. It considers a great

care and observation device to the people whose conditions are unstable and

serious and requiring intensive care after major surgery.

A typical high-end patient monitor system has five basic subsystems: ECG;

pulse oximetry; blood pressure: body temperature; and respiration, Figure .

Typically, the most critical components in each system are the sensor circuits.

Figure 9: Block diagram of a patient monitor.

Each module uses a different sensor and signal-conditioning circuit. For

example, the ECG uses electrodes to measure the electric pulse from the

heart. The pulse oximetry (SpO2) uses a light-emitting diode and light sensor

to measure oxygen content. Blood pressure is typically measured using a

piezo-resistive pressure transducer. For simplicity, several of these biometric

modules may utilize common digital, power, and IO subsystems.

19

2.4.2 Blood Pressure

In blood-pressure biometric modules, the most critical function is the

pressure-sensor circuit. Here, precision amplifiers are used to detect very

small signals from the transducer and amplify them to a level suitable for ADC

processing.

This is typically followed by an active filter to limited unwanted noise at higher

frequencies. Amplifiers with low noise, low drift and high gain are necessary to

minimize measurement errors and ensure accurate readings.

Figure 10: Block diagram of a blood-pressure system.

The most commonly used piezo-resistive silicon-based pressure sensor in

medical applications is the Wheatstone bridge. The pressure-sensing element

combines resistors and an etched-diaphragm structure to provide an electrical

signal which changes with pressure.

As the diaphragm moves under pressure, stress is concentrated in specific

areas of the silicon element.

The result is a small voltage that changes in proportion to the pressure

applied to the diaphragm.

This bridge signal is then amplified using precision op amps prior to ADC

conversion Key questions to ask when recommending an amplifier are:

what is the required accuracy and

what are the required voltages?

20

while pressure sensors have varying sensitivities and voltage

requirements. The amplifier will generally be selected to match the

requirement of the sensor. The

2.4.3 Electrocardiogram (ECG)

There are several precision amplifier and instrumentation amplifier

opportunities in ECG applications. Key blocks for lead devices are the

electrode gain amplifier,

high-pass filter (usually 0.5 Hz)

low-pass filter (around 150 Hz) and

right-leg drive circuit. For ECG

each electrode requires a precision instrumentation amp to extract a very

small signal that rides on a 300 mV to 700 mV common-mode voltage.

Typically, this amplifier will use a higher supply voltage to enable a high gain

without railing the amplifier in the presence of the high common-mode voltage

from the body. This amp can be a discrete instrumentation amplifier or an

integrated instrumentation amplifier. Second- and third-stage active-filter

amplifiers are needed to set a very specific band (0.5 Hz – 150 Hz) to capture

the ECG QRS wave signal. Typically these will be low-noise, 5V amplifiers

with good appropriate bandwidth. In addition, low-noise, low-power amplifiers

are needed for the right-leg-drive feedback function.

21

Figure 11: Block diagram of an ECG system.

In multi-channel systems, such as a 12-lead ECG monitor, it is common to

multiplex signals into a common ADC. The key typical requirements for the

multiplexer (mux) are low on-resistance and low charge injection.

Generally a specific mux is selected to match the voltage requirements of the

filter amplifiers and the ADC. It is also common for multichannel ECGs to

have automated lead detection to enable multi-configuration operations.

Generally, a low on-resistance switch is used in this circuit as well.

2.4.4 Pulse Oximetry (SpO2) Oxygen is carried in the blood in hemoglobin and is one of the key vital signs

needing detection. Pulse oximetry takes advantage of the fact the blood

absorbs certain wavelengths of light differently when it is oxygenated

compared to when it is oxygen-deprived.

22

Figure 12: Block diagram for pulse oximetry system.

The wavelength that marks the difference in absorption to identify oxygen

concentration is approximately 805 nm (nanometers) for adult hemoglobin.

Therefore, we will use two other wavelengths–one above and one below–to

calculate the percentage of oxygenated red blood cells. Usually, 660 nm and

940 nm are used.

A high-impedance, low-bias-current op amp is needed to process the

photodiodes that receive the signal at these wavelengths, Figure 4. The ADC

also needs to have the fast throughput of a 16-bit device. The DC and

background noise is subtracted out, and the pulsed signals are then scaled.

Extensive over-sampling, filtering, and signal processing eliminate noise such

as movement artifacts from the small signals, and allow the pulse rate to be

measured.

The ICU, CCU, and premature and other departments used patient monitors.

These monitors are available in a number of different parameter combinations

and have optional interconnection facilities to allow them to be used with

recorders, printers and personal computers, or as part of a Critical Care

Network with other monitors and/or central stations.

23

Figure 13: patients monitor display

2.4.5 How it can be use:

1- Plug in the patient cables to the front panel of the monitor.

2- Apply the ECG electrodes, blood pressure cuff and temperature probes

to the patient.

3- Switch the monitor on.

4- The monitor first completes its self-test routine, and the most major

2.4.6 Three modes of measurement are

available:

• Automatic. This is the default setting, in which the monitor continually

repeats measurements. The time period between measurements is

adjustable between 2-60 minutes.

• Manual. The monitor executes a measurement only when instructed.

• Statim. The monitor executes a rapid series of measurements over a 5

minute period. This is useful to obtain a blood pressure as rapidly as

possible.

2.4.7 The most problems of this device: • Power-related problem

• Display problems

• Sound problems

•

• Key function problems

24

• ECG/BP output problems

• NBP problems

2.5 Neuro-Electrophysiology Department

Neuro-Electrophysiology: the function of this department is to make graphic

for brain and heart to know if they are normal or not. To complete this function

in this department we can see EEG (electroencephalogram), ECG

(electrocardiogram).

2.5.1 EEG: (Electroencephalogram) EEG is an instrument for recording the electrical activity of the brain by

placing surface electrodes on the scalp.

The Amplitude range (5 - 300μv), Frequency content (0 –50Hz).

There are four type of EEG signals:

EEG Frequency Condition

Delta () 0-3.5 Hz Sleep-infancy

Theta () 3.5-8 Hz Stress

Alpha () 8-13 Hz Awake quite and restful

thought

Beta () 13-50 Hz Tension

Table 2: Types of EEG signals.

The amplitude of EEG is in the range of 10 volt.

EEG electrodes are smaller in size than the ECG electrodes (Ag/Agcl),

they may be applied separately or may be mounted in special bands

which can be placed on the patient scalp.

EEG may be recorded by picking up voltage difference between an

active electrode on the scalp with respect a refrance electrode on the

ear lobe(bipolar) or using only active electrodes (unipolar).

Advance EEG system: take advantage of the power of the computer

(brain electrical activity mapping) 20 electrode scalp EEG recording are

obtained and processed by the computer to obtain a color display

mapping of the electrical activity of brain. Different colors represent diff.

Frequency band or Amplitudes.

25

The electrode of EEG smaller than which in ECG and difficult.

2.5.2 ECG: (Electrocardiogram)

ECG is an instrument for recording the heart electrical activity from the body

surface. Small metal electrodes are stuck onto your arms, legs and chest.

Wires from the electrodes are connected to the ECG machine. The electrical

impulses in your heart can be detected by the ECG machine. The machine

detects and amplifies the electrical impulses that occurs each heartbeat and

records them onto a paper or computer. An ECG can confirm if you have an

arrhythmia at the time of the test.

The maximum voltage level of ECG is (0.5 – 4mv).

The Frequency content of ECG signal is (0.05 – 150Hz).

Abnormal pattern of ECG may be due to pathological state or may be due

artifacts:

1- Interference from power line. (50HZ, 60HZ)

2- Base line shifting due to movement of patient or electrodes.

3- Muscle tremor due to cold shivering.

4- Muscle activation which introduce high frequency in the ECG.

Figure.14 shows ECG signal, you can track what occurs during ECG

formation In P wave :spread excitation through atria. In P-R interval :atria

contract, and excitation within AV node. QRS complex :spread of excitation

through ventricles. Q-T interval :ventricles contract. T wave :ventricles

repolarize.

26

Figure 14: ECG signal.

Medical and Physiological Parameters:

Medical And Physiological

Parameters /Parameter Range Frequency Sensor

Blood flow 1-300 ml/s dc – 20 Hz Flowmeter (ultrasonic)

Arterial blood pressure

25-400mm Hg dc – 50 Hz Cuff, strain-gage

ECG 0.5 – 4 mV 0.01 – 250 Hz Skin electrodes

EEG 5 – 300 microV dc – 150 Hz Scalp electrodes

EMG 0.1 – 5 mV dc – 10,000 Hz Needle electrodes

Respiratory rate 2 – 50 breaths/min 0.1 – 10 Hz Strain-gage, nasal thermistor

Table 3 : Medical and Physiological Parameters:

.

27

Chapter Three Work Shop

3.1 Types of Maintenance:

There are two Types of Maintenance:

1. Preventive maintenance involves routine inspection and testing.

2. Corrective maintenance involves total calibration or replacement of

defective parts.

Most common troubleshooting cases in the devices can be listed as follows:

Fuses.

Relays used for pumps, motors and heaters.

Contacts.

Power cables and battery.

Problems result from the miss use of the user.

To deal with troubleshooting of the medical devices we followed these steps:

1. If the medical device is under the warranty by one of the companies the

manger call them so they can fix the problem.

2. If the medical device is not under the warranty by one of the companies

we and the technical open the device if it need to and we follow the

following steps:

Power check : most of the devices have a safety circuit and

contain fuses and resistors and diodes which to safe the device

28

from electrical failed so we check first the power supply and the

cable and the fuses which are damaged.

Check or replace the battery of medical devices

Component replacement.

Use the service manual if it exists to more secure help.

3.1.1 How to test some electronic parts:

3.1.1.1 Resistors The ratio of the voltage applied across a resistor's terminals to the intensity

of current in the circuit is called its resistance, and this can be assumed to

be a constant for ordinary resistors working within their ratings.

How to test them:

1- Check from the colors: To distinguish left from right there is a gap

between the 3 and 4 bands.

band 1 is first significant figure of component value (left side)

band 2 is the second significant figure (Some precision resistors have

a third significant figure, and thus five bands.)

band 3 is the decimal multiplier

band 4 if present, indicates tolerance of value in percent (no band

means 20%)

Figure 15: Color code

2- Check by digital multimeter.

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3.1.1.2 Capacitors Capacitors are components that are used to store an electrical charge and are

used in many circuits. Sometimes capacitors are used to smooth a current in

a circuit as they can prevent false triggering of other components such as

relays. When power is supplied to a circuit that includes a capacitor - the

capacitor charges up. When power is turned off the capacitor discharges its

electrical charge slowly.

How to test them:

1- Check by multimeter: after putting on capacity check. we Connect

multimeter to capacitor leads and see what the range it gives.

2- We can use a test bridge

Figure 16: capacitor.

3.1.1.3 Voltage Regulators Voltage regulators take incoming DC and hold their output voltage to a

specific value as the incoming voltage fluctuates or the load varies with

circuit operation.

Figure 17 :Voltage Regulator

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3.1.1.4 Relays Relays are switches controlled by putting current into a coil. When the

coil is energized, the resulting magnetic field pulls a metal plate toward

it, pressing the attached switch contacts against opposing contacts. In

this way, a small current can control a much larger one, just as a

transistor does in switch mode.

How to test them:

1- Use your DMM’s continuity or lowest ohms scale. Check for coil

continuity. If there’s a diode, be sure to check in both directions. The

coil shouldn’t read 0 ohms; there’s enough wire there for dozens to a

few hundred ohms. If it reads very near zero on a relay that has a

diode, suspect a shorted diode, especially if the symptom suggests that

the coil doesn’t want to pull in the switch.

2- Also check that there is no continuity between the coil and its metal

core. If there is any, you need a new relay.

3- Check the NC contacts with the meter. They should read 0 ohms or

very close to it. Use your bench power supply to energize the coil. If it

has a diode, be certain to get the polarity correct, with + to the diode’s

cathode, not its anode. (Remember, the diode is supposed to be wired

backward, so it won't conduct when power is applied.) With no diode,

polarity doesn’t matter. Once you hear the click, check the NO

contacts. They should also read 0 ohms or very close to it. When you

disconnect the power supply, the contacts should return to their original

state. The NO contacts should open and the NC contacts should close.

Figure 18: Relays

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3.1.1.5 Switches Switches permit or interrupt the passage of current. There are many,

many kinds of switches, and they’re used in just about everything.

Toggle switches, slide switches, rotary switches, leaf switches,

pushbuttons, internal switches on jacks…there’s practically no end to

the varieties.

How to test them:

Test switches with your DMM’s continuity or lowest ohms scale. The contacts

should read 0 ohms when closed and infinity when open. There’s an

exception, though: Some pushbuttons, such as the kind on remotes, laptop

keyboards and tiny products like digital cameras, use a carbon-impregnated

plastic or rubber contact to make the connection. You can identify them by

their soft feel when pressed; they don’t click. These switches are intended

only for signaling, not for handling significant current, and they may have a

few tens of ohms of resistance when in the “on” state.

Figure 19: Switches

3.1.1.6 Transformers A transformer is an electrical device designed to transfer alternating current or

voltage from one electric circuit to another by means of electromagnetic

induction .Electrical transformer converts AC voltage from one value to

another .It can be designed to "step-up" or Step-down" voltages.

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How to test them:

Calculate the voltage output for a step-down transformer by dividing the rated

output voltage by the input voltage, for example, if the transformer's output is

rated at 11 volts with a 220-volt input, then the ration will be 50

1. Disconnect the equipment containing the transformer from the wall

outlet.

2. Touch the digital multimeter's probe tips to the oscillator's output.

3. Connect the oscillator's output to the transformer's two primary wires. It

should read 5v.

4. A good step-down transformer produces from 100 millivolts to 1 volt

AC, depending on its rated output voltage. If the output reads only a

few millivolts or less on the multimeter, the transformer is bad.

4.1.1.7 Inductor An inductor is a passive two-terminal electrical component that stores energy

in its magnetic field. For comparison, a capacitor stores energy in an electric

field, and a resistor does not store energy but rather dissipates energy as

heat.

Any conductor has inductance. An inductor is typically made of a wire or other

conductor wound into a coil, to increase the magnetic field.

How to test them:

An inductor is a device consisting of one or more windings of wire with or

without a magnetic core. Frequent causes of inductor coil failures are shorted

turns, open turns, and changes in inductor value. The best test to check

whether an inductor is good or not is by testing the inductor's resistance with

your multimeter set to the ohmmeter setting.

We do this by taking the probes of the multimeter and placing them across the

leads of theinductor. The orientation doesn't matter, because resistance isn't

polarized.

The inductor should read a very low resistance across its terminals, only a few

ohms. If an inductor reads a high resistance, it is defective and should be

33

replaced in the circuit. If an inductor is reading very, very small resistance,

less than an ohm (very close to 0Ω), this may be a sign that it's shorted.

Functional inductors normally read a few ohms, greater than 1Ω and normally

less than 10Ω. This is a healthy range for an inductance value. Outside this

range and this is normally a sign the inductor is bad.

Conclusion

Field Training

Impact of Engineering and learned skills in the Training Program

After I have finished my training program I was familiar with the basics of

communication engineering and a several medical instruments and I got a solid base of

knowledge about different types of devices, this knowledge will make me able to enter

engineering practical world easily.

For example, if any problem occurred in any device then the first thing we have to do is

to study the operating manual in order to understand how the device works. After that,

we diagnose the problem and fix it. On the other hand, I have learned some new

practical skills that I have never got the chance to practice them in the university's

laboratories. Working hand by hand in a group is the most useful and beneficial aspect

that leads to a successful in the work.

We obtained good and useful knowledge from being most of the time around the

engineers and operators in the workshop. Skills that I have learned:

Using digital multimeters in electrical tests.

Making calibration for patient monitors.

Electronic parts tests and change them in devices.

References

1. . Deakin CD, Sado DM, Petley GW, Clewlow F. Is the orientation of the apical defibrillation

paddle of importance during manual external defibrillation? Resuscitation 2003;56:15-8.

2. Whitfield R, Colquhoun M, Newcombe R, Davies C. S, Boyle R. The Department of Health

National Defibrillator Programme: analysis of downloads from 250 deployments of public

access defibrillators. Resuscitation 2005;64:269 – 77.

3. J. A. Jensen. A model for the propagation and scattering of ultrasound in tissue. J. Acoust.

Soc. Am., 89:182–191, 1991a.

4. J. A. Jensen. A new calculation procedure for spatial impulse responses in ultrasound. In

press, JASA, 1999.

5. From device Manual in the hospital.

6. Medical Instrumentation note.

7. http://en.wikipedia.org. 8. http://www.sonoelectrochemistry.com

9. http://www.takagi-j.com/seihin_e/katarogu_e/om30u_e.html

10. http://www.miami-med.com/laparosc.htm

11. http://www.radiologyinfo.org

12. http://www.electronicrepairguide.com 13. http://www.kpsec.freeuk.com/ 14. http://www.ehow.com 15. http://www.ses-jo.com 16. http://www.en.zte.com.cn 17. http://www.huawei.com