ACQUISITION

1) in digital communication systems, the process of acquiring synchronism with the received signal.
There are several levels of acquisitions, and for a given communication system several of them have to be performed in the process of setting up a communication link: frequency, phase, spreading code, symbol, frame, etc.

(2) in analog communication systems,the process of initially estimating signal parameters (for example carrier frequency offset, phase offset) required in order to begin demodulation of the received signal.

(3) in vision processing, the process by which a scene (physical phenomenon) is converted into a suitable format that allows for its storage or retrieval.

Interview questions and answers on SCHMITT TRIGGER....

1)what do mean by a Schmitt trigger?
Schmitt trigger is a type of comparator which uses positive feedback. Schmitt trigger convert an sinusoidal signal to a square wave signal.

2)how many types of Schmitt trigger used?
There are two types Schmitt trigger are used.
1. Inverting Schmitt trigger.
2. Non-inverting Schmitt trigger.

3)what do you mean by threshold voltage of Schmitt trigger?
The input voltage of Schmitt trigger for which the Schmitt trigger changes their output is called threshold voltage.

4)what do you mean by hysteresis of Schmitt trigger?
Hysteresis is the voltage difference between turn-on and turn-off voltage of comparator.

OP-AMP INTERVIEW QUESTION AND ANSWERS

An ideal-opamp would have the following characteristics:-
1 Infinite voltage gain
2 Infinite input resistance
3 Zero o/p resistance
4 Zero o/p voltage when (i/p voltage is zero)
5 Infinite Band with
6 infinite common mode Rejection ratio
7 infinite slew rates.

2)what are the main features of Ics 741?
1 No external frequency compensation required.
2 short circuit protection.
3 offset null capability.
4 large common mode and differential voltage range
5 low power consumption
6 No latch up problem

3)what do you mean by differential input resistance?
differential input resistance is the equivalent resistance that can be measured at either the inverting and non inverting input terminal with the other terminal connected to ground.

4)what do you mean common mode rejection ratio (CMMR).
common mode rejection ratio define as “it is the ratio of the differential voltage Gain to the common mode gain of an op-amp.
CMMR= differential gain/ common mode gain

5)what do you mean by SVRR (supply voltage rejection ratio).
the change in an op-amp input –offset voltage, caused by variation in supply voltage is called supply voltage rejection ratio (SVRR).

6)what do you mean by slew rate of an op-amp.?
slew rate is the maximum rate of change of output voltage per unit of time.

7)what do you mean by an open loop configuration of an op-amp?
the open loop configuration of an op-amp indicate the No connection, exist between The output signal is not fed-back in any from into the input.

8)How many configuration in open-loop op-amp configuration?
there are three open-loop op-amp configurations:
1 Differential –amplifier.
2 Inverting amplifier
3 Non- inverting amplifier

9)what do you mean by voltage follower?
the lowest gain that can be obtained from a non-inverting amplifier with feed back Is 1. When the non-inverting amplifier is configured for unity, it is called a voltage Follower.

10)what do you mean by a comparator?
Comparator is an open-loop op-amplifier which compares the input voltage at other one terminal to a reference voltage at other terminal and produce a voltage at their output terminal.

11)what do you mean by a zero-crossing detector?
Zero-detector is a comparator in which a zero reference is applied at their non-inverting terminal. Zero-crossing detector switches their output from one state to another state if the input voltage crosses the zero point.

12)what do you mean by input offset current?
The algebraic difference between the current in the inverting terminals is as know as Input offset current.

13)what do you mean by input offset voltage?
Input offset voltage that must be applied between the two input terminal of an Op-amp to null the output.

14)what do you mean by input biased current?
input biased current is the average of the current that flow into the inverting and Non Inverting input terminals of the op-amps.

ULTRASOUND SCAN INTERVIEW QUESTIONS

ULTRASOUND SCAN
An ultrasound scan is a painless test that uses sound waves to create images of organs and structures inside your body. It is a very commonly used test. As it uses sound waves and not radiation, it is thought to be very safe. Doppler and duplex scans are used to visualise blood or fluids flowing through the body.

1)What is ultrasound?

Ultrasound is a high-frequency sound that you cannot hear but it can be emitted and detected by special machines.

2)How does ultrasound work?

Ultrasound travels freely through fluid and soft tissues. However, ultrasound bounces back (is reflected back) as echoes when it hits a more solid (dense) surface. For example, the ultrasound will travel freely though blood in a heart chamber. But, when it hits a solid valve, a lot of the ultrasound echoes back. Another example is that when ultrasound travels though bile in a gallbladder it will echo back strongly if it hits a solid gallstone.

So, as ultrasound 'hits' different structures of different density in the body, it sends back echoes of varying strength.

4)What does an ultrasound scan involve?*
You lie on a couch and an operator places a probe on your skin over the part of your body to be examined. The probe is a bit like a very thick blunt pen. Lubricating jelly is put on your skin so that the probe makes good contact with your body. The probe is connected by a wire to the ultrasound machine, which is linked to a monitor. Pulses of ultrasound are sent from the probe through the skin into your body. The ultrasound waves then bounce back as echoes from the various structures in the body.

The echoes are detected by the probe and are sent down the wire to the ultrasound machine. They are displayed as a picture on the monitor. The picture is constantly updated so the scan can show movement as well as structure. For example, the valves of a heart opening and closing during a scan of the heart. The operator moves the probe around over the surface of the skin to obtain views from different angles.

The scan is painless and takes about 15-45 minutes, depending on which parts of the body are being examined. A record of the results of the test can be made as still pictures or as a video recording.

4)What is an ultrasound test used for?
An ultrasound scan is a safe and painless test that creates images of organs and glands, abnormal lumps and other structures like muscles, tendons and joints. It is also used to check unborn babies during pregnancy.

It is used in many situations. The way the ultrasound bounces back from different tissues can help to determine the size, shape and consistency of organs, structures and abnormalities. So, it can:

Help to monitor the growth of an unborn child and check for abnormalities. An ultrasound scan is routine for pregnant women.Detect abnormalities of heart structures such as the heart valves. This type of ultrasound scan is called echocardiography. See the separate leaflet called Echocardiogram for more details.Help to diagnose problems of internal organs such as the:LiverGallbladderPancreasThyroid glandLymph nodesOvariesTestesKidneysBladderAppendixFor example, it can help to determine if an abnormal lump in one of these organs is a solid tumour or a fluid-filled cyst. Ultrasound also helps look for stones in the gallbladder or kidney.Help determine the nature of breast lumps. Ultrasound is one of the tests used to establish if a lump is non-cancerous (benign) or breast cancer.Help diagnose problems with muscles, tendons and joints. For example, ultrasound scans are used to help diagnose:Frozen shoulderTennis elbowMorton's neuromaCarpal tunnel syndromeDetect abnormal widening of blood vessels (aneurysms).Guide internal biopsies. A biopsy is a procedure in which a sample of tissue is taken. Some biopsies are taken using a thin needle, and the needle is guided to the right place with an ultrasound scan. For example, if you have a lump in your breast, you may have a sample of the lump taken away. The sample is then examined under the microscope to see if your lump is cancerous or not.

Some specialist ultrasound techniques

In some situations, a clearer picture can be obtained from a probe that is within the body. So a small probe, still attached by a wire to the ultrasound machine, can be:

Swallowed into the gullet (oesophagus). This may be used to obtain clearer images of the internal organs, particularly the stomach, upper gut and pancreas. See separate leaflet called Endoscopic Ultrasound Scan for more details.Placed in the vagina or rectum to obtain clearer images of inner organs, such as the womb (uterus), ovaries or prostate gland.Used to help guide a surgeon during an operation, in order to look deeper into structures.

Ultrasound may also be used for treating certain conditions, particularly those of muscles, tendons and joints. The scan may be used to guide an injection which can help to treat the problem. Doing the injection with the help of an ultrasound scan makes sure it reaches exactly the right place. For example, ultrasound-guided injections are a common way to treat shoulder problems such as a frozen shoulder.

The above are not exhaustive lists, and ultrasound scanning has various other uses.

5)What is a Doppler ultrasound scan?
A Doppler ultrasound records sound waves reflecting off moving objects, such as blood cells, to measure their speed and other aspects of how they flow through the body.

6)How does Doppler ultrasound work?
If the structure is moving then the echo comes back at a slightly different frequency (called the Doppler effect). This difference in frequency can be used to measure the speed of movement. Blood moving in an artery or vein causes small echoes and these are used to measure the speed of movement of the blood cells. The sound waves may be amplified though speakers. This allows the practitioner to listen to the flow of blood cells to determine whether or not there is normal flow. For example, listening to the flow of blood through the heart of a baby during a routine antenatal check-up. The sound waves may also be converted to colour pictures on a screen so that flow can be seen through the arteries or veins (colour Doppler). They may also be plotted on a graph showing changes in speed and direction (velocity).

What is Doppler ultrasound used for?
To listen to the heartbeat of an unborn baby (fetus) during pregnancy.To examine blood flow in arteries or veins in your arms or legs to see if you might have:Deep vein thrombosis.Peripheral arterial disease.Injury to your veins or arteries following trauma.

7)What does a Doppler ultrasound involve?
During pregnancy, the Doppler ultrasound is very similar to an ultrasound scan. A probe covered with gel is put on your skin over the pregnant womb (uterus). This is connected to a speaker. You and the practitioner are able to listen to the flow of blood through the baby's heart.

During a Doppler ultrasound of the arms and legs, blood pressure cuffs are placed along the thigh, calf, or ankle, or to different points along the arm. A paste is applied to the skin over the arteries being examined. Images are created as the probe is moved over each area.

8)What is a duplex ultrasound?
Duplex ultrasound is a special technique which combines traditional ultrasound with Doppler ultrasound. Images of the solid object being examined - for example, the artery and the blood flowing through it - are displayed on a screen or monitor. The object is usually grey and the blood flow is usually in colour (colour Doppler).

9)What is duplex ultrasound used for?
Duplex ultrasound is most commonly used to evaluate the blood flow in various arteries and veins in the body. The scan can help diagnose the following conditions:

Widening of the main artery in the tummy (abdominal aortic aneurysm). Ultrasound scans are used in the national screening programmes across the UK for abdominal aortic aneurysm.Blockage to an artery (an arterial occlusion).Blood clot.Blockage to the arteries in the neck (carotid occlusive disease).Renal duplex examines the kidneys and their blood vessels.Varicose veins.Venous insufficiency (a condition where veins have a problem sending blood back to the heart).

10)What does a duplex ultrasound involve?
This test is very similar to an ultrasound scan. A probe covered with gel is placed over the area to be examined. Images of the solid organ and the blood flowing through it are then seen on a monitor.

11)What should I do to prepare for these tests?
Usually there is no special preparation needed. Continue to take your usual medication. You should eat and drink normally before and after the test unless otherwise instructed. For example:

If certain parts of the tummy (abdomen) are being examined, you may be asked to eat a low-fibre diet for a day or so before the test (to minimise 'gas' in your gut).You may be asked not to eat for several hours before a scan of the abdomen.Occasionally for some scans, you may be given an enema to clear the bowel.To scan the bladder or pelvis, you may be asked to drink some fluid before the test so that you have a full bladder. This is particularly likely if you are having a scan in pregnancy, or a scan of your ovaries or womb (uterus).

You will be told what you need to do before any particular scan.

12)Are there any side-effects or complications from ultrasound, Doppler or duplex scans?

These scans are painless and safe. Unlike X-rays and other imaging tests, they do not use radiation. They have not been found to cause any problems or complications.

INTERVIEW QUESTIONS AND ANSWERS ON EMBEDDED SYSTEMS

1)Define Embedded Systems.
An embedded system is one that has computer-hardware with software embedded in it as one of its most important component. Software embedded into hardware is known as embedded systems.
E.g: Mobile Phones, Elevator, Computer, etc….

2)What are the components of embedded system hardware?
- Processor
- Program memory and data memory
- Timers
- Serial communication ports
- Input devices
- Output devices
- Power suply, Reset and Oscillator Circuits

3)Classification of embedded system.
ans. - Small Scale Embedded Systems
- Medium Scale embedded Systems
- Large Scale Embedded Systems

4)Define Processor.
Processor is the heart of the system. A processor implements a process or processes as per the commands given to it.

Specify the 2 essential units of the processor in a system.
. - Program Flow Control Unit (CU)
- Execution Unit (EU)

5)What are the types of General Purpose Processor?
. - Microprocessor
- Microcontroller
- Embedded Processor
- Digital Signal Processor (DSP)
- Media Processor

6)Define Microprocessor.
A microprocessor is a single VLSI chip that has a CPU and may also have some other units that are additionally present and that result in faster processing of instructions.

7)Define Microcontroller.
A microcontroller is a single-chip VLSI unit which, though having limited computational capabilities, possesses enhanced input-output capabilities ana a number of on-chip functional units.

8)What is Clock?
A fixed frequency pulses that an oscillator circuit generates and that controls all operations during processing and all timing references of the system.

Interview questions and answers on MOTORS...

1)WHAT IS AC MOTOR?*
An AC motor is an electric motor driven by an alternating current (AC). It commonly consists of two basic parts, an outside stationary stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft that is given a torque by the rotating field.

2)WHAT IS DC MOTORS?*
A DC motor is a mechanically commutated electric motor powered from direct current (DC). The stator is stationary in space by definition and therefore so is its current. The current in the rotor is switched by the commutator to also be stationary in space. This is how the relative angle between the stator and rotor magnetic flux is maintained near 90 degrees, which generates the maximum torque.

3)WHAT ARE THE ADVANTAGES AND DISADVANTAGES OF AC, DC MOTORS?* Advantages of AC Motors:
1. Low cost,
2. long life,
3. high efficiency,
4. large ratings available (to 1 MW or more),
5. large number of standardized types.

Disadvantages of AC Motors:
1. Starting inrush current can be high,
2. speed control requires variable frequency source.

Advantages of DC Motors:
1. Precision positioning,
2. High holding torque,
3. Long lifespan,
4. Low maintenance,
5. High efficiency

Disadvantages of DC Motors:
1. Some can be costly,
2. Require a controller,
3. Higher initial cost,
4. Requires a controller.

4)WHAT IS UNIVERSAL MOTOR?*
A series-wound motor is known as a universal motor when it has been designed to operate on either AC or DC power. It operate well on AC because the current in both the field and the armature (and hence the resultant magnetic fields) will alternate in synchronism and hence, the resulting mechanical force will occur in a constant direction of rotation.

5)WHAT ARE THE STANDARDS OF MOTOR?*
The following are major designs and manufacturing standards covering electric motors:
International Electro-technical Commission: IEC 60034 Rotating Electrical Machines
National Electrical Manufacturers Association (USA): NEMA MG 1 Motors and Generators
Underwriters Laboratories (USA): UL 1004 – Standard for Electric Motors

6)What is the back emf ?*
ans. When the motor armature continues to rotate due to motot action the armature conductor cuts te magentic flux, and therefore emf are induced in them the direction of this induced emf is such that it oppose the applied voltage therefore this is called Back emf. .

7)What is a stepper motor for?*

Stepper motors are DC motors that move in discrete steps. They have multiple coils that are organized in groups called "phases". By energizing each phase in sequence, the motorwill rotate, one step at a time. With a computer controlled stepping you can achieve very precise positioning and/or speed control.

8)What are the types of stepper motors?*

Permanent magnet stepper.

Hybrid synchronous stepper.

Variable reluctance stepper.

9)How do you control a stepper motor?*

Stepper motors can move an exact amount of degrees (or steps) when told to do so. This gives you total control over the motor, allowing you to move it to an exact location and hold that position. It does so by powering coils inside the motor for very short periods of time.

10)What is the use of stepper motor driver?

The EasyDriver is a simple to use stepper motor driver, compatible with anything that can output a digital 0 to 5V pulse (or 0 to 3.3V pulse if you solder SJ2 closed on the EasyDriver). The EasyDriver requires a 6V to 30V supply to power the motor and can power any voltage of stepper motor 

11)What are the advantages of a stepper motor?*

Advantages of step motors are low cost, high reliability, high torque at low speeds and a simple, rugged construction that operates in almost any environment. The main disadvantages in using a stepper motor is the resonance effect often exhibited at low speeds and decreasing torque with increasing speed.

12)What is the difference between a stepper motor and a servo motor?*

Stepper vs Servo. The basic difference between a traditional stepper and a servo-based system is the type of motor and how it is controlled. ... Steppers don't require encoders since they can accurately move between their many poles whereas servos, with few poles, require an encoder to keep track of their position.

13)How does a stepper motor controller work?*

First is the pulse generator, also known as a stepper motor controller or indexer. ... A step motor has two primary parts; the rotor, the moving piece, and the stator, the stationary piece. The stator contains coils of wire called windings. The rotor spins on bearings or bushings inside the stator.

14)Where is a stepper motor used?*

Today, stepper motor applications are all around us: they are used in printers (paper feed, print wheel), disk drives, clocks and watches, as well as used in factory automation and machinery. A stepper motor is most often found in motion systems requiring position control.

15)How does it work stepper motor?*

Stepper motors consist of a permanent magnetic rotating shaft, called the rotor, and electromagnets on the stationary portion that surrounds the motor, called the stator. Figure 1 illustrates one complete rotation of a stepper motor. ... You may double the resolution of some motors by a process known as "half-stepping".

INSTRUMENT TRANSFORMER /INTERVIEW QUESTIONS

*What do you mean by an instrument transformer?
Transformer which is used with measuring instrument is called instrument transformers. Instrument transformer is used as a protection circuit of power system for the operation of over current, under voltage, Earth fault etc.

*what are the types of instrument transformer?
there are two types of instrument transformer:
1. Current transformer- used to measure current
2. Voltage transformer - to measure voltage

*what are the Advantages of instrument transformer?
Advantages of instrument transformer are:
1. Instrument transformer s are moderate in size and used for 5A current and 100 to 200 V measurement.
2. Instruments using instrument transformer are low cost.
3. Replacement of damage parts is Easy.
4. The metering circuit is isolated the high voltage power circuit hence insulation and safety is assured for operation.
5. There is low power consumption in metering circuit.

*what do you mean by a phase Angel of instrument transformer?
The angle between secondary current and primary current of a current transformer is called phase angle of instrument transformer.

*what do you mean by transformation ratio of instrument transformer?
It is the ratio of primary winding current to the secondary winding current of an instrument transformer.

*what do you mean by Nominal ratio of instrument transformer?
It is the ratio of rated primary winding current to the rated secondary winding current of an instrument transformer.

*what do you mean by ratio correction factor of instrument transformer?
It is the ratio of the transformation ratio to the nominal ratio of an instrument transformer

Job opportunities

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Dubai based Medical Supplier looking for a Biomedical Engineer.

Cantidate should have 1-5 years of experience in  Equipment service.

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Willing to join immediately.
Interested Cantidate please send the cv to: [email protected]

2⃣
Post: Sales Executive / Sr Sales Executive 

Location: Hyderabad, Nagpur, Ahmadabad   

Products: Patient Monitor, Defibrillator,  ECG, AED, Central Nursing station etc 

Qualifications: BE/ Diploma Engineer will be preferred. Candidate with experience in Critical Care field can also apply. 

Experience: Minimum 5 year or more, Must have experience in Critical Care/ ICU equipment. Must able to speak local languages.     

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Email ID: [email protected]

3⃣
Company: Bioteknika Healthcare Pvt. Ltd.

Products: Medtronic's Product (Neuro - Surgical department)

Location: Surat and South Gujarat

Email ID: [email protected] and cc to:
[email protected]

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Company: Fanem Medical Devices India Pvt Ltd

Products: Neonatal equipment

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Experienced candidates are preferred.

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Company: Phoenix Medical Systems (P) Ltd.

Post: International Sales Executive

Products: Infant care products

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Hospital: Bhatia Hospital

Post: Biomedical Engineer

Products: Mainly required to handle OT and Pathology

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Experience: 3 to 4 years in Hospital Industry

Email Id: [email protected]

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Post: Senior biomedical Engineer

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Experience: 4 to 6 years

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
Hospital: Cloudnine Hospitals
(Kids Clinic India Pvt.Ltd.,)

Post: Biomedical Engineer with

Experience: minimum 1-2 years experience in Hospital field as BME.

Preferred: Male candidates (from Bangalore)

Location: Malleswaram, Bangalore.

Joining Date: Immediately