Instrumentation Systems : Chapter 2 : Sensors and Actuators : Important QNA

 Q. Give the symbol of thermistor.

Answer: 

Q.Write 5 features of LM35.

Answer: LM35 is a IC temperature sensors that produces output voltage proportional to the temperature.

Features are as follows:

1. Calibrated directly in °Celcius.

2. 10.0mv/C linear scale factor.

3. Range -55 to +150 degree Celcius.

4. Useful for remote applications.

5. Low cost.

Q. What will be the output of LM35 at 45 °C.

Answer: Output voltage formula: 0.01 * T(C)

Vo = 0.01*45=0.45 volts.

Q. Explain temperature monitoring system.

Answer: 

LM35- Produces voltage proportional to temperature.

ADC- Converts analog voltage into digital equivalent.

Signal Conditioner- Processes digital signal.

Display Driver- Produces required signals to display on the digital display.

Q. Explain working principle of LDR.

Answer: LDR or light dependent resistance is a two terminal device, the resistance of which depends on intensity of light incident on it.

Principle of operation–

1. It works on principle of photoconductive effect.
2. When light is incident on a semiconductor material, it’s conductivity increases due to breaking of covalent bonds.
3. When conductivity increases, the resistivity decreases.
4. LDR is made of such devices called as photo resistor or photo conductor.

Q. What are applicatons of LDR.

Answer: It is used in camera , xerox machines, cars headlight dimmer and night light control.

Q. What do you mean by PIR sensor?

Answer: PIR sensors also called as “Passive Infrared Sensors” are sensors that passively detects infrared light radiating from objects in it’s field of view.

The detected infrared radiations are converted into electrical signals, which is proportional to detected level of radiation.

Q. Give applications of tilt sensor.

Answer: Applications of tilt sensor are:

1. Camera

2. Construction equipment.

3. Aircraft flight controls.

Q. What are ultrasonic sensors? Give it's applications.

Answer: Ultrasonic sensors are acoustic sensors which can be transmitters, receivers or transceivers.

They convert electrical signals to ultrasound or vice versa.

Applications:

1. Liquid level indication.

2. Burglar alarms.

3. Medical ultrasonography.

4. Non-destructive testing.

Q. What is principle of LVDT?

Answer:

Working principle of LVDT:

1. The primary winding is connected to ac source.

2. When core is at centre of coil assembly, induced voltage is same in both windings.

3. If core is now displaced towards secondary-1 then induced voltage in it will be higher and in secondary-2, the induced voltafe will be lower.

4. Same thing happens if core is moved towards the opposite direction.