Instrumentation Engineering Interview Questions and Answers
Question - 21 : - What is the main difference between RTD and Thermistor?
Answer - 21 : -
RTD has a positive coefficient of temperature and Thermistor has a negative coefficient of temperature:
For + ve temperature coefficient, when the temperature increases the resistance of the element used for sensing increases.
For - ve temperature coefficient, when the temperature increases the resistance of the element used for sensing decreases.
Question - 22 : - How to identify between RTD & Thermocouple?
Answer - 22 : -
Connect the transmitter to a multimeter in resistance mode. If you read in ohms, otherwise it’s RTD, it’s a thermocouple.
The thermocouple always shows reading in mV.
Question - 23 : - What are Cold junction and Hot junction in a thermocouple?
Answer - 23 : -
Cold junction is the reference junction that is always kept at 0 ° C to prevent the influence of room temperature.
Hot junction is exposed to the varying heat that should be measured by the temperature. Where to join the dissimilar metals.
Question - 24 : - What is the control valve?
Answer - 24 : -
The control valve is a final control element that controls the user to regulate or restrict the fluid flow through a flow channel. It allows direct flow rate control and consequent regulation of process quantities such as pressure, temperature, and volume of liquid.
Question - 25 : - What is the use of valve positioner?
Answer - 25 : -
The valve positioner’s aim is to improve the valve action’s accuracy. Positioners are used to completely perform the function of the final control variable in the control loop.
By increasing or decreasing the air load pressure on the actuator, they place the valve in the right position.
Question - 26 : - Can we use the valve without positioner?
Answer - 26 : -
No. The positioner’s purpose is to control the stroke of the control valve to keep the valve in the desired position.
The positioner receives a signal from the controller and sends the boosted signal to the actuator to reach the desired position as the positioner cuts the boosted signal to the actuator and keeps the position.
Question - 27 : - What are the uses of valve positioner?
Answer - 27 : -
- Quick action
- Valve hysteresis
- Viscous liquids
- Split range.
- Line pressure changes on valve
- Bench set not standard
- Reverse valve operations
Question - 28 : - What is the solenoid valve?
Answer - 28 : -
A solenoid is a valve that is electrically operated. This consists of a solenoid coil passing in a magnetic plunger. This plunger is attached to the pump, opening or closing the valve. Two styles of solenoid valves are present:
- Normally opened
- Normally closed
Question - 29 : - What are the types of manometers?
Answer - 29 : -
- U – tube manometer
- Well type manometer
- Inclined type manometer
- Ring balance manometer
- Micro manometer
Question - 30 : - What is I to P converter?
Answer - 30 : -
The pneumatic signals of the instrumentation are sustained at a maximum of 3-15psi. The air compressor system delivers air at a much higher pressure which is then decreased employing restrictions and further control of 3-15psi. The I/P converter is used to provide this restriction and control.