Instrumentation Engineering Interview Questions and Answers
Question - 11 : - How DP transmitters are connected to closed tanks?
Answer - 11 : -
The bottom of the tank is attached to the transmitter’s high-pressure side in a closed tank. The top of the tank is fixed to the transmitter’s low-pressure leg. The pressure of the vessel can be measured in this way.
Question - 12 : - Do you know the working of a level troll ?
Answer - 12 : -
The variation in buoyancy level resulting from a fluid level change varies the displacer’s net weight to increase or decrease the torque armload. This change is directly proportional to fluid level change and real gravity.
The subsequent torque tube movement shifts the rotor angular motion in RVDT resulting in a rotor shift proportional to the displacement of the rotor, which is transformed and amplified to a D.C. Up-to-date.
Question - 13 : - How does the DP flow transmitter system vary on gas and liquid pipeline?
Answer - 13 : -
To stop gas condensation in the signal line and HP & LP chamber, DP is mounted above the orifice plate for the gas line.
To stop gas trapping in the signal line and the HP & LP section, DP is mounted below the orifice plate for the liquid side.
Question - 14 : - Why is the Orifice tab provided?
Answer - 14 : -
Following reasons justify for providing orifice tab:
- Indication of the orifice plate in a line
- The orifice diameter is marked on it.
- The material of the orifice plate.
- The tag number of the orifice plate.
- To mark the inlet of an orifice.
Question - 15 : - How to recognize upstream in a pipeline a newly installed orifice plate?
Answer - 15 : -
The upstream can be marked with the Tag number markings of the orifice plate. Notes are always labelled on the orifice plate’s upstream.
Question - 16 : - Where we you use square root extractors?
Answer - 16 : -
Square root extractors are used across Orifice and other DP transmitters.
The relationship between the differential pressure (^P) and flow rate (Q) are not equal. DP is proportional to the square of the flow rate Q.
To convert the signal from the flow transmitter to one directly proportional to the flow rate, the square root of the signal from the flow transmitter must be obtained or extracted.
Question - 17 : - Why thermowells are used?
Answer - 17 : -
Thermowells are equipment that protects temperature measuring devices from exposing the device to the measuring substance.
Wells are used to protecting against corrosion damage erosion and processes of high pressure. A thermowell can also be used to protect a sensor during handling and routine operations from physical damage.
Question - 18 : - What is RTD?
Answer - 18 : -
RTDs ( Resistance Temperature Detector) are temperature detectors that change their resistance as temperature rises. RTDs are used for continuous measurement of temperature, indicating a positive coefficient of temperature. The resistance of RTD decreases when the temperature increases.
Question - 19 : - What is Pt100?
Answer - 19 : - Pt100 means at 0°C temperature platinum gives 100-ohm resistance. Platinum resistance thermometer (PRT) offer excellent precision over a wide range of temperatures (-200 to + 850°C).
Question - 20 : - Why use a signal converter for Pt100?
Answer - 20 : -
The temperature sensor pt100 operates on the resistance change; i.e. if the ambient temperature is0oC, the equivalent resistance of the sensor is 100ohm.
When the thermostat pt100 is connected directly to the PLC, it must be connected to the power supply for operation; make long wire.
And also 4-20mA is the internationally accepted standard.