Thursday, 7 September 2017

INSTRUMENTATION INTERVIEW QUESTIONS

By Ask Biomedical


*What is air core inductance ?
The inductance that would be measured if the core had unity permeability and the flux distribution remained
unaltered. (A measure of the inductance of a coil without a core).

*Define Humidity.
It is basically moisture content in air or it is the quantity of water vapour retained by gas.

*Define Hygrometer.
Used to measure the moisture content in air. It also used to measure humidity.

*What is the basic principle of Hygrometer.
It consist of mechanical device measuring the dimension change of humidity sensitive materials like animal hair, animal membrane , paper etc.


*What is open loop?
An open loop is more of a manually controlled control loop exists where the process variable is not compared and action is taken not in response to feedback on the condition of the process variable but is instead taken without regard to process variable conditions.

*Whar are the common process variables used in industrial application ?
Pressure,Flow,Level,Temperature
Density,Ph,Mass,Conductivity.

*What is setpoint?
Setpoint is a value for a process variable that is desired to be maintained.

*What is error (Control loop) ?
Error is the difference between the measured variable and the setpoint and can be either positive or negative.

*What is controller in a Control loop?
A controller is a device that receives data from a measurement instrument,compares that data to a programmed setpoint and if necessary signals a control element to take a corrective action.

*What is a PLC (Programmable Logic Controller ) ?
PLCs are usually computers connected to a set of input/output devices. The computers are programmed to respond to input by sending output to maintain all processes at setpoint.

*What is a Distributed Control Systems ?
DCSs are controllers that,in addition to performing control functions,provide readings of the status of the process,maintain databases and man-machine interface.

*What is an Indicator?
An indicator is a human readable device that displays information about the process.

*What is a recorder ?A recorder is a device that records the output of measurement device.

*What is an actuator ?
An actuator is the part of a final control devices that causes a physical change in the final control device when signaled to do so.

Eg: Valve,Motor etc..

*What is meant by Manipulated variable
The fuel or energy that is physically altered by the final control element.

*What is a Transducer?
A transducer is device that translates a mechanical signal into an electrical signal.

*What is a Transmitter?
A transmitter is a device that converts a reading from a sensor or transducer into a standard signal and transmit that signal to a monitor or controller.

*What is a Pneumatic Signal?Pneumatic signals are signals produced by changing the air pressure in a signal pipe in proportion to the measured change in a process variable.

*What is an Electric (Analog) Signal?
Electric analog signals produced by changing the electrical property in proportion to the measured change in a process variable.

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