Plant Operator Selection System Test Process Control and Instrumentation

Question 1

A thermocouple measures temperature by:

Accepted Answer

Generating a small voltage at the junction of two dissimilar metals

Answer

Expanding a bimetallic strip proportional to heat

Answer

Changing resistance as temperature increases

Answer

Detecting infrared radiation emitted by the process

Question 2

In a PID controller, the 'I' (integral) term is used to:

Accepted Answer

Eliminate steady-state offset by accumulating past error over time

Answer

Respond to the current error value

Answer

Dampen rapid changes by anticipating future error

Answer

Set the maximum allowable output

Question 3

A control valve with an air-to-open (ATO) fail action will:

Accepted Answer

Close fully when instrument air pressure is lost

Answer

Open fully when instrument air pressure is lost

Answer

Remain at its last position when air pressure is lost

Answer

Open slowly over 30 seconds after air loss

Question 4

What does a differential pressure (DP) transmitter measure when installed across an orifice plate?

Accepted Answer

Flow rate based on the pressure drop across the restriction

Answer

Temperature of the flowing fluid

Answer

The absolute pressure of the upstream pipe

Answer

Fluid density at operating conditions

Question 5

On a Process and Instrumentation Diagram (P&ID), a dashed line connecting an instrument to a control element typically represents:

Accepted Answer

An electrical or pneumatic signal

Answer

A mechanical connection

Answer

A proposed future connection

Answer

A safety interlock bypass

Question 6

A level transmitter in a tank reads higher than the actual level. The most likely cause is:

Accepted Answer

A plugged or blocked impulse line on the low-pressure side

Answer

The tank is overfilled

Answer

The control valve is stuck open

Answer

The temperature sensor is reading low