Instrumentation & Measurement Flashcards
7 cards from real ITMC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Instrumentation & Measurement flashcards as text
What is hysteresis in a measuring instrument?
Answer: The difference in output for the same input depending on whether the input is increasing or decreasing
Hysteresis is the error caused by mechanical factors such as friction or backlash, resulting in different output readings for the same input value depending on the direction of travel.
Which level measurement device operates on the principle of hydrostatic pressure from the liquid column above the sensor?
Answer: Differential pressure level transmitter
A differential pressure level transmitter measures the hydrostatic head pressure exerted by the liquid column above the lower tap, which is directly proportional to the liquid level in the vessel.
In process control terminology, what does 'PV' stand for?
Answer: Process Variable
PV stands for Process Variable, the actual measured quantity (such as temperature, pressure, level, or flow) that the control loop monitors and attempts to maintain at the setpoint.
What is the purpose of a flow totalizer in an instrumentation system?
Answer: To accumulate and display the total volume of fluid that has passed a measurement point over time
A flow totalizer integrates the measured flow rate over time to calculate and display the cumulative volume or mass of fluid that has passed through the metering point.
Which type of pressure measurement references the process pressure against local atmospheric pressure?
Answer: Gauge pressure
Gauge pressure is measured relative to local atmospheric pressure, so a reading of 0 psig equals one atmosphere (~14.7 psia), and it is the reading shown by most standard industrial pressure gauges.
What does a PID controller calculate to generate its output signal?
Answer: A corrective output based on Proportional, Integral, and Derivative error terms to minimize setpoint deviation
A PID controller computes an output using three terms: Proportional (current error magnitude), Integral (accumulated past error), and Derivative (rate of error change), working together to minimize deviation from the setpoint.
What is the primary advantage of a smart (HART-enabled) transmitter over a conventional analog transmitter?
Answer: It superimposes digital communication on the 4-20 mA signal for remote configuration and diagnostics
HART (Highway Addressable Remote Transducer) protocol superimposes a digital signal on the standard 4-20 mA analog signal, allowing remote configuration, diagnostics, and multi-variable communication without additional wiring.