CCST Calibration & Testing of Control Instruments 2

Question 1

What is the key difference between accuracy and precision in instrument measurement?

Accepted Answer

Accuracy is how close a measurement is to the true value; precision is how repeatable measurements are

Answer

Accuracy is how repeatable measurements are; precision is how close to true value

Answer

Accuracy applies to analog instruments; precision applies to digital instruments

Answer

Accuracy and precision are synonymous terms in metrology

Question 2

What is 'hysteresis' in a control instrument?

Accepted Answer

The difference in output readings when approaching the same input value from increasing versus decreasing directions

Answer

The time delay between a process change and the transmitter output response

Answer

The temperature coefficient affecting sensor accuracy

Answer

The maximum overrange pressure the instrument can withstand

Question 3

Why must calibration standards used in the field be NIST-traceable?

Accepted Answer

To ensure measurements are linked through an unbroken chain of comparisons to national measurement standards, ensuring accuracy validity

Answer

To comply with OSHA regulations for field instrument technicians

Answer

To qualify the technician for ISA certification renewal

Answer

To meet EPA reporting requirements for environmental measurements

Question 4

An RTD (Resistance Temperature Detector) operates on what principle?

Accepted Answer

The predictable change in electrical resistance of a metal with temperature

Answer

The Seebeck effect — two dissimilar metals generate a voltage proportional to temperature

Answer

The expansion of a bimetallic strip with temperature change

Answer

The change in capacitance of a ceramic element with temperature

Question 5

What is 'deadband' in a control instrument or controller?

Accepted Answer

A range of input values over which no change in output occurs, used to prevent unnecessary control action

Answer

The frequency range where the instrument cannot respond to process changes

Answer

The signal loss experienced in long cable runs

Answer

The minimum pressure required to open a control valve

Question 6

When calibrating a thermocouple transmitter in the field without a reference junction compensator, which method provides the most accurate result?

Accepted Answer

Applying a millivolt source calibrated to simulate the thermocouple output at specific temperatures, accounting for CJC

Answer

Connecting a known resistance in series with the thermocouple circuit

Answer

Replacing the thermocouple with an RTD and recalibrating the transmitter

Answer

Using the transmitter's internal auto-zero function

Question 7

What does 'calibration tolerance' define in an instrument calibration procedure?

Accepted Answer

The maximum allowable error between the instrument's output and the reference standard at each calibration point

Answer

The maximum ambient temperature range in which calibration can be performed

Answer

The time interval between required calibrations

Answer

The minimum signal level the instrument can detect