CCST Troubleshooting & Maintenance of Control Systems 3

Question 1

When troubleshooting a smart HART transmitter, which tool is most effective for reading device diagnostics without interrupting the 4-20 mA signal?

Accepted Answer

HART communicator connected in parallel with the loop

Answer

A HART communicator superimposes FSK digital communication on the existing 4-20 mA signal, allowing diagnostics to be read without breaking the loop.

Question 2

After replacing a control valve packing, the valve stem requires excessive actuator force to move. What is the most likely cause?

Accepted Answer

Packing gland over-tightened

Answer

Over-tightening the packing gland compresses the packing material excessively, dramatically increasing stem friction and the force needed to stroke the valve.

Question 3

A technician finds that a PLC digital output card is not energizing a solenoid valve. The PLC ladder logic shows the output coil is energized. What should be checked next?

Accepted Answer

Check output card fuse and field wiring voltage

Answer

When PLC logic shows an output ON but the field device does not respond, the next step is checking for a blown output card fuse or missing field power.

Question 4

A temperature control loop exhibits a slow, sinusoidal oscillation with a period much longer than the process time constant. Which controller parameter is most suspect?

Accepted Answer

Integral time set too short (reset rate too fast)

Answer

Long-period sinusoidal oscillation is a classic symptom of integral instability caused by an integral time that is set too short (too aggressive reset).

Question 5

A pressure transmitter consistently reads 2 psi high across its entire range. This error is best described as:

Accepted Answer

Zero offset error

Answer

A constant error that shifts the entire output curve up or down uniformly across the range is a zero (bias) offset error, corrected by adjusting the zero.

(CCST) Certified Control Systems Technician Practice Test

(CCST) Certified Control Systems Technician Practice Test

CCST Troubleshooting & Maintenance of Control Systems 3