Troubleshooting & Maintenance Techniques Flashcards
7 cards from real CPE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Troubleshooting & Maintenance Techniques flashcards as text
A PROFIBUS DP slave remains in the 'WAIT_PRM' state and never transitions to data exchange. What is the most likely cause?
Answer: The master is sending parameterization data that does not match the slave's GSD-defined requirements
The WAIT_PRM state persists when the slave rejects the Set_Prm telegram because the parameter data length or content does not match what the slave expects per its GSD file.
What is the significance of the 'Deactivated' slave status in a PROFIBUS DP master's live list?
Answer: The slave is configured in the master but excluded from cyclic data exchange by the user
A 'Deactivated' slave is intentionally excluded from the master's active polling cycle by configuration, often used for devices installed but not yet commissioned.
When performing insulation resistance testing on PROFIBUS cable for maintenance purposes, which precaution is essential?
Answer: Disconnect all devices and terminators from the cable before applying the test voltage
All connected devices and terminators must be disconnected before applying insulation test voltage to prevent damage to sensitive electronic components in field devices and terminators.
In PROFIBUS PA, what does the 'Simulate' function block parameter enable during maintenance?
Answer: It allows the output value and status to be manually set, bypassing the actual process measurement
The Simulate parameter in a PROFIBUS PA function block allows maintenance personnel to inject test values and statuses into the function block output without requiring actual process conditions.
A PROFIBUS segment experiences communication errors only during the day shift. Plant data shows heavy welding operations nearby. Which root cause is most likely?
Answer: Electromagnetic interference from welding equipment coupled onto unshielded or improperly grounded cable
Welding equipment generates significant high-frequency electromagnetic interference that can be coupled onto PROFIBUS cables with inadequate shielding or improper grounding.
What is the purpose of the 'Ident_Number' field in a PROFIBUS slave's diagnostic response?
Answer: It identifies the device type and must match the Ident_Number in the master's GSD-based configuration
The Ident_Number is a manufacturer-assigned type identifier that must match between the slave hardware and the master's configuration derived from the GSD file; a mismatch prevents data exchange.
After replacing a PROFIBUS PA pressure transmitter, the new device shows process value 'BAD – Sensor Failure' immediately after power-up. The most likely cause is:
Answer: The device requires configuration or calibration before its sensor measurement becomes valid
A newly installed PA transmitter may report 'BAD – Sensor Failure' until it is properly configured and calibrated with the appropriate range, units, and sensor-specific parameters.