CPE Troubleshooting & Maintenance Techniques 5

Question 1

A PROFIBUS DP slave remains in the 'WAIT_PRM' state and never transitions to data exchange. What is the most likely cause?

Accepted Answer

The master is sending parameterization data that does not match the slave's GSD-defined requirements

Answer

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.

Question 2

What is the significance of the 'Deactivated' slave status in a PROFIBUS DP master's live list?

Accepted Answer

The slave is configured in the master but excluded from cyclic data exchange by the user

Answer

A 'Deactivated' slave is intentionally excluded from the master's active polling cycle by configuration, often used for devices installed but not yet commissioned.

Question 3

When performing insulation resistance testing on PROFIBUS cable for maintenance purposes, which precaution is essential?

Accepted Answer

Disconnect all devices and terminators from the cable before applying the test voltage

Answer

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.

Question 4

In PROFIBUS PA, what does the 'Simulate' function block parameter enable during maintenance?

Accepted Answer

It allows the output value and status to be manually set, bypassing the actual process measurement

Answer

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.

Question 5

A PROFIBUS segment experiences communication errors only during the day shift. Plant data shows heavy welding operations nearby. Which root cause is most likely?

Accepted Answer

Electromagnetic interference from welding equipment coupled onto unshielded or improperly grounded cable

Answer

Welding equipment generates significant high-frequency electromagnetic interference that can be coupled onto PROFIBUS cables with inadequate shielding or improper grounding.

(CPE) Certified Profibus Engineer Practice Test

(CPE) Certified Profibus Engineer Practice Test

CPE Troubleshooting & Maintenance Techniques 5