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 network operates at 1.5 Mbit/s. The maximum allowable cable length per segment at this baud rate is approximately:
Answer: 400 m
At 1.5 Mbit/s, the maximum segment length is approximately 400 m according to PROFIBUS specifications due to signal propagation and attenuation constraints.
What is the purpose of the 'Freeze' mode command in PROFIBUS DP troubleshooting?
Answer: Lock input values from multiple slaves at a single point in time
The Freeze command causes all slaves in a defined group to simultaneously latch their current input data, enabling synchronized diagnostics or process snapshots.
During a PROFIBUS segment audit, you measure a resistance of 220 Ω between the two bus lines (A and B) with the network powered off. What does this indicate?
Answer: Correct termination with two 110 Ω terminators in parallel
Two 110 Ω termination resistors (one at each end) appear as 55 Ω in parallel — a reading of 220 Ω between A and B lines confirms two properly installed terminators.
A PROFIBUS PA segment has 8 field devices consuming an average of 15 mA each. The segment coupler provides 400 mA. What is the remaining current budget?
Answer: 280 mA
8 devices × 15 mA = 120 mA consumed; 400 mA − 120 mA = 280 mA remaining, which can accommodate additional field devices.
Which PROFIBUS DP error condition is indicated when the 'Watchdog_Active' bit in Station_Status_2 is set to 1?
Answer: The slave's watchdog timer is enabled and actively monitoring the master
When Watchdog_Active is set in Station_Status_2, it means the slave has enabled its watchdog timer and is actively monitoring for periodic data exchange with the master.
What is the recommended action when PROFIBUS bus analysis shows that the signal eye pattern is significantly degraded but no communication errors are yet occurring?
Answer: Perform preventive maintenance — inspect connectors, cable bends, and termination
A degraded eye pattern indicates reduced noise margin that will eventually cause errors; proactive inspection and repair prevents future downtime.
In PROFIBUS PA, the function block status code 'BAD – Not Connected' most likely indicates:
Answer: The field device is not communicating with the process connection or sensor
'BAD – Not Connected' in PROFIBUS PA function blocks indicates the transducer block has no valid connection to its physical sensing element or process.