CPE Electromagnetic Compatibility (EMC) & Physical Layer 2

Question 1

What is the correct passive Profibus bus termination network configuration?

Accepted Answer

390 Ω pull-up to +5V, 220 Ω across A-B, 390 Ω pull-down to GND

Answer

A single 120 Ω resistor across A and B lines

Answer

Two 75 Ω resistors in parallel to ground

Answer

A single 220 Ω resistor from A to B with no biasing

Question 2

What is the consequence of operating a Profibus segment with no active bus termination at one or both ends?

Accepted Answer

Signal reflections cause intermittent data corruption

Answer

Signal amplitude increases above spec

Answer

Bus current consumption increases

Answer

Baud rate is automatically reduced

Question 3

What measurements does a Profibus bus analyzer perform to assess physical layer signal quality?

Accepted Answer

Signal voltage levels, noise margin, timing jitter, and reflection waveforms

Answer

Cable resistance only

Answer

IP address and subnet mask of each node

Answer

Power consumption of individual field devices

Question 4

What is the primary purpose of a potential equalization bonding conductor in a Profibus installation?

Accepted Answer

To equalize ground potentials between cabinets and reduce common-mode interference currents

Answer

To carry the differential Profibus data signal as a backup path

Answer

To provide +24V supply to field devices along the bus

Answer

To serve as a redundant communication path

Question 5

What physical characteristic of Profibus Type A cable primarily limits the maximum achievable baud rate to 12 Mbit/s?

Accepted Answer

Capacitance per unit length and resulting signal propagation delay

Answer

Excessive conductor resistance per unit length

Answer

Insufficient insulation voltage rating for industrial environments

Answer

Excessive cable weight per meter

Question 6

What is the maximum number of devices (stations) allowed on a single Profibus DP segment before a repeater is required?

Accepted Answer

32

Answer

16

Answer

64

Answer

126

Question 7

What common-mode voltage range must Profibus RS-485 transceivers tolerate without data corruption?

Accepted Answer

±7 V

Answer

±2 V

Answer

±5 V

Answer

±15 V