Practice Test Geeks(CPE) Certified Polygraph Examiner Practice Test
← All CPE Flashcard Decks

Electromagnetic Compatibility (EMC) & Physical Layer 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 Electromagnetic Compatibility (EMC) & Physical Layer flashcards as text

  1. What is the characteristic impedance of Profibus Type A cable as specified in EN 50170?

    Answer: 135 Ω

    Profibus Type A cable has a specified characteristic impedance of 135 Ω ±20% as defined in EN 50170, which determines the correct termination network values.

  2. What is the minimum differential input voltage that an RS-485 receiver used in Profibus must recognize as a valid signal?

    Answer: 200 mV (0.2 V)

    The RS-485 standard requires receivers to reliably detect differential signals as low as 200 mV, providing high noise immunity over long cable runs.

  3. Which grounding practice is recommended for Profibus cable shields to prevent ground loop interference?

    Answer: Single-point grounding at one end only

    Single-point grounding prevents circulating ground loop currents that would otherwise flow through the shield and induce noise onto the differential signal pair.

  4. What is the maximum allowed segment cable length for Profibus DP operating at 12 Mbit/s?

    Answer: 100 m

    At 12 Mbit/s the signal rise-time budget limits the Profibus DP segment length to 100 meters due to cable propagation delay and capacitive loading.

  5. Which passive component is commonly integrated into Profibus bus connectors to suppress high-frequency common-mode noise?

    Answer: Ferrite bead

    Ferrite beads present high impedance to high-frequency common-mode currents while having negligible effect on the lower-frequency differential Profibus signal.

  6. At what angle should Profibus signal cables cross AC power cables to minimize electromagnetic coupling?

    Answer: 90° (perpendicular)

    Crossing at 90° minimizes the coupling area between the Profibus cable and the power cable, reducing both capacitive and inductive interference transfer.

  7. What is the maximum capacitance per unit length permitted for Profibus Type A cable?

    Answer: 30 pF/m

    Profibus Type A cable is specified with a maximum capacitance of 30 pF/m, which limits signal attenuation and ensures adequate rise times at 12 Mbit/s.