Question

A pulse of 100ms duration and 1nA amplitude is injected at the beginning of a cable. What is the purpose of this pulse injection?

a) To measure the cable's capacitance
b) To measure the cable's inductance
c) To measure the cable's input resistance
d) To measure the cable's impedance

Answer 1

The correct answer is option d) To measure the cable's impedance.

Step-by-step explanation:

The injection of a 100ms duration and 1nA amplitude pulse into the cable is most likely performed to measure the cable's impedance. This is a common practice in characterizing transmission lines such as cables. By observing how the pulse propagates along the cable and how it is reflected at terminations or mismatches, technicians can gather data on the characteristic impedance of the cable. This data is crucial because it affects how signals will travel through the cable, any potential reflections, and the power handling capabilities.

Impedance is a comprehensive measure that includes both resistance and reactance (contributions from capacitance and inductance) in the cable. Therefore, injecting a pulse and observing its behavior offers insights into how the cable will perform in real applications, such as in telecommunications or signal processing where the integrity and strength of the signal are vital.