Prove yourself as an engineer! The Schematic Challenge is the perfect opportunity to test your skills. On March 5, 6, and 7, we will be posting a new schematic or problem-solving challenge. If you, as a community, are able to answer questions 1, 2, and 3 correctly by Thursday, March 8 at 11:59 PM MST, we will add three 1000 X-Series oscilloscopes to the overall Wave 2018 giveaway! **Answers should be posted** in a comment on the #SchematicChallenge posts **on the Keysight Bench or RF Facebook pages**. Work with your family, friends, coworkers, or fellow engineers in the Wave community to solve these problems. If you haven’t already, be sure to register for Wave 2018 at wave.keysight.com.

**Question 1:**

By Ryan Carlino

Status: **SOLVED! **(minimum of 8 bits)

You need to design a circuit to determine the resistance of an unknown ID resistor.

A voltage divider provides a bias that creates a voltage at the input of an ADC.

You’d like to be able to distinguish between a 15K and 20K ID resistor.

The ADC has a 0.5% internal 3.3V reference. The resistors are all 1%.**What is the minimum number of bits of resolution that the ADC needs** in order to have at least 10 codes (LSBs) between a 15K and 20K resistor?

**Question 2:**

By Ryan Gillespie

Status: **SOLVED! **( V(d)=(0.72 - 0.13i) V )

Given the doubly terminated transmission line, **calculate the voltage at d = 100 µm.**

*Hint: First you may want to solve for Zo, Wave Speed, Wavelength, V(x) and I(x)*

Your answer should be in the form of V(d) = ( # + #i ) where # are the numerical answers.

* *

Useful formulas:

**Question 3:**

By Patrick Mann

Status: **SOLVED!**

Given the block diagram in figure 1, **is the additional explicit trigger input shown in blue in figure 2 required? **Select the correct answer and **post the respective letter on the Keysight Bench or RF Facebook pages**:

- The explicit trigger is not required since the sampling oscilloscope can trigger off the data.
- The explicit trigger is required since the sampling oscilloscope cannot trigger off the data.
- The explicit trigger is not required because the precision waveform analyzer module can recover a clock and feed it to the sampling oscilloscope’s trigger circuitry.
- The explicit trigger is required because the precision waveform analyzer module cannot recover a clock and feed it to the sampling oscilloscope’s trigger circuitry.
- The explicit trigger is not required because the external time reference feeds into the sampling oscilloscope’s trigger circuitry.
- The explicit trigger is required because the external time reference feeds into the sampling oscilloscope’s trigger circuitry.

Figure 1: Precision Waveform Analyzer module (blue) and sampling oscilloscope mainframe block diagram (green)

Figure 2: Connection diagram of a sampling oscilloscope and module (left) to a pseudorandom binary sequence (PRBS) generator (right)