← All memosMemo 01 · Sense · 4 min read
How does a sensor become a decision?
Daniel McNair · Sample memo · September 2026
A sensor does not hand a computer the truth. It produces a physical signal—often a voltage—that must be measured, translated, and interpreted.
Start with a magnet
A Hall-effect sensor changes its output voltage when a magnetic field changes. Imagine its output is 2.5 volts with no field and rises by 5 millivolts for each additional gauss. A 200-gauss field would produce about 3.5 volts.
That voltage is still analog: it can take any value within the sensor’s range. A microcontroller’s analog-to-digital converter, or ADC, measures it and assigns a digital number. Software can then compare that number to a threshold and turn on an LED.
Magnetic field → voltage → ADC reading → software decision.
The engineering question
How small a change can the system detect? A 10-bit ADC spanning 0 to 5 volts has 1,024 possible codes, so one step is about 5 V / 1024 = 4.88 mV. With a sensor sensitivity of 5 mV per gauss, that is roughly one gauss per ADC step.
Resolution is only part of the answer. Electrical noise, sensor error, reference-voltage drift, and how often you sample can all limit a real measurement. If the magnetic field changes rapidly, too few samples may miss the change or make it appear slower than it is.
Why defense engineers care
Radar receivers, navigation sensors, and aircraft health monitors all convert physical signals into digital information. The software decision is only as trustworthy as the measurement chain beneath it. Engineers therefore specify the sensor, ADC, filtering, timing, and tests as one system.
Interview prompt
Question: A 12-bit ADC spans 0 to 5 volts. What voltage does one code represent?
Answer: Approximately 5 / 4096 = 0.00122 V, or 1.22 millivolts. More bits improve ideal voltage resolution, but do not remove sensor noise.
A little about me
Curious about people.
Drawn to systems.
I’m Daniel, an electrical and computer engineering student at Duke. I’m learning how circuits and code become systems people can depend on.
Where it started
A different way to serve.
I grew up in Annapolis in a family with five generations of Navy service. I initially pictured following that path in uniform. Then I read Chris Miller’s Chip War and found myself thinking about the technology behind the mission: the semiconductors, circuits, and engineers that make modern systems possible. I switched to electrical and computer engineering because I wanted to understand that work well enough to contribute to it.
What I’m following now
From a signal to a decision.
Studying engineering has given that curiosity a practical direction. I’m especially interested in embedded systems, sensors, semiconductors, and defense technology: how they work, how they fail, and how to make them reliable.
These memos are a place to work through those questions in public, one concept at a time.
Outside engineering, I’m also interested in college counseling. As a first-generation student, I know how much it helps to have someone make the process clearer, and I’d like to help other students find opportunities and tell their stories well.
Read the memos ↗Building & learning
Experience.
Engineering, investing, and research have each taught me a different way to ask better questions.
Current focus
Electrical & Computer Engineering
Duke University · Student
Building a foundation in circuits, computing, mathematics, and physics. In the lab, I’ve worked with sensors and microcontrollers to turn physical measurements into decisions in code.
Past experience
Research, analysis & people
Duke Impact Investing Group
Investment Analyst · Industrials
Researched early-stage companies, spoke with founders, and helped evaluate a potential investment in BluShift Aerospace.
LEA
Intern · Summer 2026
Supported presentation design, contact research, and outreach planning.
Beyond the classroom
Tennis & service
Tennis taught me to practice deliberately and adapt under pressure. Growing up in a Navy family shaped my interest in service and the engineering challenges behind national defense.