Physics 127AL, Analog electronics

The lab portion of this course is absolutely critical to work with and understand the concepts of electronics. It should also help you learn several important skills, including troubleshooting and proper laboratory record keeping.

Good record keeping is an important skill for research. You won't get far in undergraduate or graduate research by reporting in a research group meeting "I remember it went up when I jiggled a wire; I think it was the red one". But you will if you answer a question with "Let me check..." and then open your notebook to find the relevant data, cleanly tabulated and plotted, along with a sketch and photo of the measurement setup and a concise statement of the conclusion.

I hope you will learn that careful approach and meticulous record keeping skill in this class. This is important enough that the largest component of the Phys127AL course grade is based on the scores for your lab notebooks. The details on what is expected and how they will be graded is given below.

Proper protocols and record keeping (50%)

• Write in your e-logbook as you do the experiment, not afterwards.
  The logbook is a complete and quantitative record of what you did and what you measured. It is not an essay or summary.
  Writing a complete record, as you go, requires going a bit slower because you should spend about 20% of your time writing, but that will ultimately save time because it minimizes frantically confused debugging. Learning to do this will pay off in real research because it provides a ready answer when your supervisor asks questions followed by, "Show me". As preparation for that in this course, the TAs will ask you, while helping you debug your circuits, "Show me what you have done so far".

• Write everything in your notebook.
  Don't record data on scrap paper to be transcribed later only if you think it "makes sense".

• Draw the schematic for every circuit that you build.
  Make these detailed, including component values, label points in the circuit (such as A, B, or in, out) where you will measure things. Then you can label measurements as V_in or V_AB.

• Cross check your circuit connections.
  After you have set up a circuit, spend a minute tracing the connections to make sure that they match the schematic you drew in your logbook. This will save you headaches since you will certainly make connection mistakes eventually. Explicitly note in your logbook that you checked the connections with something like:
     15:17 Circuit connections confirmed.

• Take photos of your circuit connections.
  It doesn't take long to snap a couple photos with your phone and toss them in your logbook. You should also record in your logbook when you took the photos with
     15:18 Photos.
  This will allow you to flip through the photos in your elog, or even on your phone, to find the ones with that timestamp and reinspect the connections. You might find a missing connection or some other problem that explains (otherwise mysterious) past behavior and solves your debugging nightmare.

• Record the oscilloscope traces you get when making AC measurements.
  You can do this with a quick screen capture or saving as a png that you upload to your elog. These are usually referred to by the jargon of "scopecap" as a shorthand modification of screen-captures. To make these more useful, get in the habit of turning on the automatic measurements like peak voltage and frequency so that your scopecaps have information that may be useful later.

• Write conclusions as you go.
  For example, after you collect data, analyse it with appropriate calculations and plots, and write what you concluded. That conclusion may be "This data is garbage because I found that R₂ was 100 Ω instead of 100k Ω!", but write it anyway. This could turn out to be useful for some unexpected reason, and it is a hallmark of professionalism.

• Do not "erase" anything.
  Rather make the incorrect data or conclusions as "This is incorrect", and add a brief note about why you think it is incorrect.
  Don't delete logbook entries, just edit them with warnings about concluding that there are problems. We will eventually turn off the "delete" feature in the elog, and you will only be able to edit entries during the lab period. If you find a problem afterward, then "Reply" to the entry with the additional information.

• Timestamp every entry.
  The elog will give a timestamp for the whole entry, so you should make many small entries, but some of them may correspond to 10 or 15 minutes of work. If so, mark the time next to measurements made during the time you are writing your work in that entry, e.g.,
     4:15 Turn on power supply and measure Vout = 3.25 ± 0.01 V

• Make a new elog entry for each new step or topic. Give it a subject line that explains what is being recorded in that entry, e.g., "Measure the diode's IV curve".

• Neatness helps, but it is not a major factor in your grade as long as your logbook is understandable. Don't spend too much time on formatting initially, but as you get used to the tool you can make the formatting nicer.
  The key is organization and completeness.

• If you have questions, raise your hand in Zoom.
  

• When you finish with the lab, put an entry in your elog with "Done for today".
  Ideally, you would complete the full lab and write your (brief) conclusions before the end of the lab. If you need to come back later and do more, you should start that with an entry in your elog with "Continuing with lab 4". This is not about us "babysitting you"; in fact professional research logbooks often have entries like
  13:27 gone to lunch
  written in them so others working in the lab can tell what is up with others. And you often have
  23:52 going home
  That is not just bragging about working late, it is helpful to figure out whether a problem discovered in the morning started in the evening or the middle of the night.

• Clearly list the experiment title in the subject of the logbook entry.
  Make the title meaningful, like "Measure gain of differential amplifier", not something arcane like "Lab 3, step 4".
  If you start to move on to work that doesn't match that title, then start a new entry.

• Describe the general idea and purpose of what you are doing in a couple sentences.
  Make it descriptive but keep it short. (Don't waste a reader's time with fluff.)

• Include any relevant circuit analysis and calculations explicitly in the logbook.

• Complete each part of the lab.

• Include uncertainties on all measurements.
  Just get in the habit of quickly estimating the uncertainty based on the number of digits displayed on a meter or the amount that the reading fluctuates with time. This is a basic professionalism in science.
  However, for this lab you don't need to do error propagation calculations. And, you shouldn't spend too much time worrying about it beyond simple habits: if the measured value is fluctuating around by 0.3 V, then you can record this as V = 5.2 ± 0.3. If it is not fluctuating but is only measured to 1 digit, then just record it as V = 5.2. As long as you are consitent in doing this, then the uncertainty is implicit in the number of significant figures.

• Write all calculated values in your notebook with the method of calculation clearly specified.
  Someone reading the notebook (including you, when asked!) should be able to easily figure out how the results were calculated.

• Include plots with explicit labeling and units

• Include a brief summary at the end of what you did and what conclusions you came to.
  This can be brief, indeed it should be! It is a place for you to find the quick summary of the key points. You, or a reader, can then look back at the details as needed. Write this conclusion while still in the lab, not later at home. This will make sure it is all fresh in your mind. Make it concise hitting only the critical points; a pile of verbose BS is an insulting waste of everyone's time. If there is one key plot showing the result, copy it into the "Conclusion" entry of your elog. This is redundant since it should already be in an earlier entry, but having it there will help you see the conclusion all in one quick glance.

Dealing with the frustration of debugging problems

So, for an optimal educational outcome, I hope your circuits don't work at first! You will learn most by having to figure out things that don't initially make sense.

After all, figuring out things that don't currently make sense is what science is all about.