Lab Reports

General Information

There are many career possibilities you'll be considering in the next few years, from working in industry, to wall street, to going on to graduate school. In most of the careers you'll pursue, you will be required to present write-ups of your work on a regular basis. These write-ups will be used to justify keeping you around, or to provide you with more financing. Unfortunately, the person who presents themselves the best (not necessarily the best qualified) is often the one who succeeds.

The ability to present your work well is something you tend to pick up as you go along, as opposed to having a course devoted to the subject. In this class the lab reports are used as a tool to help you learn how to best present scientific work.

There is an optimal way to organize any scientific document:

• Abstract: a few sentences or paragraph that summarizes what you are doing, and the results.
• Introduction that expands the abstract.
• Motivation for your work (ex: perfect a data mining technique to predict changes in the stock market, develop a theory to explain an observation, etc).
• Analysis: how did you do your work/what experimental setup, what equations did you derive
• Results: what is the outcome (data collected, graphs, charts, how does your theory fit the observation, etc)
• Conclusions: summarize, typically a repeat of the abstract
• References

Often you can combine the Introduction and Motivation into one section. For your lab reports this semester, the Analysis and Results sections can often be combined.

Your reports should be clear, concise, and thorough. Someone who has never had this course before should be able to pick up your lab report, see what the purpose of the lab was (the abstract at the front), flip to any section, see exactly what you did (breadboard diagram, settings on the function generator, components), see what effects you measured, and understand why you observed those effects. The person doing the reading should not have to work very hard to draw conclusions. You want to draw the conclusions (this is the expected result because ...) for the reader, in a very clear, plain way. The basic rule of thumb is if the reader has to draw their own conclusions, they're going to draw the wrong one.

Lab Report Requirements

You will not be penalized if you don't produce the expected result from a lab. You will lose points if you do not try to explain why your observation differs from expectation.

In specific, your lab report should contain:

• Single spaced, double sided paper, date, pages numbered, your name, your partners names
  
  
• You must draw all circuit diagrams, with clearly labeled lines and components.
  • These can be hand drawn, or copied and cut and paste from your lab/HH lab book.
  
  
• You must draw all breadboard diagrams, with clearly labeled lines and components.
  • These can be hand drawn, cut and paste from your notepaper, but NOT PHOTOGRAPHS. There is a free template for Word here.
  
  
• Include the complete information for each part of the lab, so that if need be I am able to reproduce your set-up. This means all settings on the function generator/scope, voltage used, components used, etc.
  • ex: If you used the function generator, tell me what setting the f, A were on, if you were sweeping, etc.
  • ex: If the lab called for a 12.5 resistor and we only had 12 or 14, tell me which one you really used
  • ex: If the lab called for 15 pF caps and you used 3 4.7's in parallel to make 14.7 pF, tell me that's what you did.
  
  
• Label all figures and tables with a descriptive sentence.
  • ex: Figure 1: Output from a high-pass filter, using as input a 60 Hz, 2 V, square wave. R = 10k, C = 100 pF.
  
  
• Always compare your observed value with your calculated value. Do the comparison as a percent difference.
  • Percent deviation (difference): ( ( |measured - expected| / expected) * 100 )
  • ex: We calculated the driving current of the current mirror to be 1.0 mA. The measured output is 1.6 mA. This is a 60% deviation from the theoretical expectation.
  
  
• Show the complete analysis of your work. "Yes." is never accepted as an answer.
  • ex: the lab asks you if the output from a circuit is what you expect. "yes" is not appropriate. I want to see something like: "We expect that the half-wave circuit will only pass the positive swing of the input AC current. We displayed the input AC wave on the scope, along with the output of the circuit. We observed the positive swing at the output of our circuit, and a flat line at 0 during the time when the input is swinging negative. Our output matches our expectation."
  
  
• Show all data to support your statements.
  • ex: you are asked to vary frequency of the input AC wave and check that the time constant of your circuit does not change. Stating that "we varied the frequency and found tau didn't change" is not good. What's your proof? Why should I trust you? More importantly, how do I know you didn't copy the work from someone else? Include tables of results, you can make those tables into a plot to include, and you can take scope images. All of these things should be used to defend your conclusions.
  
  
• Answer all questions for each part of the lab. The HH lab manual has an interesting way of presenting material. Please ask me if you aren't sure if something should be answered.
  
  
• Lab partners results must be consistent. You should have the same images and ~the same data points (2.90 and 2.86 are fine. 2.09 and 2.19 are not). If there are any problems sharing information please let me know.
  
  
• You must have correct spelling, proper grammar, and use correct scientific terms to describe effects.

Specific Example

In your lab reports you'll have many different results to present. Your report should consist of 1 abstract, and internal to each part of the lab you should have an introduction/motivation, analysis/results, and a conclusions section. The introduction, analysis, and conclusions sections do not need to be long and involved. Here is an example where the Analysis and Results sections are separate (HH Lab 2.3, the integrator):

• Intro/Motivation: We construct an RC integrator, whose purpose is to output the integral of any input function.
• Analysis: We connected the input function generator to a 10k resistor. The resistor was connected in parallel to a grounded 0.1 microF capacitor. The output voltage is measured across the capacitor. The function generator was set to 100kHz frequency, with an amplitude of 5V.
• Results: We drove the circuit with a square wave and see ..
• Results: We drove the circuit with a triangle wave and see ...
• Results: We drove the circuit with a sine wave ...
• Conclusions: We input three functions to this circuit: a square wave, a triangle wave, and a sine wave. The observed outputs of the circuit corresponded to the integral of the input functions.

An example from Lab 2 where the Analysis and Results sections are combined is shown here.