The Formal Laboratory Report
The purpose of the laboratory report is:
- To provide an accurate account of the work that was performed in the laboratory.
- To present in a clear manner the data that was accumulated, and the conclusions that were drawn from it.
- To interpret the results and discuss them in the light of the underlying theory.
For a report to be useful, it must be logically arranged so that it is clear to the reader. The description of the various procedures must be accurate and the results obtained must be as precise as the measurements permit.
The format of a formal laboratory report is somewhat flexible depending on the particular requirements of the persons concerned, (company policy, government specifications, course requirements, and so on). For the laboratory work in the Department of Electrical and Computer Engineering the following format and sequence of presentation will be required for a formal report.
Title Sheet and CoverThe appropriate title sheet-cover is available at the college bookstore. This cover provides spaces for the experiment title, names of the group members, data and other information. It should be completed in ink or typewritten. All other parts of the report should be written in ink or typewritten unless otherwise specified.
Abstract or SynopsisThis summary includes the apparatus tested, the type of results obtained and a summary of conclusions reached. The purpose is to provide a concentrated survey of what experimental work was accomplished so that a reader of the abstract can make a decision about whether or not to read the detailed report.
ProcedureThe section consists of a concise description of the apparatus used, the manipulations made, and the observations taken. Reference should be made to the appropriate circuit diagrams that follow later in the report. The procedure should not be a mere copy of the "Instructions" printed in the laboratory manual. Any variation or differences between what is in the manual and the way that you performed the lab must be noted.
Final connection DiagramThe connection diagrams should be complete within themselves. All pertinent information concerning ratings and stockroom numbers of the measuring equipment and apparatus tested should be included. Standard electrical symbols as listed in the EE 11 Manual should be used. A neat hand drawn diagram may be scanned into your report.
- The observed laboratory data should be placed at the end of the report. The original laboratory data should be taken in ink or ball point pen and should have no erasures. All information including meter numbers, meter scales, meter factors, must be recorded. Correction of recorded data is made in the laboratory by drawing a line through the incorrect entry and writing in the new entry.
- The translated laboratory data should follow the connection diagrams. This data should be a summary of the laboratory measurements in final form. All meter multiplying factor computations should be carried out before entering readings on the final data sheet. All reports of the experiment should be identified on the data sheet by a descriptive title and reference made to the proper circuit diagram. The use of such references as "Part I" should be avoided.
Computations and ResultsThe computations should be made in a logical manner in simple computation form, with a table of results that follows. The method should be explained to the reader and all terms and symbols defined; any formulas or equations taken from reference material should be properly footnoted. The final results should appear in tabular form presented in a manner that makes them stand out. This usually requires some individual planning. In general all curves that are plotted in a report are preceded by a supporting table of results found in the "results" section.
CurvesSee "Instructions for Graphs."
Note: In some cases special graphs (semi-log, etc.) will be required. This will be pointed out in the "procedure" portion of the laboratory manual.
Phasor DiagramWhen phasor diagrams are required they should be plotted to scale. A scale should be chosen so that a quantitative appraisal of the shortest vector can be made. A neat scanned hand drawn diagram will be acceptable.
Discussion and Conclusions
Topics for discussion are usually suggested in the instructions. These suggestions provide a minimum framework around which the student should build a discussion. The discussion section provides the student with the greatest opportunity for originality in thought and logical reasoning. A thoughtfully clear discussion can greatly increase the value of a report.
It is often possible to provide clear explanations by means of curves or diagrams, and these should be used where applicable. Conclusions, results, comments on sources of error and their probable magnitude should be made. In some instances recommendations are in order. The discussion of results should be a student's individual effort.
BibliographyA complete bibliography presented in standard form must be included. This bibliography must appear if footnotes are used. The bibliography should also include any credits to the work of other individuals, even if unpublished, unless this was accomplished through footnotes.
English StyleThe report should be written in past tense third person impersonal.
Instructions For Graphs
Graphs are to be consistent with good drafting style. They should be oriented to be readable from left to right or from bottom to top (never from top to bottom). All figures should be captioned in a manner similar to that used in this manual, they should include titles, axes labels and units where appropriate.
Preparing Graphic Sheets
Graphs must indicate where, when and by whom the work was done. They must have a descriptive title. The graph sheets must contain enough information to make them sufficiently complete to be considered separately from the rest of the report.
Whenever possible, the meaning of the graph should be clarified by the addition of a small drawing somewhere on the sheet indicating, for example, how voltages were applied to the circuit or what measurements were made.
Both axes of a graph must be marked with the scale and name of the quantity e.g., voltage (not V), and the corresponding units.
Choose a scale interval such that each main division represents 1, 2, or 5 units or a multiple of ten times 1, 2, or 5.
Enlargement of a graph scale sometimes provides greater precision. However, nothing will be gained if, at the smaller scale, the plotted points already exhibit scattering about the "average" line. It is also useless to expand the scale to the point where one unit in the last significant figure is represented by much more than a few divisions of the graph paper.
Start both scales at the origin (0, 0). In the case where a large part of the graph sheet, say 50 %, would be left unused, the origin may be omitted provided it has no significance in the interpretation of the graph.
When the range of the horizontal or vertical variable is very broad, a uniform scale may result in an overcrowding of the experimental points taken in the lower part of the scale. This problem may be solved by dividing the horizontal range into several parts and plotting a separate graph for each of these parts, using a uniform scale. However, a single plot covering the whole range is often desirable and a logarithmic scale is then found to be more convenient than a uniform scale. A semilog or log-log graph is recommended in this case.
In plotting a graph from experimental data, the plotted points should always be identified by a small circle, square or similar item. In plotting a graph from an analytical expression, use enough points to determine a smooth curve. The curve should go exactly through the points, which should not be circled or distinguished in any way.
In plotting a graph of experimental values, draw a smooth average curve which may or may not pass through most of the plotted points. When the proper curve is drawn, the plotted points will exhibit a random scattering on each side of the curve and will, on average, be as close as possible to the curve. An experimental curve should never show a special wave or bump by virtue of a single plotted point. Such complications in the curve would require that several points indicate the trend.
One of the purposes for a graph is to provide the writer of the report (as well as the reader) an overall picture of the data. Sometimes it is this picture which is the desired conclusion. A direct proportion is indicated by a graph only when the graph is a straight line passing through the origin. Frequently, there is a simple explanation available to show why the graph misses the origin. A note to that effect in the discussion of the graph is desirable in such cases.
In determining the slope of a tangent or of a straight line graph, use as long a straight segment as possible. Read values off the straight line; do not use plotted values.
Remember that tabulated experimental values contain experimental errors. The graph is a means of averaging out this error. A value read from the "smooth average" curve is likely to be closer to the "true" value than the plotted values which the curve misses.
Whenever any information can be derived from the comparison of two graphs, or whenever two curves represent the same of similar tests, they should be plotted on the same sheet with the same axes. When several graphs are plotted on the same axes, distinguish between them by lettering a descriptive word or phrase along each curve. If the plotted points of two graphs tend to mingle, use different identifying marks for each set of points.