Undergraduate Laboratory Handbook: The Laboratory Logbook

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Some of the reasons you are required to do practical work as part of an Engineering Programme are:

  • To allow you to observe practical demonstrations of topics covered in your lectures and to complement the lecture modules.
  • To learn how to perform experiments correctly and to become familiar with instrumentation and laboratory practice.
  • To help you acquire a facility for recording and analysing experimental data and presenting it in a form that will be easily understood by others.

The last of the above points requires the use of a Laboratory Logbook. In most real-life situations in which experimental data is manually obtained it is directly recorded in a logbook. Such a book is an experimenter's diary containing all the information necessary for later reporting on an experiment in full. Although it is primarily for personal use--formal reports for others to read can be subsequently compiled from the logbook entries--it must be comprehensible to others in case the experimenter is moved to another project, falls ill, etc. You are therefore required to practice effective logbook techniques during all laboratory modules associated with the Programme.

You must maintain a separate logbook for each laboratory module. Logbooks should be bound and preferably hard-backed, with alternate pages of graph paper and plain ruled. Your name, class/year and name of the laboratory module should all appear on the cover.

You must supply the logbook: give it to the demonstrator at the end of the first session. Thereafter, the demonstrator is responsible for holding the logbooks, normally issuing them to students only for the duration of each laboratory session. The logbooks are normally held in a locked press in the relevant laboratory. In this way, you are restricted to writing up your reports on laboratory work actually during the laboratory sessions. This is a deliberate policy, decided by the Engineering Programme Boards, for a number of reasons:

  • It should encourage you in the discipline of maintaining effective records of experimental work while you are carrying it out.
  • It ensures that you do not expend a disproportionate time on writing up logbooks, to the possible detriment of other studies.
  • It improves the validity of assessment based on logbooks, as it ensures that it is primarily the genuine work of each individual student.


Do not remove your logbook from the laboratory. Give it to the demonstrator.

If you do take your logbook away with you, without permission, you run the risk of being given a zero mark for that exercise and/or being required to repeat it.

In general, logbooks will not be issued to you outside of scheduled laboratory sessions. Logbooks will be finally returned to you when the lab module is over and all marking has been completed. However, note that examiners may wish to review logbooks subsequently: it is your responsibility to keep them safely and make them available for such inspection on request.

Logbook Presentation

The Laboratory Manual contains the details of, and instructions for, each experiment or exercise. Your logbook, on the other hand, records the outcome of your own work on each such exercise; as such, it is a companion to, rather than some kind of substitute or replacement for, the lab manual. You must not transcribe material from the manual into the logbook. This is a distraction and a waste of time: marks will be deducted if you do this.

In broad terms, you should use the logbook to record what you intend doing, what you did do, and what the outcome was. Do this as you go along--do not leave filling in the logbook to the end of the session!

As a guide to the recording of entries in the logbook, the following general recommendations are offered:

  • At the beginning of each session record the experiment number and title, and the date.
  • If appropriate, supplement the equipment list given in your lab manual with relevant details on the equipment actually used--such as information on the make and model, range, any material differences from the given descriptions/list, etc. Make use of clearly labelled diagrams of circuits and actual physical organisation of the equipment. Again, you should not simply duplicate information already in the manual. You should record additional information only where, in your judgment, this could make a material difference to the outcome of the particular exercise(s) you are required to carry out.
  • Generally, the manual may provide theoretical background for the particular exercise. You should use the logbook to answer any specific questions asked. You may also make general comments on the information given, adding to it, or recording questions or queries you have about it. The latter is particularly important: actually carrying out a laboratory exercise is supposed to be a way for you to clarify your understanding of the theoretical material, and answer outstanding questions. The more clearly you can formulate these questions ahead of time, the more benefit you are likely to gain. But again, don't simply repeat what is said in the manual.
  • The manual will normally provide instructions on the procedure to be followed in each exercise; again, you should not simply copy this into the logbook. What you should note in the logbook are any deviations or discrepancies between the procedure given in the manual, and the procedure you actually follow. In such cases you should record (briefly) the reasons for such changes.
  • Results or outcome: Where you are required to measure a signal, readings should be taken over as wide a range as is permitted by the equipment. Tabulate data where possible and include correct units. It is often helpful to plot data roughly on a graph as you are recording, as this can indicate where extra readings may be necessary (regions of high sensitivity and/or frequent fluctuations). Where any calculations are necessary, the essential steps in such calculations should be recorded. As far as possible, state your results clearly and unambiguously. Present data in the form of graphs whenever this will make the nature of your results more obvious. All results should be those actually obtained: do not try to make the results ``look'' like what you expected, or what the manual anticipated.Not only is such a practice silly and pointless, but in the real world it can be irresponsible and dangerous; if it is detected in laboratory work, the whole exercise will be given a zero mark.
  • Discussion: Evaluate the outcome of the experiment against the stated aims and answer any specific questions. Comment critically on your results, particularly unexpected or unlikely ones. Your comments should usually refer to experimental accuracy and errors, in both qualitative and quantitative terms. Thus, for example, if an exercise involves measuring some numerical parameter, you should indicate, quantitatively, the range of uncertainty or tolerance associated with your result (e.g. ``The resistance was '', or ``The voltage gain was between 56 and 72'', or ``The power was 250 mW '' etc.); and you should also include a qualitative discussion of the factors contributing to (or limiting) this tolerance.
  • Conclusion: State concisely what (if anything) has been achieved in doing the exercise. You might comment specifically on any questions you had recorded at the start of the session, as already discussed above.


  • Each graph should have a title, e.g. ``Graph of Voltage vs. Current'' etc. This title should not be too long or cumbersome, but should have a clear and unambiguous meaning (within the context of the particular exercise).
  • A suitable choice of scales is essential and they should be shown on the appropriate axes. That is, the units (volts, watt etc.) must be indicated, and the value (in the stated units) corresponding to each division of the axes should be clear.
  • Each axis should be clearly labelled, indicating what variable the axis corresponds to.
  • All experimental points should be marked and the graph drawn with a suitable pencil.
  • Put the independent variable, i.e. the quantity which you are varying, on the X-axis.

Marking of Logbooks

Your mark for a lab module will normally be based on your logbook. In general, not all exercises will be marked, but rather a random selection (which may be different for each student) will be taken and marked. You should therefore assume that every exercise can potentially contribute to your final mark.

Marking is normally done by the demonstrators. Therefore, if you are in any doubt as to how best to complete your logbook you should discuss it with the demonstrator, at the first opportunity.

Marks will be awarded according to a scheme of the following general sort:

  • Professional presentation. The logbooks are, of course, filled out by hand; but they should be neat, legible, and show a reasonable standard of spelling and punctuation etc. Diagrams and graphs etc. may be done freehand, but a ruler should also be used where appropriate, and they should again be neat and legible. If a demonstrator finds the logbook difficult to read or interpret, he is instructed to simply award a minimal mark, without further investigation.
  • Clarity of expression: your reports should be short, concise, clear and to the point.
  • All diagrams and graphs should be properly labelled; graphs should be properly annotated with information on the scales in use.
  • All numerical results should be clearly presented with appropriate units and stated tolerances.
  • You should give a coherent discussion, including a succinct conclusion, for each exercise.
  • You should attempt to answer any questions specifically asked in the lab manual.
  • Marks will be deducted for the transcription of material from the lab manual.

Non-attendance at any laboratory session will generally result in a zero mark for the particular exercise; if you do not provide a satisfactory and timely explanation for such absence, you may be deemed to have failed the module (regardless of your mark for other exercises, or other modules) and may even be required to withdraw from the Programme.

But In Conclusion ....

Maintaining your logbook is an important aspect of the laboratory experience; and it is the primary mechanism for assessment of your laboratory work. But filling out the logbook is not the primary objective of any lab exercise. Providing that you attend each lab session, and that you make a serious attempt at each exercise, and record this concisely in the logbook, then you will have no difficulty in achieving the required pass mark on the module. So, do not let the logbook become a dominant, or even a major, element of your activities in the lab. If, in any single lab session, you spend more than about 20-30 minutes actually writing in the logbook, then you are almost certainly doing something seriously wrong. The primary point of the lab is to actually get hands-on experimental experience; this is obviously impossible if you are spending most of your time trying to create a pretty logbook report.

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