PHYSICS 623
ELECTRONIC AIDS TO MEASUREMENT
Sep 1, 2001
D. McCammon, A. Erwin

For some experiments, graph paper is useful, although most data can be plotted directly in the notebook. If graph paper is used, it should be fastened into the notebook permanently using the glue or tape provided. The write up of the experiment should be completed in the laboratory. That is, there is no need to take the book out of the laboratory in order to ``pretty'' it up. The lab books will be graded and returned at the beginning of the following lab. For best results you should do the analysis as the lab progresses. Some labs require calculations to be done in advance of the lab, in which case you can glue or tape them into your notebook.

It is essential to read and understand the directions prior to coming to the lab. Your lab instructor will answer your questions in a general meeting at the beginning of the period and will, of course, help you individually as you have questions or problems through out the laboratory.

The laboratory reports need not be elaborate, but several points are worth noting:

• Although neatness is not formally considered in the grading, a sloppy lab book will fail to communicate to the instructor the competence and diligence of its author.
• A rule of thumb you can use concerning the write up is that you should be able to figure out what you did even six months later. That is, the documentation of procedure, schematics, etc., should be recorded legibly and in an organized way.
• Where ever possible or appropriate, the measured values of quantities should be compared with expected values obtained by calculation and the error given.
• When plotting graphs, be sure to label the axes appropriately, to put the measurements on the graph as discrete data points, and to put the theoretical curve, where applicable, as a solid line.

It is a good idea to write a short summary paragraph at the end of the report stating what you learned, difficulties, etc. Suggestions for improving the laboratories are also welcome.

There are no scheduled makeup labs, although occasional access to the laboratory can be negotiated with the lab instructor.

1. Don't write too much. You don't need to put in extensive discussions of the theory or ``purpose'' of the experiment. Equipment lists are not required in this lab. Fewer words - More Pictures!
2. Don't write anything on scrap paper. Do scratch calculations in your notebook. You can cross them out later (or reserve the left hand page everywhere for scratch calculations etc ). If you bring in some work you prepared outside (eg  derivation of an equation, circuit diagram etc ), then tape it in your notebook as soon as your get to lab.
3. You should always always ALWAYS have a circuit diagram of the circuit you are working on. (If you wish you can Xerox the one from the write-up and tape it in.) You should always get the circuit diagram in your notebook first, then build the circuit – following the diagram. (If you are using Integrated Circuits (``ICs''), then put the IC pin numbers on the diagram before wiring the circuit.)

See Appendix E of Horowitz and Hill for instructions on how to draw proper circuit diagrams.

4. Note the conventional way of showing a coaxial cable (e.g. Figs. 9.40-41 in Horowitz and Hill). For most circuit setups you needn't bother to indicate that you had in fact used coax - but for some (eg  the transmission line lab) it is a crucial feature.
5. Ask about circuit symbols you don't recognize. Measuring instruments are not usually shown. (It is assumed that you are close enough to the ideal case where the instrument does not perturb the circuit - make careful note of what you did when this is not the case.) You can show the point where a meter or scope is connected – see 8. below.
6. Signals go generally left to right. Power supply line at the top, ground at the bottom (except for push-pull circuits, where ground is in center, positive supply at the top and negative supply at the bottom). Wires are just lines. In many modern digital circuits, there are so many lines that it is not possible to have jogs in the lines where they cross. It is normal now for crossing lines to not imply an electrical connection. unless the intersection is noted as a solid dot. Modern Electronic Computer Aided Design (ECAD) methods use this convention.
7. Typical Ground Symbols:
   Sophisticated circuits often have more than one kind of ground – then the distinction between these may be important. Until then - don't worry about it.
8. If you wish to refer to the voltage at a particular point in the circuit, then just label it. Then you need only use the label. Note that the voltages are always potential differences between two points. whenever there is a reference to the ``voltage at a point'', it is implied that this is the potential difference from the circuit ground which is usually marked with one of the above symbols.