Geotech Lab tips

Chart:

- Profile - should be a continuous line or curve

- Profile - do not use Trendline (Layout Analysis tab); this feature is not intended for our type of Labs. Use Chart types from Design Type tab.

- When you produce datapoints for your chart please use and leave Excel formulas so we can see how you obtained them

- Axis title and labels should be on the same side if possible

Format:

 - When preparing a table for a chart please keep it formatted, e.g., borders, headings, column names etc. Points will be deducted in the "Format and clear organization of the entire document and its parts" line

- Equations as ∑ _(i=1)^n  γ_i Z_i = γ_1 Z_1 + γ_2 Z_2 + γ_3 Z_3….+ γ_n Z_n  are not in any accepted notations and are not intelligible. Notations as σ(v) = Y(1)Z(1) + Y(2)Z(2) +Y(3)Z(3) are slightly better but still, have ambiguity, and may not be understood properly by a person distant from this specific lab and lecture.

- Use named cells

Memo:

- Keep Memo language formal; avoid words "like", "kind", "us engineers",

- Grammar - write Memo in a text processor and Copy-Paste into Excel text box. Excel does not have the spell check capability!

- If you decide to report key equations in Memo please report factors used, e.g., F = ma, where F is force, m is mass and a is acceleration

Units:

- When establishing a new data column please indicate units

- When you apply multiplication or division operator there's a good chance your units will change!

Calculations:

- Don't round intermediate results
- Specific Weight (or Unit Weight) of water is 62.4 lb/cu.ft. (changes with temperature) 

General feedback:

- Please read the Lab instructions and the lecture materials before the Lab, come prepared!

- Don't wait to submit  until 09:50 when many other students may overload the server and you may not be able to submit successfully

- Charts have a random place on a chart Quest

- When reporting units, please avoid extraneous characters, e.g., (psf_)

Lab 1 tips

1.       Due - 10 AM Friday a week after the class, for both sections.

Excel:

2.       Named Variables - don't use spaces. Good practice -- capitalize 1st letter of a word, e.g. MyFirstName. If you need to eliminate an unwanted named variable use Ctrl-F3 shortcut.
3.       Troubles with Excel -- please refer to Excel help and tutorials; it is the best and most effective solution. You can also try the IRT MS Office on-line training.
4.       Remember, Excel is a computational software; it is designed to do computations for you.
5.       Excel allows leaving comments in cells - you can use this feature when you feel a comment may add clarification.
6.       Consult the Post-It-like notes and Instructions attached to question pages for grade tips.

Units and sig figs:

7.       Conversion factors column does not need formulas; it needs conversion factors which are constants. No real rule for conversion factors sig figs.
8.       Units spelling -- refer to literature e.g. , NIST Handbook 44 - 2013 Edition, Appendix C -General Tables of Units of Measurement  OR NIST Special Publication 330, 2008 Edition. International System of Units (SI). Both are by National Institute of Standards and Technology, Washington, DC.
9.       Note:: Some questions have non-conforming unit notations, it is alright to correct them when Excel allows to.
10.   In Question 5 --  BTU/CF-DegF means Btu/ft³∙°F (and similar to it cells).

Memo:

11.   Writing Memo -- consult Prof. Mitchell's blog entry and the links he refers to.
12.   Memo subject -- "Meaningful phrase that announces the topic".
13.   Memos should have a professional tone. Limitations of the lab are not your own personal limitations or struggles but rather specific caveats related to assumptions you had to make in order to complete your calculations (ex: did you actually measure your shoulder width with a ruler?) See the earlier entry on the course blog for additional suggestions.
Misc.:
14.   If you do not have a laptop, please look at the lab prior to class time and come to the class session to ask your questions.
15. If your computer does not have MS Office -- it appears that it is OK to do it in OpenOffice (save as .xls or .xlsx file), or maybe use CADLab machines.

Conversion Factors and Methods

Conversion factors could be seen as universal constants. Some of them are exact, like 1 inch equals 25.4 mm. Most of them don't have an exact value but rather expressed as a decimal fraction with 4-8 sig figs which is enough for most engineering applications without reducing desired precision.In the lab we had to find several conversion factors. It may be OK and definitely convenient to google it, but for the lab Memo and for professional reports a google search result is not a credible reference. The best source of reference materials such as conversion factors is a relevant industry's handbook. For HVACR it would be ASHRAE Handbook - Fundamentals. An electronic edition of it is available through Drexel libraries, but for this large class' convenience I also supply a link to the Chapter 38 image file on my Google Drive. I hope the ASHRAE people won't be considering it as a serious breach of copyright. It can be cited   (2009), 2009 ASHRAE Handbook - Fundamentals (I-P Edition), Chapter 38 Units and Conversions, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. Another great reference would be ASTM/IEEESI-10-1997 Standard.
The unit-factor method is a commonly used technique to convert a value from one system of units into another, or from one unit into another within the same system. Explore it more on KhanAcademy videos. Wikipedia article on it is also a good explanation of the unit-factor method (and of course we never refer to Wikipedia in memos and reports).

Significant Figures and Rounding

   The concept of significant figures (sig figs, s.f.) arises from the concept of physical measuring of a variable. Instruments we use have finite accuracy and reliability. For example, a desk ruler has least readable unit (least count) of 1 mm, while a common Vernier caliper can measure with accuracy of 0.02 mm. Thus the reasonably reliable length of a steel plate measured with the ruler could be 26 mm (two s.f.), while measured with the caliper would be 26.14 mm (four s.f.). If one has to add two measures, let's say a plate measured with a ruler and a plate measured with the caliper, the ±0.5 mm uncertainty of the first plate will dominate the uncertainty in length of the second plate ±0.01 mm. When that person reports the combined length of 52.14 mm he or she cannot defend the final precision up to 0.02 mm because the ruler's precision of 1 mm dominates.Side-note: some technicians and researchers state that many elementary measuring devices allow an (experienced) operator to estimate the measured value one figure beyond the instrument's least count. In our ruler example, we could estimate the plate's length as 26.1 or 26.2 mm (three s.f.)

   Very often we have to use the measured values in various calculations which ordinarily give as answers with a long trail of decimals. While it is perfectly fine to carry the trails during a multi-step calculation, the final answer must be always rounded off and reported with a correct number of s.f. In other words, the accuracy of the final answer cannot exceed the accuracy of the least accurate measurements or data provided.  Four groups of different arithmetical "operations" have different rules of maintaining s.f. Those groups are Addition and Subtraction, Division and Multiplication, Logarithms and Antilogarithms, and Trigonometric functions.

   Addition and subtraction can produce and answer with a higher or lesser s.f.

   Division and multiplication results are limited by the data with least s.f. I have heard respected opinions that there's an exception to the division and multiplication rule. The opinion is based on the notion of fractional uncertainty: when an answer begins with a digit 1, the answer's accuracy would be preserved better if we maintain an extra s.f. than the original data with lowest s.f. I personally adhere to that opinion. However, I advice to proceed with caution - it appears that this "rule of 1" is not widely discussed and often omitted. Please consult relevant literature or specific industry's guidelines for further use.

   In logarithm operations the mantissa determines the number of s.f.

   For purpose of real life applications trig functions preserve the number of s.f. of the input variable.

   A few words on rounding tie-breaks (when the "digit" we want to cut off is "exactly" 5, e.g. 26.145 or 26.14500 or 26.145000). Many disciplines use the round half up or round half away from zero rules. Both those rules are asymmetrical and lead to biases. In science the most accepted tie-breaking rule is round half to even. As per 09/25/2013 1900 the Wikipedia's relevant page has a correct explanation with an example.

   My favorite intro text on s.f. with computational examples is Quantitative Chemical Analysis by Daniel C. Harris.

References:

ASTM Standard E29, 2008, "Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications," ASTM International, West Conshohocken, PA, 2008, DOI: 10.1520/E0029-08, www.astm.org.

Harris, D. C. (2007), Quantitative Chemical Analysis, 7 ed., 663 pp., W. H. Freeman, New York.

Michener, B.; Scarlata, C.; Hames, B. (2008). Rounding and Significant Figures: Laboratory Analytical Procedure (LAP). 7 pp.; NREL Report No. TP-510-42626. http://www.nrel.gov/biomass/pdfs/42626.pdf