Joys and Dangers of Excel for Engineers
Topic: Excel
Title: The Joys and Dangers of Excel for Engineers
 
Were you alive when engineering calculations were performed with a pencil and sheet of paper?  At the University of Florida (Go Gators!), we were rigorously disciplined to write at the top of our paper the “given’s” of the problem, and to draw a box around our answer at the bottom.  Seriously, it’s as if the professors had received a memo stating if they did not make us write the given’s and draw a box around our answer on graph paper they would be immediately flogged.  Why didn’t that discipline carry over to using Excel?
 
All of us use excel for something, right?  The program is pretty easy to pick up and can give us a place to run iterations on design.  It replaces the graph paper and the pencil work pretty well.  Thus, the joys of excel for the engineer include: incredible time savings, especially on repetitive work.  Whether running the calculations for a pavement design or simple conversions, excel can blister through a whole project quickly.  It may be a little time consuming to setup, but then we have a handy spreadsheet for checking our cut and fill values.  Joy!
 
But, what are the dangers?  Let me just share some of my own pitfalls with this program.
 
1. How Do I Use This?  At some point on a recent project, I created a spreadsheet and called it “Profile Calcs.”  I am pretty sure I was checking vertical changes based on horizonal offsets along an alignment.  However, even after looking back at it and the equations for a few minutes, I am not sure what the numbers mean or how I would use this again.  Here’s a screenshot:
 
Inline image 1
What’s wrong with this?  It probably served the purpose I needed at the time.  However, I left myself no notes (though apparently I intended to at the time).  I did not take the time to write out my “given’s” (and I can imagine the growls of disapproval from my UF professors).  Imagine, if I am not sure how to use this what would happen if another engineer got this and tried to use it as is for profile calcs.  At the least it would be frustrating and at the worst it would give answers that were inaccurate.  If using Excel, we engineers should do a better job noting the assumptions of our spreadsheets.  Whether a few notes in a column or a lengthy notes tab, I should have left some assumption breadcrumbs to follow.  As is I might as well put this spreadsheet in the recycle bin!
 
2. Where Do I Type?  Can any of you remember learning how to convert decimal degrees to degrees-minutes-seconds on a TI-83 graphing calculator?  Yeah, I know we can do it by hand, but it seemed like magic when I was shown that I could just convert the previous answer to DMS.  Hurray efficiency!  Well, for those at my office I decided to build a spreadsheet that performed this angle conversion.  It worked pretty well, and I even got the little degree symbol, the minute symbol, and the second symbol to show up at the bottom (ok, so I am bragging over something that’s not really that hard).  Here’s a screenshot:
Inline image 2
But, as I shared my cool creation with others in my office, I found myself having to meticulously explain how to use this spreadsheet, repeatedly.  The biggest issue others had, is I had not made it clear where they were supposed to type their inputs.  As before, I also had not left any notes or “how-to” instructions.  But, some simple highlighting to show where inputs go and a box around the answer or output would have quickly helped many use this well.  This time, I failed to put a box around my answer!  (Again, sorry prof’s).  
 
There are many joys and dangers of using Excel.  It truly can simplify our lives.  However, whether others or the future versions of ourselves, we as engineers should do the extra work of typing out our assumptions in notes and making clear where the inputs and outputs are of the spreadsheet.  It was drilled into me on graphing paper.  Write your “given’s” and draw a box around your answer at the bottom.  Maybe UF was onto something profound even for Excel?  Go Gators!