Units for Bridge Lab–Sources for Calculation Problems–Dimensions and Micro-Strain

There are two potential sources of error on the bridge lab, one of which is probably not as obvious as it ought to be.

#1 Consistent Units

It’s easy to forget to convert your lengths into consistent units – usually inches.  That often introduces big errors.

 

#2 Micro-Strain

The data for the lab are marked “ue”.   It is probably not obvious that this means the real strain is 10^6 times smaller than shown in the excel spreadsheet.  It’s shown that way in the spreadsheet to avoid showing many, many zeroes before the significant digits.

So: a strain shown on the spreadsheet as –1.23 ue  is really –1.23/10^6 = 0.00000123