# Ground Pressure Conversion Fail

I was looking at the spec’s of a specific mining machine, and looking at the track section it has ground pressure ratings:

Hmm, 1 decimal place for the psi rating, but 8 or 9 dp for kPa, looks like someone was asleep during high school science.

Charts like psi to pa this don’t help the matter, but really given that the 15.5 psi can come from any value is the range 15.45 psi to 15.5499999 you get a value interval of +-0.344737864kPa. Thus using the old rule output dp equals no more than input dp, thus 1dp or give the error is 0.3 kPa, you should almost use 0dp.

Upon showing this to a co-worker, I also noticed that the track length is noted to the half inch 181.5” (it also could be read as tenth of an inch) but the metric value is 461.01 cm, yes to the hundredth of an centimeter, called a tenth of a millimeter, that’s some very fine precession. Even at the tenth of a inch, that’s a +-1mm error.

Picky I know, but I’ve been slow on the blogging front, so any post is a good post.