accuracy of stop watch
accuracy of stop watch
(OP)
I have an odd question that is bugging me and I really need some help. We are timing a particular process that is very important by using a stopwatch and visually watching this equipment move from one point to another in only 2-2.3 seconds. I want to change this to something more high-tec, but I need proof of course that this is inaccurate so as to determine the money is well spent. Is there anywhere I can find the average visual accuity of a person to be able to measure this by hand, and the stopwatch accuracy. Would anyone out there trust doing something like this for an important peace of equipment?? I never had but the crack engineering staff here finds it normal.





RE: accuracy of stop watch
I recall a discussion with my dad about this--he's a former college sprinter and high school track coach. He had stated (I don't know his source) that 100 m times when hand-timed can be off by as much as 0.2 seconds. I also remember reading an article in Sports Illustrated about football scouting in which this same same time was stated as the error due to hand-stopwatches in clocking players' 40 yard times, so I presume that my father's source was reasonable.
Given that in both cases, the person with the stopwatch is the one doing the starting, this essentially boils down to a visual accuity issue in determining when the runner passes the end line. Your problem appears to involve a timing of both the beginning and end, so the error may be even worse.
Don't hold me to it, but based on these facts, I would say +/- 0.2 seconds of error (I would say this is a fixed error, and largely independent of total time scale). For something which takes a few minutes, that may tolerable, but for ~2 seconds . . .?
I agree with your initial feeling that they may need better equipment.
Brad
RE: accuracy of stop watch
Cheers
Greg Locock
RE: accuracy of stop watch
One way to make your argument for better timing is to perform an error analysis on the total test system. This will tell you the total possible error of the test and give you an idea of the significance of the timing error relative to the total.
RE: accuracy of stop watch