Excellent, Pat. I'm in full agreement with your post. This issue, incidently, is the exact same one I brought to this group a few months ago when we were discussing changing the bpm thing to an SI unit.
The only difference though is that I elected the cHz instead of mHz for that (ok, I know, the "percent" mindset you've been talking about... :-) ). The main rationale for my choice of cHz was that the numbers would continue to be close to the ones the public are familiar with (2 to 3 digits) and the fact that we do not need more accuracy than beyond 1 cHz for this measurement. Aside from this I have no quarrels with mHz as a choice for this application, unlike our current discussion on angles which seems to require somewhat more... digging into. BTW, since we're at it I might as well open a new... "topic" here (please feel free to rename it later on). The issue of accuracy (no, it's not the good old discussion we had before involving precision). Some of us may need to understand that *applications* (now I'm addressing the specific *practical* needs of industries out there) MAY or DO require that accuracies be of specific magnitude. Unfortunately, here is exactly where those who defend the *exclusive* use of engineering decimal powers of 3 may run into trouble. There may even be the argument to say that if one cannot achieve a specific accuracy given by a specific prefix, than it's just plain wrong to show the result of the measurement with it. It's at best a "guestimate" (like when we use our school rulers to produce a result like 43.54 cm - we can "read" up to the mm here, 5, but the 4 would be "eyeballing" at best!) Example, if our measurement comes as, say, 43 cm and the best we can do (or the uncertainty of the measurement) is within a full cm, it just doesn't make sense to present the result as 430 mm! Why? Because we have no clue whether this value is 432, 431, 436, 437... Therefore, the rationale is why bother cluttering the result with one more digit? So, I submit that the KISS principle is strongly applied here... So, in summary, it's a question of both practicality and instrument measurement accuracy. Comments, anyone? Marcus On Wed, 24 Jul 2002 10:13:48 Pat Naughtin wrote: >Dear All, > >Could you comment on this please? > >Heart beats > >Frequency measurements are often used to describe events that happen >rhythmically - like your heart beat. > >If you check the frequency of your heart beating and notice that your heart >beats once each second - then the frequency of your heart beat is one beat >per second or, to use the SI unit for frequency, your heart rate is one >hertz (1 Hz). A low frequency - like 1 hertz - probably means that you are >well rested and that you are physically fit. Through your normal day your >heart rate varies constantly according to your activities. > >Your heart beat frequency can change quickly from your resting rate of (say) >1 hertz to a rate that is appropriate for your current activity. Your heart >might beat at 1.5 hertz when you are walking briskly or jogging and it might >go to 2 hertz when you are running. Super fit athletes might have a heart >beat frequency above 3 hertz and their ultimate performance might approach 4 >hertz. > >However, using simple numbers like 1, 2, 3, and 4 might be a bit too chunky. >You might need to know details small subtle differences of your heart beat. >To do this simply use an SI prefix - millihertz would be good for this - and >will give you the same sort of details that millimetres give to length. > >Using millihertz the previous paragraph would now read: > >Your heart beat frequency can change quickly from your resting rate of (say) >1000 millihertz to a rate that is appropriate for your current activity. >Your heart might beat at 1500 millihertz when you are walking briskly or >jogging and it might go to 2000 millihertz when you are running. Super fit >athletes might have a heart beat frequency above 3000 millihertz and their >ultimate performance might approach 4000 millihertz. > >Thanks, > >Pat Naughtin CAMS >Geelong, Australia > > Is your boss reading your email? ....Probably Keep your messages private by using Lycos Mail. Sign up today at http://mail.lycos.com
