HP Forum Archive 18

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20b and logs Message #1 Posted by Mark Storkamp on 1 Aug 2008, 8:47 p.m. I realize this is primarily a financial calculator, but I've just noticed that the logs seem to fail above somewhere near 10^16. I didn't notice a page in the manual listing valid domains.

Re: 20b and logs Message #2 Posted by Mark Storkamp on 1 Aug 2008, 8:58 p.m., in response to message #1 by Mark Storkamp A few more details: it seems almost to be a hex<->dec conversion mistake. Log(10^16) is 10. And so on, 6 too small, until it then jumps to 12 too small, then 18 etc.

Re: 20b and logs Message #3 Posted by Allen on 1 Aug 2008, 9:55 p.m., in response to message #2 by Mark Storkamp Oh well, I have always found using LOG on a financial calculator to be a little unnatural. :)

Re: 20b and logs Message #4 Posted by Scott Newell on 1 Aug 2008, 11:33 p.m., in response to message #2 by Mark Storkamp Quote: A few more details: it seems almost to be a hex<->dec conversion mistake. Log(10^16) is 10. And so on, 6 too small, until it then jumps to 12 too small, then 18 etc. Verified! You must have firmware v6.24.2008. Mine has the same error. The firmware in the recently released SDK, v7.21.2008, gives log(1E16)=16. log(5E16)=16.6989

Re: 20b and logs Message #5 Posted by cyrille de Brébisson on 1 Aug 2008, 11:40 p.m., in response to message #4 by Scott Newell hello, Darn, you guys are quick at finding bugs, and discovering that they have already been fixed! I just wonder how you discovered that the LOG of number with exponent >16 (and <-16 BTW) are not working properly? I doubt that you had a real need to calculate the log of such a large number? regards, cyrille

Re: 20b and logs Message #6 Posted by designnut on 2 Aug 2008, 12:45 a.m., in response to message #5 by cyrille de Brébisson I admit playing with my calculators as a pastime. I analyzed one resistive divider until I knew all the answers. I would enter the lower resistor into the t register and enter the upper resistor, add and divide and I got the total resistance and then the fraction of the divider. I wondered what would happen if I multiplied and subtracted and the number that resulted was the output resistance of the tap. Totally unexpected. When selecting constants from the list. I wondered what would happen if I keyed a number, it selected the constant numbered from left to right and entered it as well. Worked with the 33S and later the 35S. I find your divider solution on the 50g trivial, I like mine. Sam 80 I started with the first 35. I flat hate your invisible decimal, use a bigger symbol. I use the comma for greater visibility.

Re: 20b and logs Message #7 Posted by Mark Storkamp on 4 Aug 2008, 9:29 a.m., in response to message #5 by cyrille de Brébisson Quote: Darn, you guys are quick at finding bugs, and discovering that they have already been fixed! So, is this to be some kind of guessing game then? We buy a product with known defects, but it's up to us to figure out what they are? Is that their new corporate policy?

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