WP 34S Unit conversion question
05-14-2014, 01:17 PM
Post: #1
 rkf Member Posts: 65 Joined: Apr 2014
WP 34S Unit conversion question
Hi there,

some time ago when trying to convert the meaning of "20 pound paper" within the DIY instructions of the WP 34S pocket reference into in Europe more usual "gram(me) per square meter", I wondered about the different results given by WP 34S, and HP48/49/50. Digging further into it, I detected the reason for this discrepancy. On a HP48/49/50, in accordance with the UK definition, 1 pound = 0.45359237 kg.

OTOH, within WP 34S, 1 pound = 0.4535924 kg. Not really a big deal, only a neglectable 0.03 mg difference, but nevertheless an abberation from the HP predecessors.

Is there a minute chance of reconsidering this issue in a future firmware release of the WP 34S?

Kind regards, Ralf.
05-14-2014, 04:05 PM
Post: #2
 rkf Member Posts: 65 Joined: Apr 2014
RE: WP 34S Unit conversion question
Thanks, Franz, for this clarification. But having a look at NIST Guide to SI units, one can see that all values are rounded to six decimal places, no matter if it makes sense or not. E.g.

kilometer per hour (km/h) into meter per second (m/s) 2.777 778 E-01

But thats clearly 2.7777777777... and not 2.7777780000. I doubt the kilogram per pound value was rounded the same way :-(
05-14-2014, 08:02 PM
Post: #3
 walter b On Vacation Posts: 1,957 Joined: Dec 2013
RE: WP 34S Unit conversion question
(05-14-2014 04:05 PM)rkf Wrote:  ... having a look at NIST Guide to SI units, one can see that all values are rounded to six decimal places, no matter if it makes sense or not.

We didn't take those rounded values. We took the official values published by NIST instead. Actually, I have no idea why there's a subtle difference to the value you observed - if even the keepers of that heap of ancient units don't agree I can only recommend you sort this out internally. In the meantime, the majority using SI can deal with something more sensible.

d:-)
05-15-2014, 04:19 AM
Post: #4
 rkf Member Posts: 65 Joined: Apr 2014
RE: WP 34S Unit conversion question
Strange, indeed. The predecessor to NIST, the National Bureau of Standards, yet gave the conversion 1 pound = 0.45359237 kg, see this publication on todays NIST public server. Obviously, anywhere in between the rounding took place.

Just for curiosity I sent a mail to the NIST webmaster asking for an explanation. I'll keep you informed :-)

Kind regards,
Ralf.
05-15-2014, 11:58 AM (This post was last modified: 05-15-2014 12:05 PM by Dieter.)
Post: #5
 Dieter Senior Member Posts: 2,397 Joined: Dec 2013
RE: WP 34S Unit conversion question
(05-15-2014 04:19 AM)rkf Wrote:  Strange, indeed. The predecessor to NIST, the National Bureau of Standards, yet gave the conversion 1 pound = 0.45359237 kg

It may be much easier than we think. One pound is 16 ounces (exactly). So if the 34s says that 1 oz = 28,34952 g, one pound would equal 453,59232 grams (which obviously is not correct). Now if 1 lb = 453,59237 g (exactly), this would mean that 1 oz = 28,349523125 g. Which is the correct solution according to Wikipedia. I think it is essential and important to keep the exact relation 1 : 16 in the conversion factors. Let's update the grams to ounces conversion and we're done.

Dieter
05-16-2014, 10:41 AM
Post: #6
 walter b On Vacation Posts: 1,957 Joined: Dec 2013
RE: WP 34S Unit conversion question
In a way, that whole conversion topic is way exaggerated IMHO. As mentioned in the manual, you need CONV for input of data or output of results, if at all (since scientific/engineering calculations shall be done in SI as mentioned). For input our output of converted values, a precision of six digits looks more than sufficient.

d:-)
05-16-2014, 04:18 PM (This post was last modified: 05-16-2014 04:19 PM by Dieter.)
Post: #7
 Dieter Senior Member Posts: 2,397 Joined: Dec 2013
RE: WP 34S Unit conversion question
(05-16-2014 10:41 AM)walter b Wrote:  In a way, that whole conversion topic is way exaggerated IMHO.

Accuracy is never "exaggerated". Otherwise all other conversions and even the constants could be rounded to 6 digits as well. And there is also the inverse conversion from kg to pounds which uses all 34 digits while it simply is the reciprocal of the seven-digit rounded pounds-to-kg factor. #-)

In this case, getting it all right is simple and straightforward: simply change the lb-to-grams. If not for the reason of accuracy, maybe the consistency argument convinces: 1 lb = 16 oz, and this should also be true on the 34s. So the factors should be 0,45359237 kg/lb and 28,349523125 g/oz.

Dieter
05-16-2014, 08:57 PM
Post: #8
 rkf Member Posts: 65 Joined: Apr 2014
RE: WP 34S Unit conversion question
(05-14-2014 08:02 PM)walter b Wrote:  In the meantime, the majority using SI can deal with something more sensible.

Just by the way, isn't the majority of WP 34S users located in the U.S. of A., where until now paper length, and with, is measured in inches, weight of people in stones, and car efficiency in miles per gallon?

SCNR, Ralf.
05-17-2014, 02:08 PM (This post was last modified: 05-17-2014 02:08 PM by cutterjohn.)
Post: #9
 cutterjohn Member Posts: 63 Joined: Jan 2014
RE: WP 34S Unit conversion question
(05-16-2014 08:57 PM)rkf Wrote:  Just by the way, isn't the majority of WP 34S users located in the U.S. of A., where until now paper length, and with, is measured in inches, weight of people in stones pounds, and car efficiency in miles per (US)gallon?
Just to be pedantic I fixed your comment for you. We NEVER used stones, always pounds, and the mpg thing, better make sure to specify US gallon rather than say imperial gallon(Canada used imperial, which is slightly more volume IIRC).
05-17-2014, 11:59 PM
Post: #10
 Paul Dale Senior Member Posts: 1,726 Joined: Dec 2013
RE: WP 34S Unit conversion question
(05-17-2014 02:08 PM)cutterjohn Wrote:  Just to be pedantic I fixed your comment for you. We NEVER used stones, always pounds, and the mpg thing, better make sure to specify US gallon rather than say imperial gallon(Canada used imperial, which is slightly more volume IIRC).

That is interesting. Back when Australia still used imperial, people's weights were always specified in stones and pounds.

- Pauli
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