> > Depends on the format of the original.  0.1inch is far more
> > accurate than 2.54mm
> > because 0.1 = 0.100000..............
> > Clive Broome
> By definition, 1 inch = 25.4mm exactly. This was standardised
> some decades ago.
> It's when rounded numbers are used that problems occur.
> John Haddy

I concur with the above definition. Unfortunately for users of Protel
however, Protel currently use an Internal Measurement Unit which is equal to
1 x 10**-7 inches. This means that imperial distances can be recorded in
*exact* form, but metric distances are (generally) recorded in *approximate*

If the Internal Measurement Unit was alternatively set to some *metric*
distance, e.g. 2 x 10**-9 meters, then *both* metric distances and (most)
imperial distances could be recorded in exact form. E.g. a distance of 1 x
10**-5 inches could then be recorded as 127 Internal Measurement Units
(instead of the present 100 Internal Measurement Units).

Although the present Internal Measurement Unit is a pretty small distance, I
am sure that I am not the only user who has experienced the impact of
rounding errors. Pads originally positioned to a metric pitch can go
"off-pitch" (albiet by a tiny amount) if the measurement unit setting is
changed from metric to imperial and then back to metric again.

I have commented on this in the past, but the current thread has bought this
topic to the foreground again.

Geoff Harland.
E-Mail Disclaimer
The Information in this e-mail is confidential and may be legally
privileged. It is intended solely for the addressee. Access to this
e-mail by anyone else is unauthorised. If you are not the intended
recipient, any disclosure, copying, distribution or any action taken
or omitted to be taken in reliance on it, is prohibited and may be
unlawful. Any opinions or advice contained in this e-mail are
confidential and not for public display.

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*  This message sent by: PROTEL EDA USERS MAILING LIST
*  Use the "reply" command in your email program to
*  respond to this message.
*  To unsubscribe from this mailing list use the form at
*  the Association web site. You will need to give the same
*  email address you originally used to subscribe (do not
*  give an alias unless it was used to subscribe).
*  Visit http://www.techservinc.com/protelusers/subscrib.html
*  to unsubscribe or to subscribe a new email address.
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

To post a message: <mailto:[EMAIL PROTECTED]>

To unsubscribe or subscribe we recommend using the
form at our web site:

You may also unsubscribe directly by email:
<mailto:[EMAIL PROTECTED]?body=leave%20proteledaforum>
however this may fail if you're trying to unsubscribe
an "old" email address, an alias mail account, or if
your mail client uses an unusual encoding format.

To contact the Forum Administrator:

Reply via email to