Re: Extech EX410A DVM Don't Buy

On Sun, 06 Oct 2024 07:28:19 -0700, john larkin <JL@gct.com> wrote:

On Sat, 05 Oct 2024 17:30:03 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
>

On Sat, 05 Oct 2024 14:37:55 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
(chomp)

I remember the Wellers from work, had one for years at home too.

>
I remember and like the reassuring clicking sound of the "magnastat"
contacts.  If I don't hear the clicking, I know something is seriously
wrong (such as the contacts welded together).
>

>
I think they used a Curie effect magetic path to switch the heater
contacts.

Yes, that's how they work.
<https://codeandlife.com/2012/03/06/weller-magnastat-autopsy-and-repair/>

Metcal uses Curie effect without the contacts.

I don't know much about Metcal except that some model soldering irons
use RF heating.

Seems to me that a thermocouple and a heater would work as well.

It would in the 21st century.  The Weller "magnastat" patent was first
patented in 1960:
<https://patentimages.storage.googleapis.com/c1/64/21/caa2840db8db26/US3662152.pdf>
The soldering stations electronics consisted of a 115V to 24V
transformer, a fuse, a switch, and a light.  No complicated
temperature controller needed or easily available in 1960's.  Later,
they replaced the marginally reliable contacts with proper
electronics, but kept the Curie Effect tip. 

I believe that the largest advance in soldering technology was the
hollow tip, which allowed locating the temperature sensor very close
to the tip.  We would not have tiny soldering tips, fast warm up time
and accurate temperature control, without the hollow tip.

--
Jeff Liebermann                 jeffl@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann      AE6KS    831-336-2558