Subject: Re: auto-darkening welding filters

From: David Einhorn <[email-masked]>
Date: Wed, 24 Jul 1996 08:22:20 -0400

I'm a bit baffled on these auto-darkening helmits.  I tried one
for a day, but had problems with it.  Admittably the problems may
be due to my poor welding skills.

   First off, the helmet tended 
to strobe as the result of my having difficulty in keeping an arc.
This tended to be a Catch-22, with the strobing and lack of arc
contributing to each other.

  Secondly, perhaps an engineering type
could answer my main concern about them, speed of filter versus, 
the speed of light.  It is difficult for me to comprehend how the 
filter could possibly respond to the change in light level fast 
enough to prevent at least some damaging flash to hit my eyes.
After all, isn't the **speed-of-light**  faster than the speed of the 
electrical components in the helmet?  It sure appeared to me that 
the brightness increased just prior to the helmet darkening.

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From: [email-masked] (Tom)
Date: Wed, 24 Jul 1996 12:41:17 +1000

I tried using one of these units at a test of some robotic welding equipment 
in Sweden.  After being blinded by the first couple of arc strikes and the 
thing not working, I switched to a paper advertising shield with a thin 
plastic lens.  By the end of the day, everyone had their paper shield and the 
auto-darkening units were on the floor in the corner of the room.  I hope 
these were just bad units.  If not, there's going to be a lot of blind welders 
out there.

In article <[email-masked]> David 
Einhorn <[email-masked]> writes:>From: David Einhorn 
<[email-masked]>>Subject: Re: auto-darkening welding filters
>Date: Wed, 24 Jul 1996 08:22:20 -0400

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From: [email-masked] (James P. Riser)
Date: 24 Jul 1996 17:00:54 GMT

In article <[email-masked]>,

> the brightness increased just prior to the helmet darkening.

David;
The more expensive auto-darkening filters have a delay adjustment.  This
allows you to set the delay for how long before the lens "lightens".  Mine
is cheaper and lets you adjust the level of shading only.  I've never had
any problems and think it really helps my welding quality.  FYI my filter
darkens in 1/25,000 of a second and has a fixed delay of .25 seconds to go
>from  dark to light.
Jim

-- 
James P. Riser
Home page:  http://www.azstarnet.com/~jriser

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From: [email-masked] (Chris Scott)
Date: 25 Jul 96 14:06:54 CDT

> darkens in 1/25,000 of a second and has a fixed delay of .25 seconds to go

The LCD shuttered helmets are simply wonderful.  I used to be the
arc monster, and now I could probably make novice welder.

-- 
[email-masked]  Chief Engineer, Public Radio- Western KY U
                     Telco: (502) 745-3834  Hm & Fax: (502) 781-1232
...just another insignificant VAX user.        \\\//
                                               (o o)
--------------------------------------------ooO-(_)-Ooo-----------------------

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From: Roger Gibbs <[email-masked]>
Date: Fri, 26 Jul 1996 16:52:30 GMT

>the brightness increased just prior to the helmet darkening.
The damage mechanism is due to the transfer of energy to sensitive
elements in your eye.  This transfer is related to several variables,
energy source intensity, distance between the source and your eye,
the filters characteristics, and time of exposure.  Damage to your
eye requires exposure for some amount of time (I do not know how
long).  So yes, you are correct in that the arc flash will reach your
eye before the filter can react. But this does not imply that the
auto-darkening filter is not doing it's job.  It is a lot like
getting a sunburn, you can be exposed to full sunlight at noon
without getting a burn, provided the exposure time is low enough. 

-Roger