mechanical zero on a small meter

Jeff Liebermann wrote:
On Thu, 25 Feb 2010 07:32:28 -0800 (PST), klem kedidelhopper
captainvideo462...@gmail.com> wrote:

After setting zero I moved my finger over the meter face first thing
in the morning and the needle moved up scale about 10 percent. I let
it sit on the bench for about 24 hours without touching it. When I
looked at it again it was back to zero. So the trick is to set it,
leave it for a day let it discharge, and then tweak it again. Clumsy
procedure but it works. Glad this is my own equipment and not a
customer repair job....Lenny

Nice workaround.  So it is static.  Is this NORMAL for a small panel
meter?  We don't have much of a static problem on the left coast, so I
don't see much of that.  I waved my hand around various small panel
meters around the shop.  No deflection.

The easiest and best solution is to eliminate the static charge by rubbing
the meter face with a clothes dryer anti-cling sheet. Alternatively, buy a
bottle of anti-cling spray and give the meter a ligh misting.
That will dissipate the static charge and you can handle the meter as you
wish without upsetting the zero setting.

--
David
dgminala at mediacombb dot net

On Mar 17, 11:57 am, "Dave M" <dgminala4...@mediacombb.net> wrote:
Jeff Liebermann wrote:
On Thu, 25 Feb 2010 07:32:28 -0800 (PST), klem kedidelhopper
captainvideo462...@gmail.com> wrote:

After setting zero I moved my finger over the meter face first thing
in the morning and the needle moved up scale about 10 percent. I let
it sit on the bench for about 24 hours without touching it. When I
looked at it again it was back to zero. So the trick is to set it,
leave it for a day let it discharge, and then tweak it again. Clumsy
procedure but it works. Glad this is my own equipment and not a
customer repair job....Lenny

Nice workaround.  So it is static.  Is this NORMAL for a small panel
meter?  We don't have much of a static problem on the left coast, so I
don't see much of that.  I waved my hand around various small panel
meters around the shop.  No deflection.

The easiest and best solution is to eliminate the static charge by rubbing
the meter face with a clothes dryer anti-cling sheet. Alternatively, buy a
bottle of anti-cling spray and give the meter a ligh misting.
That will dissipate the static charge and you can handle the meter as you
wish without upsetting the zero setting.

--
David
dgminala at mediacombb dot net

This all sounds terribly bizarre - Its a moving coil meter, it might
go "whack" on getting a static charge, but a steady reading?
It is NOT current flow from a static discharge that creates the

an INCREDIBLY sensitive meter movement- femtoamps? - have a look at
the output of the op amp, preferably with an analogue meter - (as
suggested) (no signal, 0 output) and the bias resistors around it.
Especially the high value (>100k ones) (any Tantalum capacitors,
replace them)
(sorry Dave - a view from the trenches)

Andrew VK3BFA.

PS - its axiomatic that the thing causing the fault is in the least
accessible section of the cct. A variation of Murphys Law.

On Mar 17, 11:57 am, "Dave M" <dgminala4...@mediacombb.net> wrote:
Jeff Liebermann wrote:
On Thu, 25 Feb 2010 07:32:28 -0800 (PST), klem kedidelhopper
captainvideo462...@gmail.com> wrote:

After setting zero I moved my finger over the meter face first thing
in the morning and the needle moved up scale about 10 percent. I let
it sit on the bench for about 24 hours without touching it. When I
looked at it again it was back to zero. So the trick is to set it,
leave it for a day let it discharge, and then tweak it again. Clumsy
procedure but it works. Glad this is my own equipment and not a
customer repair job....Lenny

Nice workaround.  So it is static.  Is this NORMAL for a small panel
meter?  We don't have much of a static problem on the left coast, so I
don't see much of that.  I waved my hand around various small panel
meters around the shop.  No deflection.

The easiest and best solution is to eliminate the static charge by
rubbing the meter face with a clothes dryer anti-cling sheet.
Alternatively, buy a bottle of anti-cling spray and give the meter a ligh
misting. That will dissipate the static charge and you can handle the
meter as you wish without upsetting the zero setting.

--
David
dgminala at mediacombb dot net

This all sounds terribly bizarre - Its a moving coil meter, it might
go "whack" on getting a static charge, but a steady reading? - must be
an INCREDIBLY sensitive meter movement- femtoamps? - have a look at
the output of the op amp, preferably with an analogue meter - (as
suggested) (no signal, 0 output) and the bias resistors around it.
Especially the high value (>100k ones) (any Tantalum capacitors,
replace them)
(sorry Dave - a view from the trenches)

Andrew VK3BFA.

PS - its axiomatic that the thing causing the fault is in the least
accessible section of the cct. A variation of Murphys Law.