Re: Triplet 630APL meter movement adjustment

<captainvideo462002@xxxxxxxxx> wrote in message
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On Apr 20, 7:28 pm, s...@xxxxxxxxxxxxx (Samuel M. Goldwasser) wrote:
captainvideo462...@xxxxxxxxx writes:
On Apr 19, 3:26 pm, "Dave M" <masondg4...@xxxxxxxxxxx> wrote:
"Samuel M. Goldwasser" <s...@xxxxxxxxxxxxx> wrote in
messagenews:k55g4w0t.fsf@xxxxxxxxxxxxxxxx

"Dave M" <masondg4...@xxxxxxxxxxx> writes:

<captainvideo462...@xxxxxxxxx> wrote in message
news:4e227b23-e32b-4c32-b2b1-7ae294163b3e@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I just picked up this meter today at a flea market. At the time of
purchase I noted that the two tiny screws that held the dial
plate to
the movement had come loose and were floating around the meter
dial.
The dial plate however was secure. I also noted that mechanical
zero
was the same whether the meter was standind up or laying down. So
I
took a chance on it and it turns out except for a bit of old
battery
corrosion, it seemed to work great. When I got it home I removed
the
clear plastic cover and then the dial to make sure I retrieved
the
tiny screws and any washers that may have come off as well. While
securing the dial back to the meter my small screwdriver slipped
at
about the 2 oclock position and.went in and hit the magnet. It
didn't
seem to damage anything. After everything was re assembled I
tweaked
mechanical zero with the unit in the vertical position and took a
known voltage reading with it. The reading after the accident
read the
same as before. It was then that I laid the meter on its back and
noticed that now mechanical zero drifts abot.250 inch downward.
Raising it back up to vertical put the needle back to zero. I
know
that I must have done this because it was fine before I slipped.
I
know that the tiny counter weight springs which are located at 9,
3,
and 6 oclock have something to do with this delicate balance and
I
would like to try to adjust them but I don't know what the
procedure
is for making this adjustment so I don't want to make things
worse or
destroy the movement completely. Can anyone familiar with
adjusting
these movements please advise me on this? Thanks, Lenny

You are correct in saying that the balance of the movement is
delicate.
The
tail weights are critical to the accuracy of your meter.
There are three weights on the bottom (tail) of the meter pointer;
the
tail
weight (on the bottom of the shaft of the pointer) and two side
weights
(on
the cross-bar). I used to service these meters while working at a
commercial cal lab in the late 60s.
The procedure for balancing a movement is thus:
(1) Center the mechanical zero tang so that it is in the middle of
its
range.
(2) Position the meter so that the pointer is level horizontally.
Adjust
the tail weight so that the pointer rests on the zero mark on the
scale

This is a bit confusing. Do you mean that the pivot is also
horizontal,
or that the entire meter is on its back? If the meter is on its
back,
then the zero position is determined entirely by the mechanical zero
adjusting the hair spring. The weights should have no effect.

If you mean pivot is horizontal with the needle also horizontal, tt
seems
like there is a step missing:

No.. the meter is not on its back; rather, stand it on the bottom left
corner. The instrument should be held in front of you so that you are
looking squarely at it. The meter should be positioned so that the
pointer
is level horizontally, and pointing to your left.

(1a) With the meter on its back, adjust the rear mechanical zero so
that
the
needle rests on the zero mark.

(3) Position the meter so that the pointer is vertical. Adjust the
side
weights so that the pointer rests on the zero mark on the scale.
(4) Position the meter so that it sits upright on the bench
(pointer is
at
45 deg). If the pointer doesn't come to exactly zero scale, more
adjustment
is needed.
(5) Repeat steps 3 & 4 until the pointer is at zero in all
positions.

You'll find that balance will be easier if you leave the tail
weight
alone
after the initial balance (Step 1) and use the side weights to do
the
final
trimming adjustments. You'll have to move the side weights inward
or
outward in unison to maintain the vertical balance. Make the
adjustments
in
very small increments.

Keep in mind the principles of balancing a lever on a fulcrum; the
heavier
end will move down. The pointer's pivot is the fulcrum. The most
difficult
part of the procedure is to make the pointer balance when the
instrument
is
upright on the bench. If the pointer is below the scale zero, then
the
side
weights need to be moved out.

This is exactly what's being done, thus the confusion. :)

Sorry for the confusion. Hope this helped to clear it up.

--
"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra

Dave M
masondg44 at comcast dot net- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Dave
I don't mean to be a pain but I'm trying to understand your last post.
I think I understand what you've written but I'm not so sure about the
drawing though. From what you said, I position the meter standing up
in front of me. I then rotate the entire instrument 45 degrees to the
left. The needle is now horizontal. At this point I adjust mechanical
zero. Then I stand the meter back up (rotate instrument 45 degrees to
the right) to see if zero is still the same?
Well I did that and mechanical zero moves downscale,(left) when the
meter is stood back up. Now to fix this am I correct to assume that
the right side weight would have to be moved out slightly? And if I
were to do this could it affect anything else? Or am I misconstuing
the theory of the procedure? Lenny.

Here is how I've interpreted and edited what has been written:

1. Center the front mechanical zero tang so that it is in the middle of
its
range.

2. With the meter flat on its back (pivot axis vertical), adjust the rear
mechanical zero tang so that the needle rests on the zero mark.

If easy access to the rear adjustment is not possible, simply adjust the
front mechanical zero tang so the needle rests on the zero mark.

Since the pivot axis is vertical, only the mechanical (hair spring)
adjustments matter.

3. Position the meter so that the pointer is level horizontally. To
clarify,
this means the pivot axis is horizontal and the entire meter is oriented
at
about 45 degrees (on most meters) with the needle pointing to the left
horizontally. Adjust the tail weight so that the pointer rests on the
zero mark on the scale.

Only the mechanical zero (performed in steps 1 and 2) and balance between
the needle and tail weight matter.

4. Position the meter so that the pointer is vertical. Adjust the side
weights so that the pointer rests on the zero mark on the scale.

(Only the mechanical zero (performed in steps 1 and 2) and balance between
the two side weights matter.)

5. Position the meter so that it sits upright on the bench (pivot axis is
horizontal, pointer is at 45 degrees). If the pointer doesn't come to
exactly zero scale, more adjustment is needed.

6. Repeat steps (4) and (5) until the pointer is at zero in all positions.

As has been said, think about what you're trying to do - balance a
rotating mass.

Suggestions/improvement welcome.


I think that I understand the mechanics of this now. I'll give it a
try. The springs are really tight We''ll see. Thanks, Lenny

Thanks for helping with the explanation, Sam. I had in my mind what I
wanted to say; guess it came out a little confused. Comes with age..

Cheers!!

--
"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra

Dave M
masondg44 at comcast dot net


.

Relevant Pages

  • Re: Triplet 630APL meter movement adjustment
    ... the movement had come loose and were floating around the meter dial. ... I also noted that mechanical zero ... There are three weights on the bottom of the meter pointer; ...
    (sci.electronics.repair)
  • Re: Triplet 630APL meter movement adjustment
    ... the movement had come loose and were floating around the meter dial. ... I also noted that mechanical zero ... There are three weights on the bottom of the meter pointer; ...
    (sci.electronics.repair)
  • Re: Triplet 630APL meter movement adjustment
    ... the movement had come loose and were floating around the meter dial. ... I also noted that mechanical zero ... There are three weights on the bottom of the meter pointer; ...
    (sci.electronics.repair)
  • Re: Triplet 630APL meter movement adjustment
    ... the movement had come loose and were floating around the meter dial. ... I also noted that mechanical zero ... There are three weights on the bottom of the meter pointer; ...
    (sci.electronics.repair)
  • Re: Triplet 630APL meter movement adjustment
    ... was the same whether the meter was standind up or laying down. ... mechanical zero with the unit in the vertical position and took a ... There are three weights on the bottom of the meter pointer; ...
    (sci.electronics.repair)
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