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Question for old-timers re: Simpson meters

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Mark Zacharias

Jan 1, 1970
0
Hi,

As some of the guys here know, I presently collect old analog multimeters.

I recall a picture I saw several years ago of a "wall" of Simpson meters -
maybe 50 or more, used to demonstrate reliability. They were all being
pulsed with DC of perhaps 0.5 hz or so for years on end and none had failed.

Anybody remember this and where can I get a JPG of this, and maybe a link to
the info?

I've tried Google images etc no luck.


Mark Z.
 
M

Mark Zacharias

Jan 1, 1970
0
Jim Yanik said:
that's not surprising;
the meter movements are very simple and sealed from contamination.
there's not much to fail,especially if you're not transporting them.

the batteries leaking or resistors going out of tolerance are the biggest
problems with Simpson meters,aside from being dropped.



--
Jim Yanik
jyanik
at
localnet
dot com


Not surprising except perhaps considering mechanical issues - bearings,
solder - to-coil connections, spring and/or taut-band failure, etc. As I
recall, they were running this way for maybe over 20 years.

They may have been naked meter movements and not complete VOM's.

Like to have that picture, though...

Mark Z.
 
M

Mark Zacharias

Jan 1, 1970
0
Jim Yanik said:
those meters on the wall were likely left in one switch position and thus
not any different than a "naked meter movement" with a resistor in series
to measure voltage instead of current.

BTW,I still have my Simpson 270-3 VOM. Works great.

--
Jim Yanik
jyanik
at
localnet
dot com


I have a 270-2 and it's one of my favorites. Just a "no-bull***t" meter that
just does it's job, and is deadly accurate. One thing I really like about it
is the meter ballistics. Readings are quick, but with no overshoot and
virtually no "settling down" time. My AVO's for example are really nice and
accurate but much slower to get a reading. As collectors pieces or
occasional use it's not a problem but in everyday shop use the faster
readings are a blessing.
My other Simpsons include a 260-6P, a 260 XLPM, a 635 Bach-Simpson, and a
303 VTVM. Several are featured as guest meters at simpson260.com.

Mark Z.
 
M

Mark Zacharias

Jan 1, 1970
0
Dave M said:
I, too, still have my 260-3 that I bought from Allied Electronics in 1965,
while serving in the Navy. It's not totally original, since I replaced
the original meter movement in the late 60s with a taut band movement from
a damaged instrument, and later selected the range resistors to improve
the accuracy. Since then, it has served flawlessly, and on the last
calibration, was still +/- 1% on all DC voltage and current ranges. AC
and resistance ranges were a bit less accurate, but still well within
specs.
In all, it was $65 well spent..

Models 260-3 and later have internal adjustments which can obtain accuracy
to a very high degree. The 10 volt range suffers a bit at full scale but I
adjust mine for best accuracy in the 5 to 5.6 volt range, where small
differences can be huge in modern equipment.
Sometimes you just have to use a good digital meter though, and I have
several of them as well. Yamaha receivers use protection circuits where the
difference between 1.2 and 1.4 volts, for example, can be critical.

Trouble is we often take the readings of a digital as "gospel". Recently a
co-workers' cheap digital was discovered to have approximately a 50% error
when we were reading a Vsus line in a plasma. We were trying to find why the
reading was 295 volts instead of the desired 195. After trying a different
power supply board, it was discovered the multimeter had come up lame.

Mark Z.
 
J

Jamie

Jan 1, 1970
0
Mark said:
Models 260-3 and later have internal adjustments which can obtain
accuracy to a very high degree. The 10 volt range suffers a bit at full
scale but I adjust mine for best accuracy in the 5 to 5.6 volt range,
where small differences can be huge in modern equipment.
Sometimes you just have to use a good digital meter though, and I have
several of them as well. Yamaha receivers use protection circuits where
the difference between 1.2 and 1.4 volts, for example, can be critical.

Trouble is we often take the readings of a digital as "gospel". Recently
a co-workers' cheap digital was discovered to have approximately a 50%
error when we were reading a Vsus line in a plasma. We were trying to
find why the reading was 295 volts instead of the desired 195. After
trying a different power supply board, it was discovered the multimeter
had come up lame.

Mark Z.
You're suppose to calibrate analog scales at 75% of their deflection.
 
M

Mark Zacharias

Jan 1, 1970
0
Jamie said:
You're suppose to calibrate analog scales at 75% of their deflection.

That's a pretty general statement... but sounds like a good idea in many
cases.
I have an RCA WV-38A one adjustment of which is for 1 mA full scale.

Mark Z.
 
M

Mark Zacharias

Jan 1, 1970
0
Jim Yanik said:
Sez who?


Simpson meter movements are usually 50uA FS,but I recall one that was less
than that. A BIG meter.

One thing to worry about with analog meters is their input Z.
It varys with range. digital DMMs don't,and usually have a higher Z.

--
Jim Yanik
jyanik
at
localnet
dot com


I was having a discussion about that with a glass-head buddy at work. He
opined that a regular VOM would load down a plate voltage reading if there
is a high value plate resistor, so one should use a DMM instead.
Trouble with that was, a 20 kOhm/volt meter on a 1000 volt range, which
would be the range often used in this situation, adds up to 20 meg - double
the input resistance of a typical DMM.

Obviously grid voltage would be another matter...

Mark Z.
 
M

Mark Zacharias

Jan 1, 1970
0
Jim Yanik said:
Sez who?


Simpson meter movements are usually 50uA FS,but I recall one that was less
than that. A BIG meter.

One thing to worry about with analog meters is their input Z.
It varys with range. digital DMMs don't,and usually have a higher Z.

--
Jim Yanik
jyanik
at
localnet
dot com


Yes, nominally one adjusts the swamp resistor for 50 uA at full scale, but
I'm not afraid to fudge that a little to get the overall accuracy where I
want it. I use these things to measure voltage, rarely current, and if I am
measuring current, it's only going to be measuring battery charge current or
the like, not a critical application.

Mark Z.
 
M

Mark Zacharias

Jan 1, 1970
0
Jim Yanik said:
The thing is,the FIRST cal check/adjustment you make is the basic 50ua
setting,then you go on to check the other ranges and make other
adjustments. That 50ua cal adjust affects ALL the other ranges and modes.
adjusting it to optimize other ranges may hide an out of tolerance
resistor.

--
Jim Yanik
jyanik
at
localnet
dot com


That's pretty much what I do. Manufacturers procedure first, then tweak as I
feel necessary to make it a little better for what I do. When I vary the
50uA adjustment a bit (maybe 1 or 2 per cent), it's because I feel the
overall accuracy of the meter is off a bit.

Mark Z.
 
M

Mark Zacharias

Jan 1, 1970
0
Jim Yanik
jyanik
at
localnet
dot com

That would be the Simpson 269, 100kOhm per volt. They look bigger all right,
never seen one in the flesh. There was also the model 262 which looked the
same but was conventional 20 kOhm per volt.

On the subject of BIG meters, I have a beautiful Hickok 209A which I need to
give the refurb treatment and make an AC probe for... now THAT is big!


Mark Z.
 
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