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.
"Mark Zacharias" wrote in news:003beb0d$0$2118$ snipped-for-privacy@news.astraweb.com:
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
18$ snipped-for-privacy@news.astraweb.com:
You might check with the guy who runs simpson260.com Regards, Wendell
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.
"Mark Zacharias" wrote in news:00c8f14f$0$1584$ snipped-for-privacy@news.astraweb.com:
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, 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..
-- David dgminala at mediacombb dot net
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.
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.
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.
"Mark Zacharias" wrote in news:00b076d3$0$16796$ snipped-for-privacy@news.astraweb.com:
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.
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.
"Mark Zacharias" wrote in news:00017320$0$2285$ snipped-for-privacy@news.astraweb.com:
I made a HV probe for my 10Meg-Z DMM,gives me 100MegZ but I have to use a lower range or divide by 10.
But how many tube circuits do you encouter these days?
-- Jim Yanik jyanik at localnet dot com
"Mark Zacharias" wrote in news:000174b0$0$2281$ snipped-for-privacy@news.astraweb.com:
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.
There are only three adjustments in the Simpson 260-3. The 50uA (250 mv) adjustment sets the basic accuracy for all functions and ranges. This is the only DC adjustment in a 260-3. The other adjustments are for the 250 VAC and 2.5 VAC voltage ranges. If one or more of the DC voltage or current ranges or the other AC voltage ranges need adjustment, you have to change the range multiplier resistors. The same applies to the resistance ranges.
All of the instrument calibrations that I have ever done (and I've done a LOT) requires the adjustments to be made at full scale (for both digital and analog instruments). The linearity checks are made at major points throughout the ranges. AC voltage/current and resistance adjustments might be made at points other than full scale, but that's highly instrument dependent, and is specified in the cal procedure.
-- David dgminala at mediacombb dot net
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.
"Mark Zacharias" wrote in news:00d82bb7$0$23796$ snipped-for-privacy@news.astraweb.com:
Yes,that's the model,269.the meter face is almost the entire front of the meter,and the face is about a 8" diagonal,IIRC.
I may still have the meter movement in my junkbox,I was making it into a capacitance meter. ISTR I did finish that project.....or did I?
-- Jim Yanik jyanik at localnet dot com
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