Simpson meter calibration/alkaline cell q?


Main question is, are alkaline cells at exactly their rated voltage, or a little higher? Just got my "new" eBay purchase today, an old Simpson 260 series 7M. Appears to be good on resistance and AC voltage, but when I measure a D cell it reads about 1.6V and a 9V battery reads about 9.4V.
Oddly enough my old Fluke 73 series II reads 1.55V and 9.30V on the exact same cells. Didn't try my newer Fluke. So is my old Fluke no bueno, or are the cells I'm measuring likely putting out higher than normal voltage?
Secondary question, does not appear to be a way to calibrate a Simpson 260 at home on VDC? true? only fix, if one is needed, to send it in for calibration?
nate
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If you go here you can find a download on how to calibrate some series of the Simpson meters, yours should be close enough to do.
http://www.simpson260.com/downloads/downloads.htm
The Simpson meters are not lab grade test equipment but made for field servicing.
Most new batteries will put out voltage somewhat higher than the rated voltage if they are not under a load and less if under a load. I thnk new mercury batteries are about the only ones that are usually very close to the rated voltage. My 40 year old Heathkit VTVM states to calibrate the meter using a new battery to 1.6 volts if that is the most accurate standard you have.
Here is what Simpson says about their meters. The voltage and current accuracy of this Instrument is commonly expressed as a
percent of full scale. This should not be confused with accuracy of reading (indication).
For example, +2% of full scale on the 10 volt range allows an error of
0.20V at any point on the dial. This means that at full scale, the accuracy reading
would be 2%, but at half scale it would be 4%. Therefore, it is advantageous to
select a range which gives an indication as near as possible to full scale
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On 04/07/2010 07:29 PM, Ralph Mowery wrote:

I did see that, thank you - but the only adjustment I saw was for VAC which is near dead nuts on as far as I can tell.
if your docs say to calibrate to 1.6V and I'm reading 1.6V then I will cease worrying about it :)
this is just one of those times where I was thinking about something, saw it for cheap, and said to myself "self, you're old enough you shouldn't have to use crap tools anymore" <G>
Of course, the times I would need a really good analog meter are when I'm doing a serious electrical overhaul on something, and I've already finished my last challenging electrical project, which was unraveling the mess that was the wiring harness on my '55 coupe. Which I somehow managed to do with a balky cheap meter and an incandescent test light :) If I need something as good as a Simpson to finish my house wiring, I would say that I'm likely doing something very, very wrong...
but still, having nice tools is a Good Thing.
nate
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Nate Nagel wrote:

I generally regard a Fluke meter as the gold standard for "normal" measurements, my Fluke 87 was actually calibrated and certified by Fluke at one point and has the calibration sticker, but it has expired.
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On 04/07/2010 08:22 PM, Pete C. wrote:

I'm pretty sure my "good" Fluke is an 87 as well, not sure what series.
Obnoxious thing about Flukes is the fuses they spec... I think it's a KTK-15 or something like that? I recall popping one once after forgetting to switch my leads to take a current reading... that was an expensive lesson, those suckers are something like $12 apiece, and darn hard to find, unless you have a Grainger nearby.
On the Simpson the one fuse is a dirt common 3AG, the other is a sorta-spendy BBS-2. Of course my "new" meter has the wrong fuses in it. Yes, I looked. Yes, I'll fix them. (who replaces a 1A fuse with a 20A fuse, anyway? That's just asking to blow up something expensive.)
nate
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A new alkaline cell should read between 1.55 and 1.6V
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Nate Nagel wrote:

Mine is the original 87 before there were any other series. I bought it in '89 I believe.

Fry's carries them, and they are normally on the rack in their stores along with just about every other Fluke goodie. Electrical supply houses also tend to have them and electrical supply houses are nearly everywhere.

Yes, thanks to our failing schools, few people seem to be able to understand what a fuse is for.
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On 04/07/2010 09:17 PM, Pete C. wrote:

<snip>
I keep hearing about this wonderful "Fry's" place but I've never seen one :( When I lived in Michigan, there was a place that I'd bet had them though. Don't remember what it was called, but it was most wonderful.
And on reflection, before anyone jumps on me, I remember now how I blew the fuse, I had just *taken* a DC current reading and then switched to either volts or ohms and forgot to switch the leads. Wups.

Eh, sorta kinda. I know where three or four are, but none of them are particularly convenient. That said, if I popped my last one, and needed to take amp readings, I would probably just go get one, but it'd take at least an hour, which is annoying. (which is why I now always have at least one spare in my roll cabinet. Haven't blown one since I got 'em either...)

you'd figure anyone who understood enough to be using a Simpson instead of something off the rack at Home Depot wouldn't be that silly though... (and they'd remember what it cost when they bought it new...)
nate
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On 04/07/2010 09:35 PM, Nate Nagel wrote:

Fuses just showed up today... still don't understand. Can't tell the difference between the BBS and KTK other than a few mm difference in length. Would only make a difference in the Simpson as the Flukes use clips. Both BBS and KTK fuses have a 100,000 amp current interrupt rating, but the KTK is 2-3x as expensive...
*shrug*
Oh well, all meters have proper fuses now
nate
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My parents bought mine in 1971 as a graduation present. Still works, the only calibration I have ever done on it is the meter "cal" screw on the front.
Jimmie
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Nate Nagel wrote:

Try: http://Frys.com
It's not as nice as wandering a retail store that has both Kitchenaid stand mixers and Tektronix TDS oscilloscopes on display, but it will get you the parts you need.
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I have not read the calibration procedure in a long time, but think that you adjust a pot to make the meter read exectally 50 uA as it is really around 40 some uA. Then just depend on the range resistors to be the correct value.
I work at a large plant as an electricial an instrument person. I get to deal with percise instruments in the milliamp range that are tracable to the goverment standards and lots of other things up to some 4160 volt circuits. The handiest thing I have for general testing is a thing made by Fluke. I don't recall the modle number but it has seveal leds on it. YOu just touch the probes to a circuit and it it has continuity one led lights. If it is AC or DC then several others light up to give an indication of how much voltage. Good from about 12 volts to 600 volts.
The reason the fuse for the Fluke costs so much is it is a special fuse made to break very large current overloads. You can use a standard fuse of the same size, but if you deal with some of what I do, you would not want to. Say you forget to change from resistance or current modes to a voltage mode and you are wanting to see if a 480 volt circuit that has 600 amp fuses on has any voltage. Instead of the fuse blowing, a standard fuse will probably arc over and you have a size 20 wire in each hand trying to carry 600 plus amps. It melts the probes and your hands become part of the circuit and you fry. I have seen some vidio the Fluke people put out on things like this. Not a good looking thing even though they use a dummy to demonstrate this.
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Yes,the first adjustment is the 50uA adjust,then the 250mV adjustment. then you go and check all the ranges,and if any are off,you find and replace the bad divider resistors,then go back and start over.I don't remember the AC adjustment procedure,there's 2 pots to adjust there.
I just checked the 270-5.pdf I downloaded for my Simpson 270,and it doesn't have the adjustment procedure(but does have the schematic and parts list. then I checked a 260-8 .pdf and it was just an d instruction(operators) manual. I suspect Simpson doesn't include cal prodecures intheir downloadable manuals.(the bastards...)
They want you to return the meter to them for cal. Of course,not many folks have the proper standards for cal.
but IMO,their manuals should still contain the adjustment procedure,parts list and schematics.
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On 4/7/2010 5:54 PM, Nate Nagel wrote:

Ok, I'm old enough to remember this. I worked in the calibration lab at an aircraft manufacturer in the late 50s, early 60s.
The old fashioned analog Volt-Ohm-Milliampere (VOM) meters didn't have any way to calibrate them other than replacing parts. All we did most of the time was to strip out defective parts and replace them. Well, if all scales were off it might mean the meter itself was off, then we had one man who specialized in them. He had a setup so that he could change the magnetization of the meter and make some adjustment that way. It wasn't something that was generally done.
To check the calibration we had very accurate meters that we used to compare the VOM reading to.
I do recall one time one of the meters came in box after it was dropped off of the wing of an aircraft. The man working on it went to the crib and got a new case, a new meter, a new front panel and a new switch assembly and put them together, then took the ID tag off of the old one and there it was the same meter fully repaired. If cost more than buying a new one, but it was possible to get money to buy parts, but not nearly as easy to buy replacements.
Ralph Mowery is correct in his explanation of how the accuracy of the VOMs was defined. So be sure to take that into account when you are trying to figure out what the reading is.
Bill
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do you have an accurate voltage source that can be set to full scale for each range? I wish I did.They are not cheap. calibration is not the adjustment,but the comparison of each range to a known standard.
First,you need a 50uA source to set the basic meter range,then a 250mV source to set the 250mV range. then you check all the other ranges,see if they're in tolerance.It's possible for higher ranges to go out of spec,or even be burned by overvoltage. Often,we would offset the basic 50uA setting (but keeping within tolerance)to bring the other ranges into tolerance,rather than setting 50uA to exact value.

heck,even back then they had the old Weston meter calibrators.they gave basic DCV and DCMA. (I used to work in USAF PME lab;their test equipment and cal labs)
Do you remember the old AN/PSM-6 VOMs? bulit like a TANK,with a heavy cast aluminum case.

The military always had a big store of parts. I used to rebuild smashed Simpson 260's and 270's.

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Well now:
9.4v divided by 9.3v = a variation of 0.11 volts in almost ten volts! A difference just over one per cent!
1.6v divided by 1.55v = variation of of 0.05 volts in about 1.6 volts! Adifferenece of about 3%!
Just what degree of accuracy/precison does one expect from non- laboratory equipment? And at what point on the scale? If measuring 1.6 volts on say a ten volt setting (analog/digital etc.) the meter is only working at 16% of that full scale. So percentage error could be much greater!.
"Within plus/minus 0.1 volts"; on a one volt scale = 10%. On a ten volt scale = 1%. On a 100 volt scale = 0.1%.
And halway across the ten volt scale 0.1 volts = 2%. Quarter way across ten volt scale could = 4% etc. etc.
Also is the OP measuring open circuit? i.e. with no current load from the cell? That's not necessarily a good way to measure battery cells, except as a quick check. Which is why alkaline cells, which have a fairly high internal resistance are excellent for some uses, while other types with very low internal resistance are better for short term high current uses.
Alkaline cells are 'primary' cells; since they MAKE electricity from chemical action. For some low current and very occasional uses I buy the cheapos; because the function is non critical and failure is non critical and easy to battery change. This includes, for example, a TV remote. And some test meters which only use the battery occasionally and only for resistance measurements. But for smoke detectors which are continuously 'listening' for fumes/vapours etc. buy high quality item. Although I've had Duracells and other leak! And not because they went flat in the device, recently in a device with four AAs one of the four leaked but other 3 were OK, voltage/load wise and had NOT leaked. BUT the four cells in series WERE a mixture of different types of cells and therefore likely of different ages etc. Message to self (AGAIN) do not leave ANY cells in unused devices! DUH!
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