[volt-nuts] Traveling Standards

Thu Sep 1 07:20:00 UTC 2011

I am thinking about doing a bit calibrating as a sort of service and to earn some money to spend on calibrating my stuff ( p.e. the 731A transfer standard) with our national standard buro. so not to make money on it, just to cover expenses.

But he problem is I, have no clue what to ask and if there is. Market. I have a mint condition guildline cabinet with known documented history and from the first user. So I can, after the return of the transfer, compare it with my guildline and have a longtime stable reference. But a calibration here is not as cheap as in the states I think. A friend had a tek current probe calibrated, that was over 500 dollar. But i think most " customers" will have a 4.5 or 5.5 DMM and in that case my cells and calibrators are allready good enough. 

I bought a new calibrated keithley 2000. As soon as It arrived I warmed it up and measured my cells and calibrators , that I allready had warm up, and documented that. The cells where less then 3 uV away from the last documented calibration and still spaced appart like they where then. So for a 5,5 digit i will be close enough. An old secondhand bought 6,5 digit will be closer then it was. 
I have a the 4 cell guildline cabinet, 731A, 332, 750, 760, 720, philips DC volt/current calibrator, and. Fluke 5xx AC calibrator. Besides that a GPS controlled thunderbold Oscillator, a HP 5 MHz standard, counters connected to the 10 MHz ref upto 18 GHz so I can do counters too. Also have timemark en pulsgenerators for scope adjustment but that really is on scopes like tek 7000 or 500 series very much labour if you do not have the calibration plugins. A normal scope is still about 10 hours work. 

The problem is I have plenty of time but i am a bit disabled so I can not work long periods and that means two hours warming up, work an hour on the instrument and rest for an hour so it would take me days. The calibration of my 7704 , witch is rather complex took me two weeks. A simple 547 3 days. A letter plugin about 2 to 4 hours. A DMM like a fluke 8000 or HP3535 is done in about 2 hours, a keithley 199 doing the memory calibration is done in an hour or so but a HP3490 is many hours of work. (and there is the problem of shipping and risk invalved. There can be people trying to missuse your service by sending not functioning gear and telling you broke it or it gets dammaged or lost in the mail.)

Are there voltnuts how do such project to earn back a calibration. Are there other Dutch volt-nuts here ?

I do not know there is market for this in the Netherlands. Not much voltnuts around and we Dutch are famous for our cheapiness. I am very active on a very big electronics forum, there are about 4 other volt nuts there, who probably would spent 50 euro or so on a calibration. The rest ( about 80 % i think) use there holy 5 tot 30 bucks multimeter. A 50 euro model is considerd to be rreal expenive and overkill. Cheap is holy around here and being cheap made to an art.  
Lot of topics about Rigol, atten and owen scopes asking if it is wise to buy because it is a lot of money and or if  someone knows a cheaper brand or model  :-( 
But a calibrion is looking what the deviation is, most think a calibration is the same as adjusting it whitin specs. I do that with my own gear and for a lot of gear that is a hell of a job. And to do that for 50 euro does not sound tempting.
Fred PA4TIM

Op 1 sep. 2011 om 07:45 heeft Stan Katz <stan.katz.hk at gmail.com> het volgende geschreven:

> Bob,
> 
> You've heard from the experts now here's some thoughts from a mere hobbyist.
> 
> First, there was discussion, on this list, in Nov. 2008 on this issue. I
> would also be happy to be able to rotate a homebuilt transfer standard
> through a kind hearted soul's home lab ( don't worry Charlie, I don't intend
> to piggyback on your good hearted offer to Bob) equipped with 732A's and
> access to an employer's NIST traceable lab gear. In fact, a master
> metrologist did take pity on me, and actually gave away a little standard
> which I had to use as soon as I got it at exactly 63.5F to perform the
> transfer.  That little standard "moved away"  300ppm in 90 days from the HP
> 3456 and ancient HP735A transfer standard I applied it to (the 3456 and 735A
> were only about 30ppm apart by then). Take a look at the Nov 2008 archive.
> Some were happy with the cost/performance of the Geller product
> http://www.gellerlabs.com/SVR%20Series.htm, Some others considered its long
> term stability suspect. If that's the case, in time, you'll just have
> another suspect clock in your collection. As my knowledge, and appetite for
> metrological perfection falls quite short in comparison to the scholars and
> master designers who dominate this list, a 10ppm transfer capability, from a
> transfer standard with a long term drift of less than 5ppm/year would be a
> joy. In that regard, my own preference would be to build the clone of the HP
> 3458A reference board described by Max Carter
> http://www.maxmcarter.com/vref/. The use of metal film resistors on the
> board as shown I will generously presume to have been placed there after the
> builder ran out of funds for Vishay wirewounds, or thin films. In any event,
> I can't afford precision, low tempco resistors either. I would also use
> metal films, but I would ovenize as per your off-the-cuff, and HOPE the heat
> blows off the humidity. I would build an aluminum plate "coffin" around all
> components except the LTZ1000 (is it also position sensitive like LM399s?),
> build a precision heater control circuit to heat either resistor arrays or
> pilot lamps sprinkled around the board, fill the "coffin" with insulating
> foam, and seal. Maybe this arrangement would have better long term stability
> than the Geller, or maybe it's DOA. Comments from scholars and master
> designers welcome. I realize, with the whole board ovenized, shipping under
> battery power may be a bit impractical.
> 
> As far as relying on the kindness of strangers, that's ok for a one off.  To
> regularly (e.g. yearly) calibrate whatever homebuilt transfer standard you
> come up with, is a different matter. I realize the list members with the
> highest level of standards control, are also the same ones immersed in
> highly complex lab project on their own precious time. They can't be
> expected to waste time tearing open scores of packages, and then repackaging
> standards for return. May I ask if there's someone on this list who has a
> wife, child, nephew, niece, or cousin, willing to run a small business from
> dad's/grandpa's home lab? While Geller charges $10.00 to recalibrate your
> Geller "transfer reference" by throwing it across an HP3458A, a volt-nut
> Grandpa Lab may just be OCD enough to demand to have the little family
> business do a right and proper transfer right from grandpa's bank of 732A's.
> In which case, you aren't going to get away with $10.00 cal+ship. Grandpa's
> lab would have to charge at least $50.00. I would certainly be willing to
> pay $50.00 vs. $500 to a commercial lab. What a bargain!
> 
> Regards,
> Stan
> 
> 
> 
> On Thu, Aug 25, 2011 at 1:14 PM, Bob Smither <smither at c-c-i.com> wrote:
> 
>> Fellow voltage aficionados ,
>> 
>> If this has already been discussed - my apologies.  I could not find this
>> topic in the past several months of list archives.
>> 
>> Like many of us, I have an ever growing collection of voltmeters and
>> related instruments.  Like the man with two clocks who is never sure of the
>> time, I now have enough volt meters to have doubts about all of them.
>> 
>> So - I was wondering if those on this list with really good voltage
>> measurement capabilities would be willing to help those of us without.
>> 
>> What I have in mind is creating a small voltage reference circuit based on
>> one of the many available IC references that is stable enough in both time
>> and temperature to use as a transfer standard.  I am thinking that the
>> actual voltage is not important, just the stability.  Using the ICs that I
>> am familiar with the actual reference voltage would be around 5, 7, or 10
>> volts.  Said reference would be mailed to a willing list member who would
>> record his reading of the reference and mail it back.
>> 
>> I don't have such a reference yet, but have breadboarded a couple and the
>> idea seems like it might work.
>> 
>> My first objective would be to obtain a reference that I could use to get
>> all my meters to agree.  Since the best meters I have are an HP3455A (best
>> accuracy about 20 - 40 ppm, and only for 24 hours) and an ancient (but very
>> usable) Fluke 883AB (best accuracy is 100ppm), I would be very happy to have
>> a reference that I could trust to 10ppm.
>> 
>> So - two questions for the list:
>> 
>> 1.  Does this sound feasible?  Am I overlooking anything that would keep me
>> from being able to transfer a 10ppm known reference?
>> 
>> 2.  Any list members that would be willing to help with this?  I envision
>> mailing a small package with the reference in it along with an enclosed,
>> postage paid, return box.  I am asking for a member that would take the
>> reference, apply power, let it warm up, record the room temperature and the
>> reference voltage to within 10ppm, and return it to me.  If you prefer to
>> respond off-list - smither at c-c-i.com.
>> 
>> BTW - I live in Friendswood, Texas (near Houston).  Any fellow nutters
>> close enough that I could hand deliver the reference?
>> 
>> Best regards,
>> 
>> Bob Smither
>> 
>> 
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