Author Topic: Fluke 732 calibration price list and procedure  (Read 6174 times)

0 Members and 1 Guest are viewing this topic.

Offline Moon Winx

  • Regular Contributor
  • *
  • Posts: 68
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #50 on: October 28, 2017, 04:53:33 am »
MisterDiodes, this is from Fluke's 732/734B manual describing a step in one the calibration options:

Quote
Fluke sends you a calibration report that assigns a value to your 732B 10V output relative to the Fluke Volt. The Fluke Volt is maintained by means of a Josephson Junction array in the Fluke Primary Standards laboratory. Periodic transfers to NIST also maintain traceability to the U.S. Legal Volt (at greater uncertainty) for those who are required to maintain NIST traceability.

The Fluke Volt, in this case, is a bank of zener references. The "transfers to NIST" are referring to zener references. So Fluke has a calibration against their JVS-calibrated zeners, AND they have a calibration against their NIST-calibrated zeners. The calibration against the NIST-calibrated standards obviously has a higher uncertainty. So, like it says, if you require NIST traceability for DC volts (which I can't think of a good reason for) instead of traceability directly to the SI, you are going to have to settle for a higher uncertainty.

...and frankly, I don't understand the practical difference between a 17025-accreditted certified voltage measurement and a 17025-accreditted calibration certificate. If they are both accredited, both can be used in an accredited measurement chain. What's special about the certificate?

...and no, I don't have a verifiable number from Fluke Cal. The data I was referencing earlier is a customer's 732b calibration using our 734B zener bank as the standard. That measurement for the 732B has an uncertainty of 0.16 ppm because of the standard I'm using.

We have 2 conventional DC JVS systems and a zener bank system... One JVS produces a typical 732B measurement uncertainty of 0.05 ppm, the other cryo-cooled system produces 0.05 ppm, and the zener bank system produces 0.16 ppm. All of these are realistic uncertainty specs. They've been verified countless times in a myriad of ways. It's expensive to operate a JVS so most labs just fire it up to calibrate a zener bank, or they may schedule calibrations during a few months out the year when they have helium. We have a closed-loop helium system so it's not a problem for us to use the JVS for every measurement.

When USING a 732B as a standard, you have to add other sources of uncertainty (dacman describes this above), as well as a stability specification. Maybe that's where the miscommunication is happening? The difference between measuring the voltage output and using the voltage output?
« Last Edit: October 28, 2017, 04:57:55 am by Moon Winx »
 

Offline MisterDiodes

  • Frequent Contributor
  • **
  • Posts: 454
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #51 on: October 28, 2017, 05:21:12 am »

...and frankly, I don't understand the practical difference between a 17025-accreditted certified voltage measurement and a 17025-accreditted calibration certificate. If they are both accredited, both can be used in an accredited measurement chain. What's special about the certificate?


Please read my previous post, and the answer lies within.

CalMachine:
Yep, it does look like to me you have a Certificate of Calibration.  How that is 0.06ppm uncertainty eludes all sense from everyone I've talked to at Fluke Park and Service Center, that is down in the mud.  As Fluke told me this morning:  If they provided an uncertainty of .06ppm, that is certainly doable with their on-site process, but that measurement uncertainty would be only valid for a few hours on a 732 at best - unless perhaps it was a specially characterized unit.

I take it that was a Ship-To Cal from Fluke?  And that has a lot of history, so maybe that is the difference?

I'll check when I get a chance, but frankly it's not on my top priority list anymore - I've got more important fish to fry today.
 

Offline MisterDiodes

  • Frequent Contributor
  • **
  • Posts: 454
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #52 on: October 28, 2017, 05:34:35 am »
CalMachine:
Maybe I missed it, but do you have a specified TUR? That -should- be on the last page with the voltage measure displayed.  That's where your Cal Cert and mine differ. Otherwise that is more like a 1:1 measure against their JVS (Except they are using 732a's to cal your 732b..gotta love the old stuff!) - and again that uncertainty on a 732 would not last long enough to ship that to you and still be traceable - at least that's what they tell me.

That would explain why your listed uncertainty is much lower, but my question is - how does that get on a Calibration Certificate on a unit that is shipped to you?.

The puzzler is - nobody at Fluke will admit to providing a shippable 732 CAL Cert with uncertainty that low, and neither will anyone at NIST.  You'd think someone would be willing to sell that service outright, if it's valid.

I'll ask -again- Fluke Park Labs, but probably not until next week.  I do see what you're saying though.


 
« Last Edit: October 28, 2017, 05:36:53 am by MisterDiodes »
 

Offline CalMachine

  • Frequent Contributor
  • **
  • Posts: 388
  • Country: us
  • Metrology Nut
    • ENILABS
Re: Fluke 732 calibration price list and procedure
« Reply #53 on: October 28, 2017, 05:59:34 am »

...and frankly, I don't understand the practical difference between a 17025-accreditted certified voltage measurement and a 17025-accreditted calibration certificate. If they are both accredited, both can be used in an accredited measurement chain. What's special about the certificate?


Please read my previous post, and the answer lies within.

CalMachine:
Yep, it does look like to me you have a Certificate of Calibration.  How that is 0.06ppm uncertainty eludes all sense from everyone I've talked to at Fluke Park and Service Center, that is down in the mud.  As Fluke told me this morning:  If they provided an uncertainty of .06ppm, that is certainly doable with their on-site process, but that measurement uncertainty would be only valid for a few hours on a 732 at best - unless perhaps it was a specially characterized unit.

I take it that was a Ship-To Cal from Fluke?  And that has a lot of history, so maybe that is the difference?

I'll check when I get a chance, but frankly it's not on my top priority list anymore - I've got more important fish to fry today.

Yes, this unit has traveled to Fluke many times.  Every time, previous, it had been to their standards lab where I would receive your same reported uncertainty of 0.3 PPM.  But, just this most recent trip, I sent it to the Standards lab where I always received the 0.06 PPM.  With known history and a verified method of predicting drift, this is significant.


CalMachine:
Maybe I missed it, but do you have a specified TUR? That -should- be on the last page with the voltage measure displayed.  That's where your Cal Cert and mine differ. Otherwise that is more like a 1:1 measure against their JVS (Except they are using 732a's to cal your 732b..gotta love the old stuff!) - and again that uncertainty on a 732 would not last long enough to ship that to you and still be traceable - at least that's what they tell me.

That would explain why your listed uncertainty is much lower, but my question is - how does that get on a Calibration Certificate on a unit that is shipped to you?.

The puzzler is - nobody at Fluke will admit to providing a shippable 732 CAL Cert with uncertainty that low, and neither will anyone at NIST.  You'd think someone would be willing to sell that service outright, if it's valid.

I'll ask -again- Fluke Park Labs, but probably not until next week.  I do see what you're saying though.

Read the last paragraph on the front page.  It cites the method and procedure for reporting the accredited uncertainty.  The lab I work for is accredited through A2LA, while this certificate is from NVLAP.  NVLAP is generally known for being more stringent in their accrediting process than A2LA.  And you are correct, the TUR isn't explicitly stated anywhere. 
All your volts are belong to me
 

Offline Moon Winx

  • Regular Contributor
  • *
  • Posts: 68
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #54 on: October 28, 2017, 06:07:30 am »
|O

MisterDiodes: Z540.3 requires TUR to be listed on the measurement report. ISO 17025 does not (as of now). What you must have received is a Z540.3-compliant calibration. TUR is a metric of how well you can measure an item relative to that item's specification. Since the 732B is more like an artifact than an instrument, it doesn't really have an obvious specification to compare the measurement uncertainty to. If I had to guess, they probably are using the 2 ppm stability spec, and claiming a measurement uncertainty of 0.2 ppm and a TUR of 10:1.

And what you don't seem to believe, but is true, is that a certificate's reported measurement uncertainty has NOTHING TO DO WITH FUTURE USE. It's always AT THE TIME OF MEASUREMENT. So your "not good X minutes after the measurement" argument doesn't hold or make much sense when you realize this. You MUST include the stability specification combined with the measurement uncertainty when you use the item!
 
The following users thanked this post: bck

Offline MisterDiodes

  • Frequent Contributor
  • **
  • Posts: 454
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #55 on: October 28, 2017, 06:21:56 am »
...Which is why CalMachine's cert clearly states that the uncertainties listed must be added to the stability information listed in the operator manual at the time of use, in lieu of other stability information.  Clearly this isn't going to be a good number unless you know what the stability is in the first place - and -all- uses of that voltage measure on the 732 will take place "in the future". 

CalMachine:  You do have a lot of history on this unit, and is this part of a DVMP group?.  What do you calculate the uncertainty of measurement at the moment the unit came back to your lab and you took your first transfer from it?  As per page 1-7 of the 732b manual?
 
The following users thanked this post: TiN

Offline CalMachine

  • Frequent Contributor
  • **
  • Posts: 388
  • Country: us
  • Metrology Nut
    • ENILABS
Re: Fluke 732 calibration price list and procedure
« Reply #56 on: October 28, 2017, 07:51:16 am »
I do not have this unit currently enrolled in Fluke's maintenance program.  I do send it out every year for an accredited calibration, though.  This unit has been our only reference standard for years, so I am unable to really use this -in the dirt- uncertainty to its fullest potential.

Just within this last year I've beefed up our lab and accumulated a decent sized bank of references and some of the other necessary equipment.  With our history on this, now deemed transfer reference, and the lab's new bank of references, I hope to reduce our uncertainty to a level where the difference of receiving an uncertainty of 0.3 PPM vs 0.06 PPM could possibly be a significant contributor.  All in due time :)

I will be able to provide accurate data of a transfer between the bank of references and the reported transfer reference value next year.
All your volts are belong to me
 
The following users thanked this post: MisterDiodes

Offline dacman

  • Frequent Contributor
  • **
  • Posts: 344
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #57 on: October 28, 2017, 09:03:54 am »
DVMP is the on-site program.  Here is a document that describes it but they are now giving (as low as) 0.06 uV/V vice 0.1 uV/V: "http://download.flukecal.com/pub/literature/2001531_A_w.pdf"

If I calculated a standard error of 0.1 uV/V for the stability, the uncertainty at time of use would initially be 0.28 uV/V.
 
The following users thanked this post: MisterDiodes, CalMachine

Offline MisterDiodes

  • Frequent Contributor
  • **
  • Posts: 454
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #58 on: October 29, 2017, 04:59:15 am »
That's correct.  The specified uncertainty at the time of measure -at Fluke- is a good number as an academic measure for calculating yearly drift trends and for prediction calcs...  Certainly it is a "snapshot" of measured value at that time of your unit's measured value, and that is a very consistent and good way to build a drift history. But the -real- traceable uncertainty of the -single- unit -at time of use- is very difficult to get down much below 0.3uV/V (at time of use).  But do-able if you're careful.  Having multiple cal'd references helps keep that low uncertainty verified.

This is no news to CalMachine or dacman but for anyone unfamiliar -

Remember that .06uV/V uncertinaty measure + known history stability calc is the uncertainty of the Cal'd 732 itself, and you haven't transferred that value or  comparison between another local lab reference yet - and that process in itself has some other small non-zero uncertainty during comparison. That all will be documented differently if you use a null meter / DMM or whatever method is used.

Time of use here means for instance:  Fluke takes last measure at .06uV/V uncertainty Tuesday Morning, ships express overnight, say you get it late on Weds, now as per manual procedure you have to let it be still and plugged in on mains power to stabilize for 24hrs, and then you can start taking measures, maybe late Thurs or early Friday.  So you're looking at say the passage of time of around 3 or 4 days since that measure of .06uV/V uncertainty was taken, and you have to take that passage of time into account and add that drifted value + uncertainty to your unit's first measure in your lab.  Plus there is the sometimes unknown effect of how much did your unit get bounced around on the trip, so it's good to have local accurate reference comparison measures before and after the unit was shipped to Fluke.

Theirs nothing easy or trivial about keeping a sub-ppm reference in your lab, that's for sure.

There other factros as well, but these are some of the highlights.

CalMachine:  I would suggest look at DVMP for your situation if you haven't already - a lot of our customers use that service for 0.1 to 0.2ppm traceable uncertainty docs (I'll check on how that works for .06ppm, since I'm curious about that myself) and from a business standpoint:  I'd want to let Fluke risk their own Vref during shipping.  Your Vrefs get more and more valuable with each calibration cycle and better and longer drift history - and it doesn't take long for a 732 to have more business profit value in the calibrations than the actual box itself.  It is good to have a way to keep your lab aligned to the outside world without risking those very valuable and sometimes irreplaceable references - especially when they age & relax enough to get really, really good.

That's like looking at a 200 year-old tree your front yard and trying to put a value on it.  Sure the wood is worth some xx monetary  amount of worth, but you can't just replace it.  In that sense the tree is priceless.  We feel that way about working, well aged, well characterized and very stable Vref's :) 
 
The following users thanked this post: Edwin G. Pettis, chuckb, CalMachine

Offline chuckb

  • Regular Contributor
  • *
  • Posts: 171
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #59 on: October 30, 2017, 02:54:14 am »
I was wondering about the labs that need to show "Tracability to NIST". Are they allowed to use an assumed drift rate of the zener references between calibrations?

Does the in house calibration lab need to show the calibration history and the linear or log drift equations? Is there any documented guidance for that procedure other than the Fluke application notes?
 

Offline Moon Winx

  • Regular Contributor
  • *
  • Posts: 68
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #60 on: October 30, 2017, 05:42:25 am »
I was wondering about the labs that need to show "Tracability to NIST". Are they allowed to use an assumed drift rate of the zener references between calibrations?

Does the in house calibration lab need to show the calibration history and the linear or log drift equations? Is there any documented guidance for that procedure other than the Fluke application notes?

It depends. 17025 compliant parts of a cal certificate will not contain predicted values. The certificate may have a predicted value formula or charts but that section will not be "accredited".  However, as the owner of the item you are free to do the analysis and justification for the values you use and as long as you can show your work, your justification, and it is legitimate and verifiable, then you can certainly use it.

I linked to a paper earlier in this thread that provides an industry-accepted method of applying drift rate and removing seasonal variations fo the output voltage. The more data points you have, the more confident you can be in your predictions.
 
The following users thanked this post: chuckb

Offline dacman

  • Frequent Contributor
  • **
  • Posts: 344
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #61 on: October 30, 2017, 02:43:32 pm »
The drift rate would not be assumed, it would be calculated.  What the study on 140 Zeners shows is that Zeners are more accurate than their specification at one calibration and can be predicted to even better uncertainty with two calibrations.  What is significant about that is, with the formulas I use, I need three points to make a calculation of the uncertainty of the prediction.  With two points, the calculation for the uncertainty would be infinite.
 

Offline ap

  • Regular Contributor
  • *
  • Posts: 218
  • Country: de
    • ab-precision
Re: Fluke 732 calibration price list and procedure
« Reply #62 on: October 30, 2017, 07:24:55 pm »
What is significant about that is, with the formulas I use, I need three points to make a calculation of the uncertainty of the prediction.  With two points, the calculation for the uncertainty would be infinite.

What calculations do you refer to?
Metrology and test gear and other stuff: www.ab-precision.com
 

Offline dacman

  • Frequent Contributor
  • **
  • Posts: 344
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #63 on: October 31, 2017, 11:47:19 am »

What calculations do you refer to?

I'm calculating the uncertainty of the predicted value of the Zener.  One term is STEYX() in Excel, which requires at least three data points.  If the Zener is not calibrated on a periodic basis, then the returned value (which is the standard deviation term) needs to be multiplied by what's after the standard deviation term below in order to calculate the increasing uncertainty with time.
« Last Edit: October 31, 2017, 12:04:58 pm by dacman »
 

Offline ap

  • Regular Contributor
  • *
  • Posts: 218
  • Country: de
    • ab-precision
Re: Fluke 732 calibration price list and procedure
« Reply #64 on: October 31, 2017, 04:45:09 pm »
Thanks, but the standard error function STEYX calculates the standard error of an existing line of best fit accross given historical cal data points. What you would like to get though is a predicted value at a certain time with a given uncertainty (usually K=2; 95%). STEYX always looks at the total and calculates that SE. So maybe I am missing something, but STEYX imo does not support this.
(not really on topic, but I guess worth while discussing briefly.)
Metrology and test gear and other stuff: www.ab-precision.com
 

Offline dacman

  • Frequent Contributor
  • **
  • Posts: 344
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #65 on: November 01, 2017, 11:54:32 am »
STEYX() is a shortcut way of calculating sigma-hat.  (If you look at the graphic I posted with a formula, it has a sigma-hat term.)  Sigma-hat is similar to the sample standard deviation except it has n-2 in the denominator vice n-1 (and so does STEYX).  If you were to calculate m and b in the linear regression formula, y=mx+b, and  calculate each y value at each cal point (x values are dates), and calculate the difference (or residual) between the trend line and calibrated value, and take the standard deviation of the differences with n-2 in the denominator vice n-1, the result will be the same as using STEYX on the raw data.  This is then multiplied by a prediction term to the right of sigma-hat to arrive at the standard error of the prediction.  In the formula in the graphic, x is the date of the prediction (or the date of the calibration, which could be used for charting).  As the date increases from the last calibration point so does the standard error of the prediction.

STEYX calculates sigma-hat for a linear prediction.  Non-linear predictions can also be used, and the F-Test can be applied to determine the best fit.
« Last Edit: November 04, 2017, 09:46:58 am by dacman »
 

Offline MisterDiodes

  • Frequent Contributor
  • **
  • Posts: 454
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #66 on: November 04, 2017, 10:24:04 am »
Just a quick update - I did finally get some info out of Fluke that I can share here.  Disclaimer:  At sub-ppm uncertainty you will have to get your arrangements setup directly with Fluke - this is not an exhaustive description for every lab situation.

Mind you I had to pester Fluke a few times to get real information on real uncertainties, and my questions had to get "Escalated" a few times through the tech support system before I could talk to someone in the lab at Fluke Park, so this is the new corporate Fluke policy - it's a little harder to get real information compared to a few years ago.  I still don't have all questions answered, but I'll wait for another time.

Also my research into this has nothing to do with accreditation, ISO17025 / NVLAP etc.  I was on the search for the actual processes involved.

All the info provided before is accurate on the uncertainties you'll get on a 732 a/b Cal certificate.  As "standard procedure" you'll get 0.3uV/V uncertainty on the lower cals, and 0.2uV/V uncertainty on the primary lab cal.  Everett Service Center group does the lower level cals and repairs, Fluke Park Lab down the street does primary lab level cals.

IN ADDITION - IF your unit has gone in for several other calibrations before (like for at least three consecutive years prior, might be longer) AND it is deemed stable enough, your cal certificate will show a lower uncertainty of measure, not lower than 0.06uV/V, and will not be lower than the 95% uncertainty of measure while your unit was at Fluke.  This is your snapshot absolute value and uncertainty for your long term drift rate calcs as compared to Fluke's reference.  The uncertainty listed on the cert will be where you -start- adding all the other documented uncertainty historical rates for this unit over the years while it travels back and forth from one location to another.  For true traceable uncertainty on a single 732 unit as shipped to your lab ready for use this uncertainty will probably be around 0.3uV/V (plus or minus, depends on your situation and drift/stability history) and when you are ready to start doing your first transfers / comparisons.  This can be lowered over time with more cal cycles and more Vref's to verify.

So yes, CalMachine and dacman have very good, predictable 732's.  That's the only way you get .06uV/V uncertainty on the cal certificate.  They have had successful repeat trips to Fluke calibration and they have developed a good documented history of performance.

The 732 is a good predictable reference for sure, but that description applies to around 95% of 732's built.  That leaves about 5% or about 1 unit in 20 (about) that might not be as predictable as the rest, and that's why the real way to validate Vref performance is to keep measuring against a JVS over time: you always want see how close the Vref predicted value measured up to the real calibration measure.

On the question on why CalMachine's Cert is showing that it was measured against four 732a's and not the JVS - that was an easy answer:  Those four 732a's are the "Fluke Four" - these are some older very well documented 732a's that are legendary around the lab as having extraordinary performance and their predictability calcs are spot-on when they are frequently calibrated to their JVS.  In other words they are "stellar performers".

This way they can use the Fluke Four 732a's working on keeping the production rate high on 732 primary calibrations when the JVS is undergoing its own maintenance and diagnostic procedures.

Fluke also offers a service on well known & documented 732's where they will print on your unit's cal cert the expected absolute value + uncertainty on the 1st of each month over the next year, but that is not accredited.

By the way - Fluke's JVS uncertainty is currently about 10nV/V - what they list on their online scope description is slightly out of date.

This person also talked about a new 732C model in the pipeline - the hope is that they can provide lower than 0.06uV/V uncertainty measures on that design - but none of that will happen until it is proven over time.

I also asked about the real usable uncertainty available with their DVMP - and they prefer that to be saved for a conversation directly with Fluke, because every lab will have a different situation (number of references, drift history on those references, etc.).  If you're unfamiliar, the DVMP process involves Fluke sending you a 732b to your accredited lab, you pull some measures from Fluke's 732b and then they look at the test results to see how you did.  If you pass you can join the DVMP club.

From then on Fluke sends you a 732b that you pull your transfer measures to compare each of your references, then you ship the traveling 732b to the next lab in the group, round-robin style.  When the 732b gets back to Fluke it is re-measured, and then Fluke tells each lab what the absolute value is of each of the references measured.

As I said before achieving true traceable fractional ppm uncertainty at your lab location is not trivial, nor is it cheap.  It is do-able but the lower uncertainty you go the required calibrations and documentation labor cost goes up.  At some point it becomes more profitable for a lab to just purchase and operate a JVS of their own, and maybe sell JVS measures to other nearby labs to help offset costs. 

Every situation and requirement is different - use what works best.
« Last Edit: November 04, 2017, 10:28:32 am by MisterDiodes »
 
The following users thanked this post: TiN, dr.diesel, e61_phil, Edwin G. Pettis, CalMachine

Offline dr.diesel

  • Super Contributor
  • ***
  • Posts: 2072
  • Country: us
  • Cramming the magic smoke back in...
Re: Fluke 732 calibration price list and procedure
« Reply #67 on: November 04, 2017, 10:29:42 am »
This person also talked about a new 732C model in the pipeline - the hope is that they can provide lower than 0.06uV/V uncertainty measures on that design - but none of that will happen until it is proven over time.

Mmmmmm, does this suggest a new/tweaked/modified design?

EDIT:  I mean, tweaked oven/LTFLU/circuit etc.
« Last Edit: November 04, 2017, 10:31:43 am by dr.diesel »
 
The following users thanked this post: razvan784

Offline ManateeMafia

  • Frequent Contributor
  • **
  • Posts: 705
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #68 on: November 04, 2017, 10:32:01 am »
Multiple LTFLU inside?
 

Online TheSteve

  • Supporter
  • ****
  • Posts: 2537
  • Country: ca
  • GHz or bust
Re: Fluke 732 calibration price list and procedure
« Reply #69 on: December 03, 2017, 06:33:07 pm »
My new toy, just got new batteries and capacitors. Charge levels were already correct. Trescal was very kind and provided me with the 2015 cal data.
VE7FM
 

Offline ManateeMafia

  • Frequent Contributor
  • **
  • Posts: 705
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #70 on: December 03, 2017, 06:41:50 pm »
Looks great. Two more to go.
 

Offline MisterDiodes

  • Frequent Contributor
  • **
  • Posts: 454
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #71 on: December 06, 2017, 05:21:09 am »
TheSteve,
That unit looks to be the same one from the Harris Semiconductor plant closing auction if I'm not mistaken, and if so it's been cold for over a year (It was cold at that auction at least).  The rule of thumb from Fluke is to keep the unit powered up and hot for at least the same amount of time it was powered off -before- sending in for calibration.  So if you're planning on having that calibrated at Fluke I would do that no earlier than sometime in 2019, if you don't have other information.

Handy tip: Always keep test test leads short, twisted and shielded, and for best results make use of that Guard and Ground....

You can always keep an eye on the temp sensor output - that should always be fairly stable no matter what the ambient temperature does, and if that's working well probably the Vref voltage is working too.  We've had to repair the oven controller on (very) rare occasion, so just something to keep an eye on.
 
The following users thanked this post: TheSteve, CalMachine

Online TheSteve

  • Supporter
  • ****
  • Posts: 2537
  • Country: ca
  • GHz or bust
Re: Fluke 732 calibration price list and procedure
« Reply #72 on: December 06, 2017, 01:31:43 pm »
TheSteve,
That unit looks to be the same one from the Harris Semiconductor plant closing auction if I'm not mistaken, and if so it's been cold for over a year (It was cold at that auction at least).  The rule of thumb from Fluke is to keep the unit powered up and hot for at least the same amount of time it was powered off -before- sending in for calibration.  So if you're planning on having that calibrated at Fluke I would do that no earlier than sometime in 2019, if you don't have other information.

Handy tip: Always keep test test leads short, twisted and shielded, and for best results make use of that Guard and Ground....

You can always keep an eye on the temp sensor output - that should always be fairly stable no matter what the ambient temperature does, and if that's working well probably the Vref voltage is working too.  We've had to repair the oven controller on (very) rare occasion, so just something to keep an eye on.

Thanks for the reply MisterDiodes - my unit is indeed the ex Harris unit. This was also confirmed by Trescal when I asked them for the last cal data. The seller claimed it was stored powered on, he also did mention to me that the batteries wouldn't last long enough for shipping(so he knew a little about it). If it really was stored powered on the last year we'll never really know of course. I know when I received it I powered it up and within a few hours it was happily sitting at 10.000122x on my uncal'd 3458A. The last cal value for the unit is 10.0001044. I have had it a little over a week now, powered it off once to change the batteries and caps and it is still at 10.000122x. I am now using shielded twisted pair copper with with the shield going to guard. My only tools to measure how quiet/stable it is are a pair of 3458A's. One is more temp stable then the other but even then I can see the temp changing in the house quite easily(2-3 degree C swing through-out the day). I am hoping I can have a local lab measure the 10 volt value for me at some point. Not sure I want to invest in a Fluke cal in the near future as this stuff is all just for fun. If I do decide to go for the Fluke cal they are only a 2 hour drive away which is nice.

Does anyone have a 24 hour plot of a 732A with a 3458A so I know what I might be looking for in terms of deviation etc?
VE7FM
 

Offline MisterDiodes

  • Frequent Contributor
  • **
  • Posts: 454
  • Country: us
Re: Fluke 732 calibration price list and procedure
« Reply #73 on: December 07, 2017, 04:42:32 am »
...If you're comparing a 3458a to a working 732a...you'll be looking at mostly the drift in the 3458a more than the 732a (probably).  You'll need another known working 732a/b or use multiple known Vref's / DMMs to really get an accurate idea.  Otherwise just comparing two Vrefs doesn't tell you a whole lot - it just tells you how they drift -relative- to each other.  Multiple 3458a's help, but a well aged, working 732a will probably drift a bit less per year than your DMM.  A lot of older 3458a are very good performers also, so it could be close.

For instance:  We've got some 3458a's that drift around 0.8 ppm per yr, and 732a's drifting around 0.5ppm / yr or less.  This is not a trivial measure, and you won't do it accurately with unknown, uncal'd equipment.  You annual calibration budget will soon add up to more than the purchase price of the tools - so be ready for that.  IF you're in it as a business. 

Don't forget you have to run AutoCal on your 3458a at a minimum every 24 hrs -OR- when temp changes 1 degC - we usually run it every 8 or 12 hrs. if you're chasing PPM - even when temp. is steady.

Really you want three ea. 732's and at least one of those should be in current cal from Fluke if you're interested in accurate traceable uncertainty on your voltage measures.  Otherwise it's just another unknown but steady voltage source.  Hopefully you will be able to check your unit against a cal'd unit soon, and then check it again in 6 or 12 months.  That will tell you a lot.

Your 732a temp sensor is a very valuable indicator of the health of the box, so add that measure to your scanner switch list.

Yes, I saw that at a couple auction sites before it wound up on eBay, and it was cold for those photos also - but you never know.  It sounds fairly stable though - just keep an eye on it for the next 6 or 12 months to verify, and then it's probably fine once YOU know it's fine and meets your needs.

That's a very good sign that its steady within a ppm for the first week or so after you powered up.  That shows you're in the ballpark at least.

 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf