Author Topic: Geller Labs SVR and SVR-T  (Read 35084 times)

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Offline Dr. Frank

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Re: Geller Labs SVR and SVR-T
« Reply #25 on: August 16, 2013, 04:50:58 am »
Just for fun, I ran my Geller SVR-T against a Fluke 731B for the last day or so using the DC volts ratio feature of a 34461A.  Screen capture is attached.  Ambient temperature spread was 23.7 to 25.6 deg C.  Unfortunately, there was some kind of glitch early on (probably an AC power glitch that got through the power supply) so the minimum value isn't valid.

They appear to be tracking within a couple of ppm.

I too am happy with the SVR-T.  I suppose the 731B has the advantage of the 1V output, but it's not in cal to my knowledge so it is of limited use.

Orin.

Just a metrological hint:
measuring both references back to back, i.e. their difference, would provide much faster (2x) readings and higher resolution, directly detecting changes in the sub ppm range.

Frank
 

Offline orin

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Re: Geller Labs SVR and SVR-T
« Reply #26 on: August 16, 2013, 05:36:11 am »
Just for fun, I ran my Geller SVR-T against a Fluke 731B for the last day or so using the DC volts ratio feature of a 34461A.  Screen capture is attached.  Ambient temperature spread was 23.7 to 25.6 deg C.  Unfortunately, there was some kind of glitch early on (probably an AC power glitch that got through the power supply) so the minimum value isn't valid.

They appear to be tracking within a couple of ppm.

I too am happy with the SVR-T.  I suppose the 731B has the advantage of the 1V output, but it's not in cal to my knowledge so it is of limited use.

Orin.

Just a metrological hint:
measuring both references back to back, i.e. their difference, would provide much faster (2x) readings and higher resolution, directly detecting changes in the sub ppm range.

Frank


Good point.  What was I thinking?  I remember; the tempco of the 34461A is pretty much eliminated in this configuration.  Of course, a tempco of one or two ppm isn't going to matter much in a differential measurement of a few 10s of uV and I need to worry about thermal EMFs instead.

I had considered using my 845AR's recorder output while using the 10uV scale, but decided the 845AR probably drifted too much.

I'll go and reconfigure the connections for the differential measurement and give it another day or so.  Thanks for the hint!

Orin.


 

Offline bingo600

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Re: Geller Labs SVR and SVR-T
« Reply #27 on: August 16, 2013, 03:02:49 pm »
Just a metrological hint:
measuring both references back to back, i.e. their difference, would provide much faster (2x) readings and higher resolution, directly detecting changes in the sub ppm range.

Frank

Would someone pleas elaborate this "back to back" ??

How would one conect that for the above measurement ?

/Bingo
 

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Re: Geller Labs SVR and SVR-T
« Reply #28 on: August 16, 2013, 03:27:23 pm »
Connect the negative terminals of the references together. Connect the DMM between the two positive terminals. It now measures the difference between the two references with a higher accuracy and resolution because it can be on a lower range.
 

Offline orin

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Re: Geller Labs SVR and SVR-T
« Reply #29 on: August 18, 2013, 06:53:17 am »
So I set everything up for differential measurement, then yesterday morning, everything went crazy when I nudged something on the bench.  Results all over the place.  I removed the possible culprits - a monitor and keyboard (pushed into a speaker and on auto-repeat) and now everything is back to 'normal'.

The first attachment ...6305C is with an HP 6205C power supply (typo in the filename).  After a while, things got kind of noisy.  I suspected the power supply*, so I breadboarded an LM317L** set to 15.00V and fed it 18.5V from a different supply.  Much better; see second attachment.

In both cases, the SVR-T and 731B track each other within a couple of ppm (+/- 0.35ppm meter uncertainty; 100mV range 90 day spec for the 34461A).

This is not a best case scenario for the SVR-T.  It's in the open on the bench, so it's possible the temperature sensing thermistor that is under the board sees a different temperature than the chip that's on the top of the board.  I'm going to put the SVR-T in an enclosure and see what effect, if any, that has.

I still have to work out what causes the glitches.  With the 100 plc integration, I'm sure they are worse than they seem.

Got to love the 34461A for this.  I'm using the web interface to monitor it from the other end of the house.  It will download a screenshot from the meter on demand, or show the current reading/statistics in real time.  No GPIB necessary, just using the ethernet interface (admittedly bridged over wireless by a laptop in the 'lab', but that just makes it more amazing that it all works).

Orin.

*The 6205C barely worked when I got it and needed much contact cleaner in the slide switches.  I suspect I didn't clean them well enough.

** See the TI datasheet.  10uF tantalum across the "R2" resistor and 1uF tantalum on the output.  "R1" is 243 ohm, R2 is 2610 in series with a 200 trimpot.
 

Offline orin

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Re: Geller Labs SVR and SVR-T
« Reply #30 on: August 27, 2013, 06:04:49 am »
Well, the SVR-T is now in a nice metal box and here is a couple of days of comparison with the Fluke 731B, differential measurement, Fluke '+' to 34461A Lo and SVR-T '+' to 34461A Hi. Fluke '-' to SVR-T '-'.  Temperature spread was 20.4 to 24.2 C.

They are within 1ppm of each other over 48 hours and 3.8 deg C.

So, the SVR-T at $75 is a great deal IMO.  Add a box and some clean power and it's still less than the bargain basement, uncalibrated, batteryless 731B and I shudder to think what Fluke would want to calibrate the 731B!  (Fortunately, it was only $30 for a new NiCd pack for the 731B at the local BatteriesPlus.  You don't want to run a 731B without a battery as the reference section then gets powered by unfiltered DC from the battery charge circuit.)

Orin.

 
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Online Electro Fan

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Re: Geller Labs SVR and SVR-T
« Reply #31 on: August 27, 2013, 06:38:07 am »
How critical is the quality of the power supply to the results produced by the Geller devices?

(What are the minimum attributes/specs for a power supply that Geller users would recommend in order to make it worthwhile to use a Geller?)

Thx, EF
 

Offline Dr. Frank

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Re: Geller Labs SVR and SVR-T
« Reply #32 on: August 27, 2013, 09:10:28 am »
Orin,

wow, I did not expect the Geller reference, nor the 731B to be that stable over time and temperature.

Both seem to have a T.C. below 0.1ppm/K, and 2 days stability below 0.5ppm, as your nice graphic shows.

Respect!  :clap:

Frank
 

Offline quantumvolt

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Re: Geller Labs SVR and SVR-T
« Reply #33 on: August 27, 2013, 10:43:59 am »
How critical is the quality of the power supply to the results produced by the Geller devices?

(What are the minimum attributes/specs for a power supply that Geller users would recommend in order to make it worthwhile to use a Geller?)

Thx, EF

Short term transfer accuracy applies in the short term at the reported temperature and at the specified power supply voltage (15.0V for 10V SVR references) after of warm up period of 30 to 60 minutes, <10 ppm within 5 minutes.

The SVR requires an external (not supplied) single 15 VDC power supply, preferably using a linear regulator. With no load on the SVR board, the board draws on the order of 2 mA. A 15 VDC linear power supply rated at 80 milliamps or more is recommended. For relatively low accuracy applications (.01%), two 9V batteries in series can power the board at about 18 V.

...

The reference chips we use are rated at 100 uV / V (power supply), however most perform much better.

...

The details of high precision use, 30 to 60 minute warm-up, use as close the temperature where we did the calibration, power supply voltage of 15V +/- 0.1V are all just to squeak the last ppms possible (to get as close as possible to our 732B voltage) using this relatively inexpensive method. At relatively low precision (e.g. 0.01%), these are all non-issues.


Quotes from / more at http://www.gellerlabs.com/Voltage%20References.htm
 

Offline orin

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Re: Geller Labs SVR and SVR-T
« Reply #34 on: August 28, 2013, 03:58:21 am »
Orin,

wow, I did not expect the Geller reference, nor the 731B to be that stable over time and temperature.

Both seem to have a T.C. below 0.1ppm/K, and 2 days stability below 0.5ppm, as your nice graphic shows.

Respect!  :clap:

Frank

Thanks!  It's Agilent's nice graphic really - the 34461A is connected via Ethernet and I access it remotely with a web browser.  It will show the meter's display either numerically or graphically.  I just take a screenshot and cut the interesting part out.

For the record, I attached pictures of the SVR-T & its new home.

Orin.

[Edited: stupid typo]
 

Offline bingo600

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Re: Geller Labs SVR and SVR-T
« Reply #35 on: September 21, 2013, 09:36:03 am »
Just got my 3457A back from cal.

Room temperature is 22.8 deg Celcius , SVR's calibrated @23.0C.

Freshly (7days ago) calibrated HP 3457A , connected to Geller SVR-T  (Turn on ~2.5 hr's)
May-2011 calibrated keithley 2015-THD , connected to Geller SVR  (Turn on ~4 month)

The SVR's are connected to a HP E3610 , but not in a box (yet)

Edit: I really like my SVR's  :-+

/Bingo
 

Offline quarks

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Re: Geller Labs SVR and SVR-T
« Reply #36 on: September 21, 2013, 01:05:28 pm »
 :-+ perfect results!
« Last Edit: September 21, 2013, 05:22:22 pm by quarks »
 

Offline saturation

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Re: Geller Labs SVR and SVR-T
« Reply #37 on: September 21, 2013, 02:21:15 pm »
Thanks bingo6000, that is good news.
Best Wishes,

 Saturation
 

Offline bingo600

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Re: Geller Labs SVR and SVR-T
« Reply #38 on: September 21, 2013, 02:35:36 pm »
@quarks

I got a very nice offer from a Cal-Lab in Germany.

They offered a ISO9000 Cal. with Justage , for 99€ + VAT and return shipping to DK (UPS).
Total 153.00€

Contact info:
Quote
Beatrice Jauch

Esenwein GmbH
Porschestraße 17
D-73269 Hochdorf
Tel. 07153 . 30 80 951
Fax. 07153 . 30 80 977
eMail: jauch at <same as webpage>
web: kalibrierlabor.de

Thats not a bad price.

/Bingo
« Last Edit: September 21, 2013, 08:35:00 pm by bingo600 »
 

Offline quarks

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Re: Geller Labs SVR and SVR-T
« Reply #39 on: September 21, 2013, 07:53:39 pm »
Just in case someone missed this info
http://www.gellerlabs.com/DMMtempco.htm
 

Offline Galaxyrise

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Re: Geller Labs SVR and SVR-T
« Reply #40 on: December 26, 2013, 05:13:01 pm »
Too good a deal to last, it seems:

However, the sad truth is, our present business plan is not commercially viable. It is not bankruptcy, just an ideal time to make a good business decision.  The present plan is to wind the current business down around the end of this year.

Sad I missed my opportunity!  I had a bunch of local experiments I wanted to do before I was "ready" for something calibrated.
I am but an egg
 

Offline bronson

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Re: Geller Labs SVR and SVR-T
« Reply #41 on: December 26, 2013, 05:49:02 pm »
Dangit, that's too bad.  I gotta say, the SVR-T seemed a great deal for what you get.  I wonder if Joe could have charged twice as much for them, and if that would have made his home lab more viable...?

Here's a random pic of my SVR-T from a few months ago.  Random Pomona banana cords, random old power supply from the 80s.  Ignore the Fluke -- I already knew it needs a recal.

Drat, I just noticed the 3457 is only displaying to 5 1/2 digits.  How did I do that?  Guess I'm going to have to redo the test.  And that requires waiting for the shop to warm up...
 

Offline bingo600

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Re: Geller Labs SVR and SVR-T
« Reply #42 on: December 26, 2013, 10:58:39 pm »
Note that Joe told me it wasn't a good idea to run several meters from the same SVR.

/Bingo
 

Online Vgkid

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Re: Geller Labs SVR and SVR-T
« Reply #43 on: December 27, 2013, 07:28:26 am »
Bingo, how is the E-100?
If you own any North Hills Electronics gear, message me. L&N Fan
 

Offline bingo600

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Re: Geller Labs SVR and SVR-T
« Reply #44 on: December 27, 2013, 09:38:47 am »
Bingo, how is the E-100?
I haven't had much time to play with it yet ....
But it seems to be functioning , and not "far off"

I have gotten the Deox-IT for the wheels , but  still need to open it up and write down all the ELCO' values/voltages for a (recapping).

Hope to do this in Q1 of 2014.

/Bingo
 

Offline bronson

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Re: Geller Labs SVR and SVR-T
« Reply #45 on: December 28, 2013, 02:28:15 am »
Yea, for absolute precision I agree with Joe: hooking multiple meters in parallel seems to destabilize things a bit.  In this case, at 5 1/2 digits, I don't think it matters.

I'd like to know why though...  Seems like hundreds of gigaohm input impedance in parallel with teraohm input impedance should be fairly undetectable.  Oscillation between the charge reinjection circuits?  Constructive interference of the sampling noise?

Did Joe say anything more?
 

Offline bingo600

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Re: Geller Labs SVR and SVR-T
« Reply #46 on: December 28, 2013, 11:02:06 am »
@Bronson


How is your 3457A doing with temperature deviations ?
My 3457A seems to be extremely temp sensitive.

I have a SVR-T on the 3457 , and a SVR on the Keithley 2015

When the room temp changes (2 degrees) the 3457A shows a 4..5 ppm change , even with a SVR-T connected.

If i then swap the SVR & SVR-T , the Keithley is still "spot on"

This makes me think that the environment temp has a big influence on the 3457A.

I am wondering if i should open the 3457A , and "isolate" the V-Ref board with some foam padding.


/Bingo
« Last Edit: December 28, 2013, 11:07:56 am by bingo600 »
 

Offline bronson

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Re: Geller Labs SVR and SVR-T
« Reply #47 on: January 10, 2014, 08:26:37 pm »
Hi bingo600, I've been meaning to run some tests but haven't gotten around to it.  I'll reply when I do.

You saw this of course?  http://www.gellerlabs.com/DMMtempco.htm

My problem is that I have my single SVR-T and the 3457...  I'm sure I'll see tempco swings but I won't know who to blame. :-//  Given the age and pedigree of each device I'm inclined to think most of the swing would be the 3457 but dunno.

Also I need to set something up to log ambient temp...  Just stick a K thermocouple into the Fluke and GPIB it?  Or is there an easier way that I'm overlooking?

Seems like this would be an easy project since my EE shop is an unheated detached single car garage and the temp swings have been huge lately...
 

Offline bingo600

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Re: Geller Labs SVR and SVR-T
« Reply #48 on: January 10, 2014, 09:30:41 pm »
@Bronson

I'll take back the "Bad Mouthing" about the 3457A .....
I have goofed , and didn't put the Keithley out of "AutoRange" , so it shifted to the 100v range , when the SVR hit 10.xx volt and stayed there. And i didn't even notice that a digit was missing  :palm:

After i have put the Keithley on manual 10v range , they are both affected my temperature.

And in the 2 days since i have discovered this error , it seems that they are quite equal in the temperature drift.

(Sorry HP)   :'(

But i just finished my GPIB logging setup , and have written a loggerprogram in python
https://www.eevblog.com/forum/reviews/linux-gpib-and-python-keithley2015-hp3457a-10v-logging/

Now i can really start to collect data.

/Bingo
 

Offline Dr. Frank

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Re: Geller Labs SVR and SVR-T
« Reply #49 on: March 31, 2015, 04:00:59 pm »
Hello,

I have had got the possibility to make some measurements on a Geller SVR-T, which HighVoltage lent me recently.

I'd like to share stability  measurements, I've done in comparison with my 3458A, NPLC100 (2sec aperture).
The room temperature during this 29h run was exceptionally stable, <= 0.2°C change.

It turns out, that the Geller SVR-T competes even with the LTZ1000 references in terms of noise ~ 400nV, standard deviations for 10min. transfer stability sigma = 0.06ppm , 2h sigma = 0.07ppm and 24h sigma = 0.1ppm.
Also see stability figures, noise ~ 200nV, and Allan deviation from a LTZ1000 in comparison.
(The room temperature was less stable, about 0.7°C)

These Allan diagrams were normalized to ppm.

I also did a rough, estimate measurement on the T.C. of the Geller SVR-T, see my usual beer box setup.
I heated the whole box to about 31°C, from originally 20.4°C, measured by a thermo couple and a pyrometer, on the surface of the reference aluminium box, after temperature stabilization.

The voltage deviation vs.  time graph reveals several effects concerning temperature change and lagging, but clearly demonstrates  the very low T.C. of around -0.1ppm/K over a 10°C range .. that also competes very nicely with the LTZ reference.


Concerning the absolute long term stability:

I got a poor-mans-calibration from quarks at about September 2013.
His gear (actually his 8508A) had a brand new calibration, and my 3458A was 0.3ppm low compared to his instrument.

Since 5 years, I monitor the drift of my 3458A against two external LTZ1000, and one 5442A, and the overall drift between all these four references is <= +/- 1.5ppm over the whole time period.

Therefore, this recent measurement of HighVoltages SVR-T should be within 2ppm absolute uncertainty, as estimated.

This also is feasible, as it turns out, that the SVR-T is measured to 10.0000223V (+/-100nV) , only 2ppm off from the intended calibration value from Joe Geller, 2 years ago.
I measured no bigger differences than 1µV to that value, but I omitted to measure the warm-up behaviour.

HighVoltage promised to present comparative measurements with his new 34470A, which fall really very well within assumed limits. (Can't be accidentally)

As a resumée, the Geller SVR-T is really a very stable reference, very precise and also long term stable.. A pity that Joe Geller went out of business.

Frank
« Last Edit: April 01, 2015, 06:18:33 am by Dr. Frank »
 


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