Author Topic: Geller Labs SVR and SVR-T  (Read 35036 times)

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Offline Andreas

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Re: Geller Labs SVR and SVR-T
« Reply #50 on: March 31, 2015, 07:20:47 pm »
A pity that Joe Geller went out of business.

Hello Frank,

thats right. But on the other side:
Joe used the AD587LQ (comercial grade) references for his SVR-T.
They are obsolete now (perhaps thanks ROHS).

The only alternative would be the AD587UQ (military grade).
But I have heard that this one behaves much worse near room temperature than the LQ reference.
(they are trimmed to the temperature extremes).

By the way: in your diagram you write "AD586" = 5V reference instead of "AD587" = 10V reference.
In my ADCs  I use the AD586LQ as 5V references. (Which are still available).

With temperature compensation and after a run in phase of 6-12 months some of them are very stable
(within some ppm / year).

With best regards

Andreas



 

Offline quarks

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Re: Geller Labs SVR and SVR-T
« Reply #51 on: April 01, 2015, 09:34:48 am »
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.

Hello Frank,
that is excellent information, thanks a lot for sharing :-+

And big thanks also to Joe Geller for his great work.

bye
quarks
 

Offline JohnnyBerg

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Re: Geller Labs SVR and SVR-T
« Reply #52 on: April 01, 2015, 09:53:37 am »
I've got some voltage refs ready in a week or two. I could spare a few for testing.
Would be nice to see how they compare to the Geller SVR?

So if anyone is interested to do some testing, send me a PM.
 

Offline HighVoltage

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Re: Geller Labs SVR and SVR-T
« Reply #53 on: April 01, 2015, 04:57:24 pm »
A great thank you to Dr.Frank for testing my Geller Labs SVRT in such detail and creating a baseline for comparison.

I had the SVRT running in my lab for several days now.
And today I took the first data with my new Keysight 34470A and a few other meters in comparison.

Soon I will hook up the Pro Version of BenchVue and take some long term data.
But I think I would need to place the SVRT in a protected box to remove temperature changes.
Right now the temperature in my lab is between 22 and 24 degrees, depending on the time of the day.

And a big thank you also to Joe Geller to produce such a great reference.




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Offline Dr. Frank

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Re: Geller Labs SVR and SVR-T
« Reply #54 on: April 01, 2015, 06:25:09 pm »
[b...and creating a baseline for comparison.[/b]

I had the SVRT running in my lab for several days now.
And today I took the first data with my new Keysight 34470A and a few other meters in comparison.

Soon I will hook up the Pro Version of BenchVue and take some long term data.
But I think I would need to place the SVRT in a protected box to remove temperature changes.
Right now the temperature in my lab is between 22 and 24 degrees, depending on the time of the day.

And a big thank you also to Joe Geller to produce such a great reference.

HighVoltage,

yep, the baseline for the SVR-T is much more stable than what you see,
so the sad truth about the 34470A is, that it is less temperature stable thane the Geller Ref, and despite its inner LTZ1000A reference.

They simply used less sophisticated components for the A/D voltage reference amplifier, obviously, as specified with 1ppm/K ..

I think, your 34470A needs a box to protect its inner temperature..

Frank
 

Offline HighVoltage

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Re: Geller Labs SVR and SVR-T
« Reply #55 on: April 01, 2015, 06:49:00 pm »
Hello Frank

Sadly I think you are right and the Geller Labs SVRT seems more stable than the brand new Keysight 34470A.
Sometimes I see a flat line in the display of the 34470A for like 30 min or so and then suddenly for no apparent reason, I get a drift up or down.

Once I have BenchVue all setup and ready to go, I am planning to hook up 4 DMM's at the same time, since BenchVue supports 4 instruments at one time.

This is my plan:

1 x 34401A
1 x 34410A
1 x 34461A
1 x 34470A

I will have my second 34461A monitor the case temperature of the Geller Labs SVRT with a stable 5k Thermistor.

Do you think it is wise to have all 4 multimeters in the same box and the SVRT in a different box for temperature stabilization?
Or do you have any suggestions.

This way I would get a good and reliable correlation between the instruments and the SVRT.





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Offline Dr. Frank

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Re: Geller Labs SVR and SVR-T
« Reply #56 on: April 01, 2015, 07:57:23 pm »
Dear HighVoltage,

for sure it would be possible to determine which of the  DUTs is drifting, by thermally separating source and DMM...

Whether these lower grade 6 1/2  instruments really give some useful information, I doubt that.

Is it possible on the 34470A, to read its calibration temperature?
(The HP3458A got this feature  ;D)

Anyhow, both of our instruments, 3458A and 34470A are apart a few ppm only.. again demonstrating the stability of the Geller ref, as a transfer standard.

Btw.: Don't you own a nice, dry and temperature stable basement, as in each good German house?

The results would be much more stable.

Frank
« Last Edit: April 01, 2015, 08:09:45 pm by Dr. Frank »
 

Offline HighVoltage

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Re: Geller Labs SVR and SVR-T
« Reply #57 on: April 19, 2015, 07:31:57 am »
Btw.: Don't you own a nice, dry and temperature stable basement, as in each good German house?
The results would be much more stable.
Frank
Dear Dr.Frank
No basements where I live, because we are close to a small river and basements would overflow when the storm comes.

But what I noticed is that a close by WiFi and Cell Phone activity will have a massive influence on the data. Much more than I would have expected, even is the cell phone is 2 to 3 m away.

With this information in mind and all wireless activities turned off as far as possible, I did another test on the SVR-T that you had measured.

Here are the results from 3 Agilent 34461A's and the new Keysight 34470A.
All 4 pictures are from 4 different instruments, hooked up in parallel to the SVR-T
I would suspect the slight difference to be just a calibration issue between the instruments

Screen_1 = 34461A
Screen_2 = 34470A
Screen_3 = 34461A
Screen_4 = 34461A

I think what this proofs one more time the ultra stable SVR-T

« Last Edit: April 19, 2015, 10:52:12 am by HighVoltage »
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Offline HighVoltage

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Re: Geller Labs SVR and SVR-T
« Reply #58 on: April 19, 2015, 07:38:54 am »
And here are the same data as trend charts

Screen_A1 = 34461A
Screen_A2 = 34470A
Screen_A3 = 34461A
Screen_A4 = 34461A

« Last Edit: April 19, 2015, 10:52:30 am by HighVoltage »
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Offline Andreas

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Re: Geller Labs SVR and SVR-T
« Reply #59 on: April 19, 2015, 10:47:37 am »
But what I noticed is that a close by WiFi and Cell Phone activity will have a massive influence on the data. Much more than I would have expected, even is the cell phone is 2 to 3 m away.

Hello,

did you already try a blocking capacitor (10-100nF) at the output of the SVR-Reference. (near pin 4+6 of the AD587).
I always try to place one (as long as the reference does not oscillate) to reduce RFI effects.

With best regards

Andreas


 

Offline Dr. Frank

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Re: Geller Labs SVR and SVR-T
« Reply #60 on: April 19, 2015, 11:08:44 am »
Hi HighVoltage,

All your 4 instruments confirm the very good stability of the SVR-T, essentially the same magnitude as with my 3458A.

All these references, especially the LTZ, are very sensitive to AF noise, especially from switch mode PSUs.

So in my basement, where my analogue lab is situated, there are conventional lamps (50Hz) only, no WLAN, no cellular phones and no DECT station.

The steel wires in the concrete roof also filters most of radiation from outside.
(FM radio can be received, through a small window, anyhow.)

So, a (good German) basement gives a near perfect shielded lab.

A pity, that in many areas of northern Germany , you don't have basements in the houses.
(My brother in law doesn't have one, either, he's living in the Oldenburger Münsterland, where they have moorland. So he use to bury many of his tools in his 1/2 hectare garden..   |O)

PS: When will you have the opportunity to compare the SVR-T etc to a DKD lab?

Frank
« Last Edit: April 19, 2015, 11:12:52 am by Dr. Frank »
 

Offline bingo600

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Re: Geller Labs SVR and SVR-T
« Reply #61 on: April 19, 2015, 01:35:07 pm »
But what I noticed is that a close by WiFi and Cell Phone activity will have a massive influence on the data. Much more than I would have expected, even is the cell phone is 2 to 3 m away.

Hello,

did you already try a blocking capacitor (10-100nF) at the output of the SVR-Reference. (near pin 4+6 of the AD587).
I always try to place one (as long as the reference does not oscillate) to reduce RFI effects.

With best regards

Andreas

Joe Geller warned me about Cellphones nearby the SVR's , he had the same discovery.

/Bingo
 

Offline HighVoltage

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Re: Geller Labs SVR and SVR-T
« Reply #62 on: April 19, 2015, 03:22:16 pm »

Joe Geller warned me about Cellphones nearby the SVR's , he had the same discovery.

/Bingo

Very interesting, especially since I have a the SVR-T in a fully enclosed metal housing
I will make a picture later of  trend chart with a cell phone next to it
It is unreal how bad it is.
 
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Offline HighVoltage

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Re: Geller Labs SVR and SVR-T
« Reply #63 on: April 19, 2015, 03:28:47 pm »

PS: When will you have the opportunity to compare the SVR-T etc to a DKD lab?

Frank

Hello Frank,
The SVR-T and the LTZ1000A will go to the DKD lab tomorrow morning
They are already running for a few days on 24V battery power and will be transported to the DKD lab in an ON state.
They will stay in the DKD lab at 23 degree C for another day, before they will start measurements with a HP 3458A and a Fluke 8508A
Then I will have two confirmed references and will send you the LTZ1000A

Will keep you informed of the progress.
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Offline HighVoltage

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Re: Geller Labs SVR and SVR-T
« Reply #64 on: April 19, 2015, 03:35:34 pm »
But what I noticed is that a close by WiFi and Cell Phone activity will have a massive influence on the data. Much more than I would have expected, even is the cell phone is 2 to 3 m away.

Hello,

did you already try a blocking capacitor (10-100nF) at the output of the SVR-Reference. (near pin 4+6 of the AD587).
I always try to place one (as long as the reference does not oscillate) to reduce RFI effects.

With best regards

Andreas

Hello Andreas,

The SVR-T has not been touched and nothing has changed, since it left Joe Geller.
Except, I placed it in an extruded Aluminum housing and added gold plated MC connectors.

Do you think, the blocking capacitance will help, with the cell phone RF sensitivity, although the SRV-T is already in a good metal housing.
May be the RF energy is coupled in to the wires from the reference to the multimeters?
I will post a screen shot later with an iPhone 1 m away from the reference
It is so bad, that at first I thought something is wrong with the reference


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Offline Dr. Frank

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Re: Geller Labs SVR and SVR-T
« Reply #65 on: April 19, 2015, 03:55:16 pm »
Remembering teardown of a 732B, they placed ferrite rings around the output jacks.
Maybe that helps even better..
Capacitor on the output may cause oscillation.

Frank
 

Offline HighVoltage

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Re: Geller Labs SVR and SVR-T
« Reply #66 on: April 19, 2015, 04:20:58 pm »
That is a great idea for testing.
You think each of the wires should have their own ferrite ring or should both go through the ring as a twisted pair?

I will do some test's after the reference is coming back from the DKD lab.
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Offline Andreas

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Re: Geller Labs SVR and SVR-T
« Reply #67 on: April 19, 2015, 06:41:52 pm »
Do you think, the blocking capacitance will help, with the cell phone RF sensitivity, although the SRV-T is already in a good metal housing.
May be the RF energy is coupled in to the wires from the reference to the multimeters?

Hello,

That is exactly the way where the RF-field comes into the housing.
Depending on parasytic capacitances the metal housing may also increase the effect.
The best method finding the sensitive lines is to put your hand on the input/output lines or the batteries or the housing.
Another would be setting a non isolated metal tip on every pin of the reference under field effect or using a switchmode power supply.

With my precision measurements I now have nearly at every IC-Pin going to a external line some type of filtering.

Capacitor on the output may cause oscillation.

References usually are not sensitive to capacitive loading (except very low power devices like ISL21009).

You think each of the wires should have their own ferrite ring or should both go through the ring as a twisted pair?

Both will help against external RF fields in the same way. The twisted pair method is only necessary if there are large frequencies on signal lines which should not be dampened in the same way as the RF interference.
Essential is the length of the wire within ferrite material. (high RF impedance against Z0 = 377 Ohms).
So best would be if you can do both: a ferrite + the blocking capacitor. A additional feed through capacitor on each pin through the housing (for power supply and the output) would give further improvement.

With best regards

Andreas

 

Offline Dr. Frank

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Re: Geller Labs SVR and SVR-T
« Reply #68 on: April 19, 2015, 08:45:09 pm »
That is a great idea for testing.
You think each of the wires should have their own ferrite ring or should both go through the ring as a twisted pair?

I will do some test's after the reference is coming back from the DKD lab.

Fluke calibrators have 3..4 jacks, and each one had its own fat ferrite ring.. no twisted pair (how should  that work, anyhow?)

The photo was somewhere on bbs38hot, I suppose

Frank
 

Offline lars

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Re: Geller Labs SVR and SVR-T
« Reply #69 on: April 20, 2015, 08:20:31 pm »
On my eight SVR boards, that I have put into boxes, I have added ferrite beads both to the banana jacks and PS connector. I can't for sure say that it helps at all. If I have a call on the cell phone within 1meter I see a disturbance on the reading. I'm not sure if the SVR board or the measuring device is the problem.

Probably I should have put some capacitors to chassi on the box also.

Setting up a test is not easy. For what frequencies? What field strength? At work we have a EMC room but even if I could set it up where I need a way to measure it without error due to the measuring device being disturbed.

/Lars
 

Offline lars

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Re: Geller Labs SVR and SVR-T
« Reply #70 on: April 20, 2015, 09:17:10 pm »
More than a year ago I bought a AD587UQ and AD587JQ from Digikey. Now I have finally made a temperature test on them. As said in an earlier post the AD587UQ seems to have a high temperature coefficient at room temperature. I got +11ppm/C at 23°C. The JQ was +2ppm/C. Both of them had the familiar "U"-shaped curve up side down. The second order tempco was -0.03ppm/(C*C). This is similar to what I got on the SVR boards from Geller labs that I added a NTC+resistor to compensate for both first and second order temperature coefficients. The AD587LQ seems to have had around +2ppm/C very often and that was perfect to use one non-linear NTC resistance to compensate for both first and second order. I did quite rough compensations but I'm quite sure Joe made them even better. On my last four SVR's Joe had already  put the NTC's (SVR-T's  ;) ).

The +2ppm/C I got for the JQ is perfect to compensate with an NTC. But the sad thing about the about 15-20 JQ's I have checked is that about one fourth have had several ppm p-p noise and about three quarters have unusable temperature coefficients.

I don´t have a Fluke 732 or similar stable voltage reference but I have four temperature compensated REF102CM that have been powered since 2000. With external checks 2003 to 2013 they have drifted almost nothing (with uncertainty +-10ppm) over 10 years. I have been fortunate to check against several DMM and calibrators during the last 15 years. The last good check was against a Fluke 8508 . My SVR board was +0.2ppm. Of course this was pure luck. The expanded uncertainty of the 8508 was 2.7ppm. I myself think I have an expanded uncertanty of 5ppm for my 10V references.

The eight SVR has stayed within 2ppm from the REF102CM's the last years. The regression lines is within 0.2ppm/year.

What I have seen on almost all SVR boards and also the REF102CM is about 0.8ppm jumps between two levels. On a HP34970A I have followed for almost 20 years I still see jumps of 1.5ppm that I conclude comes from the LM399. By the way it still drifts about 1ppm/year (internal LM399 almost always powered on).

Geller labs specified 5ppm as transfer accuracy for the SVR if I remember correct. My first SVR board was +4ppm from what I thought it should be. I was happy to take it on the plane to a sub-supplier I visited the week after I received the SVR board. They have a Fluke 5700 that is calibrated every year by Fluke UK. Comparison with that showed about 3-4ppm high for the SVR board. Half a year later I sent it back to Geller labs and it was +4ppm on the protocol. All the other seven has been within 1ppm from my "10V" (except one that I destroyed at power up due to reversed wiring and I put in a AD587KQ and selected a new NTC+resistor).

/Lars

 

Offline kubatyszko

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Re: Geller Labs SVR and SVR-T
« Reply #71 on: August 16, 2015, 11:14:13 pm »
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]

Hi Orin, I'm looking at building a couple of references similar to SVR-T , but when I look at your picture, it looks exactly like SVR with a perfboard on the side, can you perhaps elaborate what is its purpose ?
From the SVR-T schematic it seems that the THR trimming should literally be a thermistor and a resistor but your board has a few more components.

Thanks
 

Offline orin

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Re: Geller Labs SVR and SVR-T
« Reply #72 on: November 28, 2015, 06:12:31 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]

Hi Orin, I'm looking at building a couple of references similar to SVR-T , but when I look at your picture, it looks exactly like SVR with a perfboard on the side, can you perhaps elaborate what is its purpose ?
From the SVR-T schematic it seems that the THR trimming should literally be a thermistor and a resistor but your board has a few more components.

Thanks


The perfboard is just a voltage regulator using an LM317L to produce 15V for the SVR-T.  I feed it about 18.5V.  Details are in an earlier post.

Orin.
 

Offline HighVoltage

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Re: Geller Labs SVR and SVR-T
« Reply #73 on: November 28, 2015, 11:28:58 am »
Just a few days ago, I hooked up my 34410A again to the SVR-T that was powered on constantly since about August 2015.

August 2015:
Lab temperature: 23 to 24 °C
34410A showed 10.000,02 V with a 1.3 uV StdDv.

November 28, 2015:
Lab temperature: 20 to 21 °C (20.6 °C right now)
34410A shows 10.000,05 V with a 1.237 uV StdDv.
MIN: 10.000,04
MAX: 10.000,05

So, there is a 3 uV drift since August.
But it is probably contributed to a drift in the 34410A and the SVR-T
Or is this contributed to the 2 degree difference in temperature?

I still think that the SVR-T is outperforming all my 6 1/2 digit meters and also outperforming the 34470A 7 1/2 digit meter, as we have seen before.

 
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Offline F64098

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Re: Geller Labs SVR and SVR-T
« Reply #74 on: December 20, 2015, 07:02:35 pm »
Hello,

i'm just trying to build a SVR-T, using a chinese AD587LQ.
Does anybody know the dimension of the fixed resistor R04 who is in series to the 100k thermistor THR1?
Are both resistors SMD?
I tried to use a little glas-thermistor in series with a 1 meg trimmer but i got no success, the output voltage ist drifting like a rally car.
Without that "compensation" the output is rocksolid for the actual temperature...

Thanks in advance

Frank
 


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