Author Topic: Geller Labs SVR and SVR-T  (Read 35095 times)

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Offline quarks

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Geller Labs SVR and SVR-T
« on: August 04, 2013, 01:40:38 pm »
Hello all,

I have already bought and tested several SVR from Joe Geller and reported that they are great and accurate (<5 ppm agreement to my 6.5 to 8.5 digit gear).

Yesterday I received the SVR-T which is an improved version that uses a secondary temp compensation (developed by Lars Walenius).

For more details see:
http://www.gellerlabs.com/SVR%20Series.htm

I meassured/compared it with my very best calibration gear and meters.

Here is a short setup info:
>4h DMM meter warmup
man. 10VDC range with 8.5 digit and averaging
using high quality PFTE low emf cable with crimped spade lugs and crimped pure copper alligator clips
checking and making sure DC offset is well below 1µV before meassurement started
using good/stable 15.00 V linear power supply 
ambient 25.1 to 25.4 °C (stable over the meassurement time)

  9.999 978 7 V (seconds after turn on)
  9.999 990 3 V (after 2 min.)
  9.999 997 7 V (after 5 min.)
10.000 000 6 V (after 10 min.)
10.000 001 3 V (after 15 min.)
10.000 001 4 V (after 30 min.)
10.000 001 3 V (after 60 min.)
10.000 001 3 V (after 90 min.)
10.000 001 3 V (after 120 min.)
10.000 001 2 V (after about 3 h)

Whatever my real absolut meassurement accuracy might be, after only 5 min. warmup time, this little device (compared to my gear) stays easily within <0.5ppm of the stated

"Calibration:    Jumper in:   10.000 00 V  at 24 °C ambient" in Joe Gellers "SVR-T Calibration Paper" that came with my SVR-T.

For me that really is a great improvement to the already very good SVR!

I would be interested to hear from other SVR useres what they found out and like to see some results.

bye
quarks   
« Last Edit: August 05, 2013, 02:00:10 pm by quarks »
 

Offline Circuitous

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Re: Geller Labs SVR and SVR-T
« Reply #1 on: August 04, 2013, 03:41:10 pm »
I agree, the SVR-T is a neat little device.  I got one a year ago, and just fired it up again last week.  It showed 10.00000 on my Agilent 34410A. 
My two year old SVR (not the T model) was calibrated about 18 months ago, and it showed 10.00004

Offline saturation

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Re: Geller Labs SVR and SVR-T
« Reply #2 on: August 05, 2013, 07:25:55 pm »
The Geller has been a great way to obtain a 10V check via mail.  However, I've experienced that its sensitive to ambient temperature and humidity, my unit is now over 1.5 years old and reads about 6uV high.  It had tended to swing 10-100uV positive with higher room temps or low humidity and read low with high humidity or cooler room temps.  I've been able to control temp exposure but not humidity, such as when it rains heavily and the atmosphere is saturated with water vapor, so when I do voltage checks I insure ambient is as close to similar to when Geller did the original calibration.

Could you do a simple test?  Raise the ambient temperature of the reference to higher  room temperature, say 30oC?  Can you retest the voltage? 


« Last Edit: August 05, 2013, 07:37:12 pm by saturation »
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Offline bingo600

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Re: Geller Labs SVR and SVR-T
« Reply #3 on: August 05, 2013, 08:03:25 pm »

Post edited to reflect the correct readings (i consequently left out a zero ... ie. 10.0004 should be 10.00004)

My Geller  a SVR (Calc'ed @ 23C) , are typically 10.00004 v @26 Deg , and was 10.00008 @28.5C.
I have never seen it drift above 10.00009 that was around 29.3C.
It doesn't seem to be affected noticably by "humidity" ... Meaning raining outside ...
Measured @ Keithley 2015  (Cal  expired May-2012)

My new SVR-T also Calc'ed @ 23C , is to new to talk behaviour about right now ...
But it also seems unaffected by rain outside.

Right now the SVR is 10.00008 @28.6 (Keithley) , and the SVR-T is also 10.00008  , but measured by my 3457 (Cal unk. , and it's a few ppm high)

Well .... I just swapped the SVR-T & the SVR

SVR-T is 10.00000 on Keithley @28.6C    :-+
SVR is 10.00015 @3457 , so i guess my 3457 is 7..8 ppm high  :-\

Well the 3457 is an old fella i got used this spring for $260 (incl 8 chan scanner) ....

If i ever find out how i'll cal the 10v range .... And i still trust the Keithley

/Bingo
« Last Edit: August 06, 2013, 02:10:15 pm by bingo600 »
 

Offline saturation

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Re: Geller Labs SVR and SVR-T
« Reply #4 on: August 05, 2013, 08:47:09 pm »
Thanks bingo600.  From what you report, the Geller has drifted far off calibration. It also tracks positive largely with temperature.

Assuming your SVR-T is correct as it is new, then you report at 28.6oC the SVR-T is reading 10.000 00V on the Keithley.  Lets assume then the Keithley is still in spec.

Using Keithley, SVR reads 10.000 08, that is 800uV or 80 ppm off, at 28.5oC.  Its far different even if the temperature difference is 0.1oC.

Since you measured 10.000 04 or 400uV or 40 ppm off at 26oC, and is shows the Geller rose nearly double ppm in +2.5oC.

How much your Geller SVR has drifted off is above my expectation, my unit has not exceed 100uV positive at worst, and is now about 6uV high measured in the best ambient conditions.  But if the ambient conditions are not near exact as when Geller did the cal, it can be far worse than 6uV off.

If you drop your ambient to 24oC, I would expect the SVR to be only 20 ppm off.


My Geller  a SVR (Calc'ed @ 23C) , are typically 10.0004 v @26 Deg , and was 10.0008 @28.5C.
I have never seen it drift above 10.0009 that was around 29.3C.
It doesn't seem to be affected noticably by "humidity" ... Meaning raining outside ...
Measured @ Keithley 2015  (Cal  expired May-2012)

My new SVR-T also Calc'ed @ 23C , is to new to talk behaviour about right now ...
But it also seems unaffected by rain outside.

Right now the SVR is 10.0008 @28.6 (Keithley) , and the SVR-T is also 10.0008  , but measured by my 3457 (Cal unk. , and it's a few ppm high)

Well .... I just swapped the SVR-T & the SVR

SVR-T is 10.00000 on Keithley @28.6C    :-+
SVR is 10.00015 @3457 , so i guess my 3457 is 7..8 ppm high  :-\

Well the 3457 is an old fella i got used this spring for $260 (incl 8 chan scanner) ....

If i ever find out how i'll cal the 10v range .... And i still trust the Keithley

/Bingo

« Last Edit: August 06, 2013, 02:00:45 pm by saturation »
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 Saturation
 

Offline quantumvolt

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Re: Geller Labs SVR and SVR-T
« Reply #5 on: August 06, 2013, 12:04:10 am »
I got a new SVR-T from his last production batch a week ago. It reads quite steady 10.0001 (28 C) which is well within specs of my only instrument 34401A (last calib 2003). The value change a bit with 24 h temperature change (maybe 5-6 degrees and 10.00009-10.00015) and cables/noise from switching supplies in other instruments, but very little. I am very pleased anyway because I have got my DMM confirmed for 10 DC.

I also have a 5 V ref from a competitor. It has steadily drifted from 5.00022 to 5.00054 in 3 months, and now I know that it is out of spec 0.01%. I also have other 0.01% initial accuracy 10 V ref chips that have been steady for a long time. So I do not stress too much about it now that I know that the DMM is around 10 ppm.

I am making a slow multiplexing relay card w. microprocessor and LT2400 ADC. When this is working with logging and statistics to PC RS232 and double measurement with both 34401A and LT2400, I will send maybe 3-5 references 2.5 - 10 V for measurement elsewhere. I have a very cheap offer from a person with a calibrated 3458A. When I get them back and connected to the "DAQ" I will start to log drift.

But with only 6 1/2 digit DMM 15+4 ppm short time accuracy if calibrated I think the SVR-T is the closest I can come to a matching 10 V ref. I think I will buy one more (if this one turns out steady).

 

Offline bingo600

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Re: Geller Labs SVR and SVR-T
« Reply #6 on: August 06, 2013, 05:13:10 am »
Thanks bingo600.  From what you report, the Geller has drifted far off calibration.  It also tracks positive largely with temperature.

Assuming your SVR-T is correct as it is new, then you report at 28.6oC the SVR-T is reading 10.000 00V on the Keithley.  Lets assume then the Keithley is still in spec.

Using Keithley, SVR reads 10.000 8, that is 800uV or 80 ppm off, at 28.5oC.  Its far different even if the temperature difference is 0.1oC.

Since you measured 10.000 4 or 400uV or 40 ppm off at 26oC, and is shows the Geller rose nearly double ppm in +2.5oC.

How much your Geller SVR has drifted off is above my expectation, my unit has not exceed 100uV positive at worst, and is now about 6uV high measured in the best ambient conditions.  But if the ambient conditions are not near exact as when Geller did the cal, it can be far worse than 6uV off.

If you drop your ambient to 24oC, I would expect the SVR to be only 20 ppm off.

@Saturation

My bad .....

I consequently left out a zero  (blush) .....  :palm:
The Keithley is a 2015-THD 6.5 digit meter (mode slow)  , and the 3457 (100 NPLC) is also running in 6.5 digit mode.
The 10.0004 should be 10.00004 , 10.0008 should be 10.00008 and so on ...

I'm sorry about that  :-[

I'll see if i can make my AVR-USB based DS18B20 temp ref finished , in a short time.
Then i can use GPIB to measure volts/temp , and present some serious data.

Btw: both of my SVR's came with a Ceramic chip , and i think they are less humidity sensitive than the "Plastic dips".

I'm actually quite happy with both my SVR's , and if you add my missing digit to your equations above.
They're actually performing quite well.   The SVR-T is quite impressive , even @+5C it's "spot on"


/Bingo
« Last Edit: August 06, 2013, 05:19:44 am by bingo600 »
 

Offline saturation

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Re: Geller Labs SVR and SVR-T
« Reply #7 on: August 06, 2013, 01:58:42 pm »
Thanks bingo600, in that case my original results have to be reduce by 10.  If then, its only 4-8ppm the Geller is within spec including the rise with temperature.  I've corrected the last post.
« Last Edit: August 06, 2013, 02:01:08 pm by saturation »
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 Saturation
 

Offline saturation

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Re: Geller Labs SVR and SVR-T
« Reply #8 on: August 06, 2013, 02:12:41 pm »
Thanks quantumvolt.  Those drifts are fairly high for a new reference in a 24 hr period particularly with its built in temperature compensation, but its inline with Geller's estimate of 1ppm/C for the no temperature compensation SVR board, so the drift of about 60uV is close to the worse case.


I got a new SVR-T from his last production batch a week ago. It reads quite steady 10.0001 (28 C) which is well within specs of my only instrument 34401A (last calib 2003). The value change a bit with 24 h temperature change (maybe 5-6 degrees and 10.00009-10.00015) and cables/noise from switching supplies in other instruments, but very little. I am very pleased anyway because I have got my DMM confirmed for 10 DC.

I also have a 5 V ref from a competitor. It has steadily drifted from 5.00022 to 5.00054 in 3 months, and now I know that it is out of spec 0.01%. I also have other 0.01% initial accuracy 10 V ref chips that have been steady for a long time. So I do not stress too much about it now that I know that the DMM is around 10 ppm.

I am making a slow multiplexing relay card w. microprocessor and LT2400 ADC. When this is working with logging and statistics to PC RS232 and double measurement with both 34401A and LT2400, I will send maybe 3-5 references 2.5 - 10 V for measurement elsewhere. I have a very cheap offer from a person with a calibrated 3458A. When I get them back and connected to the "DAQ" I will start to log drift.

But with only 6 1/2 digit DMM 15+4 ppm short time accuracy if calibrated I think the SVR-T is the closest I can come to a matching 10 V ref. I think I will buy one more (if this one turns out steady).


« Last Edit: August 06, 2013, 08:35:26 pm by saturation »
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Offline quantumvolt

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Re: Geller Labs SVR and SVR-T
« Reply #9 on: August 06, 2013, 06:24:16 pm »
I think those 6ppm are 60uV . But to be fair, I guess my numbers are "worse" than worst case. Due to space limitations I have my references on a shelf almost 3 feet away from the bench and DMM, and since all is temporary now, they run on an old printer switched PS with an LM317. The cheap fleabay measuring cables have crocodile clips in 2 places and pass all kinds of lighting and PSUs in a "rack". So I cannot really report  reliable numbers before I get a setup rigged in a shielded box close to the DMM and with a decent cable and external PSU.

To be honest, I did not buy the board for the AD587 reference chip (I have LM399, AD588, LT6655, LT1019 and other good chips). I bought the calibrated 3458A measurement value in order to check the 34401A. And since the 34401A has at best 0.0015% + 4LSB (19ppm). the board is still within the DMM's spec even with this temporary sloppy setup. Adding Geller's customer service level as I perceive it, I am very pleased.
 

Offline quarks

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Re: Geller Labs SVR and SVR-T
« Reply #10 on: August 06, 2013, 06:37:00 pm »
Could you do a simple test?  Raise the ambient temperature of the reference to higher  room temperature, say 30oC?  Can you retest the voltage?

I can do that probably tomorow and expect to see max. 1ppm/K, but would not be surprised if it is much better.
I will make sure that only the SVR-T will be at higher temp.
If others also want to do this test, please let us know some details about your setup. In my test I tried to have as little as possible influence by the power supply and the cable connection. When I repeat this test, I think/hope this setup is almost exactly identical and therefore only influenced by the ambient changes (temp and humidity).
« Last Edit: August 06, 2013, 07:02:38 pm by quarks »
 

Offline JimmyMz

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Re: Geller Labs SVR and SVR-T
« Reply #11 on: August 06, 2013, 06:59:44 pm »
I think those 6ppm are 60uV . To be honest, the Agilent 34401A has, at best, 0.0015% + 4LSB (19ppm). The Geller board is still within the DMM's spec, even with this temporary sloppy setup.
Would you mind typing the equation you are using to calculate the 'ppm' values? I want to understand the mathematics behind the figures  :)

Thank You
JimmyMz
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Offline quantumvolt

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Re: Geller Labs SVR and SVR-T
« Reply #12 on: August 06, 2013, 07:19:38 pm »
I think those 6ppm are 60uV . To be honest, the Agilent 34401A has, at best, 0.0015% + 4LSB (19ppm). The Geller board is still within the DMM's spec, even with this temporary sloppy setup.
Would you mind typing the equation you are using to calculate the 'ppm' values? I want to understand the mathematics behind the figures  :)

Thank You
JimmyMz

Sorry, maybe I should have quoted.

1) The reference drifts from 10.00009 to 10.00015 V = 60uV for lets say 24 to 30 = 6 degrees C temp change. This is 10 uV pr degree. For 10V (10 000 000 uV, i.e. 10 million microvolts) magnitude it is 10 uV / 10 V = 1 part per million. So we have that 60 uV change in 10 V is 6 ppm for 6 degrees change of temp (1 ppm / degree C).

2) The 34401A has basic DC accuracy in this range 0.0015% of reading + 0.0004% of FS. Worst case 0.0019% is then a factor of 0.000019 of value. This is 19ppm.

---
EDIT: Please forget the 4LSB in the quote on top. I have written the Agilent 34401A spec wrong. It is  +- 0.0015 % of displayed value pluss 0.0004 % of range at 23 degrees C.
« Last Edit: August 06, 2013, 07:55:59 pm by quantumvolt »
 

Offline bingo600

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Re: Geller Labs SVR and SVR-T
« Reply #13 on: August 06, 2013, 08:12:50 pm »
If others also want to do this test, please let us know some details about your setup.

I'm powering the SVR & SVR-T from an Agilent E3610 Linear PSU , to avoid switcher noise.
The Croks i'm using are Hirschmann , and the Banana cables are Hirschmann.

Both the Keithley 2015 and the HP 3457 have been powered up since mid april.
My SVR is around 1 year old , and the SVR-T is from April (Both powered up since mid-april).

I also have an Agilent 34401A (i seem to remember its around 4ppm low @10v)  , but i'm using it as my Lab meter.

Once i get my DS18B20 temp probes ready , i'll start to use the 8-port scanner in the 3457 , and then also connect my LM399 , and my two diy "Gellers"  ... Geller PCB's but Plastic DIP Ref's  & 1% metal resistors ....
I could use 1% SMD resistors if they have better tempco (hints welcome).


/Bingo
« Last Edit: August 06, 2013, 08:17:32 pm by bingo600 »
 

Offline saturation

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Re: Geller Labs SVR and SVR-T
« Reply #14 on: August 06, 2013, 08:38:08 pm »
Whoops sorry, my bad I corrected that missing zero  :palm:.  These zeroes seem to be dropping faster than I can write  ::).  Corrected my post.

Yes, overall I surmise the Geller is doing quite well based on a 6.5 digit DMM, its the same reason I got one but I should get a follow up cal from him soon.

I think those 6ppm are 60uV . But to be fair, I guess my numbers are "worse" than worst case..
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 Saturation
 

Offline quarks

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Re: Geller Labs SVR and SVR-T
« Reply #15 on: August 07, 2013, 10:04:01 am »
meassured again today with same setup as before:
>4h DMM meter warmup
man. 10VDC range with 8.5 digit and averaging
using high quality PFTE low emf cable with crimped spade lugs and crimped pure copper alligator clips
checking and making sure DC offset is well below 1µV before meassurement started
using good/stable 15.00 V linear power supply 
ambient 24.4 to 24.6 °C and 60% - 61% rel. humidity (stable over the meassurement time)

9.999 969 8 V (after turn on)
9.999 981 1 V (after 2 min.)
9.999 995 7 V (after 5 min.)
9.999 998 4 V (after 10 min.)
9.999 998 9 V (after 15 min.)
9.999 998 9 V (after 20 min.)

After that I put the SVR-T for about 15 min. to stable 27.9 - 28.1 °C also 61% rel. humidity
meassured DC offset at start was -0.3µV at start and -0.2µV when I stopped
9.999 979 7 V (after 15 min.)
9.999 981 1 V (after 20 min.)
9.999 982 3 V (after 30 min.)
9.999 983 1 V (after 40 min.)
9.999 983 5 V (after 50 min.)
9.999 983 8 V (after 60 min.)

This is around -15µV (= 1.5ppm of 10V) change with temp. delta of 3.5 °C.
That makes it overall a little better than 0.43 ppm/K.   

bye
quarks
« Last Edit: August 07, 2013, 10:06:35 am by quarks »
 

Offline saturation

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Re: Geller Labs SVR and SVR-T
« Reply #16 on: August 07, 2013, 03:22:23 pm »
Thanks quarks, that's goo data  :-+
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 Saturation
 

Offline branadic

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Re: Geller Labs SVR and SVR-T
« Reply #17 on: August 07, 2013, 07:22:12 pm »
Quote
1) The reference drifts from 10.00009 to 10.00015 V = 60uV for lets say 24 to 30 = 6 degrees C temp change. This is 10 uV pr degree. For 10V (10 000 000 uV, i.e. 10 million microvolts) magnitude it is 10 uV / 10 V = 1 part per million. So we have that 60 uV change in 10 V is 6 ppm for 6 degrees change of temp (1 ppm / degree C).

To be correct you have to use the start point what means 1ppm = 10,00009µV so in this example the drift is <6ppm and so temperature coefficient is <1ppm/K.
And one more detail, quarks you are from germany so you should have noticed that temperature differences are given in units of Kelvin, not degree Celsius. This is why only ppm/K is the correct physical unit for a drift.
It's sad that most manufactors do the same mistake, okay they are no physicist.
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Offline quantumvolt

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Re: Geller Labs SVR and SVR-T
« Reply #18 on: August 07, 2013, 07:55:13 pm »
Quote
1) The reference drifts from 10.00009 to 10.00015 V = 60uV for lets say 24 to 30 = 6 degrees C temp change. This is 10 uV pr degree. For 10V (10 000 000 uV, i.e. 10 million microvolts) magnitude it is 10 uV / 10 V = 1 part per million. So we have that 60 uV change in 10 V is 6 ppm for 6 degrees change of temp (1 ppm / degree C).

To be correct you have to use the start point what means 1ppm = 10,00009µV so in this example the drift is <6ppm and so temperature coefficient is <1ppm/K.
And one more detail, quarks you are from germany so you should have noticed that temperature differences are given in units of Kelvin, not degree Celsius. This is why only ppm/K is the correct physical unit for a drift.
It's sad that most manufactors do the same mistake, okay they are no physicist.


The quoted text and the errors/blame are all mine. As Pedantischer Besserwisser I politely advise you not to remove the quote's author ???
 

Offline branadic

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Re: Geller Labs SVR and SVR-T
« Reply #19 on: August 08, 2013, 08:27:24 pm »
If people deal with physical units I demand that this is done in the correct way and yes, in this point I'm captious. It's the same like the difference between VA (volt ampere) and W (watt). Sorry about that.
I follow the device: "You want to learn something? You should learn it in the correct manner."
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Offline quantumvolt

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Re: Geller Labs SVR and SVR-T
« Reply #20 on: August 09, 2013, 03:55:43 am »
I have done wrong towards the SVR-T by my sloppy setup. It is much better than I reported earlier.

Yesterday I used some very short leads (about 20 cm), placed the board just in front of the 34401A, used a linear PS (wall wart unregulated 18-19 V with LP filter / cap bank around 2 meters away from the ref board and a LM317 to within 1% of 15 V placed only cm's from the ref board), placed the ref board with PS and the sensor from a cheap fleabay thermometer in an aluminum cake box, "sealed" the box with styrofoam, turned off all other electric appliances and lighting, waited a bit,  pushed the STAT button of the DMM with a 1.5 m long broomstick and left the room.

When I came down this morning the DMM read MAX 10.000 014, MIN 9.999 996 and MEAN 10.000 007 (STAT-mode gives one digit more than the normal display). The thermometer had MAX 29.6 and MIN 25.2. So probably less than 20 uV change for maybe 4 degrees change in temperature (to be somewhat conservative). And the meter seems to be just a few uV off the nominal 10 V (first and last calibration 1983 stored in meter  - calibration is before sales date and must be the initial calibration from Agilent).

I hardly believe it  :-* :-DD
 

Offline quarks

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Re: Geller Labs SVR and SVR-T
« Reply #21 on: August 09, 2013, 07:55:03 am »
I hardly believe it  :-* :-DD

Your result is almost the same as mine, which is a very good confirmation.
So I think you can be happy and believe it.
« Last Edit: August 09, 2013, 07:57:03 am by quarks »
 

Offline quantumvolt

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Re: Geller Labs SVR and SVR-T
« Reply #22 on: August 09, 2013, 08:34:57 am »
Sure. It is just that it is the first time I get anything confirmed to around 0.001% (my other paid-for 3458A-measured reference from a competitor was off 0.004% off at delivery and has now drifted out of spec 0.01% in 3 months). I have many stable references with datasheet initial accuracy 0.01%, and I can now trust those that measure off 0.005% and less. I am also pleased that I do not need any calibration (I only need to trust DC 1 - 10V for references and precision voltage dividers, for everything else I am OK with a good handheld meter).
 

Offline quarks

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Re: Geller Labs SVR and SVR-T
« Reply #23 on: August 09, 2013, 10:58:46 am »
I am very happy with my Geller SVRs!
There is only one little thing, that could make it even better for me, that is a statement of the uncertainty of the calibration.
But because I have my own "cal lab" and can compare to very accurate gear, I guess the absolute accuracy of my SVR-T is pretty close to 1ppm at the stated cal temp.
« Last Edit: August 09, 2013, 12:08:37 pm by quarks »
 

Offline orin

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Re: Geller Labs SVR and SVR-T
« Reply #24 on: August 16, 2013, 02:09:07 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.
 


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