Re: [volt-nuts] Just back from cal

[Tom Miller]

You really won't know what is going on until you do the next calibration 
cycle and examine the as received data for both units. Or find someone with 
a better meter or reference and compare them.


Who did the calibration?

You might leave both units powered up for a few days/weeks and see how they 
behave together. Also, you are two degrees C above you lab calibration 
temperature. That could add to the uncertainty.





- Original Message - 
From: "Joseph Gray" 

To: "Discussion of precise voltage measurement" 
Sent: Thursday, April 07, 2016 11:20 PM
Subject: [volt-nuts] Just back from cal



In February, I sent my HP 3457A in for cal. In late March, I sent my
EDC VS330 DC Voltage Reference in for cal. Today, I just got the VS330
back and thought I'd compare the two instruments.

Both instruments have been on for a couple of hours. It is about 25 C
in the room.

Setting 10.0 on the VS330, I measure 9.99891 VDC on the 3457A.

According to the manual, on the 30 VDC range, the 90 day spec is
0.0035% of reading, plus 19 counts.

The VS330 lists the "Limit of error accuracy" as 0.003% of setting
plus 0.001% of range (30 V range). The "Calibration accuracy" is
0.002% of setting plus 0.0005% of range.

Now, if we take the worst case for both instruments, what I am reading
is marginally inside the total error for both instruments. However,
considering that both instruments were recently calibrated and
adjusted, I would expect much better.

The report on the 3457A, dated 16 Feb says the 30 VDC range read
29.9991 VDC. The report on the VS330, dated 31 Mar says 10 VDC read
10.0001 VDC. Both instruments required adjustment.

These numbers would lead me to believe that I should be getting a lot
closer agreement to 10 VDC for both of these instruments. Am I
expecting too much?

Joe Gray
W5JG
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to 
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there. 


___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Just back from cal

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 8 Apr 2016 04:21, "Joseph Gray"  wrote:
>
> In February, I sent my HP 3457A in for cal. In late March, I sent my
> EDC VS330 DC Voltage Reference in for cal. Today, I just got the VS330
> back and thought I'd compare the two instruments.

Did you send them to the manufacturers or a third party lab? I am
personally VERY skeptical of the competence of a number of so-called
calibration labs. A few months back there wss a 40 GHz vector network
analyser on eBay for auction which included a cal certificate.  The
certificate listed the items used for the calibration.  The calibration kit
used was a 6 GHz economy type N kit made by HP. The N connector will not
work properly at 40 GHz, but even if it did,  the use of a calibration kit
is insufficient to calibrate a VNA.

I have seen countless examples of this sort of thing. I would not
personally consider getting any of my HP kit calibrated by anyone other
than Keysight.

> Both instruments have been on for a couple of hours. It is about 25 C
> in the room.

That is quite warm.  Are both specified at that temperature?

> Setting 10.0 on the VS330, I measure 9.99891 VDC on the 3457A.

I would try to find a local volt-nut with a 3458A.

I would also keep a log of the differences between your voltage standard
and multimeter.  If the difference is changing significantly over time, it
would tend to indicate one or both are unstable.  If however the difference
remains very similar then I would be more suspicious that one is
incorrectly calibrated.

> The report on the 3457A, dated 16 Feb says the 30 VDC range read
> 29.9991 VDC. The report on the VS330, dated 31 Mar says 10 VDC read
> 10.0001 VDC. Both instruments required adjustment.

I have heard several reports of 3457As being in spec many years after they
were last calibrated.  The fact your unit required adjustment seems a
little unusual.

If the VS330 was out by 1  on the last digit,  that suggests to me it
didn't require adjustment.

> These numbers would lead me to believe that I should be getting a lot
> closer agreement to 10 VDC for both of these instruments. Am I
> expecting too much?

I have not checked your numbers,  but would agree if both units have been
recently calibrated,  the agreement between the two should not be just
inside the limits if you take the worst case of each. I would expect much
closer agreement.

If the two appear to be drifting with respect to each other the the
purchase of another 3457A, even if uncalibrated,  would probably allow you
to determine what one of your

> Joe Gray
> W5JG

Dave, G8WRB.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Just back from cal

[Joseph Gray]

In February, I sent my HP 3457A in for cal. In late March, I sent my
EDC VS330 DC Voltage Reference in for cal. Today, I just got the VS330
back and thought I'd compare the two instruments.

Both instruments have been on for a couple of hours. It is about 25 C
in the room.

Setting 10.0 on the VS330, I measure 9.99891 VDC on the 3457A.

According to the manual, on the 30 VDC range, the 90 day spec is
0.0035% of reading, plus 19 counts.

The VS330 lists the "Limit of error accuracy" as 0.003% of setting
plus 0.001% of range (30 V range). The "Calibration accuracy" is
0.002% of setting plus 0.0005% of range.

Now, if we take the worst case for both instruments, what I am reading
is marginally inside the total error for both instruments. However,
considering that both instruments were recently calibrated and
adjusted, I would expect much better.

The report on the 3457A, dated 16 Feb says the 30 VDC range read
29.9991 VDC. The report on the VS330, dated 31 Mar says 10 VDC read
10.0001 VDC. Both instruments required adjustment.

These numbers would lead me to believe that I should be getting a lot
closer agreement to 10 VDC for both of these instruments. Am I
expecting too much?

Joe Gray
W5JG
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] ADA4522

[Daniel Mendes]

Ada4522-2 and 4522-4 are stocked at mouser. What about summing all outputs
to reduce noise? Or use as buffered outputs with good reverse isolation...

Daniel
Em 07/04/2016 13:31, "Randy Evans"  escreveu:

> Has anyone looked at the ADA4522 precision op amp from Analog Devices.  It
> looks very intriguing with it's extremely low offset voltage drift of 22
> nV/°C maximum.  The offset voltage is as high as 5 uV but this could be
> nulled out and it should be very stable over temperature after that.  It
> could be a great choice for a voltage reference circuit.  Looks quite
> inexpensive also, although AD only sell in tubes of 96 right now.
> ___
> volt-nuts mailing list -- volt-nuts@febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
> and follow the instructions there.
>
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Solartron 7061 "CAL NOT DONE" error

[David Garrido]

Hello All,

I recently picked up a 7061 and found it to have a “CAL NOT DONE” error on 
start-up.  I understand this to mean that I need to calibrate the unit of 
course, but I was hoping some might have a little experience based guidance for 
the newbe owner of a solatron/schlumberger 7061.  The last cal sticker is 
intact and probably needs a new battery as well as a good cleaning, but what 
else should I look for or replace while I am in there.  I will take it to a 
friend with a few standards in house to calibrate it.  I know I will find the 
zener ref data written somewhere toward the rear of the inside and that will be 
needed for calibration.  I have not fully digested the manual at this point and 
was hoping someone would know off the top of their head whether or not it needs 
to be calibrated with specific software or do we simply need voltage and 
resistance standards?

Cheers,

David
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] ADA4522

[Randy Evans]

Has anyone looked at the ADA4522 precision op amp from Analog Devices.  It
looks very intriguing with it's extremely low offset voltage drift of 22
nV/°C maximum.  The offset voltage is as high as 5 uV but this could be
nulled out and it should be very stable over temperature after that.  It
could be a great choice for a voltage reference circuit.  Looks quite
inexpensive also, although AD only sell in tubes of 96 right now.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.