Author Topic: USA Cal Club: Round 2  (Read 9630 times)

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Offline bitseeker

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Re: USA Cal Club: Round 2
« Reply #150 on: July 26, 2018, 01:35:52 pm »
Wow, that's quite a catch. Way to go, Randall! :clap:

Interesting that the cal sticker has ten years between last and next cal.
« Last Edit: July 26, 2018, 01:39:59 pm by bitseeker »
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Offline RandallMcRee

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Re: USA Cal Club: Round 2
« Reply #151 on: July 26, 2018, 02:03:23 pm »

Yeah, seems normal for the Advantest? You can see the same sticker in TiN's writeup here:
https://xdevs.com/fix/r6581t/ It's specs aren't as impressive as a 3458 so I don't think that ten years means that it has any "special powers".

There was a bit of anxiety upon first powering it on. It comes on without the display enabled and the trigger off. So had to figure that out. (Let me come clean--I just pushed buttons randomly and it started working. I cannot lie.)  Plus, of course set to rear not front panel...but it was pretty easy in the end to get the usual: 100 PLC, 8.5 digits, auto off, etc. Unlike my other meters, GPIB can toggle between the front and rear panel, so I can put that to good use for monitoring two sources.

I have a Fluke 731B for a 10volt calibration but now I suddenly need a 10K standard resistor. Or have someone measure mine, perhaps?
 

Offline TiN

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Re: USA Cal Club: Round 2
« Reply #152 on: July 26, 2018, 02:09:27 pm »
Be sure to read thru 6581 repair thread. Many came to conclusion that 6581(T) is quite a disappointment and declared specs are, well, too optimistic. Hopefully you paid under 1k for it :)
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Offline RandallMcRee

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Re: USA Cal Club: Round 2
« Reply #153 on: July 26, 2018, 02:42:47 pm »
Be sure to read thru 6581 repair thread. Many came to conclusion that 6581(T) is quite a disappointment and declared specs are, well, too optimistic. Hopefully you paid under 1k for it :)

Uhh no, over $1500. But, I did read through the thread and I'm not sure where the disappointment comes from? The 3458 goes for +$4000 and the Keithley 2002 is in the same stratosphere. So in the $2000 ballpark what would else be possible? Is it considered to be a 7.5 digit meter?

 

Offline Muxr

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Re: USA Cal Club: Round 2
« Reply #154 on: July 27, 2018, 02:43:46 pm »
Glad to see this is still going on.. nice going cellularmitosis!

I haven't done too much on my metrology lab in a while. Just been ageing few of the reference I built since the last time. Time to fire up the instruments and do some new measurements! My K 2015 bit the dust and will need repairs, but my 3458a and my 8846A are still going strong.
 

Offline TiN

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Re: USA Cal Club: Round 2
« Reply #155 on: July 27, 2018, 02:49:23 pm »
Welcome back Muxr. Metrology like wine, only better (and more expensive judging from ebay) with time  :popcorn:

And I'm still waiting on my February Vishay resistors order....
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Offline Muxr

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Re: USA Cal Club: Round 2
« Reply #156 on: July 27, 2018, 03:31:49 pm »
Welcome back Muxr. Metrology like wine, only better (and more expensive judging from ebay) with time  :popcorn:

Thanks TiN!

was just admiring the work you did on your F5720A calibrator, nuts! :)


And I'm still waiting on my February Vishay resistors order....
Wow still? I finally got another LTZ1000A like 6 months later or something, will need to build another LTZ1000 reference.
 

Offline nikonoid

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Re: USA Cal Club: Round 2
« Reply #157 on: August 06, 2018, 12:42:41 pm »
I got the new ref last week. Here are first impressions:

To start with I powered it with Keithley 2450 @ 12.00V and measured with Keithley 2002. 2002 was calibrated by CalMachine 9 months ago and read 0.1ppm high on 10V range at the time of calibration. It does not get much better than this. (Thanks CM).

I used 2450 to precisely track power consumed by reference. On the start it took 25mA and then consumption slowly drifted down to 22mA, where it reached thermal equilibrium. After getting stable it would fluctuate very slightly with room temperature.

Unfortunately I could not get enclosed temperature monitor to work. There is some sort of issue with Arduino drivers on my computer. My lab temperature is very stable though varying less than 0.5C around 21C.

Average reading from K2002 was 7.0456737. This is about 4ppm high comparing to other results reported. I assume my Keithley 2002 could have drifted that much in 9 months.

Noise levels coming from K2002 were quite high. At times reaching 0.8ppm or about 5.5uV peak to peak. At this time we should consider noise coming from 2450 and also large amount of equipment concentrated in a same space.

For the second log, I used 2 of 6V SLA battaries to power reference, used 3458a for logging (TiN logging parameters: https://xdevs.com/article/hp3458a_gpib/) and relocated reference and 3458a away from other equipment. This time noise improved a lot to about 0.08uV peak to peak over a course of few minutes. I would say that this is a remarkably low.

I am considering using Datron 4910 (buffered out) with SR1010 (1kOhm per step) as a voltage divider to create very stable 7.0000V and then use that in series opposition with the PX reference to measure noise directly against Datron. More results and upload of files is to follow.
 
Cellular, this is an excellent reference, especially considering the size and weight.
 
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Online mzzj

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Re: USA Cal Club: Round 2
« Reply #158 on: August 08, 2018, 05:43:37 am »
When do we get the intercomparison report with all the EN-values and stuff?  8)
 

Offline martinr33

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Re: USA Cal Club: Round 2
« Reply #159 on: August 10, 2018, 10:51:18 am »
When I measured the unit, I saw only about 150nV of noise on my 3458a. I used 100NPLC and the math average function over a few minutes. I have noticed that the Keithley 2002 can be very noisy (700nV SD), but it seems a bit less drifty with temperature than the 3458a. It also averages out nicely if you put the filtering on.
 

Offline nikonoid

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Re: USA Cal Club: Round 2
« Reply #160 on: August 10, 2018, 10:56:57 am »
When I measured the unit, I saw only about 150nV of noise on my 3458a. I used 100NPLC and the math average function over a few minutes. I have noticed that the Keithley 2002 can be very noisy (700nV SD), but it seems a bit less drifty with temperature than the 3458a. It also averages out nicely if you put the filtering on.

Keithley 2002 usually auto calibrates to temperature on every reading (it can be disabled). In contrast 3458a requires explicit call to ACAL DCV to adjust to temperature change.
 

Offline TiN

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Re: USA Cal Club: Round 2
« Reply #161 on: August 10, 2018, 02:54:22 pm »
Quote
Keithley 2002 usually auto calibrates to temperature on every reading (it can be disabled).
I'm not sure that is right. It does autozero, but it's not related to temperature. At least I see clearly visible tempco with temperature excursions, which would be corrected otherwise if it does temp correction.
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Offline nikonoid

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Re: USA Cal Club: Round 2
« Reply #162 on: August 19, 2018, 09:39:23 am »
Quote
Keithley 2002 usually auto calibrates to temperature on every reading (it can be disabled).
I'm not sure that is right. It does autozero, but it's not related to temperature. At least I see clearly visible tempco with temperature excursions, which would be corrected otherwise if it does temp correction.

I am not sure how effective is this autozero, but this is what I found in the manual:


AUTOZERO: In order to maintain stability and accuracy
over time and temperature
, the Model 2002 intermittently
measures internal voltages corresponding to offsets and
gains of amplifiers
. This process is known as autozeroing.
There are three types of autozero: synchronous, normal, and
off. The characteristics of each are described below.

• Synchronous (the default mode) is the most accurate,
but slowest mode. In this mode, each trigger causes
three A/D conversions: one for input signal, one for an
internal zero, and one for an internal gain. This mode
also yields a constant reading rate


It might be a cool test to log Keithley 2002 over range of temperatures with Synchronous autozero and with autozero Off.
 

Offline ManateeMafia

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Re: USA Cal Club: Round 2
« Reply #163 on: August 19, 2018, 12:08:33 pm »
I am sure TiN wouldn't mind using my 2002 with a reference and test the different settings. However, my A/C might change the room temperature too quickly.
 

Offline nikonoid

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Re: USA Cal Club: Round 2
« Reply #164 on: August 19, 2018, 01:30:13 pm »
The reference is back to Cellular. I am uploading files to TiNs FTP Server.

I logged the PX reference with Keithley 2002, then yet to be calibrated 3458a (noise assessment) and finally freshly calibrated 3458a (Thank you, Cal Machine).

Code: [Select]
Keithely 2002
Calibrated 11/7/2017
Calibration point 19V:   19.0000026
Log Date: 8/5/2017
PX Reference powered by Keithely 2450 at 12V
Average logged value: 7.0456737
Corrected for calibration: 7.0456747

Code: [Select]
HP 3458a
Calibrated on 08/06/2018
10V value was calibrated as: 9.9999992
Logged on 8/13/2018
PX Voltage reference is powered by 12V SLA battery
Positive logging average: 7.045661201
Negative logging average: -7.04566173
PX Reference value (corrected for calibration): 7.04566147

3458a just arrived from calibration and exhibited a bit of drift/erratic behavior. It seems to settle ever since, but the log that was taken right after it arrived can be off by as much as 0.5ppm.

It looks like my Keithley 2002 drifted 1.9ppm in 9 months.
 

Offline cellularmitosis

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Re: USA Cal Club: Round 2
« Reply #165 on: Yesterday at 02:51:27 pm »
Ref back in hand!  I'll log some data and get it shipped back out.

At this point I have two other LTZ's which have about 3 months of ageing on them, so I can start to provide relative measurements between them, which should lessen the influence of my meter.
LTZs: KX FX MX CX PX Frank A9 QX
 

Offline TiN

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Re: USA Cal Club: Round 2
« Reply #166 on: Yesterday at 03:00:37 pm »
Quote
Keithley 2002 usually auto calibrates to temperature on every reading (it can be disabled).
I'm not sure that is right. It does autozero, but it's not related to temperature. At least I see clearly visible tempco with temperature excursions, which would be corrected otherwise if it does temp correction.
I am not sure how effective is this autozero, but this is what I found in the manual:
...
It might be a cool test to log Keithley 2002 over range of temperatures with Synchronous autozero and with autozero Off.

Perhaps I'd need to be more specific. K2002 AZ autocorrects for gain and offsets drift (synchronous corrects on every sample set, while normal only on range/function change). So if drift/offset error caused by thermals change, those will be corrected as byproduct, however this function does not actually take internal temperature measurement (K2002 does have a sensor though, available in TEMP mode, showing difference to TCAL) to correct the tempco of the parts used in signal path. So TCR of shunts/current source references for resistance is not removed/compensated for, it's still there. So in best case meter readings have tempco of the internal working standards involved for specific function/range. Hope this is bit more clear.

To stay on topic, CalClub's 10V reference going thru testing this week and tentative shipping in 2 weeks. Sorry that it took so long.  :phew:
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Offline cellularmitosis

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Re: USA Cal Club: Round 2
« Reply #167 on: Yesterday at 04:01:12 pm »
To stay on topic, CalClub's 10V reference going thru testing this week and tentative shipping in 2 weeks. Sorry that it took so long.  :phew:

Awesome!!!  :-+
LTZs: KX FX MX CX PX Frank A9 QX
 


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