AC equivalent for the 5440b/af

[Tony_G]

Hi all,

I managed to luck into a Fluke 5440B/AF. It does DC to 7.5 digits according to the manual.

Is there a matching AC one? I can't find anything close other than the 5500+ series and I'm not going to get one of those for $200.

Just hoping that I could have both AC & DC for less than an arm and a leg.

Thanks,

TonyG

[ManateeMafia]

You have a couple of choices depending on how much AC output you need.

Fluke 5200A. It is limited to 120VAC. You will need a separate amplifier to reach ~1000V.

Datron 4200A. With all options it will take up less space than F5200A with F5205A/F5215A amplifiers.

F5100B with 4.5 digit output but gives you wideband if you have the added option. Nice for RF voltmeter calibration.

I am sure there are more, but these have been available for quite a while and certainly cost less than a F5500 series.

[Tony_G]

Thanks - Everything other than the Fluke 5200 was in the "way too much money" category.

I'll see if I can score one of those to go with the 5440.

[ManateeMafia]

They look nice but the reason I went with a F5100 was that I also got the DCI, ACI, and resistance capabilities. My first calibrator is the F5440B and I have no plans on getting rid of it.

BTW, I have a collection of equipment racks getting full of gear so you may want to keep an eye open for something. It is addictive...

[Tony_G]

Thanks - As a NOOB on this calibration stuff, is it possible to increase the apparent accuracy of the calibrator through measuring with additional equipment?

For example, the 5100B is stated to be for calibrating 4.5 digit equipment - If I had a DMM that was calibrated and could say read to 85 digits, would I be able to use the two of them to calibrate something rated to 7.5 digits?

While it clearly is a lot more complicated than this, isn't the basic idea:

1. Create voltage
2. Measure that voltage to a given accuracy
3. Measure that voltage again with the DUT
4. Adjust DUT until it's reading is within it's accuracy spec

TonyG

[Dr. Frank]

Thanks - As a NOOB on this calibration stuff, is it possible to increase the apparent accuracy of the calibrator through measuring with additional equipment?

For example, the 5100B is stated to be for calibrating 4.5 digit equipment - If I had a DMM that was calibrated and could say read to 85 digits, would I be able to use the two of them to calibrate something rated to 7.5 digits?

While it clearly is a lot more complicated than this, isn't the basic idea:

1. Create voltage
2. Measure that voltage to a given accuracy
3. Measure that voltage again with the DUT
4. Adjust DUT until it's reading is within it's accuracy spec

TonyG

This may work, but it depends on the specification of the calibrator.

A first trick is, to calibrate these calibrators in shorter time periods than the usual 1 year, like every 3 months, or each month, to calibrate the DMM regarding its 1 year specification.
So the calibrator has a better uncertainty, but only for the case that it's already specified for 1 year, 3 months, 1 month, 24h and 10 min (Transfer stability), and if the calibration of the calibrator itself is sufficiently uncertain, of course.

In the extreme case, what you describe, is using the Transfer stability (10 min.) to transfer the 8.5 digit DMMs uncertainty to the 7.5 digit DUT - DMM.

So, if you look into the 5100B specification, you will find that this calibrator is relatively unstable, and  the specification is incomplete or really bad, as no 24h, 3 mo., specs are given.. They did not even specify, over which time the spec. is valid, I assume 1 year, maybe.

But they give a 10 min. Transfer Stability, for DCV it is about 10ppm plus 2 ppm of range, 25ppm for 500V.

So to answer your question:
Nope, this is NOT sufficient for 7.5 digit DMM, even not for 6.5 digits.
These have 20ppm or better 24h specification, and the T.U.R. (test uncertainty ratio) is too low, about 20ppm/12ppm ~ 1.7, so you would need something more stable or more uncertain, to have a TUR of 3..4 or better.

What you could try instead, is to hook the 8.5 digit DMM and the DUT in parallel and measure the calibrators output in parallel, over the same time window.
The crucial thing is, you need also to determine the standard deviation of the calibrators output, using the 8.5 digits DMM statistics function, and also the DUTs'.
3 times the STD will give the 95 % transfer uncertainty of this setup, and MIGHT be better than the spec. of the calibrator.
If the calibrator is too noisy, or too unstable, you will fail, anyhow, as the STD might be too high.

Also, the T.U.R. between the 8.5 digit DMM and the DUT might again be too low.

But this may also be handled, by using a "Golden Standard", that is an instrument, with tested tighter uncertainty limits, than specified.

Fluke and Keysight do this, they use "Golden" 5720A/30A calibrators and also "Golden" 3458As to calibrate  3458A DUTs.

Sounds confusing, I fear.. I can recommend the Fluke and Keysight Web Seminars about these techniques, and also Flukes nice ANs about this subject.

Frank


PS: I also own a 5442A and a 5200A, and a 3458A.
I use the 3458A together with Swerleins Algorithm, to create precise AC voltages for calibration of 6.5 digit DMMs, the 5200A used as an AC source only.

[Tony_G]

Thanks for the detailed response Dr. Frank - I'll check into the sources that you list.

In your PS you mention that you own a 5442A, 5200A and a 3458A and that you use the 5200A as an AC Source only.

If you have the time, I'd appreciate if you could expand on that piece - From reading about the algorithm from his paper, it still seems that you'd need a stable, repeatable source to apply that technique through other meters. I'm probably wrong but it seems to me that you're using the 5200A to provide an AC Voltage then measuring it with both the 3458A and the meter to be calibrated and then calibrating the meter.

Look forward to hearing from you on this.

Thanks,

TonyG

[Dr. Frank]

Thanks for the detailed response Dr. Frank - I'll check into the sources that you list.

In your PS you mention that you own a 5442A, 5200A and a 3458A and that you use the 5200A as an AC Source only.

If you have the time, I'd appreciate if you could expand on that piece - From reading about the algorithm from his paper, it still seems that you'd need a stable, repeatable source to apply that technique through other meters. I'm probably wrong but it seems to me that you're using the 5200A to provide an AC Voltage then measuring it with both the 3458A and the meter to be calibrated and then calibrating the meter.

Look forward to hearing from you on this.

Thanks,

TonyG

Ok, shall I list some sources?
http://eu.flukecal.com/training/web-seminars/On-demand
Check the six Back to Basics seminars in the Electrical Calibration section.

The application notes are here: http://eu.flukecal.com/category/literature-type/articles-and-education/electrical-calibration/application-notes

Read about "Calibrating the Agilent 3458A..." and also everything about artifact calibration, and "..Reference Multimeter..."
Artifact Calibration applies also to the 544x calibrators..

Keysight has several videos covering similar stuff, either here: https://www.youtube.com/channel/UCG8BVoXwdZqz-PlZxeO56Tw,
or search for "Keysight Calibration & Repair".



Swerleins algorithm is also available for free as a VB program.
I use it to increase the the uncertainty for frequencies up to 1kHz, or so, above the already good uncertainty of the 3458As SETACV SYNC function.

The 5200A is very stable, about 70ppm / 10min, compared to its 200pm absolute uncertainty.
So it fulfills the stability requirement, so I exactly use these two instruments, as you assumed.
My 5200A is even more stable than specified, so it's no problem to make 3458A measurement and DUT calibration in slightly different time frames.

If you also have access to both instruments, I recommend that you just play around with these, to get a feeling about the stability over different frequency ranges.


Btw.: There is no real AC-counterpart to the 5440/42, as the 5200A is the counterpart to the 332/335 DCV calibrator, and Fluke designed the 57xx series instead, but no other ACV source in that era.
Therefore, the 5200A is the best choice.

Frank

 
 

[Tony_G]

A hearty thank you for both of your posts - I've just started down the path to doing home calibration (primarily because I scored that 5440) and I appreciate you taking the time to provide your insight and informational sources.

TonyG