Products > Test Equipment

Keysight's new 34465A (6.5 digit) and 34470A (7.5 digit) bench multimeters

<< < (94/145) > >>

Alex Nikitin:
Thank you. One interesting observation - a repeated ACAL on the 34465A returns a somewhat different measured values for LTZ1000, with around 1-1.5ppm variations (easily visible on the averaged 7.5 digit value). My suspicion is that variation is due to the LM399 noise, which is about 1ppm p-p.

Cheers

Alex

Dr. Frank:

--- Quote from: Alex Nikitin on October 11, 2016, 11:14:02 am ---Thank you. One interesting observation - a repeated ACAL on the 34465A returns a somewhat different measured values for LTZ1000, with around 1-1.5ppm variations (easily visible on the averaged 7.5 digit value). My suspicion is that variation is due to the LM399 noise, which is about 1ppm p-p.

Cheers

Alex

--- End quote ---

That may be the root cause.
I also see some variations between consecutive ACALs.

The ACAL mechanism of the 34465A/470A is not as precise as the one of the 3458A, as Scott Stever last year explained, in a discussion about that feature (it also cannot do a full re-calibration, of course).
He estimated the accuracy to be about 5..10ppm only.

So it might as well arise from the basic ACAL-principle.

After correction of the FW, as of vers. 2.14, the mechanism improved, and I estimate / observe the precision to about +/- 1ppm for 10V and 1V, and about +/- 2ppm for 100V, 1kV and 100mV.

I did not investigate on how it behaves under bigger environmental temperature excursions.

Frank

Alex Nikitin:

--- Quote from: Dr. Frank on October 11, 2016, 11:26:21 am ---The ACAL mechanism of the 34465A/470A is not as precise as the one of the 3458A, as Scott Stever last year explained, in a discussion about that feature (it also cannot do a full re-calibration, of course).

So it might as well arise from the basic ACAL-principle.

--- End quote ---

The ACAL on 34465A is also very quick, which means it is based on a spot reference value and not on an averaged one. I would probably be happier with a somewhat slower but more consitent ACAL. It is still accurate to 1-2ppm though, which for that meter class (and price) is very good.

Cheers

Alex

Dr. Frank:

--- Quote from: Alex Nikitin on October 11, 2016, 11:34:43 am ---
--- Quote from: Dr. Frank on October 11, 2016, 11:26:21 am ---The ACAL mechanism of the 34465A/470A is not as precise as the one of the 3458A, as Scott Stever last year explained, in a discussion about that feature (it also cannot do a full re-calibration, of course).

So it might as well arise from the basic ACAL-principle.

--- End quote ---

The ACAL on 34465A is also very quick, which means it is based on a spot reference value and not on an averaged one. I would probably be happier with a somewhat slower but more consitent ACAL. It is still accurate to 1-2ppm though, which for that meter class (and price) is very good.

Cheers

Alex

--- End quote ---

Well, we currently are digging 10 times below the specification limits.. and it's intended to compensate for temperature driven drifts on the order of tens of ppm. It cannot and should not be compared with the 3458As ACAL performance.
That's what Scott Stever also wanted to stress.

Even the 34470A, promoted as 7,5 digits class (!!)DMM, does not benefit accordingly, though it has the less noisy reference inside.
But it works better than suggested by Keysight.. I did not figure out how they realized it, and they didn't want to explain in detail.

Comparing with the possibilities of the other ACAL methods (superlinear A/D and D/A converters, Hamon type, precision transformer), I suggest, that the ACAL in the 465/470A can't be as precise , for physical reasons, even at longer integration times.

Alex Nikitin:
My first (sort of) disappointment with the 34465A . On resistance (both 2-wire and 4-wire) it is noisy. If you do ACAL, the next few readings usually come with a decent accuracy, however when I've tried to see how stable a 10K resistor is with temperature (as our HP3458A is currently with Keysight UK for calibration), the noise-like variations on the meter readings were so large that any resistor changes with about 3-4 degrees C room temperature variations are completely invisible. Here is a graph with a 2 hour run using my LTC450C 10K "standard" (measured by HP3458 about a week ago and by Keysight 34465A today) . Overnight variations were even larger - about 25ppm p-p. Is this a typical behaviour for the 34465A ?

Cheers

Alex

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod