Products > Test Equipment
Keysight's new 34465A (6.5 digit) and 34470A (7.5 digit) bench multimeters
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tszaboo:

--- Quote from: Dr. Frank on March 04, 2015, 10:47:45 am ---
--- Quote from: NANDBlog on March 04, 2015, 09:23:41 am ---
I'm also interested how did they make the good old artefact calibration in the meters.

--- End quote ---


You mean the AUTOCAL feature of the 3458A?

That is NOT implemented in the new '465A and'470A, quite obviously, although they also call it AUTOCAL.

If you have a look in the manual for these new meters, service / calibration section, you will note, that these instruments both have to calibrated in the usual manner, i.e. by individual Cardinal Points for each mode and for each range.

They may only correct for some internal temperature drifts of amplifiers, what they call AUTOCAL here, but the A/D is far too bad (nonlinear) to realize a real / full artefact calibration, by only two references.

Frank

--- End quote ---
I dont know, is it? For sure, they call it the same way. The manual said it takes 20-30 seconds to do this, it takes several minutes on the 3458A, because the 1000 NPLC on the 3458A, while the xx65 and 70 are 100NPLC. We need to see a service manual, because the user manual is missing the details. Maybe after the teardown it will be more clear. Maybe Dave should cover this if he makes a review of the meters or ask HP/Agilent/Keysight to clarify.
Dr. Frank:

--- Quote from: NANDBlog on March 04, 2015, 11:08:19 am ---I dont know, is it? For sure, they call it the same way. The manual said it takes 20-30 seconds to do this, it takes several minutes on the 3458A, because the 1000 NPLC on the 3458A, while the xx65 and 70 are 100NPLC. We need to see a service manual, because the user manual is missing the details. Maybe after the teardown it will be more clear. Maybe Dave should cover this if he makes a review of the meters or ask HP/Agilent/Keysight to clarify.

--- End quote ---

This manual is already available, that is document 34460-90901.pdf.
This manual now contains special chapters for 34465A and 34470A, also describing their calibration routines, see snapshot from the DCV section.

Therefore, no artefact calibration!
See page 527,  a Fluke 5270A is required, 10V and 10k artefacts won't do the job.

The A/D is only 1 .. 1.5ppm linear, which may correct gain 10 errors in the order of 10..15 ppm only, impossible to achieve a full autocal calibration. (compare that to 0.02ppm linearity of the HP3458A) 


Then , the third indicator is in the specs.

All ranges diverge over time, i.e. the uncertainty gap between two distinct ranges increases over time.

On the 3458A, this gap is always constant, even after 1 year, as this instrument corrects all ratio uncertainties to the 24h specification, every time AUTOCAL is engaged.

Frank
Dr. Frank:
Thinking a little bit further about the 10V DCV drift specifications (most stable range) I come to the conclusion, that the 34465A will probably have an LM399H reference inside, (20ppm/year drift), and the 34470A will probably have the LTZ1000A reference of the 3458A (8ppm/year drift).

As the operational ambient temperature is also specified for 55°C, they again have to run the references on about 90°C oven temperature.

Frank
tszaboo:

--- Quote from: Dr. Frank on March 04, 2015, 11:20:04 am ---
--- Quote from: NANDBlog on March 04, 2015, 11:08:19 am ---I dont know, is it? For sure, they call it the same way. The manual said it takes 20-30 seconds to do this, it takes several minutes on the 3458A, because the 1000 NPLC on the 3458A, while the xx65 and 70 are 100NPLC. We need to see a service manual, because the user manual is missing the details. Maybe after the teardown it will be more clear. Maybe Dave should cover this if he makes a review of the meters or ask HP/Agilent/Keysight to clarify.

--- End quote ---

This manual is already available, that is document 34460-90901.pdf.
This manual now contains special chapters for 34465A and 34470A, also describing their calibration routines, see snapshot from the DCV section.

Therefore, no artefact calibration!
See page 527,  a Fluke 5270A is required, 10V and 10k artefacts won't do the job.

The A/D is only 1 .. 1.5ppm linear, which may correct gain 10 errors in the order of 10..15 ppm only, impossible to achieve a full autocal calibration. (compare that to 0.02ppm linearity of the HP3458A) 


Then , the third indicator is in the specs.

All ranges diverge over time, i.e. the uncertainty gap between two distinct ranges increases over time.

On the 3458A, this gap is always constant, even after 1 year, as this instrument corrects all ratio uncertainties to the 24h specification, every time AUTOCAL is engaged.

Frank

--- End quote ---
You are right. The calibration process still contains a lot more steps than what you would need for artefact. We should see some block diagrams, otherwise we have no idea what is going on inside the meter when we press the button.
AndyC_772:

--- Quote from: 6thimage on March 03, 2015, 11:19:16 pm ---One thing I've found a 6.5 digit multimeter really useful is measuring the current of a microcontroller. Not because it was drawing a tiny amount, but because the difference between the burden voltages of adjacent ranges was enough that it triggered the micro's brown out logic. With the 6.5 digits being enough to give a decent level of precision on the higher range.

--- End quote ---

This is something I hope to now be able to do with reasonable accuracy. I design a lot of battery powered products using microcontrollers, and typically they spend a lot of time asleep, but wake at regular intervals to do something interesting before going back to sleep again. A fast, accurate, logging meter should be able to record current over a period of time, and even if it can't integrate total charge internally, it's simple enough to add up all the measurements in a spreadsheet.

My 34465A is ordered. Should be here tomorrow  :-DMM
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