Fluke 8558A/8588A 8.5-digit DMMs

[TiN]

About 18 years after release of first Fluke's 8.5-digit DMM based on acquired technology from Wavetek merger and Datron 1281 project.
Yes, I'm talking about Model 8508A that compete with respected ultralinear industry golden standard - Keysight 3458A. Now in 2019 we finally get an update:




Fluke started to release some docs on subject:

Fluke 8588A/8558A operators manual
Fluke 8588A/8558A Remote programmers manual

So now we know that 8588A is a replacement for 8508A Reference Multimeter and has specifications suited for the calibration and metrology applications.

Cheaper 8558A 8 1/2 Digit Multimeter is more in line for general lab work, that need high resolution meter, but relaxed on accuracy.

Fluke 8558A specifications
Fluke 8588A specifications

Common features from manual:

* Visual Connection Management active 5-way low thermal binding posts terminal illumination, like Fluke 5730A/5790B
* Versatile resolution and reading rate settings: 8 1/2 to 4 1/2 digit resolution
* Now can adjust aperture time settings from 0 ns to 10 seconds (200 ns min resolution)
* Speed up to 100 KSPS at 4 1/2 digits (18-bit) resolution in remote to rival 3458A
* Digitizer up to 5 MSPS at 18 bits with up to 20 MHz bandwidth
* 30A range for 8588A, but only 2A range for 8558A model.
* Programmable front/rear inputs, automatic ratio ohms, voltage, and more using the front/rear inputs. (no more overpriced Option 001? yay?)
* Analyze, with graphing, trending and statistics
* Capacitance measurements to calibrate multi-product calibrators
* RF power meter readout for R&S NRP series power sensors
* GPIB SCPI, Ethernet, and USB remote interfaces
* PRT and thermocouple readouts
* Front and rear USB memory ports for data transfer
* Software emulation of the Fluke 8508A and HP/Agilent/Keysight 3458A remote interfaces
* Analog Zero to remove residual offsets, for example, from thermal EMFs.

Based on quick browsing thru the manual few notes I make:

* Fall for modern trend with colorful LCDs with poor color/font choices
* Added 8-digit up to 100Mhz frequency meter, added support for R&S power sensor for RF stuff
* Fixed issue with 8508A when ranges to only to 199900000 counts. Now full-scale overrange is 202000000 counts.
* ...But not for ACV functions! ACV functions limited to 1.212x FS. Old hotty 8508A had 1.9990x at least Keithley 2002 is still the champ on FS range.
* Still no specified linearity for ADC
* No thermal sensor for AC/DC transfers. I was kinda hoping for this, since Fluke have the technology for decades (used in 57xx/792A).
* Marketing pitch of "no need ACAL" is present as well.
* Now meter have a fan. Yay! I was not happy about having hot 8508A near my other gear, offseting the measurements. Had to place it on separate location due to that.
* Remote protocol is now SCPI-compatible, as expected.

Anyone getting a demo unit to play with?

[Dr. Frank]

TiN, thanks for the headup.

Seems that these are just technical updates of the 8508A, like done on 732C and 5730, as probably:
- update of component technologies and obsolete parts
- through hole => SMD
- replace Vishay BMF by Fluke precision Thick Film Arrays.
- additional faster 18Bit A/D for 100kHz and faster (like KEI7510)
- new, updated user interface
- improved data handling, like memory and fast transfer over GPIB, USB, Ethernet

A quick scan shows me, that specification did not change much compared to 8508A, especially A/D seems still to be the old one, as 8 digits (DCV, Ohm) still require 2-10sec acquisition time.. see page 32 of operation manual.. and linearity is again not specified, only again indirectly by transfer accuracy of (0.05 + 0.05) ppm.
OHM mode really has been improved further, great accuracy for high ohm values, due to 20V/200V current sources.
 
So price may be more competitive to 3458A. Let's see, what other volt-nuts here find out, when they join the official hands-on presentations by FLUKE.

Frank

[HighVoltage]

Thank you TiN for an early preview.
The official release date in Germany is in abut 2 weeks.

[splin]

Hmm.  8588A resistance specs for 100 ohms to 100k (page 26) have better 2 year Tcal +/- 5C absolute accuracy than 2 year Tcal +/- 1C relative accuracy! Probably got all the right numbers,  just not necessarily in the right order....      **

The 8558A specs have similar issues but different numbers. I wonder how many people proof read or reviewed the documents?

Also curious is the DC 10V 365 day Tcal +/- 1C relative accuracy spec is 2.7ppm rdg + .05ppm range,  compared to the 365 day Tcal +/- 1C absolute accuracy spec of 2.8 +.05. Does that imply that their calibration standard uncertainty is only 0.1ppm? Seems incredible - the 8508A adds 0.3ppm and the 3458A adds 2ppm for NIST traceability.

Why don't they specify absolute 24h and 90 day specs?  They don't provide those for the 8508A either.

[EDIT] The Datron 1281 specified an additional 2.5ppm typical calibration uncertainty.

** For the youngsters or non-UK readers - Eric Morecombe 'playing' Grieg's piano concerto, conducted by the late Andre Previn.

[e61_phil]

and linearity is again not specified, only again indirectly by transfer accuracy of (0.05 + 0.05) ppm

Not even indirectly. The transfer is only allowed within 10% of the initial value. Therefore, 0.05 + 0.05 does not apply for a 1V to 10V transfer.

[PTR_1275]

The million dollar question, how much can I not afford it by

[quarks]

just heard about it a short time ago

thanks for sharing

I will update my comparison charts and post it asap

[quarks]

here is a DCV comparison chart

Looks strange, but if I did not make a mistake, the 8508A is still better overall, exept for 8588 linearity in 10 (20) Volt range.

[Kleinstein]

The range much below 10 mV does not really matter. For the rest the 8588 is pretty close to the 8508 and the "cheap" 8558 is a little high in uncertainty.

The difference is so small that it's no significant, as the uncertainty levels are only some kind of best guess or even aims set by the marketing department. Especially for a new instrument the specs may be conservative. For an only slightly modified old design the new values may be just updates estimates due to experience even if the internals have not changed.

There is not much sense in absolute specs for very short time - the 24 h would be essentially over when delivered and warmed up. Not many would run a 90 days or similar cal cycle - and if so they should know how to calculate the numbers from the cal lab uncertainty and relative accuracy.

The added 2nd faster ADC makes absolute sense, especially if used for digital RMS anyway.

What is the purpose of a 1 M input impedance mode ? It looks rather odd to me.

[CalMachine]

What is the purpose of a 1 M input impedance mode ? It looks rather odd to me.

Some high voltage probes have a 1 MOhm output impedance.  A lot of Ross Engineering probes do, I believe

[e61_phil]

Some high voltage probes have a 1 MOhm output impedance.  A lot of Ross Engineering probes do, I believe

Does it make sense to calibrate such probes with an 8.5 digit meter? Most of them have a couple of % as spec.

[CalMachine]

Some high voltage probes have a 1 MOhm output impedance.  A lot of Ross Engineering probes do, I believe

Does it make sense to calibrate such probes with an 8.5 digit meter? Most of them have a couple of % as spec.

The Ross Engineering VD probes are 0.01% at DC.  https://www.rossengineeringcorp.com/products/measurement/hv-voltage-dividers.html

Normally I've seen then used with a little impedance matching box, too.  The 1 MOhm function negates that.  I'd admit it is a little overkill, though.  I'm sure there are probably other applications that might call out for a specific input impedance

[macboy]

What is the purpose of a 1 M input impedance mode ? It looks rather odd to me.

Some high voltage probes have a 1 MOhm output impedance.  A lot of Ross Engineering probes do, I believe

Do they have a 1 MOhm output impedance, or are they specified for a (i.e. expecting a) 1 MOhm input impedance instrument? Not the same at all.

[CalMachine]

What is the purpose of a 1 M input impedance mode ? It looks rather odd to me.

Some high voltage probes have a 1 MOhm output impedance.  A lot of Ross Engineering probes do, I believe

Do they have a 1 MOhm output impedance, or are they specified for a (i.e. expecting a) 1 MOhm input impedance instrument? Not the same at all.

Touche!

Here is what Ross Engineering states 

In the standard 1000/1 or 10,000/1 Ross voltage dividers the low voltage capacitors and resistors are selected to provide correct ratios when shunted by 1 megohm, 20-50pF oscilloscope (or other load), plus 2, 3, 6, 15, or 20 feet (please specify the shortest practicable length) of low capacitance RG59 or special Ross Engineering Corporation coaxial cable unless otherwise required

[try]

From the manual of the 8588A:

4 1/2 digits (18-bit)

Pretty strange.

[Inverted18650]

Hopefully this will allow the rest of us to get the "old" Fluke 8508A's for less than $10K.

[e61_phil]

Hopefully this will allow the rest of us to get the "old" Fluke 8508A's for less than $10K.

I don't think so. Unfortunately, the documents are no longer available due to the links above.

If I remember correctly the relative spec of the 8588A (20V 1 year) was 2.7ppm and the relative uncertainty of the 8508A is also 2.7ppm. There is no improvement in the new meter. The adder for the range has improved (0.05ppm vs. 0.2ppm) but I can imagine that is due to some experience over the years.

Our 8508A was calibrated with an uncertainty of 0.7ppm. If we assume the noise is stable over the range that will also lead to 2.8ppm/year.

I would expect the new meter has to show some years of really good performance before anybody with a 8508A will change to the new one. Especially if they changed the gain setting resistors to something new instead of the expensive ones used in the 8508A.
The highspeed stuff isn't an argument imho. If I want to have something like that I would go for an 7510 or something like that additional to my 8.5 digit meter.

[Dr. Frank]

Yes, 95% and 99% confidence DCV specifications are nearly identical, maybe the absolute specs are better due to usage of better standards like JJ array.
And transfer specs are much better.

It's always good to directly download such leaked documents.. 

Frank

[e61_phil]

Are the transfer specs really better? I think the old ones aren't limited to 10%

[splin]

Unfortunately, the documents are no longer available due to the links above.

If I remember correctly the relative spec of the 8588A (20V 1 year) was 2.7ppm and the relative uncertainty of the 8508A is also 2.7ppm. There is no improvement in the new meter. The adder for the range has improved (0.05ppm vs. 0.2ppm) but I can imagine that is due to some experience over the years.

Here you go:



But how are we to interpret the 0.1ppm difference between the highlighted values? They make no sense to me; it would be surprising if the factory calibration uncertainty was much better than 2ppm. Clearly Fluke have the capability for sub ppm 10V calibration, but in that case why not specify absolute uncertainties for periods less than 365 days?

If I were paying $17k+ I'd want it to be freshly calibrated, preferably within 48 hours - not from a distributer with potentially only a few weeks left of a 12 month calibration. I guess that would be an expensive option like the 3458A meteorological calibration option.

I see TEquipment are showing the 8508A as discontinued.

[Dr. Frank]

The 8588A is better specified than the 8508A, when making near 1:1 transfers, like 10V against 9.0...11V (+/- 10%).

The 8508As transfer specifications do not contain such a limitation, and in the explanations of the transfer specification, there's even an example of a 5V => 10V transfer/comparison. So you're right about the 8588A. Maybe the 8508A would also give 1:1 transfers as good as the 8588A (same / similar A/D ?)

In contrast, the 8588A now is not specified any more concerning transfers of random ratios, instead you have to use the 24h specification, which is much worse than the 8508A transfer spec for ratios > 1.1.

Frank

[e61_phil]

But how are we to interpret the 0.1ppm difference between the highlighted values? They make no sense to me; it would be surprising if the factory calibration uncertainty was much better than 2ppm. Clearly Fluke have the capability for sub ppm 10V calibration, but in that case why not specify absolute uncertainties for periods less than 365 days?

If I were paying $17k+ I'd want it to be freshly calibrated, preferably within 48 hours - not from a distributer with potentially only a few weeks left of a 12 month calibration. I guess that would be an expensive option like the 3458A meteorological calibration option.

What is the problem with the relative specs? That is what the meter does and it is what HP also specified for the 3458A. If you want to have fully traceable specs you have to use absolute specs from Fluke or add the 2ppm for the 3458A. Or you RSS the traceability uncertainty with the rel specs like described in the Fluke datasheet. The nice thing on Fluke specs is, they give you absolute values which you can take without using your brain. But they cannot know how you calibrate the meter and therefore you have the rel specs.

As we ordered our 8508A is came directly from Fluke and was calibrated with 0.7ppm uncertainty for 10V. Which gives 2.8ppm for 10V exactly as the new meter. The new better absolute value is no improvemt of the meter, it is improvement of the calibration.

They calibrated the 8508A with a characterized 5720A. There is no need for a JJA to calibrate such a meter.

[ScoobyDoo]

Hello folks - here is already a short commercial of the 8588A



ScoobyDoo

See you all soon on 20th of March at Fluke event in Kassel !

Herzliche Grüße/Meilleures salutations/Best regards

ScoobyDoo

[e61_phil]

Who would be in Kassel on 20th of March? I planned to go

[Krampmeier]

I'll be there, together with a colleague. It would be great to have a chat with some other EEVblog forum members - look out for Andreas and Johannes (me)!