Restoration : Wavetek 4920/4920M teardown, repair and usage cases, come join!

[ManateeMafia]

I hope so, looks like my cheap calibration option is finished  . Now I will have to ship it to Taiwan.

[TiN]

Too good for too cheap never lasts. So NIST TVC is in the remote distant plans.

[acbern]

One thing to add, and TiN has realized it anyhow, e.g. even the 90day uncertainties in the 100 to 500kHz frequency range of the 5720, where most of the calibration takes place (1MHz ratio is not much better), are about a factor of 10 as big as those of the 4920M. So the Fluke is totally inadequate to properly calibrate the 4920M. You really need a Fluke 792 or a Balantine 1605. (Or, if time is not an issue, and you have a lot of tranquilizer and the reverse switch setup in your tool box, a set of calibrated TVCs). And the 792 has no GPIB, so lots of manual work (the Ballantine has; a very underrated device...)

[CalMachine]

One thing to add, and TiN has realized it anyhow, e.g. even the 90day uncertainties in the 100 to 500kHz frequency range of the 5720, where most of the calibration takes place (1MHz ratio is not much better), are about a factor of 10 as big as those of the 4920M. So the Fluke is totally inadequate to properly calibrate the 4920M. You really need a Fluke 792 or a Balantine 1605. (Or, if time is not an issue, and you have a lot of tranquilizer and the reverse switch setup in your tool box, a set of calibrated TVCs). And the 792 has no GPIB, so lots of manual work (the Ballantine has; a very underrated device...)

I recently purchased a Datron 4950 I plan on bouncing my 4808 off of to cal my 4920 when it comes due!  It will be my first time self calibrating it...  My most recent cal came from Fluke. no one else would touch it lol.

[TiN]

Hope you have nanovoltmeter and nanovolt source, proper TVCs, and wiring. Would be very fun to see the worklog and photos of DIY 4920 cal.
I'm still processing data and writing on mine...

[CalMachine]

Hope you have nanovoltmeter and nanovolt source, proper TVCs, and wiring. Would be very fun to see the worklog and photos of DIY 4920 cal.
I'm still processing data and writing on mine...

The nano voltmeter I use here in the lab is a Keithley 181.  As far as TVCs go, my 4950 should provide a higher degree of accuracy than TVCs.  Really, the best I can see myself getting is around a 2:1 TUR, if that, as the 4920 is insanely accurate.

[TiN]

Any teardowns of 4950 planned? It would be joy to see insides.

Different TVCs provide different accuracy. Best of them do <10ppm which is hard to beat.

[CalMachine]

Any teardowns of 4950 planned? It would be joy to see insides.

Different TVCs provide different accuracy. Best of them do <10ppm which is hard to beat.

Hmm really!?  Could you give me a source to some of these TVCs?  Most, if not all, I've seen have got a best spec of like +/ 0.0095%  I'd greatly appreciate it. 

I'm not sure if/when a taredown of the 4950 will happen.  We just recently purchased it and we are still searching for a place to provide a 17025 accredited cal.  It will probably end up going to fluke and then sent to England for cal, like our 4920.

[ManateeMafia]

@CalMachine

Try contacting Keysight in Loveland. I spoke to them a few months ago and they told me they are can calibrate MFC's. They can also characterize each of the functions and ranges. I didn't think to ask them about my D4920 but a D4950 shouldn't be much more difficult than a F5720A. It will be a matter of getting a copy of their Scope of Accreditation and determining if it fits your needs.

[CalMachine]

@CalMachine

Try contacting Keysight in Loveland. I spoke to them a few months ago and they told me they are can calibrate MFC's. They can also characterize each of the functions and ranges. I didn't think to ask them about my D4920 but a D4950 shouldn't be much more difficult than a F5720A. It will be a matter of getting a copy of their Scope of Accreditation and determining if it fits your needs.

I would think a Datron 4950 would be the hardest cal to find... as it's the 'calibrator of calibrators' and has some of the tightest specs out there.

[ManateeMafia]

I would think very few labs have the capabilites to calibrate a calibrator. The 4950 was touted as being able to calibrate 4.5 - 8.5 digit meter calibrators so the spec's can vary and the 4808 is certainly one of the best ever built.
I found Loveland's Scope of Accreditation and they have a full setup but it looks like Fluke would be a better choice.

http://www.keysight.com/upload/cmc_upload/All/KeysightLovelandCertScope-ANAB-V006.docx.pdf
http://us.flukecal.com/support/accreditations
 
Looking at the datasheet for the 4950, the transfer stability is only listed for 30 and 90 days. Do you plan on sending it once per year or on 90 day intervals?

[TiN]

Any teardowns of 4950 planned? It would be joy to see insides.

Different TVCs provide different accuracy. Best of them do <10ppm which is hard to beat.

I'm not sure if/when a taredown of the 4950 will happen.  We just recently purchased it and we are still searching for a place to provide a 17025 accredited cal.  It will probably end up going to fluke and then sent to England for cal, like our 4920.

Teardown sounds logical to me, if I would have 4950. Replace battery with fresh one, check boards, replace electrolytic caps, IEC mains filter, etc, save old calibration dump before sending to cal. There is no fun if you send box to cal, pay big money for it and unit loose this calibration after 2 months because of 2$ battery go poof.

[lukier]

I would think very few labs have the capabilites to calibrate a calibrator. The 4950 was touted as being able to calibrate 4.5 - 8.5 digit meter calibrators so the spec's can vary and the 4808 is certainly one of the best ever built.

I wonder why Fluke dropped 4808 then. For 7001 reference the argument was that it wasn't as good as 732B.

Glaswegians can get it cheap it seems, suspiciously cheap (and on craigslist?):
http://glasgow.craigslist.co.uk/bfd/5835760255.html

If I had more spare cash I would be tempted, but it's far away from London and I don't think dealing on Craigslist is particularly safe.

[CalMachine]

I would think very few labs have the capabilites to calibrate a calibrator. The 4950 was touted as being able to calibrate 4.5 - 8.5 digit meter calibrators so the spec's can vary and the 4808 is certainly one of the best ever built.
I found Loveland's Scope of Accreditation and they have a full setup but it looks like Fluke would be a better choice.

http://www.keysight.com/upload/cmc_upload/All/KeysightLovelandCertScope-ANAB-V006.docx.pdf
http://us.flukecal.com/support/accreditations
 
Looking at the datasheet for the 4950, the transfer stability is only listed for 30 and 90 days. Do you plan on sending it once per year or on 90 day intervals?

Yeah, we sent one of our 4808s to Tektronix and we're getting ready to send the other one to Keysight's Loveland facility...  Fluke won't touch 4808s anymore, which is a shame    I have yet to hear back from fluke on whether or not they will calibrate the 4950.  I plan on sending the 4950 in every 90 days for calibration.  Our 4808s, the 4950, 4920, Fluke 732B, and Datron 4910 will all be our main standards we will send out every 90 days for the first 2 years or so.  Then I think we're going to back down to every year and track the stability and drift of the units.

Any teardowns of 4950 planned? It would be joy to see insides.

Different TVCs provide different accuracy. Best of them do <10ppm which is hard to beat.

I'm not sure if/when a taredown of the 4950 will happen.  We just recently purchased it and we are still searching for a place to provide a 17025 accredited cal.  It will probably end up going to fluke and then sent to England for cal, like our 4920.

Teardown sounds logical to me, if I would have 4950. Replace battery with fresh one, check boards, replace electrolytic caps, IEC mains filter, etc, save old calibration dump before sending to cal. There is no fun if you send box to cal, pay big money for it and unit loose this calibration after 2 months because of 2$ battery go poof.

I will very much do that!  Good thinking.  You can expect some pictures in the next month or 2.

I would think very few labs have the capabilites to calibrate a calibrator. The 4950 was touted as being able to calibrate 4.5 - 8.5 digit meter calibrators so the spec's can vary and the 4808 is certainly one of the best ever built.

I wonder why Fluke dropped 4808 then. For 7001 reference the argument was that it wasn't as good as 732B.

Glaswegians can get it cheap it seems, suspiciously cheap (and on craigslist?):
http://glasgow.craigslist.co.uk/bfd/5835760255.html

If I had more spare cash I would be tempted, but it's far away from London and I don't think dealing on Craigslist is particularly safe.

They dropped the 4808 to push their 5700 series I think.   And yeah... 1500 lbs?  That's extremely cheap... it could be hot

[TiN]

Fluke dropped 7001,1281,4808 instruments because it's a lot of work and overhead to support two lines of similar products, so they'd rather focus on their single line of own designs, which are 732,8508,55xx/57xx instead. Well expected move, actually.

You can expect some pictures in the next month or 2

Looking forward. 

[e61_phil]

Sorry, but I have to ask an offtopic question: What exactley does a Datron 4950 do? I had a look at the manual which says it is a transfer standard. My understanding of a transfer standard is a unit like the Fluke 732A/B or something like that. The manual looks like the 4950 is a kind of multimeter with very tight specs. Is this right? Or is there anything more special?

[Dr. Frank]

Any teardowns of 4950 planned? It would be joy to see insides.

Different TVCs provide different accuracy. Best of them do <10ppm which is hard to beat.

Hmm really!?  Could you give me a source to some of these TVCs?  Most, if not all, I've seen have got a best spec of like +/ 0.0095%  I'd greatly appreciate it. 

Try these: https://www.nist.gov/node/1108526/sri-6002-multi-junction-thermal-converter

That's not that expensive.. AC/DC transfer uncertainty of these primary TVC standards is between 2..10 ppm for frequencies from 10 Hz up to 500kHz:
https://www.nist.gov/calibrations/voltage-measurements-calibrations#533

Appropriate switching box and nV amplifier required..

An actual SRM 6002.b even may have AC/DC uncertainty of << 10ppm up to 1MHz 
Frank

[acbern]

Or you buy a TVC from the bay and have it calibrated. Cost me less than half of the price of the NIST unit. But then you still just have one voltage range. So the problem just starts there. Still no way around something like a Fluke 792 or a Ballantine 1605 or a set of TVCs to do a ladder calibration. Doing that with a set of TVCs is painfull, takes forever, lots of manual work, so I gave it up after 3 converters, and moved on with the 1605.

[TiN]

What exactley does a Datron 4950 do?

It's the multimeter, but it's scale is very limited to "transfer values". So unlike regular meter, which on 10V range goes from -10V to -10V + overrange, 4950 does only -1 to +1V, +9 to +11V and +18V to +19.5V, and negative ranges like this. Since these values are usual cardinal points for calibration of generic DMMs and MFCs, hence the 4950 name as transfer standard. Also this is why specifications are so tight and different, as it's not absolute accuracy specification, but transfer specifications.

E.g. 4950 calibrated to 10VDC with absolute uncertainty 2.5ppm. Using 4950 to measure 10V after would allow you to know absolute value within 2.5ppm + 1.5ppm = 4ppm total, within 30 days and +/-1C from calibration temperature.
Using 3458A calibrated to same source would give you 2.5+2.65 ppm = 5.15 ppm total, within 1C over 90 days, or 2.5+0.1ppm = 2.6 ppm total within 10 minutes, +/-0.5C from ACAL.

Datron/Wavetek 4950 User's Manual.

[VintageNut]

You are the mayor of the volt-nut village. Congratulations!

What exactley does a Datron 4950 do?

It's the multimeter, but it's scale is very limited to "transfer values". So unlike regular meter, which on 10V range goes from -10V to -10V + overrange, 4950 does only -1 to +1V, +9 to +11V and +18V to +19.5V, and negative ranges like this. Since these values are usual cardinal points for calibration of generic DMMs and MFCs, hence the 4950 name as transfer standard. Also this is why specifications are so tight and different, as it's not absolute accuracy specification, but transfer specifications.

E.g. 4950 calibrated to 10VDC with absolute uncertainty 2.5ppm. Using 4950 to measure 10V after would allow you to know absolute value within 2.5ppm + 1.5ppm = 4ppm total, within 30 days and +/-1C from calibration temperature.
Using 3458A calibrated to same source would give you 2.5+2.65 ppm = 5.15 ppm total, within 1C over 90 days, or 2.5+0.1ppm = 2.6 ppm total within 10 minutes, +/-0.5C from ACAL.

[CalMachine]

Sorry, but I have to ask an offtopic question: What exactley does a Datron 4950 do? I had a look at the manual which says it is a transfer standard. My understanding of a transfer standard is a unit like the Fluke 732A/B or something like that. The manual looks like the 4950 is a kind of multimeter with very tight specs. Is this right? Or is there anything more special?

What TiN said!  It's used to transfer cardinal values within +/- very few ppm to other calibrators.

What exactley does a Datron 4950 do?

It's the multimeter, but it's scale is very limited to "transfer values". So unlike regular meter, which on 10V range goes from -10V to -10V + overrange, 4950 does only -1 to +1V, +9 to +11V and +18V to +19.5V, and negative ranges like this. Since these values are usual cardinal points for calibration of generic DMMs and MFCs, hence the 4950 name as transfer standard. Also this is why specifications are so tight and different, as it's not absolute accuracy specification, but transfer specifications.

E.g. 4950 calibrated to 10VDC with absolute uncertainty 2.5ppm. Using 4950 to measure 10V after would allow you to know absolute value within 2.5ppm + 1.5ppm = 4ppm total, within 30 days and +/-1C from calibration temperature.
Using 3458A calibrated to same source would give you 2.5+2.65 ppm = 5.15 ppm total, within 1C over 90 days, or 2.5+0.1ppm = 2.6 ppm total within 10 minutes, +/-0.5C from ACAL.

Datron/Wavetek 4950 User's Manual.

The 4950 is far superior in every other aspect than the 3458A (with opt 02), when it comes to calibrating a calibrator.  The 10 DCV range is fairly close in specs as you show but, for resistance, DCI, and especially ACI and ACV the 4950 is significantly better.

Any teardowns of 4950 planned? It would be joy to see insides.

Different TVCs provide different accuracy. Best of them do <10ppm which is hard to beat.

Hmm really!?  Could you give me a source to some of these TVCs?  Most, if not all, I've seen have got a best spec of like +/ 0.0095%  I'd greatly appreciate it. 

Try these: https://www.nist.gov/node/1108526/sri-6002-multi-junction-thermal-converter

That's not that expensive.. AC/DC transfer uncertainty of these primary TVC standards is between 2..10 ppm for frequencies from 10 Hz up to 500kHz:
https://www.nist.gov/calibrations/voltage-measurements-calibrations#533

Appropriate switching box and nV amplifier required..

An actual SRM 6002.b even may have AC/DC uncertainty of << 10ppm up to 1MHz 
Frank

I'm going to look into these!! Thanks you

[Pipelie]

attach the firmware of datron 4920M

[TiN]

Thanks. Uploaded:

Pipelie 4920M's 1.0, 12.07.1990 A binary
Pipelie 4920M's 1.0, 12.07.1990 B binary

With help of simple python snake:

Code: [Select]

# xDevs.com combiner tool
import os

print "Combine tool for 2 FW ROMs into 1 256KB ROM, for Wavetek 4920M"
with open('4920M-40093S-1.0A-12.7.90.BIN','rb') as b:
    with open('4920M-40093S-1.0B-12.7.90.BIN','rb') as a:
        with open('w4920-1_0_12_07_1990.BIN','wb') as x:
            for cnt in range(0, 65536):
                x.write ("%c" % a.read(1) )
                x.write ("%c" % b.read(1) )
                x.write ("%c" % a.read(1) )
                x.write ("%c" % b.read(1) )

Combined human-readable with little-endian

[Pipelie]

Thanks. Uploaded:

Pipelie 4920M's 1.0, 12.07.1990 A binary
Pipelie 4920M's 1.0, 12.07.1990 B binary

With help of simple python snake:

Code: [Select]

# xDevs.com combiner tool
import os

print "Combine tool for 2 FW ROMs into 1 256KB ROM, for Wavetek 4920M"
with open('4920M-40093S-1.0A-12.7.90.BIN','rb') as b:
    with open('4920M-40093S-1.0B-12.7.90.BIN','rb') as a:
        with open('w4920-1_0_12_07_1990.BIN','wb') as x:
            for cnt in range(0, 65536):
                x.write ("%c" % a.read(1) )
                x.write ("%c" % b.read(1) )
                x.write ("%c" % a.read(1) )
                x.write ("%c" % b.read(1) )

Combined human-readable with little-endian

Thanks, here is the ROM of my friend's  4920.

[TiN]

Thanks, this one is good, but it says 4920M in the code, not 4920.
Combined, LE dump.