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Keithley 2002 8.5 digit DMM review and teardown
« on: February 18, 2014, 07:24:40 pm »
Finally, it's here. I had no luck to get infamous 3458A affordable enough, so went to very familiar route, with
Keithley. Like some say it can't be enough DMMs, no matter how many one have.
As some members know, i'm Keithley addict in a way, and have few Model 2001 meters, which were violently abused and
tear down to pieces on daily basis, covering journey in this thread at EEVBlog and my own project tracker.

Welcome Model 2002 in it's beauty, probably smallest 8.5 digit meter on market. It's still current model, and
officially avalable thru official manufacturer website, just like 20'year old 3458A :).
To my surprise this one don't require any fixing/repairing or other mess, very unlike my 20 year old 2001's :D

Everybody who saw Keithley 200x/7001/24xx/26xx ones, will know how 2002 look like, so I'll post overall view
and menu/settings tricks later. PDF manuals.

As with all recent Keithley gear, schematics or detailed construction information is not available.
Best we have is repair manual troubleshooting hints, self-test diagnostics description and part list (which is helpful too).

For now we start with real stuff, teardown and

I actually shoot video-review (planned to be short, but it blew to 24 minutes). Sorry, my english require
lot of improvement and it's not my native, and it's almost my first video, so don't judge too harsh :)



And resources + hi-resolution photos of things inside below:
All photos clickable/zoomable :D



Digital board. It's 2001-142, Revision K. Very same board as in my second Keithley 2001.

Differences on BOM level:

* High-voltage DC-DC module (block near front panel connector) (+5V to filament VAC and +60VDC for VFD) moved from digital board to front panel.
* STD option used DALLAS DS1243 (NVRAM with Phantom RTC clock), MEM2 likely to use bigger version, such as DS1248 or DS1251
* Extra I2C 24C16 EEPROM on position U633 for calibration constants/data?
* Firmware for Model 2002
* Missing protection diodes on GPIB port interface (while www.38hot.net BBS 2002 had them on)
* Small ALTERA MAX5064 CPLD for trigger-link replaced by TEKMOS 2001-801-A05 ASIC
* 4MHz clock moved to front panel too.



Analog board is different story tho...



In general construction and functional units are same, but in critical areas using more precise components with tigther tolerances/less tempco.
Voltage reference changed from aged/selected LM199/399 to LTZ1000ACH.
There are now two switching capacitor building blocks (Linear LTC1043CSW) paired with KEMET PC or PP film capacitors.
Current source for resistance is using Vishay foil's. Switching between ranges now using MAX326's.
Ohm measurement is almost same, 0.1ohm 1% kelvin resistor (but better tempco, +-10ppm by label on it) + 0.91ohm and
Caddock 1737-53 network (same as 2001).
Same bootstrap circuitry as 2001's (four big caps near transformer) with avalance diodes between them,
same True-RMS AD637JR.



2002-162 4-layer PCB with ADC module now mostly completely SMT, designed in 1993 (yes, 21 years ago!).
It's revision B.

Featuring ALTERA EPM7160 in PLCC84 package, configured to 2002-802-A01 RTL, and clocked from 12MHz FOX XO.
As reminder, Model 2001 was using 7.68MHz with EPM7128 in PLCC64 :)

Some resistors now are in SO-16 networks (R827 and R825 on left side)
Also I could not spot integrating capacitor, it's probably one of NP0 SMD caps.
Model 2001 ADC was using bulky film thru-hole cap rated to 400V.



No components on back side, only nicely labelled interfacing connector. Reference voltage supplied differentially,
REFLO and REFHI? I measured REFHI, it's 7.13..V

Let's go back to analog board...



Mains switching / control curcuitry is same as in 2001. It handles selection 90-132 or 180-250VAC ranges automatically, as
well as provide frequency zero-cross signal for ADC to trigger in right at required NPLC cycles, to increase CMRR and PSRR.



Optical isolation with digital board was done with separate daughterboard, labelled 2001-132-01A. It carry two NVE IL717, which
are four-channel 110Mbps digital isolators. But if look closely - pin interface between boards matching original TLP582's,
so my guess that TLP582 couples were difficult to get in stock, so they added this adapter board, to keep analog board
design intact.



Power transformer have same configuration and pinout as 2001, marked HIREL systems, TR-280 Revision D.
It have magnetic shielding with copper foil around winding.



2002 equipped with very similar or same bootstrap circuitry, which provides +39 and -39V for analog needs, as well as +8/-8VF
for ohm/amps measurements. Those pesky C116,C115,C118,C119 capacitors tend to leak with age/elevated temperatures and
commit complete disaster on PCB, eating traces, leaking electrolyte all over precision circuits... This meter is only 8 years
old, so they are still fine, but next year I will replace them to freshies for sure :)





Input side.



PCB Fuse :) Old 2002 analog board don't have this, at least from what I can say looking on crappy photo
from chinese forum mentioned before. 2001 also don't have this. Wonder what that one does, maybe some
last step emergency protection?

Combined Caddock resistor network.



Consists from two resistors, bigger TF050R, and glued TF020R on back of it.



Reed relays made by Americal Relays Inc in this meter, A051A300H0C model, which likely to be custom, and
usual DK1a1b-6V relay. Circut here same or almost same as 2001.



Old 8-bit DAC from 2001 meter (MP7528) got replaced by same thing, which is Analog Devices AD7528, dual matched DACs, which
are used for TRMS filter circutiry to adjust operation of meter's AC conversion block. This section is very similar or same to 2001.



Same with TrueRMS convertor itself, which is AD637JR with bunch of DG444,DG408 and DG41 switches around.
There are also AD848J, LT1097, LT1223, AD711J and LM79L05A -5V negative LDO in this area.
All same stuff as 7.5 digit Keithley brother.







7V VREF:



Famous Linear ultra-zener reference, LTZ1000.



It have dedicated plastic cup from both sides of to seal reference from any airflow and reduce temperature influence from rest of the world.
Probably it's reference standard connection, can see 120 ohm 0.1% resistor nearby, as well as few PTF56 low-tempco resistors.
Also two blue resistors networks nearby, but those may not be related to voltage reference, at least one of such networks
can be found in 2001 too.



Back side of PCB with LTZ.



LTZ have popular companion Linear LT1013 in SO8 package with Q204 is heater drive transistor in SMT package.



There is also temperature sensor somewhere on board, as Keithley 2002 can measure it's internal temp, which it reports as
delta to calibration temperature. This measurement is readily available by temperature function, by selection INTERNAL TEMP mode.
In my case, reported value was -3.4°C , with ambient temp +24°C, while meter run around half-hour.
If I just power on cold meter it says -23.2°C and descreasing (to lesser delta) while meter warms up.



Current measurement parts, two MOSFETs to switch ranges for high amp ranges, long Vishay Z201 resistor (R277).
Right side of photo is for resistance measurements.



Same CADDOCK as in 2001 for low current ranges. This is actually standard network 1737-53, available even on Digikey :)



And not so standard Vishay PG hermetic oil-filled bulk foil resistors, with tolerance 1%. Absolute tolerance is not so important
in this case, as it's software calibrated anyway, but stability and tempco is what needed most. And there are only
few resistors on market which are better than these.

Resistors here used to set precise currents for sourcing thru unknown resistance for measurement. Switching is done
by MAX326's nearby. All heavily guarded and carefully designed precision voodoo.



There is also lonely Vishay PG hermetic oil-filled resistor network with tolerance 0.02% and 500.00 + 24500 resistances in it, likely setting gain for buffer amplifier (which is LT1007ACN8
in DIP8 package nearby). Switching of different gains done by DG444 and DG408 switch IC's nearby.







Switching capacitor dividers/multipliers, using film KEMET capacitors and Linear LTC1043CSW blocks. Keithley 2001 meter have only
one LTC1043 in DIP package.



Blob in center look like corrosion/salt, and I actually cleaned it carefully, but that was waste of time.
Why?
Because it is from insulator sponge, placed on protective/shielding/thermal bottom cover.



:)

More bottom side components.



0.91 ohm current sensing resistor shunt, unlike 2001, here its populated on bottom side of PCB. On 2001 it was right under 4-wire
resistor.



Those smudges/fingerprints seem to be on soldermask, as they are not erasable with alcohol. Looks dodgy, but it seem
not affecting performance..

Dual guard traces around sensitive high-impedance resistance measurement circuitry. Beauty!



Overview of bottom side of analog board, without cover.





Back cover/shield is same as 2001's, and actually bearing 2001-325 Rev.B tag on it.



Analog board is labelled 2002-102-04E-E5, designed in 1994, made in USA :)

Firmware

I have A09.

ROM, ODD
ROM, EVEN

As usual, now I have tracker and documentation project on my redmine for Keithley 2002.
Anybody welcome to download available stuff or participate in related endavours.

That's it for now..

Feel free to ask any suggestions, requests what can do/test with this meter.
I don't plan to do official calibration for it (as it's double price of 2001) at this moment, and
it seem to be pretty spot on already, at least it matches both Kei2400 and Kei2001 (which are still
only 3 weeks period from adjustment/cal) real close.

I do plan to work later on recovering schematics of Model 2002 as well, but have to finish 2001's one prior to that.

Want to try morph some functions from 2002 into 2001 (NPLC range, LTZ1000 reference, 8.5 digit native mode), as
already digital side of both meter's is same.

If anybody around have Model 2002 too, and can open it and remove analog board cover for internal photos - such
work greatly appreciated!
I want collect photo of different revisions/years for 2001/2002 series, but not going to
buy every single meter out there. Only 2002 photos found online were some old unit  (1997 datecode) on bbs.38hot.net.
Obviously not much owners tear down 6K$ MSRP DMM's, so that's why...

BR, TiN :)

P.S. Video is uploading, it will take couple hours, internet is not good here when need upload 2GB of FullHD video to tube  :phew:
« Last Edit: April 24, 2015, 01:23:02 pm by TiN »
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Offline dr.diesel

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #1 on: February 18, 2014, 08:18:04 pm »
Wow, excellent post my friend!    :-+    :-+    :clap:

Offline don.r

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #2 on: February 18, 2014, 08:20:37 pm »
OMG! Thanks so much for a post that will take hours of my time to view... and drool over.
 

Online Vgkid

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #3 on: February 18, 2014, 08:38:00 pm »
Thanks for the pics, who made the 4 wire kelvin sense resistor?
If you own any North Hills Electronics gear, message me. L&N Fan
 

Offline Macbeth

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #4 on: February 18, 2014, 08:51:51 pm »
Why is the video not available (in the UK at least?)

ETA: I just checked in youtube and it says the video is being processed and come back in a few minutes. Whatever that means, I look forward to it :)

8.5 digits!? insane.
« Last Edit: February 18, 2014, 08:53:50 pm by Macbeth »
 

Offline robrenz

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #5 on: February 19, 2014, 12:40:38 am »
Very nice video and post TiN :clap: :-+

Online Dr. Frank

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #6 on: February 19, 2014, 07:21:50 am »
Nice pictures.
Keithley also used the LTZ1000 - A version, and I somewhere found the hint, that it also runs on about 90°C, perhaps indirectly from the datasheet. It's as unstable per year as the 3458A...

Would you mind identifying the divider ratio of the LTZ1000A circuitry, for determining its temperature stabilization?

Maybe that's R268, the blue metal foil (?) divider beneath the 120 Ohm resistor, or the blue resistor (?? R265??) .

As those parts seems to be custom specific, the inscript may not tell the content, so please measure the resistances, please.

Thanks.

Datasheet: operating temperature is 0..50°C, similar to HP 3458A, therefore, also around 90°C required.
I meant R268, sorry, made a typo.
Looking for a 1k / 13...15k divider..
Frank
« Last Edit: February 19, 2014, 07:44:09 am by Dr. Frank »
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #7 on: February 19, 2014, 07:34:04 am »
R285 is 3K, 12K, 0.1%, 100MW, THINFILM, according to repair manual BOM
Other network R268 is 13.1K, 13.3K, 0.1%, 100MW, THINFILM.
PTF56's are 68.1K, 0.1%, 1/8W METAL FILM, and 120 ohm is .1%, .25W, PRECISION WIREWOUND
BJT is PXT3904.

I'll recover full schematics of 2002 later, as still have 2001 to finish up.  :-//
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Offline plesa

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #8 on: February 19, 2014, 07:44:39 pm »
Nice pictures.
Keithley also used the LTZ1000 - A version, and I somewhere found the hint, that it also runs on about 90°C, perhaps indirectly from the datasheet. It's as unstable per year as the 3458A...

Would you mind identifying the divider ratio of the LTZ1000A circuitry, for determining its temperature stabilization?

Maybe that's R268, the blue metal foil (?) divider beneath the 120 Ohm resistor, or the blue resistor (?? R265??) .

As those parts seems to be custom specific, the inscript may not tell the content, so please measure the resistances, please.

Thanks.

Datasheet: operating temperature is 0..50°C, similar to HP 3458A, therefore, also around 90°C required.
I meant R268, sorry, made a typo.
Looking for a 1k / 13...15k divider..
Frank

The resistance for temperature controll seems to be 80k.
 

Offline quarks

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #9 on: February 19, 2014, 08:03:12 pm »
Great post, thanks for sharing :-+
 

Offline mrflibble

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #10 on: February 19, 2014, 11:49:50 pm »
Very nice post! Thank you for taking the time to put that together. :)
 

Offline retiredcaps

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #11 on: February 20, 2014, 12:11:46 am »
Thank you for documenting another teardown.   :-+

It is unlikely I will ever have one of these so this is the next best thing.
 

Offline skipjackrc4

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #12 on: February 20, 2014, 12:19:27 am »
Thank you so much for that!  That thing sure looks nice.
 

Offline saturation

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #13 on: February 20, 2014, 12:50:21 pm »
Great work!  Thanks for sharing.
Best Wishes,

 Saturation
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #14 on: February 20, 2014, 01:05:53 pm »
One of neat features of 2002 - user accessible internal relative temperature. Calibration procedure include storing actual internal temperature, and then difference
can be shown any time.

I had +24.5°C in room, powered on cold meter, it show -22°C (minus means that current internal temperature is 22 lower, than one which was during calibration).
After 5 minutes idle running temperature difference raised quickly to -17c..



..after 38 minutes



Now meter was measuring LM399 output, logging readings every 20 seconds, temperature difference reached -4.8...-4.83 °C

This could be useful for volt-nutting, to strive to last ppms of absolute accuracy :)
« Last Edit: February 20, 2014, 01:11:39 pm by TiN »
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Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #15 on: February 23, 2014, 09:57:00 am »
Captured some thermal shots with Fluke Ti32 today.

LTZ1000A, had meter running a hour to warmup, then removed cover and captured shots (while still running).
Square thing on top of LTZ - is sticked piece of tape, to get surface temperature. (Because shiny metal on thermacam is just a reflection of nearest objects, not temperature of surface directly).

So surface temp of LTZ package is around +45°C. This is not die temp, as we have 400°C/W ?jc per datasheet.
Ambient was +26.2°C



More to come...
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Offline tszaboo

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #16 on: February 23, 2014, 11:02:30 am »
Subscribed to the thread. I'll check out carefully in my working hours though. Thank you for sharing!
 

Online Dr. Frank

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #17 on: February 23, 2014, 04:39:44 pm »
TiN,

would you mind measuring the BE voltage of the temperature sensing transistor Q2 of the LTZ1000A, to determine its stabilization temperature? That's pin 6 -7.

Thanks.
Frank
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #18 on: February 23, 2014, 06:24:46 pm »
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Offline Noise Floor

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #19 on: February 24, 2014, 01:42:18 am »
Great teardown, thanks.  :clap:
 

Offline riktw

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #20 on: February 24, 2014, 11:58:06 am »
Amazing teardown and very nice quality pictures.
I now want a DMM like that even more  :-[
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #21 on: February 27, 2014, 07:07:27 pm »
Reversed schematics of ADC module of 2002 ... Pretty big difference compared to K2001.


PNG-pic, 1000KB

PDF

Any idea how it works?  ;)
« Last Edit: July 22, 2014, 04:23:11 pm by TiN »
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Offline uoficowboy

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #22 on: February 27, 2014, 07:17:11 pm »
Reversed schematics of ADC module of 2002 ... Pretty big difference compared to K2001.

PNG-pic, 500KB
PDF

Any idea how it works?  ;)
Slightly off topic - but what is your technique for getting these schematics? I've been measuring out a board recently and would love any suggestions that might speed things up :)
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #23 on: February 27, 2014, 07:49:23 pm »
No any special technique. Just a trusty Fluke 87V in ohm mode with buzzer (it's much quicker response and not so much test voltage as in diode mode)
and one probe on component pad, and then poke every component on board, to trace where are connections, and draw schematics in ECAD.
Plus some common sense, like first i trace all power rails, decoupling, then connector nets, then digital stuff, then go to analog. Also I combine top and bottom side photos in photoshop,
and paint out already verified components, so would reduce hassle and not test same stuff over and over (as I do this usually few hours a day, sometimes with
weeks delays in between, so might forget what already traced).

Sometimes on bigger analog board i use Keithley 2400 in voltage source mode, output 1V, 1uA, set reference fail level to 0.01V, and trace components.
I have buzzer on digital output from K2400, so i can trace copper conductors only, not worrying about opening diodes or resistors like 2 ohm, etc.


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Offline anotherlin

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #24 on: February 28, 2014, 04:46:50 pm »
Reversed schematics of ADC module of 2002 ... Pretty big difference compared to K2001.

PNG-pic, 500KB
PDF

Any idea how it works?  ;)

Probably an integrating ADC ?

You mentionned you used "ECAD" for schematic capture, can you give a link to the website of this tool, please ?
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Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #25 on: March 04, 2014, 06:01:46 pm »
Reversed schematics of ADC module of 2002 ... Pretty big difference compared to K2001.

PNG-pic, 500KB
PDF

Any idea how it works?  ;)

Probably an integrating ADC ?

You mentionned you used "ECAD" for schematic capture, can you give a link to the website of this tool, please ?

Yes, it's integrating ADC, but not as usual/widely used schematic.

As for schematics tool - it's commercial Cadence Orcad. ECAD stands here for electronics-CAD :)
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Offline branadic

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #26 on: April 05, 2014, 04:23:20 pm »
Quote
would you mind measuring the BE voltage of the temperature sensing transistor Q2 of the LTZ1000A, to determine its stabilization temperature? That's pin 6 -7.

Tryed this today but without success. Couldn't work out where to find pin 6 on the topside of the pcb and I've to admit that I'm not prepared to take the device completely apart.
Would have helped if there were of photo of the pcb with backlight, to turn out the nessecary measurement point.
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Offline janaf

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #27 on: May 01, 2014, 06:04:49 pm »
Great post!

And my first post here  :)

And thanks for making an posting the schematics. Great work.

I'm really interested in how they implemented the ADC. After a look at the schematics, I can not really say I get any grasp except some blocks. but then I'm kind of new to ADC topologies.

Input anyone?

PS Pin 6 of the LTZ reference should most likely be connected to a precision resistor pair, with a ratio of about 1:13, i.e. 1K / 13K or similar.
my2C
Jan
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #28 on: July 13, 2014, 05:33:56 pm »
Hi all,

I got into 2002 again, recovered schematics of voltage reference section..

Quote
would you mind measuring the BE voltage of the temperature sensing transistor Q2 of the LTZ1000A, to determine its stabilization temperature? That's pin 6 -7.

It's 0.498322 VDC.

Schematics:



----

Some extra photoshoot:

If someone forgot how 2002 looks like...

.

Lovely custom VFD, same as 2001,24xx,26xx,700x series equipment from KEI.

.

A09 firmware and MEM2 hacked memory option :)

.

Calibration dates and 10V from EDC MV106.

.

1K0000 VPG VHP202 0.01% resistor.

.

Self-diagnostics test.

.

.

.

Back side same as 2001, and top side internals without cover.

.

ADC board removed, digital board is exactly hardware same as 2001.

.

.

Voltage reference output measurement from LTZ1000 and setup.
VREF Voltage is ~7.13491 VDC. To do more precise measurement it would require more complicated probing with all covers and shields on to ensure proper temperature stability.

.

R264 and R265 voltage measurement.

.

Emitter of Q204 (heater node of LTZ1000A) and MECCA to system common voltage delta.

.


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Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #29 on: July 13, 2014, 06:23:09 pm »
Alright, I'll check 13k/1k and 1.1k ratios with my LTZ ref's, to check if that's a typo in Keithley's manual.

I don't want to desolder resistor from instrument, yet  :-/O
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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #30 on: July 14, 2014, 11:48:37 am »
Hello TiN,
It's difficult to measure the resistance, when both R's are built in the circuitry.
Therefore the ratio can be better measured by the voltages across both R268, R269, as I proposed a bit ago.

I assume you measured 0.4392V on R265 or (+) OpAmp, (as shown in the photograph), which is virtually identical to the Ube voltage or (-) Opamp.
Therefore, the ratio is 7.1349V/0.4392V = 16.3.

That would mean the LTZ1000A is also running on >90°C.
That would also fit to the bad longterm stability, like the 3458A.


I don't understand right now the difference between the direct measurement on Ube (0.4983V), and the indirect one on R265 (0.4392V). Are you sure about the first value?

Frank
« Last Edit: July 14, 2014, 11:58:11 am by Dr. Frank »
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #31 on: July 14, 2014, 12:32:32 pm »
It may be difference in temperature, as everything was running open, just like on photos.
Both measurements were taken within 5 minutes from each other, so it may be due to difference of LTZ die temperature.
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Online Dr. Frank

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #32 on: July 14, 2014, 12:50:49 pm »
Well, measurements directly on Ube are very critical, as it may disturb the regulation.

That's a very sensitive node, and maybe you caused sort of oscillation by your DMM, or injected strong AC noise by the measurements leads, originating  from switching power supplies in your lab.

Frank
 

Online Dr. Frank

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #33 on: July 18, 2014, 07:59:42 am »
It may be difference in temperature, as everything was running open, just like on photos.
Both measurements were taken within 5 minutes from each other, so it may be due to difference of LTZ die temperature.

Hello TiN,

no that's definitely not the case!

First of all, there's a temperature stabilisation on the LTZ1000, which makes it nearly independant from outer temperature variations. The stabilization temperature may change by about 0.1..0.3 °C per °C external change only.

The observed difference of 0.498V directly on Ube and OP(-) vs. 0.439V on OP(+) is 59mV, which would be a difference of almost 30°C of the chip temperature!!
That can't be the explanation at all, as that would require an external RT change of at least 100°C.


Looking closer on your photographs, titled "R264 and R265 measurements", I discovered non appropriate cables, that you are using.

You use Kelvin clamps with 4 cables, but on a DCV measurement!
That means, that the two cables connected to Ohm Sense are hanging totally free in thin air, that means they act as antennas for all kind of AC disturbances, especially from switch mode power supplies.

If you measured the 0.498V on the sensitive node Ube the same way, that's no wonder, why it's so different to the 0.439V on the same OP. The AC noise, coupled in over these cables, is rectified by the BE diode and added to the DC bias. Maybe also, that those long cables let the OpAmp oscillate, as soon as you connect to the OP(-).

To avoid disturbances, switch off all switch mode PSUs on your bench, and use a pair of short, drilled twisted and/or shielded cables, being convenient for sensitive DCV measurement.

Measure at OP(-) (Ube) and OP(+), directly after each other, and both values have to agree within << 1mV.
( A residual injection of AC noise is expected).

It would be very kind, if you could repeat this measurement, please.

Frank
« Last Edit: July 18, 2014, 11:08:00 am by Dr. Frank »
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #34 on: July 18, 2014, 08:31:58 am »
Alright, you got it.

I'll open meter up and make a video for tube  :-DMM
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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #35 on: July 20, 2014, 05:07:56 pm »
Here are correct results, measured by cal'd K2001 with pair of Fluke 87V probes, twisted together.
The only switching power supplies in room is my workstation and monitors, which are around meter away + LED lights.
I repeated measurements without LED lights on - result was same.



Meas points. I probed all voltages on schematics just directly with probe touching leg of LT1013 SO8.



Video (values little differ because I shot it two times, so there was some time delay).

« Last Edit: July 20, 2014, 05:57:21 pm by TiN »
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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #36 on: July 20, 2014, 07:11:46 pm »
Hello TiN,
thanks a lot for re-measurement!

Now it's clearly proven, that the divider has a 14.3 ratio, which may be realized by a 13.3k / 1k divider.
This sets the stabilization temperature to about 70°C.
That should normally be good for about 1..2 ppm/a stability.


Therefore, the one year stability of the Keithley 2002 in the 20V range not only depends on the LTZ1000 reference, but additionally on range determining / gain resistors.
You may further re-engineer this instrument, to understand, how it operates exactly in the 2V / 20V ranges.

In contrast to that, the 3458A depends ONLY on its LTZ ref concerning its DCV longterm stability, as it features true autocal, which compensates for any gain drifts.
As no other DMM has that autocal function, all other DMM need ultra stable resistors for ranging/gain to achieve their high stability in the different DCV ranges... and also for the other modes.

Frank
« Last Edit: July 20, 2014, 07:43:39 pm by Dr. Frank »
 

Offline wiss

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #37 on: July 21, 2014, 10:59:25 am »
Reversed schematics of ADC module of 2002 ... Pretty big difference compared to K2001.

PNG-pic, 500KB
PDF

Any idea how it works?  ;)

Where is the integrator? What is the voltage-rating of C832?

Or do we have multiple integrators? U815 - U817?

What is up with U813? non-inverting input goes where?
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #38 on: July 22, 2014, 04:26:57 pm »
Where is the integrator? What is the voltage-rating of C832?

Or do we have multiple integrators? U815 - U817?

What is up with U813? non-inverting input goes where?

C832 and C833 are just thruhole ceramic caps for decoupling. :)
According to KI 2002 service/repair manual they are CAP, 2200P, 10%, 100V CERAMIC

U813 is fixed now, thanks for reporting.


PNG-pic, 1000KB

PDF
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Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #39 on: April 24, 2015, 02:38:22 pm »
Revive, revive!

Updated top post for faster photo loading, moved them to static serve, rather than repository engine post.

On of our members shared older firmware A06, and tadaaaa, MEM2 option contents.
It's DS1248Y NVRAM. I got it before and tried it, but was no luck... Hmmm.... Time to open 2002 up again and try again...

ODD ROM for A06
EVEN ROM for A06
MEM2 NVRAM dump

I saw one of 2002's on bay have A10 firmware, so mine is not latest..

His meter photos (it's made in 1997, 10 years older than one I have):







Digital board is exactly same as mine Rev K in both 2002 and 2001 with B-firmware
A/D board is same revision B too
Analog board is little different, his is Rev E, while mine is E-E5.

Differences so far spotted by eye:

* On digital board, mine does not have CR627,CR628,VR602,VR603 diodes on GPIB port (cost-down to save few pennies? :))
* R346 resistor assembly is different, using 4 ceramic substrate resistor networks, while mine just have two resistors glued together. Newer 2001 have similar network, while older ones (all mine) are just blue resistor network there.
* Optoisolation is same as 2001, while mine had wonky PCB with IL717 isolators.
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Offline ManateeMafia

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #40 on: May 02, 2015, 07:37:41 pm »
I installed a new DS1248Y and didn't get any error messages. The secret init command worked and I guess it is good for another 20 years. I think you may have a defective rtc in your nvram.
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #41 on: May 02, 2015, 09:03:54 pm »
Thanks for info. Probably my 1248's are fake or RTC faulty. I have two, both doing same stuff, bought from ebay from two different sellers.
They work fine as 1245, keeping data, so internal battery likely be okay...
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Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #42 on: May 14, 2015, 02:32:22 pm »
Another DS1248Y come, seems I got real lucky with fakes... different seller, same part, same result?



Here are "DS1248" chips I got and real DS1243 which was in 2002 as STD option.



You can spot DS1315 Phantom Time Chip in 1243, while nothing on "1248".



Tried to debunk it, but it's not so disassemble without nasty acids, so I just broke thing apart with pliers. There were two CR 3V batteries, SRAM die and PCB from looks of it.

Further destruction reveals DS1215 in it, so there is a phantom controller actually there.



To be exactly correct, chip does store it contents and works as DS1245 well, so it's not completely useless. I don't have programmer which can support DS1248, and not sure if it's worth the effort to borge some CPLD gear to try read registers in these DS1248's to see what's wrong

Data commands and diagrams both both are same at first glance, so not sure where is a caveat just yet.  :-//
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Offline ManateeMafia

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #43 on: May 14, 2015, 03:18:40 pm »
The DS1215 and DS1315 datasheets show a simple interface to SRAM. I wonder if you can reverse engineer the board to see if there is a design flaw? What are the odds one or more parts are also counterfeit? It looks like they normally have three lines printed below the DALLAS name, where your new parts have four.

I have attached a pic of the old and new DS1248Y for comparison.
 

Offline slurry

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #44 on: May 14, 2015, 03:43:52 pm »
I have attached a pic of the old and new DS1248Y for comparison.

Why would a serious manufacturer leave out the trashcan-symbol (batteries inside) on a later productions?,
it not like the rigorous environmental regulations for Electronics have been eased up and suddenly makes it OK to toss batteries with household garbage? - no way  :--

Based on only that i assume it is fake.
 

Offline ManateeMafia

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #45 on: May 14, 2015, 06:44:13 pm »
The top nvram is the new replacement. That is fully functional sourced from Mouser.
The bottom one is dated 1996 and actually still functions.
 

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #46 on: May 14, 2015, 07:02:20 pm »
ah, 1996..
the toss-it-anywhere-you-like-era before trashcan-symbols  ;)
 

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #47 on: June 12, 2015, 04:43:32 am »
Bingo, TL866 got new software 6.13 which finally supports DS1245 NVRAM.



Now I finally was able to erase and programm my DS1248Y to get MEM2 and RTC going on 2002.




Steps, NVRAM dump and details for those who interested here, as usual.
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Offline VintageNut

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #48 on: June 14, 2015, 02:54:55 am »
That is a truly spectacular result. Congratulations for making the memory upgrade work. I want one very much.

I used a 2002 to (attempt to) linearize my Fluke 332A using the 20V range of the 2002. When I moved to the 200V range of the 2002, it appeared that the 2002 was more than 25ppm off measuring 100V.

There appeared to be almost perfect agreement for the 2V range compared to the 20V range but not good agreement for the 200V range and 1000V range.

Do you have a way to compare the 20V range to the 200V range? The best way is a 100V source and a Kelvin Varley Divider.
working instruments :Keithley 260,261,2750,7708, 2000 (calibrated), 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD, Fluke 731B X2 (calibrated), Fluke 5450A (calibrated)
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #49 on: June 14, 2015, 10:39:22 am »
I don't have anything stable enough for high voltages just yet, if not counting 2400 SMU for that.
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Offline VintageNut

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #50 on: June 14, 2015, 12:55:40 pm »
I don't have anything stable enough for high voltages just yet, if not counting 2400 SMU for that.
The 2400 is a good idea. It is not necessarily accurate enough, but it may be stable enough.

Let both 2400 and 2002 warm up for 3 hours. Local sense on the 2400 is probably good enough for this test. Set the 2002 for 20VDC, 10NPLC, 10 Digital Filter, Window:NONE, Filter Type:REPEAT. Resolution 8.5 digits.

Set the 2400 to output 10V. Turn output on.  On the 2002 turn the filter off. Filter on. Record the reading on the 2002 after a minute or two for settling.

Do not change anything on the 2400.

Change range on the 2002 to 200V DC. Filter off. Filter on. (saves time) Record the reading on the 2002 after a minute or two for settling.

Change range on the 2002 to 20V DC.

Set the 2400 to output 20V. Filter off. Filter on. Record the reading on the 2002 after a minute or two for settling.

Do not change anything on the 2400.

Change range on the 2002 to 200V DC. Filter off. Filter on.  Record the reading on the 2002 after a minute or two for settling.

Set the 2400 to output 100V. Filter off. Filter on. Record the reading on the 2002 after a minute or two for settling.

Set the 2400 to output 200V. Filter off. Filter on. Record the reading on the 2002 after a minute or two for settling.

The last two steps may not indicate anything but they should be included for completeness.

Post a table of results and we can see if there are any obvious differences between the 20V and 200V DC measure ranges on the 2002. The 2002 I used had a noticeable repeatable offset between the ranges. 


« Last Edit: June 14, 2015, 12:58:56 pm by VintageNut »
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Online Dr. Frank

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #51 on: June 14, 2015, 01:53:43 pm »
You need a precise 10:1 and a 100:1 transfer to calibrate 100V and 1kV.
Additionally, the 100:1 transfer on 1kV level must be compensated for self heating effects, which is quite difficult to realize.


Either a KV divider like the 720A or the Keithley 2002 might provide a 10:1 transfer from 10V to 100V, with about 1ppm uncertainty.

(Both are linear to 0.1ppm of input, that is 1ppm of output).

So your proposed transfer from 20V range to 200V range might  work, but I recommend to do the transfer from 10 to 100V, instead of 20 to 200V.
The 200V self heating might already affect the 2002 accuracy.

The self heating effect inside the 2002 HV divider will kill your uncertainty if you try to transfer from 100V to 1kV, as it is having about 20ppm heating effect, see footnote (9) in the specification.

Therefore, you'll need a Hammon type transfer standard, like the Fluke 752A or similar.

This has 0.2ppm of output for 10:1 and 0.5ppm of output for 100:1 transfer, latter including self heating effects.

As I also wanted to calibrate my former 332B/AF, I've designed my own ratio transfer standard, estimated (by design and by measurements) to have 0.5 and 1ppm transfer capability.
It's been described somewhere else on EEVBlog.

Frank
« Last Edit: June 14, 2015, 02:12:50 pm by Dr. Frank »
 

Offline VintageNut

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #52 on: June 14, 2015, 02:43:56 pm »
Hi Dr. Frank

You make very good points and I will have to do some reading to understand some of what you discuss.

The only reason for my suggestion TiN is that the 2002 I used (it was within the 1 year calibration)  seemed to be out of spec measuring 100V on the 200V range. This was demonstrable by measuring a stable voltage on the 20V range and immediately measuring that voltage on the 200V range.
working instruments :Keithley 260,261,2750,7708, 2000 (calibrated), 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD, Fluke 731B X2 (calibrated), Fluke 5450A (calibrated)
 

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #53 on: July 21, 2015, 06:44:42 pm »
Bingo, TL866 got new software 6.13 which finally supports DS1245 NVRAM.
Steps, NVRAM dump and details for those who interested here, as usual.

Just upgrade my 2002 from STD to MEM2 (128k). With Dallas DS1248Y-70+ without programmer, only through secret menu and works OK on FW A09.
Thanks for sharing info.
« Last Edit: July 21, 2015, 07:11:52 pm by plesa »
 

Offline egonotto

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #54 on: July 22, 2015, 12:31:54 am »
Hello,


in the video https://youtu.be/v887C9I9hCE one sees the noise of a shortend
Keithley 2001.
Is these in a Keithley 2002 similar?
When yes, what is the last digit worth?

Best Regards
egonotto


 

Offline ruffy91

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #55 on: July 22, 2015, 04:39:34 am »
I think you're measuring the thermoelectric effect, not noise. Try to touch each side of the shorting jumper. The voltage should go up when touching near the positive input and down when touching near the negative input (or inverse).
 

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #56 on: July 22, 2015, 05:40:47 am »
Hello,

thanks for the answer. It can be, but for the Keithley 2010 you can find DC NOISE PERFORMANCE.
For instance for 5PLC 7,5 Digits and 100mV Range they have 110 nV RMS (2 min).

In Video https://youtu.be/J1tCSehiNyM they show a example at times 6:00.
They got a STD DEV from 71 nV. So the last digit seams meaningless.

Best regards
egonotto
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #57 on: July 22, 2015, 11:27:36 am »
2002 have less bouncing for last digits.

plesa
Did you managed to fix your 2002? :)
Thanks should also go to ManateeMafia, as he was the one to confirm that 2002 using DS1248.
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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #58 on: July 22, 2015, 04:43:27 pm »
Repair is in progress, last time I suspected Q211 and Q212 (3N163 and 2N3906) both were OK.
I can confirm that with the 5V version (DS1248Y-70+) it works like charm.
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #59 on: December 26, 2015, 04:07:54 pm »
One of our members uploaded Keithley 2002 A10 firmware, thanks! I did not see it anywhere before, so far.

I need to get new UV EPROMs to try it, as mine meter came with OTP ROMs without UV window :(.
ROM binaries available for grabs, as always

P.S. Also added internal photos of 2440 SMU.
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Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #60 on: December 26, 2015, 05:36:20 pm »
I did few tests before, with results here and here. CSV files with short on terminals (no leads) are there as well.
10 or 1NPLC 20VDC range results noise ~0.4-0.8uV.

Perhaps you can post your data?
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Offline Macbeth

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #61 on: December 26, 2015, 05:38:36 pm »
I need to get new UV EPROMs to try it, as mine meter came with OTP ROMs without UV window :(.
Is there not an EEPROM Flash available? I would imagine much cheaper and more convenient than old UV EPROMS.

For my K2000 and K2015 I've found a pair of AM29F040B work perfectly as replacements for the OTP despite being twice the capacity and a fraction of the price. Easy reprogramming on the TL866 is a bonus!
« Last Edit: December 26, 2015, 05:42:09 pm by Macbeth »
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #62 on: December 26, 2015, 05:48:26 pm »
I don't mind oldschool UV erasure, more fun to it. Was looking on 29F040 but those have A18, VPP, WE~ pins different from OTP ROM in my meter, so I did not want to do bodgery and jumpwiring in case it would not work drop in.
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Offline Macbeth

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #63 on: December 26, 2015, 05:56:56 pm »
so I did not want to do bodgery and jumpwiring in case it would not work drop in.
Hahaha! When have you ever NOT done bodgery and jump wires  :-DD

But yeah, I haven't had to do that at all in my case. Of course if yours are wired up different then I agree.

I'm also annoyed at finding an old school 27C256 UV EPROM that despite an hour total in my PCB UV exposure box it didn't erase anything! Wrong wavelength it seems.
 

Offline SeanB

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #64 on: December 26, 2015, 06:08:31 pm »
125W mercury vapour arc tube at 2cm from the Eprom for 5 minutes pretty much guarantees erasure, or a melted EPROM. My first eraser was one with a 20W choke ballast, inside a box with a "safety" microswitch. Pretty much cooked the plastic box after a year or so, being used for 5 minute increments.
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #65 on: December 26, 2015, 06:36:20 pm »
Remove any leads and just toss piece of fresh-cut copper wire into terminals. Secure them with ear cotton swabs (tin's patented technology), so you get nice contact there.
Keep any LED/CCFL or other equipment away from meter. Let it sit for 1 hour at least to warm up. Repeat measurements.
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Offline Macbeth

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #66 on: December 26, 2015, 06:45:21 pm »
Remove any leads and just toss piece of fresh-cut copper wire into terminals. Secure them with ear cotton swabs (tin's patented technology), so you get nice contact there.
Keep any LED/CCFL or other equipment away from meter. Let it sit for 1 hour at least to warm up. Repeat measurements.
Hahaha. I am not the only one to do this it seems! I even bought a length of copper bar to turn on my little lathe and then worried about oxidation. Looked into gold plating thinking a simple electrolysis would do the job and soon realised that aqua regia, etc, is not so easy.

Just stripping some mains flex and jamming in with ear buds seems to do ok!
 

Offline plesa

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #67 on: December 26, 2015, 07:07:33 pm »
I just built a very short banana jack short, and the result is the same.

Another strange thing is in ACmV mode the noise is lower than DCmV, only less than 2uV pp, most of the time it is just 1uV pp.

The DCmV noise is now 12uV pp, at 8.5 digit, 1PLC, no filter, line sync ADC, line sync zero.

I think I will return this thing before its 30 day warranty expires.

As TiN mentioned use clean copper wire and also do not forget to clean input terminals (oxide cleaner like Deoxit or Kontakt Chemie Kontakt 61).
Before returning unit I will rather ask for discount instead of returning such a good meter :)
 

Offline plesa

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #68 on: December 26, 2015, 07:26:10 pm »
I just built a very short banana jack short, and the result is the same.

Another strange thing is in ACmV mode the noise is lower than DCmV, only less than 2uV pp, most of the time it is just 1uV pp.

The DCmV noise is now 12uV pp, at 8.5 digit, 1PLC, no filter, line sync ADC, line sync zero.

I think I will return this thing before its 30 day warranty expires.

As TiN mentioned use clean copper wire and also do not forget to clean input terminals (oxide cleaner like Deoxit or Kontakt Chemie Kontakt 61).
Before returning unit I will rather ask for discount instead of returning such a good meter :)

Just did exactly what TiN suggested. No improvements at all.
Same results form front and rear terminals? What about cleaning input jacks?
 

Offline plesa

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #69 on: December 26, 2015, 07:37:35 pm »
I don't mind oldschool UV erasure, more fun to it. Was looking on 29F040 but those have A18, VPP, WE~ pins different from OTP ROM in my meter, so I did not want to do bodgery and jumpwiring in case it would not work drop in.

Which type you are using? I would like to upgrade C05 to 6517A electrometer with upgrade 2002 to A10.
I remember that for some Keithley firmware there was mentioned in attached document what are the compatible chips.
 

Offline plesa

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #70 on: December 26, 2015, 08:26:39 pm »
Same results form front and rear terminals? What about cleaning input jacks?

The rear jacks are WTF. It reads ~50mV when shorted, and drifts heavily that can not be effectively RELed. Definitely needs a return.

By rear jacks I mean banana socket on rear side, this can help to isolate issue with front/rear switch. It depends on price you paid for it ($2k for working and $500 for not working unit). Keithley gear is good candidate for repairs ( K2002 is based on of the shelf components).
Did you pass self test after warm up?
 

Offline plesa

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #71 on: December 26, 2015, 08:40:03 pm »
All tests passed, this unit comes with a fresh cal cert, I paid 3k for it. I already contacted the seller, since I do not want to mess around with it. I paid 3k, not 500, so I do not want to destroy it by a mistake.
After receiving this refund, I will go for a low noise one, maybe a 7050, or wait until Keithley releases 8050. I do not need one urgently, since I have access to a 3458.

Oh now I understand it. 8050 or 8510 (join venture with Danaher/Fluke 8508A) seems to be in Volt nuts dreams more and more often :)
 

Offline plesa

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #72 on: December 30, 2015, 04:07:12 pm »
One of our members uploaded Keithley 2002 A10 firmware, thanks! I did not see it anywhere before, so far.

I need to get new UV EPROMs to try it, as mine meter came with OTP ROMs without UV window :(.
ROM binaries available for grabs, as always

P.S. Also added internal photos of 2440 SMU.

Sucessfully upgraded from A9 to A10 firmware. Used EPROMS were UV erasable 27C4001 and not OTP.
 

Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #73 on: December 31, 2015, 12:57:42 am »
Did you get 9th digit now? :)
I wish we could know what's changed. My UV chips are on their way in postal system.
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Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #74 on: January 28, 2016, 08:01:47 pm »
Updated ROMs to A10. Everything works OK, no recal needed.

Btw, I compared A06 and A09 firmwares, and here's what I found:

Firmware version A09 added next:
* Support for Type N thermocouples
* Support for SPRTD which was absent in A06
* New format setting : HPR (HPRECISION)
* Unknown command ISN?
* Coefficient settings for SPRTD: A4, B4, A7, B7, C7
* RTD custom user setting RZERO, RZER, to set resistance at 0°C
* It also seems that A06 have also only 9 settings profiles (SAV0 to SAV8), while A09 and later have 10 (SAV0 to SAV9).

No strings difference between A09 and A10  :'(
« Last Edit: January 29, 2016, 02:23:37 am by TiN »
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Offline ManateeMafia

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #75 on: January 29, 2016, 05:02:13 am »
Thanks for the list of improvements, I guess my A06 fw needs upgrading too. More vacation time is needed.
 

Offline zlymex

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #76 on: September 14, 2016, 02:32:13 am »
Thanks very much for the teardown.
I once had a broken 2002(with Ver. 06 firmware I think), broken display with cover plastic missing.
I replace them with those from 7001.
 
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Offline TiNTopic starter

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Re: Keithley 2002 8.5 digit DMM review and teardown
« Reply #77 on: September 14, 2016, 04:15:56 am »
It was your fault, zlymex that I got into Keithley's in first place  :-DD.
Thanks for your countless threads and photos here and at 38hot BBS. I can't read any chinese, so pictures help a lot!  :clap:
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