Keithley 2000 vs 2000-20 What's the difference?

[voltsandjolts]

I have a K2000 DMM (2006 vintage, latest firmware) which probably won't support a 20 channel scan card.
I say that because there is a specific version (K2000-20) which does support a 20 channel card.
Does anyone know what the differences are between K2000 and K2000-20?
Is it just firmware?
They certainly look identical.

[eplpwr]

Interesting questions.

I don't have any answers, just more questions: Is the 20-ch card supported in K2001, K2002, K2010? If so, is certain firmware versions req'd?

[alm]

I bought a Keithley 2000-20 without the card a couple of years ago (because it was much cheaper than a normal Keithley 2000, and identical apart from the scanner as far as I can tell). I thought that the connector for the scanner card looked different from the one in the normal Keithley 2000, but I don't know for sure, and don't have any pictures. If you want, I could check, but it's a bit of a project because there is some other equipment stacked on top, so it would involve disconnecting and moving some other equipment. From the manual, it seems like it's backwards compatible, so my memory may well be wrong (source):


If that's the case, it might be only firmware, but then I wonder why they bothered releasing a different model, instead of just developing a firmware update, like they did for some of the other cards.

[voltsandjolts]

The Model 2000-SCAN 10-Channel works with Keithley 2000, 2010, 2001, 2002 and DMM6500.

Seems that DMM6500 also supports 20 channel card on default firmware:
https://www.eevblog.com/forum/testgear/new-keithley-dmm6500/msg2401032/#msg2401032

So, in theory, all the other meters should just need appropriate firmware to support a 20 channel card.

I thought that perhaps K2000-20 firmware could be programmed into a K2000 to enable 20 channel scan card.
But maybe there are other differences.

If that's the case, it might be only firmware, but then I wonder why they bothered releasing a different model, instead of just developing a firmware update, like they did for some of the other cards.

Hmm, good question. Was it for technical or marketing reason?

[TheUnnamedNewbie]

It might be an updated model with some parts replaced to deal with obsolescence or such, but to keep backwards compatibility with existing ATP and integrated systems using the meter?

[voltsandjolts]

I don't think so because the K2000-20 is no longer available but the K2000 is still on sale, for now.

[alm]

Seems that DMM6500 also supports 20 channel card on default firmware

That shows that the DMM6500 supports a 20 channel card, not necessarily the Keithley 2000-SCAN-20. Though it makes it plausible to me that it would work.

So, in theory, all the other meters should just need appropriate firmware to support a 20 channel card.

I thought that perhaps K2000-20 firmware could be programmed into a K2000 to enable 20 channel scan card.

If you're feeling adventurous and want to try flashing the 2000-20 firmware into the 2000, I could look into dumping the firmware of my Keithley 2000-20 (if this is not yet available on the usual sites like xdevs.com and ko4bb) and taking some pictures. I have a model 2000 that needs repair that I could use for comparison. Probably wouldn't happen this week, though. No warranty against corrupting the calibration memory

I find it interesting indeed that the Keithley 2000-20 was released as a different model, and then discontinued before the normal model 2000. Was it marketing? Aiming for a specific big contract, like an army contract? Like the Keithley 2001-M? Or did they need some hardware changes, like running extra 'address' lines, or different power requirements?

[voltsandjolts]

Thanks for the offer alm.
It seems there is very little information out there on the K2000-20, I poked around the internet for firmware but nothing found.
I'm sure TiN would appreciate a copy of the firmware on xdevs!

I am tempted to try 2000-20 firmware in the 2000, so if you can provide that would be great.
No hurry though, I have another K2000 and 10 channel card on order to get me through this next job.
I might have time next month to try the firmware change.

[alm]

Okay, I'll look into digging out the K2000-20 and dumping its firmware when I have time. I'd also take some pictures while I have it taken apart.

I'm curious, have you seen the K2000-SCAN-20 card for sale? Or are you considering building your own 20 channel card?

[voltsandjolts]

OK, thanks alm.
20 channel cards appear on evilBay every so often but I'll just make my own.

[alm]

Keithley 2000-20

This weekend I took both the Keithley 2000-20 and a Keithley 2000 (with to be diagnosed fault in the digital part) apart, took pictures, and dumped their firmware and EEPROM. This post contains the data on the Keithley 2000-20, and my subsequent post will contain the pictures of the Keithley 2000.

The most obvious place in my mind, would be the board that connects to the scanner:



Then the main board, containing both digital and analog electronics:


The card slot itself:



The firmware OTP ROMs have 2000-803/804 numbers. This unit has firmware revision A08. I also dumped the I2C EEPROM. I extracted the EEPROM in circuit with the DMM powered off, and a SOIC-8 IC clip connected to a GQ-4X programmer. The TL-866 failed to find the device under the same conditions, quite possibly because it could not supply the VCC to power the entire board. The GQ-4X read and verified without problem, however, and the results look sensible to me. The odd and even ROM images and calibration EEPROM are in this zip file (because of forum attachment limitations):
 Keithley 2000-20 firmware.zip (135.42 kB - downloaded 41 times.)

[alm]

Standard Keithley 2000


The scanner connector board:



Main board:


The Keithley 2000 had firmware revision A12, which is available on xdevs, though surprisingly the odd ROM was very different from the one on xdevs.com, while the even one was identical. I'm wonder if this unit has corrupted ROMs related to the digital fault, or if there is something wrong with the firmware on xdevs.com. A zip file with the ROM images and EEPROM for this unit is here:
 Keithley 2000 firmware.zip (135.25 kB - downloaded 26 times.)

[alm]

Comparison
The boards have the same part numbers, and I did not notice any difference between the PCBs apart from ROM versions. Feel free to study the pictures and see if I missed anything. I was expecting maybe a jumper to be different, a beefed up power supply, or some extra traces ran to the scanner.

The Keithley 2000-20 identifies itself like any other unit via GPIB, no change in the model number:
KEITHLEY INSTRUMENTS INC.,MODEL 2000,0698950,A08  /A02

In no way that I can see does the unit identify itself differently. A superficial glance at the EEPROM differences looks like the differences just concern different calibration constants, serial number and checksum, although it's definitely possible that there is a flag in there somewhere:


So right now it looks to me like the -20 designation was just to identify the unit as bundled with a scanner card. Somewhat similar to how Tektronix had the AM503S, which was just a bundle of a TM502A mainframe, AM503 amplifier plugin and storage drawer plugin. It may be that only certain firmware versions support the 2000-SCAN-20.

Let me know if there's anything else you want me to check. Probably in a couple of days, the Keithley 2000-20 will go back in the stack, and will be much more of a hassle to get out.

My suggestions for trying to use a 20 channel scanner in a standard Keithley 2000 would be to first test if it just works, if not, try using the A08 firmware that I attached, and if that still does not work, maybe try loading the EEPROM dump I uploaded, with the obvious caveat that it will mess up your calibration and serial number, so better make a backup first. If the EEPROM replacement works, then it might be worth trying to isolate which byte is causing the difference.

[voltsandjolts]

Wow, thanks for all that info alm!

It is encouraging that there are no obvious visual differences and, as you say, it identified as K2000 also.
You are right, I should try the 20 channel card in my standard K2000 just in case it works out-of-the-box.

I am waiting for PCBs for a switchable 10 / 20 channel card to arrive, pics attached. Hopefully I will get some time to build and experiment in next couple of weeks.

[voltsandjolts]

Well, I'm very surprised to find that my K2000 does indeed work with 20 channels cards without modification.
I had no idea! Maybe all K2000 owners knew except me!
Perhaps this feature was added to the K2000 firmware after the 2000-20 was withdrawn 

Thank you, alm, for being so helpful. I wouldn't have started the project if you had not offered to read out the 2000-20 firmware.

20 channel solid state scan card details here:

https://www.eevblog.com/forum/circuit-studio/example-project-20-channel-solid-state-scan-card-for-k2000-dmm/

or 10 channel armature if you prefer here:

https://www.eevblog.com/forum/circuit-studio/example-project-relay-scan-card-for-k2000-dmm/