Keithley 193 vs 196

[Traceless]

Does anyone have experience with old Keithley meters and happens to know if there is any significant difference between the Keithley 196 and the 193, except the form-factor? They both seem to be 6.5 digit DMMs from the same era.

[AVGresponding]

Their respective user manuals indicate the 196 has better ultimate accuracy, and is a 3,000,000 count readout as opposed to 2,000,000.

[Kleinstein]

TheK196 only has 300 V ranges as the maximum, while the 193 goes to 1000 V.

[kawal]

Both are good meters and have very nice display.

[Traceless]

Thanks @AVGresponding and @Kleinstein for pointing out the differences in accuracy, and volts range. I also saw that the 193 manual talks about AC/DC amps options (namely Option 1930 and 1931), whereas the 196 manual does not speak of an "option" does that mean the 193 may lack those features and the 196 always has those? Were those options modular?

[TurboTom]

The 196 comes full-featured, no range options or whatever. It's got a lightning-fast autorange and in general, considering its age and the price you can sometimes get it for at the second hand market, is a very good choice, provided the 300V limit isn't a problem for your usage case.

I haven't got a 193 so no comment on that one. The 195A (one may consider it the predecessor to the 196) also requires an option (1950) in order to enable it to measure AC signals and currents. Seems like Keithley considered it a good option to milk more cash from the customers these days, or maybe many of those instruments were really only used in fixed installations that didn't require AC or current ranges...

One more nice detail of those "brownie" series of instruments is that they are made of more or less standard parts (unless you need a mains transformer...) and full service documentation is available. On the down side, from a mechanical point of view they leave a lot to wish for, instruments with heavy mains transformers (220 / 230 current /voltage sources, 617 electrometer to name a few) may suffer internal damage during transport. Also broken plastic casings are not unheard of.

My advise would be: If you can get the Keithley multimeter for comparably little money and you're prepared to repair/tinker if necessary, go for it. If you want a troublefree daily driver, get something more modern...

[Kleinstein]

At the time it was not so uncommon to have the AC functions as an option. Many old Fluke meters also had the AC part optional. The RMS converter and fast amplifier with trim for the compensation added quite a bit to the costs.  Because the physical size it anyway made sense to split the circuit over multiple boards - with some older meters also the current ranges were optional on a separate board.
I would still expect the AC option to usually be installed at the factory and rarely later by the user.

For use in an automated test system the AC functions are rarely used. So quite a few of the meters that can get away without it.

[alm]

The 193 also needs an option for ACV (1930), DC current (1931) and AC current (1930+1931). Without those options it would be less versatile than the more modern 196.

The 196's form factor would make it more convenient for bench use. The 196 has offset compensated ohms which as far as I know the 193 doesn't have, while the 193 can measure AC+DC voltage in addition to AC voltage, while the 196 can only measure the AC component and you have to measure the DC separately and calculate the root of sum of squares. Based on this, I'd prefer the 196.

Their respective user manuals indicate the 196 has better ultimate accuracy, and is a 3,000,000 count readout as opposed to 2,000,000.

Careful, the Keithley 193 (from 1985) is 5.5 digit, 200,000 counts, while only the later 193A, which came out around the same time as the 196, is 6.5 digit, 2,000,000 counts. Looks like they might have used some of the improvements developed for the 196 to upgrade the 193 to also 6.5 digit. The 196 also has a 5.5 digit sibling: the 199 which has the same form factor and most features except offset compensated Ohms.

My advise would be: If you can get the Keithley multimeter for comparably little money and you're prepared to repair/tinker if necessary, go for it. If you want a troublefree daily driver, get something more modern...

I use a 199 (very similar to the 196) as my daily driver for things where the handheld doesn't do well (like monitoring things) and I don't need more than 5.5 digits or functions it doesn't have (diode test and continuity are the ones I miss most). I got them cheap. I find the user interface very easy (just press the button for the function you need), and the display is excellent and readable from pretty much any angle, distance or lighting. Easier to read than a VFD in my opinion, never mind LCD.

[AVGresponding]

I think the only thing about the Brown Boxes that I don't like is the godawful buttons.

[alm]

Which buttons do you dislike? The square ones that tend to fall off, like on the older brown boxes like the 192/195(A) and 220/230? Or the rectangular ones that feel more like tactile buttons in the later 196/199/617/263? I think the later buttons are fine, and the earlier buttons are usable as long as they don't fall off.

[AVGresponding]

I've a 195A, with several of the buttons n/f. I ended up buying a cheap 705 to use as a donor, but in all honesty it's still in the repair queue.

[Traceless]

The 196 comes full-featured, no range options or whatever. It's got a lightning-fast autorange and in general, considering its age and the price you can sometimes get it for at the second hand market, is a very good choice, provided the 300V limit isn't a problem for your usage case.

I haven't got a 193 so no comment on that one. The 195A (one may consider it the predecessor to the 196) also requires an option (1950) in order to enable it to measure AC signals and currents. Seems like Keithley considered it a good option to milk more cash from the customers these days, or maybe many of those instruments were really only used in fixed installations that didn't require AC or current ranges...

One more nice detail of those "brownie" series of instruments is that they are made of more or less standard parts (unless you need a mains transformer...) and full service documentation is available. On the down side, from a mechanical point of view they leave a lot to wish for, instruments with heavy mains transdormers (220 / 230 current /voltage sources, 617 electrometer to name a few) may suffer internal damage during transport. Also broken plastic casings are not unheard of.

My advise would be: If you can get the Keithley multimeter for comparably little money and you're prepared to repair/tinker if necessary, go for it. If you want a troublefree daily driver, get something more modern...

Thank you Tom, actually I already have two bench DMMs (4.5 digit and a 6.5 digit), which I use as daily drivers. If I have to go > 300V I could always use those. The actual reason I'm looking for a used DMM is that I'm curious to learn more about how DMMs work internally and thus thought it might be a good idea to get an older DMM that is cosmetically still in decent shape but may require some repairs as a fun project/learning experience. Personally I really love the old HP instruments like the 3455A, 3456A, 3457A and of course the 3458A (who doesn't love the 3458A ). The 345XAs seem to be really hard to get in Germany for a reasonable price (well, the 3458A is probably hard to get anywhere). The old Keithleys seem to be on offer more frequently, less expensive and are also well documented. Since you mentioned the Keithleys are mostly made of standard parts, they are probably even better suited for a restoration project than I initially expected. I assume HP spare parts will be a lot more proprietary.

... with some older meters also the current ranges were optional on a separate board.
I would still expect the AC option to usually be installed at the factory and rarely later by the user.

For use in an automated test system the AC functions are rarely used. So quite a few of the meters that can get away without it.

You are probably right that most original owners ordered the options they needed from the factory and didn't upgrade later. I'm more curious if those options came as daughter-boards that can be added in later or if upgrading to those options actually implies a mainboard swap. If the options are available as upgrades I could consider cheaper offers without options installed and install the upgrades afterwards. Otherwise I'd have to keep looking for meters with all options installed. Another question in this context is of course, if the upgrades are even available on the market seperately. Alternatively it might even be a nice exercise to redesign the options from the documentation, have boards made by PCBWay and then assemble them manually. Not sure yet how feasible that is though.

The 193 also needs an option for ACV (1930), DC current (1931) and AC current (1930+1931). Without those options it would be less versatile than the more modern 196.

Yes the 196 definitly seems to be the better option.

Which buttons do you dislike? The square ones that tend to fall off, ...

That comment made my day - @alm, @AVGresponding: Is there a proper fix for the 192/195 buttons or would you recommend to just go for a 196 instead?

[alm]

Since you mentioned the Keithleys are mostly made of standard parts, they are probably even better suited for a restoration project than I initially expected. I assume HP spare parts will be a lot more proprietary.

HP definitely used more proprietary parts, although the popularity means spare parts and boards are more likely to be available.

You are probably right that most original owners ordered the options they needed from the factory and didn't upgrade later. I'm more curious if those options came as daughter-boards that can be added in later or if upgrading to those options actually implies a mainboard swap. If the options are available as upgrades I could consider cheaper offers without options installed and install the upgrades afterwards. Otherwise I'd have to keep looking for meters with all options installed. Another question in this context is of course, if the upgrades are even available on the market seperately. Alternatively it might even be a nice exercise to redesign the options from the documentation, have boards made by PCBWay and then assemble them manually. Not sure yet how feasible that is though.

What I've seen in Keithley, Datron and Fluke meters are generally daughter boards that could in theory be field upgradable, though I'm not sure if they were ever sold as such. In addition to the daughter board you may need to change some wires or jumpers. The service manual or schematic might make installation evident. Occasionally different options are mutually exclusive. Like some DMMs have both an average-responding AC and true RMS AC option, but only one can be installed at a time. This doesn't appear the case for the 193. You can see the option 1930 and 1931 daughter boards in the 193 teardown you linked to.

However, except for popular meters that are often parted out like the Fluke 8840A, I think it's very rare for those daughterboards to be offered for sale. So I'd say your best bet is to either buy a meter with all the options (careful that you can't 100% count on the markings on the back matching the actual installed hardware), or buy a parts unit with the options you want.

Cloning should in theory be possible, except for firmware or custom ICs that might be on the boards. Also for AC the layout and grounding may be somewhat critical.