| Products > Test Equipment |
| Keithley 193 vs 196 |
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| 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:
--- Quote from: TurboTom on July 18, 2022, 02:45:54 pm ---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... --- End quote --- 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. --- Quote from: Kleinstein on July 18, 2022, 03:42:37 pm ---... 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. --- End quote --- 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. --- Quote from: alm on July 18, 2022, 04:46:38 pm ---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. --- End quote --- Yes the 196 definitly seems to be the better option. --- Quote from: alm on July 18, 2022, 05:06:43 pm ---Which buttons do you dislike? The square ones that tend to fall off, ... --- End quote --- :-DD 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:
--- Quote from: Traceless on July 18, 2022, 08:28:57 pm ---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. --- End quote --- HP definitely used more proprietary parts, although the popularity means spare parts and boards are more likely to be available. --- Quote from: Traceless on July 18, 2022, 08:28:57 pm ---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. --- End quote --- 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. |
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