Products > Test Equipment
Keithley 197A owners' corner
Kinkless Tetrode:
Hi all, I'm a new proud owner of a couple the Keithley 197 (Military Version AN/USM-486A) units. I bought them from a seller who must have got them from a military surplus auction, and other than some desert dust on them, they are both in great condition. I don't know if and when they were last calibrated, but the two units read very closely to each other; within about 10 mV on the 200 mV range.
Does anybody have any idea how common this military model is compared to the regular 197/A models? Or, how long they were in production? Other than the references given earlier in this thread, I really don't see anything mentioned about them on the internet.
Thanks.
rastro:
--- Quote from: Kinkless Tetrode on June 16, 2019, 09:47:37 am ---...
Does anybody have any idea how common this military model is compared to the regular 197/A models? Or, how long they were in production? Other than the references given earlier in this thread, I really don't see anything mentioned about them on the internet.
Thanks.
--- End quote ---
Congratulations on your purchase.
I am not sure about the history of the 197 line but here are some observations:
- Based on the technology the military model came out after the original 197/A models
- The 197M(AN/USM-486A) shows a date of December 1994.
- Last year I came across two 197A models that did not have back light but had the new processor like the military mother board but without the 10A current fuse. Date on the that motherboard was 1992.
- I bought my initial 4 military models about 5 years ago new old stock from an auction house - this was an uncommon find at the time.
- In the last 2 years I've seen more military models showing up on ebay; usually new/lightly used. Probably the US govt getting around to purging old stock.
Anyway I think the military model is the best choice if you don't need the back-light or GPIB option.
rastro
Kinkless Tetrode:
--- Quote from: rastro on June 16, 2019, 02:36:29 pm ---
--- Quote from: Kinkless Tetrode on June 16, 2019, 09:47:37 am ---...
Does anybody have any idea how common this military model is compared to the regular 197/A models? Or, how long they were in production? Other than the references given earlier in this thread, I really don't see anything mentioned about them on the internet.
Thanks.
--- End quote ---
Congratulations on your purchase.
I am not sure about the history of the 197 line but here are some observations:
- Based on the technology the military model came out after the original 197/A models
- The 197M(AN/USM-486A) shows a date of December 1994.
- Last year I came across two 197A models that did not have back light but had the new processor like the military mother board but without the 10A current fuse. Date on the that motherboard was 1992.
- I bought my initial 4 military models about 5 years ago new old stock from an auction house - this was an uncommon find at the time.
- In the last 2 years I've seen more military models showing up on ebay; usually new/lightly used. Probably the US govt getting around to purging old stock.
Anyway I think the military model is the best choice if you don't need the back-light or GPIB option.
rastro
--- End quote ---
Rastro, Thanks for your insightful observations.
Also, I notice that on the bottom of our units there is some US Gov't contract information. My unit says "contract daah01-92d-0031" and since gov't contracts are public information, we might be able to get a bit more information on the 197-M series from government archives. Hmm...this makes me very curious...
A Google hit shows that an M model, with case and probes, was sold on eBay late last year for $360. So it looks like there are a few floating around. And I completely agree, it's a really great portable/bench 5.5 digit unit. I really like the extra shielding and toroid upgrade.
KT
Brian of Romsey:
Re: Replacement display technology.
I have been pondering this today. I would assert that there are no suitable OLED displays easily available. There are tiny ones but nothing with the sort of size needed to replace the existing display.
There also don't seem to be any TFT LCDs with the right sort of aspect ratio. By the time you get to something wide enough, they are way too tall for the case and also getting quite expensive.
It's my opinion that the best replacement is LED displays. But even this is hard and by no means perfect. The readout needs a small text field on the left (Auto, Rel, dB, Stor, Recl, Bat, etc), a 7-segment numeric field for the value, including a leading minus sign (seven displays), and a small text field on the right (multiplier, units, and maybe "AC"). I think that the text fields can be handled by 5x7 displays. Either two VQC10, two HDSP-2000, or eight TIL305 displays. Maybe even HDSP-2113.
rastro:
--- Quote from: Brian of Romsey on July 22, 2019, 11:05:39 pm ---Re: Replacement display technology.
I have been pondering this today. I would assert that there are no suitable OLED displays easily available. There are tiny ones but nothing with the sort of size needed to replace the existing display.
There also don't seem to be any TFT LCDs with the right sort of aspect ratio. By the time you get to something wide enough, they are way too tall for the case and also getting quite expensive.
It's my opinion that the best replacement is LED displays. But even this is hard and by no means perfect. The readout needs a small text field on the left (Auto, Rel, dB, Stor, Recl, Bat, etc), a 7-segment numeric field for the value, including a leading minus sign (seven displays), and a small text field on the right (multiplier, units, and maybe "AC"). I think that the text fields can be handled by 5x7 displays. Either two VQC10, two HDSP-2000, or eight TIL305 displays. Maybe even HDSP-2113.
--- End quote ---
Yes it's difficult to find a good functional fit to replace the old LCD display.
I believe several of the display suggested are obsolete or difficult to readily source (VQC10, HDSP-2000, TIL305).
You also need to consider part costs. The HDSP-2113 is available but in small quantities costs $37.00 from mouser.
Dave Jones did a thread/video on making custom LCD's. This could be a direct replacement for a leaky/broken LCD. The difficulty is there is a fair amount of up front setup costs and design effort to duplicate a replacement. You would need to get enough sponsors sharing the cost to make this route feasible. Then there is also the problem of getting new zebra connectors to replace 30 year old ones just hanging on. Probably not going to get off the ground.
Another solution I thought about is making a PCB that replaces the current display board (same size) but has SMD LEDs replacing the LCD along with a plastic template/screen for symbols/words. Getting the double sided (?) PCB produced in small quantities would be reasonable. However soldering all those SMD LEDs would be certainly be a labor of love. However I think this would be the cleanest and most attainable solution. It would also upgrade the K197(brown) to better viewing than a K197A(grey) with LCD/back-lighting. Lot's of work on PCB design routing the drivers and probably programing a controller for display generation. Once complete it could also be adapted for other Keithleys of that series. Wish I had time to start something like this...
rasto
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