HI, I have a clean-looking Keithley 600B electrometer.
Problem is, no manual, and no clue what kind of batteries it needs.
There's a small battery holder that maybe could hold a small old-style (1/3 AA) mercury battery. And FOUR clips that would fit your basic 9V
006P, except the holding bracket for them is about 8 times too volume-iffic.Any hints appreciated.
Reagards,
George
George:
I also have a 600B. The four batteries are indeed 9V, but a very early model. They are 1 3/8" x 1 3/8" x x 2 5/8". I kept one just for the heck of it that I removed from my original meter. It is a zinc carbon EVEREADY no. 246. (NEDA 1602) Don't known if still available, but I would guess if they are you would pay an arm and leg for them. I use regular size 9 V alk. batteries with reasonable battery life.
You guessed correctly the small cylindrical battery is indeed a mercury cell (1.35 volts if I remember). I kept it also but can't seem to locate it right now. Good luck finding a replacement. I went looking for one several years ago and found that it is illegal (Federal Environmental Law) to sell or even import batteries containing mercury. Never found a source. If you do let me know. Since it is used for the linear Ohms scale using a regular alkaline battery will make the scales significantly inaccurate. I think the drain is extremely low so I thought about designing a voltage regulator circuit running off a higher voltage battery but never got around to doing it.
The 600B is a nice meter. I picked mine up for $10 at Dayton HF one year. Don't have a schematic though. If you get a lead on that let me know.
Dave Woolf - K8RSP (If reply> HI, I have a clean-looking Keithley 600B electrometer.
Try a Zinc-Air battery. My reference book sez "once activated, the voltage stabilizes between
1.40 and 1.45V. Drawing discharge current quickly lowers the voltage to 1.30 volts..". So, maybe, one could start with an activated zinc-air cell and put a calibrated load for a fixed (timed) period - just enough to result in a no load voltage of 1.35V. The next question would be how stable and for how long that voltage remains.Another possible solution, with better chance of stable long-term voltage: a silver-oxide cell opposing a lithium cell (3.0V-1.6V=1.4V).
It originally took 2 mercury D-cells on top, and 2 22 (or were they
28V batteries beside the D-cells.Down on the side there are indeed 4 9V transistor batteries.
I have one of these, as well as a manual. When they are working, they are nice units. I'm trying to visualize how these are held, but I can't recall exactly. I don't recall them looking like the holders were too big.
Email me directly and remind me to look at my 600B and the manual.
------------------------------------------------ Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
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Jim, I'd very much like to look at your 600B manual, or at least the schematic page.
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Thanks,
- Win
(email: use hill_at_rowland-dotties-org for now)
Like most multimeter schematics, it's pretty hard to follow because of all the multipole switch contacts, but it can be done. If either of you want a copy just email me your address and I'll Xerox one for you. I may have more than one version of the manual, so let me know if you're looking for a particular serial number.
I also have replacement subminiature tubes for these, as well as a circuit and method for matching them.
I've resurrected several of these, and their AC powered mates, over the years.
------------------------------------------------ Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
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"Winfield Hill" schrieb im Newsbeitrag news: snipped-for-privacy@drn.newsguy.com...
it is downloadable from
Rgds Achin
Thanks, I got the manual from Keithley's website. I have my technician tear these apart for the teflon switches and Gig-ohm resistors, but he did save some of the miniature tube assemblies.
--
Thanks,
- Win
(email: use hill_at_rowland-dotties-org for now)
HF = hamfest??
Use a 1.5V alkaline button cell and recalibrate? Or else use 4.5V or more battery and a micropower voltage regulator with a couple resistors that give a 1.35V output. The current drain should be very low.
old-style
9V
If one were to use one of those micropower regulators, one would need to use a 1.25V adjustable and two resistors in a voltage divider...
How does he remove them without getting his sweaty fingerprints all over, and ruining the insulation properties? I'd guess he has to wear gloves.
I used an open gate of a 2N7000 FET to probe for leakage. I found that paper on a humid day works almost like the carbon element from a potentiometer. I could probe from the negative to positive, and the closer I got to the positive, the higher the FET current. It's kind of amazing, when one thinks about it, but all this 'electron movement' is going on between PCB tracks, and between wires in a bundle, etc. We just don't kotice it because all the other much higher currents overwhelm the leakages.
I was reading that they are having problems with the nanometer geometries of the latest chip fabrications. The electrons get so leaky that it's becoming a problem telling the signals from the leakage.
I had him remove intact the amplifier assembly that contains the tubes. But it's trivial to degrease items after handling them.
Yes, paper, absolutely. Ever notice how much water it can absorb on a humid day? It can get so wet you can't write on it with a pencil!
That's why I like extracting the teflon-terminal switches, etc., from these old beauties. But even without them it's not too hard to make fixed-range pA and fA sensitivity electronics, by using "in-the-air" wiring, soldering items together suspended in air. For example, the inverting input of a cmos opamp can be bent out from the rest, and not put in a socket or soldered to the printed circuit board.
--
Thanks,
- Win
(email: use hill_at_rowland-dotties-org for now)
I think a good answer is to replace the tube amplifier with a cmos opamp, e.g. something from NSC's LMC6001 family. They say the LMC662 has an input current of only 2fA typical. You should add additioanl static protection, which can consist of a pair of back-to-back JFET gate-source diodes.
--
Thanks,
- Win
(email: use hill_at_rowland-dotties-org for now)
The LPC661 may be a better choice. It's an NSC single cmos opamp with 2fA typical bias, but it works at a lower power level using 55uA from a 3 to 16V source, better suited for battery power.
--
Thanks,
- Win
(email: use hill_at_rowland-dotties-org for now)
Winfield Hill
[...]
Win,
Do you have any recommendation for a low-leakage JFET? Wouldn't it degrade the 2fA bias current? I understand from Paul Grohe's posts that the bias current comes from the existing input protection circuitry. Is there a good reason to add more protection?
Just for reference, here are some old links to these parts.
Paul Grohe talks about to obtain the low input current in
Bob Pease talks about testing and cleaning them them in
Paul discusses the source of leakage and how to clean them in
Thanks,
Mike
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