The "zener" effect we're using is actually the avalanche effect, which has quite robust physics, and doesn't use any of the usual BJT mechanisms. Except for inverted-mode beta at high currents. That could cause a small change in zener voltage. I'm looking forward to doing some long-term tests.
They have analogue voltage outputs, n'est ce pas? A LabJack is good medicine for that sort of job.
The 72BD has BCD outputs as well IIRC, but I've never used them.
Cheers
Phil Hobbs
But probably not with recurrent ampere-level pulses. Some things are too far out on the lunatic fringe even for you. ;)
Cheers
Phil Hobbs
John has the equipment, and is up for such a test. Me too, I'm going to do 1A and 10A repetitive tests, even if that seems a bit unrealistic, for typical applications.
The Keithley 610 is a pretty good instrument. Its bottom range is 10 fA FS, which is more aspirational than functional, but the 100 fA range is pretty solid, considering.
Some modern CMOS op amps will blow the 610 into the weeds.
Cheers
Phil Hobbs
The Boonton 72AD has BCD outputs.
The 7200 series has IEEE-488 interface for automated testing
I don't have either of these, but I do have the 42, 92, 4200 and 9200 serie s meters. The older analog models allow remote range selection, but do not have an A/D converter. Only those ending in D have these, in their two numb er model series.
My capacitor charging thing could get well into the aA range. I just need a good SPDT switch.
Dracula's knife switch would at least give lots of clearance.
NT
Not with my safety glasses.
10 amps is easy, just a pulse generator and a mosfet. Put a resistor in the mosfet source for constant-current pulsing.
Wasn't it Dr. Frankenstein who had the big knife-switch?
And, if I recall correctly, that switch was always festooned with cobwebs. This might create paths for excessive leakage, especially if the weather is damp (which it usually was during the doctor's normal work hours... something about thunderstorms...)
Were his teeth bolted on? ;)
Cheers
Phil Hobbs
(I suspect you meant Frankenstein.)
Only one side of one switch needs really low leakage.
That probably needs some home-made switch.
A small antenna and a high-z voltmeter does interesting things as a cloud passes over. A lightning shot can really change the e-field.
What's S1 for? (S2 resets cap and measures offset V.) George H.
they were both the same era, but IIRC Dracula had not yet modernised to getting electricity.
Yes, some aspects I think one could improve on, including the ebonite. Once you've picked your materials, a knife switch could be a good format.
If one were willing to go to vacuum, springy metal in a vacuum could be used, rotate the container to switch it.
NT
S1 isolates the integrating node from the opamp input current.
S2 ground-checks the opamp, to measure offset.
Pushing both discharges the cap.
How would we test this? The biggest resistor that I have is 1T. 1 volt across that is 1,000,000 aA.
Just charging up its ~50 fF capacitance to 1V takes 50,000 aC.
Cheers
Phil Hobbs
Mercury tilt switch, perhaps? Lots of the reed-switch relays of yesteryear had good insulation standoff distances, with dry inert atmosphere fill.
A reed might be OK, activated by a magnet.
Some simple mechanical thing would be better. Air is a good insulator.
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