NPN protective zener

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.

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Reply to
Winfield Hill
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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

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Dr Philip C D Hobbs 
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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

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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.

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 Thanks, 
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Reply to
Winfield Hill

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

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Phil Hobbs

The Boonton 72AD has BCD outputs.

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The 7200 series has IEEE-488 interface for automated testing

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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.

Reply to
Michael Terrell

My capacitor charging thing could get well into the aA range. I just need a good SPDT switch.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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John Larkin

Dracula's knife switch would at least give lots of clearance.

NT

Reply to
tabbypurr

Not with my safety glasses.

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John Larkin         Highland Technology, Inc 
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John Larkin

10 amps is easy, just a pulse generator and a mosfet. Put a resistor in the mosfet source for constant-current pulsing.
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John Larkin         Highland Technology, Inc 
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John Larkin

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...)

Reply to
Dave Platt

Were his teeth bolted on? ;)

Cheers

Phil Hobbs

(I suspect you meant Frankenstein.)

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Phil Hobbs

Only one side of one switch needs really low leakage.

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That probably needs some home-made switch.

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John Larkin         Highland Technology, Inc 
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Reply to
John Larkin

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.

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John Larkin         Highland Technology, Inc 
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John Larkin

What's S1 for? (S2 resets cap and measures offset V.) George H.

Reply to
George Herold

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

Reply to
tabbypurr

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.

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John Larkin         Highland Technology, Inc 
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John Larkin

Just charging up its ~50 fF capacitance to 1V takes 50,000 aC.

Cheers

Phil Hobbs

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Reply to
Phil Hobbs

Mercury tilt switch, perhaps? Lots of the reed-switch relays of yesteryear had good insulation standoff distances, with dry inert atmosphere fill.

Reply to
whit3rd

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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John Larkin         Highland Technology, Inc 
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John Larkin

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