On Friday, January 24, 2003 at 8:03:08 AM UTC-5, Winfield Hill wrote:
> Paul Grohe wrote...
> >
> > al from Technical University Berlin, Germany posted:
> >>
> >> how are very low currents (fA range) measured?
> >
> > See: http://www.elecdesign.com/Index.cfm?Action=Pease
> > Read the "Teflon" and "Femtoampere" articles.
> >
> > [edited] The best "Teflon Capacitor" we tried was a few
> > centimeters of RG-188 Teflon coax (outer braid to output
> > and center to the summing point) "trim" by snipping off
> > small pieces. 10-15pF is a convenient value for measuring
> > in the fA range. use the second channel of the 662 dual
> > for the integrator...
> > Paul Grohe (The "Paul" mentioned in the Teflon article).
> Yes, Paul, I remember your name in that fascinating account.
> One painful issue, as Pease discusses, is a suitable circuit
> to reset the integrator. Bernie Gottschalk, an engineer at
> the Harvard cyclotron, used NSC cmos opamps and had a clever
> solution: reverse the supply voltages. He used a resistor in
> series (perhaps 3.3k, etc.) with both opamp supply leads to
> limit the reversal current. The resistors with the opamp's
> protection diodes act as a bridge to zero the capacitor (the
> opamp's + input is grounded, although I'm not sure that's
> important). Significantly, when restoring the supply-voltage
> polarity the NSC opamp's protection-diode charge-transfer is
> balanced, leaving the integrating-capacitor voltage properly
> reset. Of course, in integrator applications like this, the
> exact capacitor voltage at reset isn't very critical.
> Very impressive, cute and elegant!
> A single HC4053 chip could be used to make a +/-5V supply-
> reversal circuit.
> The scheme is especially attractive with many channels, where
> one supply-reversal circuit resets all the channels at once,
> without any extra parts!
> I haven't tried this trick myself, but Bernie didn't mention
> any problems or special considerations (e.g., no additional
> bypass caps for the opamps after the series resistors, IIRC),
> so try it and let us know how it works out.
> Thanks,
> - Win

Just exhuming this very interesting thread from 20 years back. Recently we were talking about the trick of inverting the power supplies to reset an op amp integrator, and I think this is the first mention with attribution.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations LLC / Hobbs ElectroOptics

On Fri, 24 Mar 2023 10:13:44 -0700 (PDT), Phil Hobbs
<pcdhobbs@gmail.com> wrote:

>On Friday, January 24, 2003 at 8:03:08?AM UTC-5, Winfield Hill wrote:
>> Paul Grohe wrote...
>> >
>> > al from Technical University Berlin, Germany posted:
>> >>
>> >> how are very low currents (fA range) measured?
>> >
>> > See: http://www.elecdesign.com/Index.cfm?Action=Pease
>> > Read the "Teflon" and "Femtoampere" articles.
>> >
>> > [edited] The best "Teflon Capacitor" we tried was a few
>> > centimeters of RG-188 Teflon coax (outer braid to output
>> > and center to the summing point) "trim" by snipping off
>> > small pieces. 10-15pF is a convenient value for measuring
>> > in the fA range. use the second channel of the 662 dual
>> > for the integrator...
>> > Paul Grohe (The "Paul" mentioned in the Teflon article).
>> Yes, Paul, I remember your name in that fascinating account.
>> One painful issue, as Pease discusses, is a suitable circuit
>> to reset the integrator. Bernie Gottschalk, an engineer at
>> the Harvard cyclotron, used NSC cmos opamps and had a clever
>> solution: reverse the supply voltages. He used a resistor in
>> series (perhaps 3.3k, etc.) with both opamp supply leads to
>> limit the reversal current. The resistors with the opamp's
>> protection diodes act as a bridge to zero the capacitor (the
>> opamp's + input is grounded, although I'm not sure that's
>> important). Significantly, when restoring the supply-voltage
>> polarity the NSC opamp's protection-diode charge-transfer is
>> balanced, leaving the integrating-capacitor voltage properly
>> reset. Of course, in integrator applications like this, the
>> exact capacitor voltage at reset isn't very critical.
>> Very impressive, cute and elegant!
>> A single HC4053 chip could be used to make a +/-5V supply-
>> reversal circuit.
>> The scheme is especially attractive with many channels, where
>> one supply-reversal circuit resets all the channels at once,
>> without any extra parts!
>> I haven't tried this trick myself, but Bernie didn't mention
>> any problems or special considerations (e.g., no additional
>> bypass caps for the opamps after the series resistors, IIRC),
>> so try it and let us know how it works out.
>> Thanks,
>> - Win
>
>Just exhuming this very interesting thread from 20 years back. Recently we were talking about the trick of inverting the power supplies to reset an op amp integrator, and I think this is the first mention with attribution.
>
>Cheers
>
>Phil Hobbs

The best integrator is a single capacitor, with some sort of
mechanical contact to connect it to the readout+reset circuit.

One could probably integrate a few electrons per second. Cosmic rays
might be the biggest error source.

On 2023-03-24 13:35, John Larkin wrote:> On Fri, 24 Mar 2023 10:13:44
-0700 (PDT), Phil Hobbs
> <pcdhobbs@gmail.com> wrote:
>
>> On Friday, January 24, 2003 at 8:03:08?AM UTC-5, Winfield Hill
>> wrote:
>>> Paul Grohe wrote...
>>>>
>>>> al from Technical University Berlin, Germany posted:
>>>>>
>>>>> how are very low currents (fA range) measured?
>>>>
>>>> See: http://www.elecdesign.com/Index.cfm?Action=Pease Read the
>>>> "Teflon" and "Femtoampere" articles.
>>>>
>>>> [edited] The best "Teflon Capacitor" we tried was a few
>>>> centimeters of RG-188 Teflon coax (outer braid to output and
>>>> center to the summing point) "trim" by snipping off small
>>>> pieces. 10-15pF is a convenient value for measuring in the fA
>>>> range. use the second channel of the 662 dual for the
>>>> integrator... Paul Grohe (The "Paul" mentioned in the Teflon
>>>> article).

>>> Yes, Paul, I remember your name in that fascinating account. One
>>> painful issue, as Pease discusses, is a suitable circuit to reset
>>> the integrator. Bernie Gottschalk, an engineer at the Harvard
>>> cyclotron, used NSC cmos opamps and had a clever solution:
>>> reverse the supply voltages. He used a resistor in series
>>> (perhaps 3.3k, etc.) with both opamp supply leads to limit the
>>> reversal current. The resistors with the opamp's protection
>>> diodes act as a bridge to zero the capacitor (the opamp's + input
>>> is grounded, although I'm not sure that's important).
>>> Significantly, when restoring the supply-voltage polarity the NSC
>>> opamp's protection-diode charge-transfer is balanced, leaving the
>>> integrating-capacitor voltage properly reset. Of course, in
>>> integrator applications like this, the exact capacitor voltage at
>>> reset isn't very critical. Very impressive, cute and elegant! A
>>> single HC4053 chip could be used to make a +/-5V supply- reversal
>>> circuit. The scheme is especially attractive with many channels,
>>> where one supply-reversal circuit resets all the channels at
>>> once, without any extra parts! I haven't tried this trick myself,
>>> but Bernie didn't mention any problems or special considerations
>>> (e.g., no additional bypass caps for the opamps after the series
>>> resistors, IIRC), so try it and let us know how it works out.
>>> Thanks, - Win
>>
>> Just exhuming this very interesting thread from 20 years back.
>> Recently we were talking about the trick of inverting the power
>> supplies to reset an op amp integrator, and I think this is the
>> first mention with attribution.
>
> The best integrator is a single capacitor, with some sort of
> mechanical contact to connect it to the readout+reset circuit.

For certain values of 'best', sure. It's often important to keep the
terminal voltage of your integrator low, which is a lot easier to do
with an active deice.
>
> One could probably integrate a few electrons per second. Cosmic rays
> might be the biggest error source.

Cheers

Phil Hobbs>

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On Friday, March 24, 2023 at 6:26:05 PM UTC, Phil Hobbs wrote:
> On 2023-03-24 13:35, John Larkin wrote:> On Fri, 24 Mar 2023 10:13:44
> -0700 (PDT), Phil Hobbs
> > <pcdh...@gmail.com> wrote:
> >
> >> On Friday, January 24, 2003 at 8:03:08?AM UTC-5, Winfield Hill
> >> wrote:
> >>> Paul Grohe wrote...
> >>>>
> >>>> al from Technical University Berlin, Germany posted:
> >>>>>
> >>>>> how are very low currents (fA range) measured?
> >>>>
> >>>> See: http://www.elecdesign.com/Index.cfm?Action=Pease Read the
> >>>> "Teflon" and "Femtoampere" articles.
> >>>>
> >>>> [edited] The best "Teflon Capacitor" we tried was a few
> >>>> centimeters of RG-188 Teflon coax (outer braid to output and
> >>>> center to the summing point) "trim" by snipping off small
> >>>> pieces. 10-15pF is a convenient value for measuring in the fA
> >>>> range. use the second channel of the 662 dual for the
> >>>> integrator... Paul Grohe (The "Paul" mentioned in the Teflon
> >>>> article).
>
> >>> Yes, Paul, I remember your name in that fascinating account. One
> >>> painful issue, as Pease discusses, is a suitable circuit to reset
> >>> the integrator. Bernie Gottschalk, an engineer at the Harvard
> >>> cyclotron, used NSC cmos opamps and had a clever solution:
> >>> reverse the supply voltages. He used a resistor in series
> >>> (perhaps 3.3k, etc.) with both opamp supply leads to limit the
> >>> reversal current. The resistors with the opamp's protection
> >>> diodes act as a bridge to zero the capacitor (the opamp's + input
> >>> is grounded, although I'm not sure that's important).
> >>> Significantly, when restoring the supply-voltage polarity the NSC
> >>> opamp's protection-diode charge-transfer is balanced, leaving the
> >>> integrating-capacitor voltage properly reset. Of course, in
> >>> integrator applications like this, the exact capacitor voltage at
> >>> reset isn't very critical. Very impressive, cute and elegant! A
> >>> single HC4053 chip could be used to make a +/-5V supply- reversal
> >>> circuit. The scheme is especially attractive with many channels,
> >>> where one supply-reversal circuit resets all the channels at
> >>> once, without any extra parts! I haven't tried this trick myself,
> >>> but Bernie didn't mention any problems or special considerations
> >>> (e.g., no additional bypass caps for the opamps after the series
> >>> resistors, IIRC), so try it and let us know how it works out.
> >>> Thanks, - Win
> >>
> >> Just exhuming this very interesting thread from 20 years back.
> >> Recently we were talking about the trick of inverting the power
> >> supplies to reset an op amp integrator, and I think this is the
> >> first mention with attribution.
> >
> > The best integrator is a single capacitor, with some sort of
> > mechanical contact to connect it to the readout+reset circuit.
> For certain values of 'best', sure. It's often important to keep the
> terminal voltage of your integrator low, which is a lot easier to do
> with an active deice.
> >
> > One could probably integrate a few electrons per second. Cosmic rays
> > might be the biggest error source.
> Cheers
>
> Phil Hobbs>
>
>
> --
> Dr Philip C D Hobbs
> Principal Consultant
> ElectroOptical Innovations LLC / Hobbs ElectroOptics
> Optics, Electro-optics, Photonics, Analog Electronics
> Briarcliff Manor NY 10510
>
> http://electrooptical.net
> http://hobbs-eo.com

Anyone know if Win is keeping well? It's been a while since he's posted. Hope he's not upstairs arguing with Jim.

Am 24.03.23 um 22:08 schrieb John May:
> On Friday, March 24, 2023 at 6:26:05 PM UTC, Phil Hobbs wrote:
>> On 2023-03-24 13:35, John Larkin wrote:> On Fri, 24 Mar 2023 10:13:44
>> -0700 (PDT), Phil Hobbs
>>> <pcdh...@gmail.com> wrote:
>>>
>>>> On Friday, January 24, 2003 at 8:03:08?AM UTC-5, Winfield Hill
>>>> wrote:
>>>>> Paul Grohe wrote...
>>>>>>
>>>>>> al from Technical University Berlin, Germany posted:

> Anyone know if Win is keeping well? It's been a while since he's posted.

Hope he's not upstairs arguing with Jim.

Last time he disappeared, we were rewarded with AOE V3.
And all the best to TUB, even if the reference is old.

Gerhard

On Fri, 24 Mar 2023 22:48:52 +0100, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

>Am 24.03.23 um 22:08 schrieb John May:
>> On Friday, March 24, 2023 at 6:26:05?PM UTC, Phil Hobbs wrote:
>>> On 2023-03-24 13:35, John Larkin wrote:> On Fri, 24 Mar 2023 10:13:44
>>> -0700 (PDT), Phil Hobbs
>>>> <pcdh...@gmail.com> wrote:
>>>>
>>>>> On Friday, January 24, 2003 at 8:03:08?AM UTC-5, Winfield Hill
>>>>> wrote:
>>>>>> Paul Grohe wrote...
>>>>>>>
>>>>>>> al from Technical University Berlin, Germany posted:
>
>
>> Anyone know if Win is keeping well? It's been a while since he's posted.
>
>Hope he's not upstairs arguing with Jim.
>
>Last time he disappeared, we were rewarded with AOE V3.
>And all the best to TUB, even if the reference is old.
>
>Gerhard
>

I asked Paul Horowitz about Win, less than a year ago, and he said
that Win was fine.

On Saturday, March 25, 2023 at 3:38:29 AM UTC, Anthony William Sloman wrote:
> On Saturday, March 25, 2023 at 8:08:43 AM UTC+11, John May wrote:
> > On Friday, March 24, 2023 at 6:26:05 PM UTC, Phil Hobbs wrote:
> > > On 2023-03-24 13:35, John Larkin wrote:> On Fri, 24 Mar 2023 10:13:44
> > > -0700 (PDT), Phil Hobbs <pcdh...@gmail.com> wrote:
> > > >> On Friday, January 24, 2003 at 8:03:08?AM UTC-5, Winfield Hill wrote:
> > > >>> Paul Grohe wrote...
> > > >>>> al from Technical University Berlin, Germany posted:
> > Anyone know if Win is keeping well? It's been a while since he's posted.. Hope he's not upstairs arguing with Jim.
> I e-mailed him about six months ago about a personal matter, and got a aimiable reply. At our age that doesn't mean that he is still okay.
>
> --
> Bill Sloman, Sydney

Thank you Bill, I'm glad to hear that he has just decided that there's better things to do than post on SED. I can't say I blame him, it seems to have turned into an open sewer over the last few years.

On Thursday, March 30, 2023 at 9:10:07 AM UTC-4, John May wrote:
> On Saturday, March 25, 2023 at 3:38:29 AM UTC, Anthony William Sloman wrote:
> > On Saturday, March 25, 2023 at 8:08:43 AM UTC+11, John May wrote:
> > > On Friday, March 24, 2023 at 6:26:05 PM UTC, Phil Hobbs wrote:
> > > > On 2023-03-24 13:35, John Larkin wrote:> On Fri, 24 Mar 2023 10:13:44
> > > > -0700 (PDT), Phil Hobbs <pcdh...@gmail.com> wrote:
> > > > >> On Friday, January 24, 2003 at 8:03:08?AM UTC-5, Winfield Hill wrote:
> > > > >>> Paul Grohe wrote...
> > > > >>>> al from Technical University Berlin, Germany posted:
> > > Anyone know if Win is keeping well? It's been a while since he's posted. Hope he's not upstairs arguing with Jim.
> > I e-mailed him about six months ago about a personal matter, and got a aimiable reply. At our age that doesn't mean that he is still okay.
> >
> > --
> > Bill Sloman, Sydney
> Thank you Bill, I'm glad to hear that he has just decided that there's better things to do than post on SED. I can't say I blame him, it seems to have turned into an open sewer over the last few years.

What other fake name have you been using to post to sed? There doesn't seem to be a lot going for the "John May" fake name.

So the fake thinks sed is an "open sewer"- my, my my.