> On Sat, 11 Jun 2016 20:17:02 -0700, Jeff Liebermann <jeffl@cruzio.com>
> wrote:
>
>> On Fri, 06 May 2016 19:43:33 -0500, John Fields
>> <jfields@austininstruments.com> wrote:
>>
>>> On Thu, 05 May 2016 17:11:36 -0700, John Larkin
>>> <jjlarkin@highlandtechnology.com> wrote:
>>>> http://www.analog.com/en/products/amplifiers/operational-amplifiers/ada4530-1.html#product-overview
>>>> Input current is typically 0.1 fA at room temp. Noise and offset specs
>>>> are impressive for a fA opamp.
>>>> 0.1 fA is 625 electrons per second.
>>
>>> Wowie Zowie...
>>> Show your work.
>>> John Fields
>
>> How to Convert Amps to Electrons Per Second
>> <https://www.youtube.com/watch?v=xPlAHcc4p4o> (1:11)
>
> Sorry, I hit send before I was done...
> Looks like it's off by x10.
>
> 1Amp = 1 coulomb/sec = 6.25*10^18 electrons/sec
> 1fA = 1*10-15 Amps
> 1fA = 6.25*10^3 = 6250 electrons/sec
>
He posted 0.1 fA not 1 fA. That would be 10^-16 A.
Reply by Jeff Liebermann●June 12, 20162016-06-12
On Sat, 11 Jun 2016 20:17:02 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
>On Fri, 06 May 2016 19:43:33 -0500, John Fields
><jfields@austininstruments.com> wrote:
>
>>On Thu, 05 May 2016 17:11:36 -0700, John Larkin
>><jjlarkin@highlandtechnology.com> wrote:
>>>http://www.analog.com/en/products/amplifiers/operational-amplifiers/ada4530-1.html#product-overview
>>>Input current is typically 0.1 fA at room temp. Noise and offset specs
>>>are impressive for a fA opamp.
>>>0.1 fA is 625 electrons per second.
>
>>Wowie Zowie...
>>Show your work.
>>John Fields
Sorry, I hit send before I was done...
Looks like it's off by x10.
1Amp = 1 coulomb/sec = 6.25*10^18 electrons/sec
1fA = 1*10-15 Amps
1fA = 6.25*10^3 = 6250 electrons/sec
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Reply by Jeff Liebermann●June 12, 20162016-06-12
On Fri, 06 May 2016 19:43:33 -0500, John Fields
<jfields@austininstruments.com> wrote:
On Sunday, June 12, 2016 at 9:14:57 AM UTC+10, Robert Baer wrote:
> whit3rd wrote:
> > On Thursday, May 5, 2016 at 5:11:43 PM UTC-7, John Larkin wrote:
> >> http://www.analog.com/en/products/amplifiers/operational-amplifiers/ada4530-1.html#product-overview
> >>
> >> Input current is typically 0.1 fA at room temp. Noise and offset specs
> >> are impressive for a fA opamp.
> >>
> >> 0.1 fA is 625 electrons per second.
> >
> > Well, that's getting down there. A fifty-year old Cary 31 electrometer
> > has about 1E-18 A input current, so there's only another decade or two
> > before solid state catches up. To vacuum tubes.
> >
> > Gold-plated elecrodes, cast iron case, sapphire insulators... they
> > say a lot of the cost is in the packaging.
> >
> > The chopper for that old amp operated with a 440 Hz (that's A above
> > middle C, to a musician) tuning fork oscillator.
> ..are you suggesting that one can BUILD one using a tuning fork for
> the vibrating reed?
Cary did. The Cary 401 Vibrating Reed Electrometer is firmly embedded in the scientific literature.
--
Bill Sloman, Sydney
Reply by Robert Baer●June 11, 20162016-06-11
John Larkin wrote:
> On Fri, 6 May 2016 10:39:41 -0700 (PDT), whit3rd<whit3rd@gmail.com>
> wrote:
>
>> On Thursday, May 5, 2016 at 5:11:43 PM UTC-7, John Larkin wrote:
>>> http://www.analog.com/en/products/amplifiers/operational-amplifiers/ada4530-1.html#product-overview
>>>
>>> Input current is typically 0.1 fA at room temp. Noise and offset specs
>>> are impressive for a fA opamp.
>>>
>>> 0.1 fA is 625 electrons per second.
>>
>> Well, that's getting down there. A fifty-year old Cary 31 electrometer
>> has about 1E-18 A input current, so there's only another decade or two
>> before solid state catches up. To vacuum tubes.
>>
>> Gold-plated elecrodes, cast iron case, sapphire insulators... they
>> say a lot of the cost is in the packaging.
>
> ebay has at least one, but the shipping looks expensive.
>
>>
>> The chopper for that old amp operated with a 440 Hz (that's A above
>> middle C, to a musician) tuning fork oscillator.
>
> I looked for a manual for the Cary but didn't find one. I think maybe
> a vibrating reed acted like a variable capacitor and modulated the
> input voltage into an AC amplifier. Is that how it worked? If so, a
> vibrating reed with a solid-state amplifier would be at least as good
> as the tube version.
>
>
Seems that you are spot-on!
Reply by Robert Baer●June 11, 20162016-06-11
whit3rd wrote:
> On Thursday, May 5, 2016 at 5:11:43 PM UTC-7, John Larkin wrote:
>> http://www.analog.com/en/products/amplifiers/operational-amplifiers/ada4530-1.html#product-overview
>>
>> Input current is typically 0.1 fA at room temp. Noise and offset specs
>> are impressive for a fA opamp.
>>
>> 0.1 fA is 625 electrons per second.
>
> Well, that's getting down there. A fifty-year old Cary 31 electrometer
> has about 1E-18 A input current, so there's only another decade or two
> before solid state catches up. To vacuum tubes.
>
> Gold-plated elecrodes, cast iron case, sapphire insulators... they
> say a lot of the cost is in the packaging.
>
> The chopper for that old amp operated with a 440 Hz (that's A above
> middle C, to a musician) tuning fork oscillator.
..are you suggesting that one can BUILD one using a tuning fork for
the vibrating reed?
Reply by Phil Hobbs●May 8, 20162016-05-08
On 05/07/2016 11:10 PM, whit3rd wrote:
> On Saturday, May 7, 2016 at 11:57:32 AM UTC-7, Phil Hobbs wrote:
>> On 05/07/2016 01:04 AM, bill.sloman@ieee.org wrote:
>
>>> A changing capacitance in an electric field generates an AC current.
>>>
>>> Analog Devices had a solid state competitor to the vibrating reed
>>> with a back-biased varactor bridge which worked much the same way.
>>
>> Really? The only one of those I remember is the Philbrick P2.
>
> See here: <https://archive.org/details/AnalogDevicesDataAcquisitionProductsCatalog1979>
>
> AD310 (inverting) and AD311 (noninverting)
> were the part numbers. Those, Keithley 427 current amplifiers, and
> the Cary electrometer were all useful for accurate ion-chamber measurements
> of X-rays, gammas, C14 dating. The predecessors were gold-leaf electroscopes, used with
> stopwatches...
>
Cool, thanks.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net
Reply by whit3rd●May 8, 20162016-05-08
On Saturday, May 7, 2016 at 11:57:32 AM UTC-7, Phil Hobbs wrote:
> On 05/07/2016 01:04 AM, bill.sloman@ieee.org wrote:
> > A changing capacitance in an electric field generates an AC current.
> >
> > Analog Devices had a solid state competitor to the vibrating reed
> > with a back-biased varactor bridge which worked much the same way.
>
> Really? The only one of those I remember is the Philbrick P2.
See here: <https://archive.org/details/AnalogDevicesDataAcquisitionProductsCatalog1979>
AD310 (inverting) and AD311 (noninverting)
were the part numbers. Those, Keithley 427 current amplifiers, and
the Cary electrometer were all useful for accurate ion-chamber measurements
of X-rays, gammas, C14 dating. The predecessors were gold-leaf electroscopes, used with
stopwatches...
Reply by whit3rd●May 7, 20162016-05-07
On Friday, May 6, 2016 at 8:07:31 PM UTC-7, John Larkin wrote:
> >Well, that's getting down there. A fifty-year old Cary 31 electrometer
> >has about 1E-18 A input current, so there's only another decade or two
> >before solid state catches up. To vacuum tubes.
> >
> >Gold-plated elecrodes, cast iron case, sapphire insulators... they
> >say a lot of the cost is in the packaging.
> I looked for a manual for the Cary but didn't find one. I think maybe
> a vibrating reed acted like a variable capacitor and modulated the
> input voltage into an AC amplifier. Is that how it worked?
Yep, that's the principle. The cast-iron probe head, and selected
tubes for low microphonics (and there were Nuvistor upgrades
recommended) were necessary elements. I found one
for the old lab, around thirty years ago, but the manual was
a faded mimeograph.
Reply by John Larkin●May 7, 20162016-05-07
On Sat, 7 May 2016 14:57:27 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
>On 05/07/2016 01:04 AM, bill.sloman@ieee.org wrote:
>> On Saturday, May 7, 2016 at 1:07:31 PM UTC+10, John Larkin wrote:
><sniiip>
>>> I looked for a manual for the Cary but didn't find one. I think
>>> maybe a vibrating reed acted like a variable capacitor and
>>> modulated the input voltage into an AC amplifier. Is that how it
>>> worked? If so, a vibrating reed with a solid-state amplifier would
>>> be at least as good as the tube version.
>>
>> A changing capacitance in an electric field generates an AC current.
>>
>> Analog Devices had a solid state competitor to the vibrating reed
>> with a back-biased varactor bridge which worked much the same way.
>
>Really? The only one of those I remember is the Philbrick P2.
>
>Cheers
>
>Phil Hobbs
TI briefly made an integrated opamp that had a varactor-modulator
front end.
--
John Larkin Highland Technology, Inc
lunatic fringe electronics