On Wed, 12 Feb 2014 08:14:07 -0500, Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:>On Wed, 12 Feb 2014 18:18:03 +1100, the renowned "Phil Allison" ><phil_a@tpg.com.au> wrote: > >> >>Doubt he needs to go for fancy lab pre-amp units. >> >> >> >>... Phil >> > >The fancy lab pre-amp units are not much more than a JFET front end on >a low-noise op-amp.=20 > > >Best regards,=20 >Spehro PefhanyYou betcha. The pricey Endevco charge amps are just 747s with fet = inputs. Part of the price though is the calibration certificate. ?-)
current amplifier or current to voltage op-amp
Started by ●February 11, 2014
Reply by ●February 13, 20142014-02-13
Reply by ●February 13, 20142014-02-13
On a sunny day (Thu, 13 Feb 2014 09:34:56 +0100) it happened Jeroen Belleman <jeroen@nospam.please> wrote in <ldi03e$15e$1@speranza.aioe.org>:>On 2014-02-13 07:29, Jan Panteltje wrote: >> On a sunny day (Thu, 13 Feb 2014 14:24:38 +1100) it happened "Phil Allison" >> <phil_a@tpg.com.au> wrote in <bm2s7fF81dkU1@mid.individual.net>: >> >>> >>> "Bill Sloman" >>>> >>>> The trouble with physicists is that while they can be >>>> shaky on electronic details, they tend to have a reasonable >>>> gasp of physical reality. >>>> >>> >>> >>> ** Thinking a tiny clock crystal makes a good ultrasonic microphone is not >>> very realistic. >>> >>> Quote from the OP: >>> >>> " I am using the quartz tuning fork as a very sensitive force detector to >>> pick up sound wave at its resonance frequency. " >> >> Long time agao I did read about acoustic coupling between xrystals. >> Selectivity should be great. >> > >I'd think these crystals would be designed to minimize acoustic >coupling. > >Jeroen BellemanI dunno, IIRC I once did an experiment with some higher frequency ones (6 MHz?), and you can do it yourself, Make a crystal oscillator, and put a second crystal of the same frequency on the scope against the oscillating one. Mind the tuning capacitance. Old crystals I had were just a quartz plate with gold electrodes hanging from some wires, not sure that makes a lot of damping. Even the small round 32 kHz ones (have one in a PIC lightning detector here) are like that I think, opened one once from a cheap watch.
Reply by ●February 13, 20142014-02-13
On Thu, 13 Feb 2014 09:34:56 +0100, Jeroen Belleman <jeroen@nospam.please> wrote:>On 2014-02-13 07:29, Jan Panteltje wrote: >> On a sunny day (Thu, 13 Feb 2014 14:24:38 +1100) it happened "Phil Allison" >> <phil_a@tpg.com.au> wrote in <bm2s7fF81dkU1@mid.individual.net>: >> >>> >>> "Bill Sloman" >>>> >>>> The trouble with physicists is that while they can be >>>> shaky on electronic details, they tend to have a reasonable >>>> gasp of physical reality. >>>> >>> >>> >>> ** Thinking a tiny clock crystal makes a good ultrasonic microphone is not >>> very realistic. >>> >>> Quote from the OP: >>> >>> " I am using the quartz tuning fork as a very sensitive force detector to >>> pick up sound wave at its resonance frequency. " >> >> Long time agao I did read about acoustic coupling between xrystals. >> Selectivity should be great. >> > >I'd think these crystals would be designed to minimize acoustic >coupling. > >Jeroen BellemanI don't know. Some of the recent "mesa" etch types I've seen would make excellent microphones if de-cased. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●February 13, 20142014-02-13
On 2/13/2014 3:34 AM, Jeroen Belleman wrote:> On 2014-02-13 07:29, Jan Panteltje wrote: >> On a sunny day (Thu, 13 Feb 2014 14:24:38 +1100) it happened "Phil >> Allison" >> <phil_a@tpg.com.au> wrote in <bm2s7fF81dkU1@mid.individual.net>: >> >>> >>> "Bill Sloman" >>>> >>>> The trouble with physicists is that while they can be >>>> shaky on electronic details, they tend to have a reasonable >>>> gasp of physical reality. >>>> >>> >>> >>> ** Thinking a tiny clock crystal makes a good ultrasonic microphone >>> is not >>> very realistic. >>> >>> Quote from the OP: >>> >>> " I am using the quartz tuning fork as a very sensitive force >>> detector to >>> pick up sound wave at its resonance frequency. " >> >> Long time agao I did read about acoustic coupling between xrystals. >> Selectivity should be great. >> > > I'd think these crystals would be designed to minimize acoustic > coupling. >Yup. Acoustic coupling equals loss. 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 ●February 13, 20142014-02-13
On Wed, 12 Feb 2014 19:14:22 -0800 (PST), Bill Sloman <bill.sloman@gmail.com> wrote: [snip]> >The trouble with physicists is that while they can be shaky on electronic details, they tend to have a reasonable gasp of physical reality.They certainly do GASP >:-} ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●February 13, 20142014-02-13
On Friday, 14 February 2014 02:10:46 UTC+11, Jim Thompson wrote:> On Wed, 12 Feb 2014 19:14:22 -0800 (PST), Bill Sloman > <bill.sloman@gmail.com> wrote:=20 > [snip]=20 > > >=20 > >The trouble with physicists is that while they can be shaky on electroni=c details, they tend to have a reasonable gasp of physical reality.> =20 > They certainly do GASP >:-}"Physical reality" is the reality defined by physicists. As a chemist by tr= aining, I'm attuned to the fact that "chemical reality" and "physical reali= ty" aren't quite the same thing - though physicists will argue that since S= chroedinger chemistry has merely been a branch of physics, just as - since = Watson and Crick - biology has merely been a branch of chemistry. Not the kind of joke that Jim could be expected to get. --=20 Bill Sloman, Sydney
Reply by ●February 13, 20142014-02-13
On Wed, 12 Feb 2014 10:34:57 -0800 (PST), Xunchen Liu <xunchen@ualberta.ca> wrote:>Hi sorry for cross posting from sci.optics. I just summarize what I want to do: > >I am trying to use a quartz crystal tuning fork at 32768 Hz, 12.5 pF, 35 kOhm as a sensitive sound detector at its resonance frequency from its piezoelectric signal.I'd think that external vibration would couple very poorly into a tuning-fork crystal. Reciprocity, COE, high-Q, stuff like that. If you could couple into just one tine, it would be very sensitive. You could probably detect light pressure or something. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation
Reply by ●February 13, 20142014-02-13
On Thu, 13 Feb 2014 18:07:35 -0800, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:>On Wed, 12 Feb 2014 10:34:57 -0800 (PST), Xunchen Liu <xunchen@ualberta.ca> >wrote: > >>Hi sorry for cross posting from sci.optics. I just summarize what I want to do: >> >>I am trying to use a quartz crystal tuning fork at 32768 Hz, 12.5 pF, 35 kOhm as a sensitive sound detector at its resonance frequency from its piezoelectric signal. > >I'd think that external vibration would couple very poorly into a tuning-fork >crystal. Reciprocity, COE, high-Q, stuff like that.And other such buzz words >:-}> >If you could couple into just one tine, it would be very sensitive. You could >probably detect light pressure or something....Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●February 13, 20142014-02-13
On 2/13/2014 9:07 PM, John Larkin wrote:> On Wed, 12 Feb 2014 10:34:57 -0800 (PST), Xunchen Liu <xunchen@ualberta.ca> > wrote: > >> Hi sorry for cross posting from sci.optics. I just summarize what I want to do: >> >> I am trying to use a quartz crystal tuning fork at 32768 Hz, 12.5 pF, 35 kOhm as a sensitive sound detector at its resonance frequency from its piezoelectric signal. > > I'd think that external vibration would couple very poorly into a tuning-fork > crystal. Reciprocity, COE, high-Q, stuff like thatAmbient vibration, quite so. However, if the OP is using the crystal in a poor's scanned probe microscope, the coupling could be quite a bit stronger locally.> > If you could couple into just one tine, it would be very sensitive. You could > probably detect light pressure or something.Given enough integration time. ;) 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 ●February 13, 20142014-02-13
On Thu, 13 Feb 2014 19:44:13 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Thu, 13 Feb 2014 18:07:35 -0800, John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >>On Wed, 12 Feb 2014 10:34:57 -0800 (PST), Xunchen Liu <xunchen@ualberta.ca> >>wrote: >> >>>Hi sorry for cross posting from sci.optics. I just summarize what I want to do: >>> >>>I am trying to use a quartz crystal tuning fork at 32768 Hz, 12.5 pF, 35 kOhm as a sensitive sound detector at its resonance frequency from its piezoelectric signal. >> >>I'd think that external vibration would couple very poorly into a tuning-fork >>crystal. Reciprocity, COE, high-Q, stuff like that. > >And other such buzz words >:-}The meaning should be obvious to any reasonable engineer. Do I need to spell it out for you? Do you think that external vibration will couple well into a tuning fork crystal? Say why or why not. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation
