Reply by josephkk April 24, 20122012-04-24
On Tue, 17 Apr 2012 19:13:53 -0700, "Mr.CRC"
<crobcBOGUS@REMOVETHISsbcglobal.net> wrote:

> >>>> Teflon is not a good idea, due to microphonics. >>> Depends on how much signal he has. I'd expect an engine explosion to >>> make lots of signal. >>=20 >> That also depends on how much gets to the sensor crystal. It can't =
take
>> direct exposure to the combustion chamber gasses, for heat and =
chemical
>> issues. Thus attenuation, maybe a lot of it, before the sensor =
crystal
>> "sees" it. > > >Our engine in-cylinder pressure sensors are flush with the head, so see >the combustion chamber environment directly. I think all they have is a >thin metal foil over the sensor material surface. >
We may never know unless someone sections one. ?-)
Reply by Mr.CRC April 17, 20122012-04-17
josephkk wrote:
> On Sun, 15 Apr 2012 14:58:31 -0700, John Larkin > <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >> On Sun, 15 Apr 2012 23:15:07 +0300, Tauno Voipio >> <tauno.voipio@notused.fi.invalid> wrote: >> >>> On 15.4.12 8:05 , John Larkin wrote: >>>> On Sun, 15 Apr 2012 08:10:23 -0700, josephkk >>>> <joseph_barrett@sbcglobal.net> wrote: >>>> >>>>> On Fri, 13 Apr 2012 07:19:40 -0700 (PDT), Geoffrey >>>>> <gmortimer2003@yahoo.com> wrote: >>>>> >>>>>> On Apr 11, 2:49 am, josephkk<joseph_barr...@sbcglobal.net> wrote: >>>>>>> On Tue, 3 Apr 2012 07:53:52 -0700 (PDT), Geoffrey >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> <gmortimer2...@yahoo.com> wrote: >>>>>>>> Hi there >>>>>>>> I have a charge amplifier, used to amplify the signal from a piezo >>>>>>>> electric transducer, with 2nF of reference capacitance shunted with >>>>>>>> 1GOhm. I need to be able to reset the amplifier, preferably with a >>>>>>>> solid state device (the circuit has to be very compact, and operate in >>>>>>>> a high-vibration environment). One possibility which comes to mind is >>>>>>>> to simultaneously short the amplifier output and input to ground. The >>>>>>>> input is the inverting input of the amplifier, and is nominally at the >>>>>>>> same ground potential as the non inverting input. I am considering the >>>>>>>> use of a mosfet as the shorting switch for the input. When the mosfet >>>>>>>> is off, its gate will be at ground potential, as will its drain >>>>>>>> (virtual ground) and source. Is there a mechanism whereby a leakage >>>>>>>> current could still flow from drain to source? Every nanoampere of IDS >>>>>>>> gives 1V of offset at the output, and it should be noted that the >>>>>>>> circuit must work at 120 deg C. >>>>>>>> Any help appreciated. >>>>>>>> Best regards >>>>>>>> Geoff >>>>>>> As a test engineer at an earlier time i am troubled by the conditions you >>>>>>> are subjecting your charge amplifier to. What constraints do you have >>>>>>> that you cannot put your charge amplifier in a benign location, away from >>>>>>> the heat and vibration? >>>>>>> >>>>>>> ?-)- Hide quoted text - >>>>>>> >>>>>>> - Show quoted text - >>>>>> The amplifier will be placed in the Vee of a motor racing engine, the >>>>>> piezo sensor being used to measure the pressure in the combustion >>>>>> chamber. It is possible that a solution involving longer cables could >>>>>> be found, but there are high levels of EMI due to ignition systems and >>>>>> other power electronics. The temperature is a bit of a bother - few >>>>>> charge amps are specified at 125 degrees due to the high leakage and >>>>>> bias currents at that temperature. >>>>> I was wondering. There is no need to subject the charge amplifier to that >>>>> environment. It belongs in the driver compartment. Far less heat, and a >>>>> bit less vibration. Of course you are paying about US$18/ft for the >>>>> special shielded cable for either placement. (Shake and bake >>>>> piezoelectric accelerometer cable from Endevco[, and perhaps Ling or >>>>> Umhholz-Dickie].) >>>>> >>>>> ?-) >>>> What's special about piezo cable? Any teflon coax, or semi-hardline >>>> for super shielding, would work. He'll probably have lots of signal. >>>> >>>> >>> Teflon is not a good idea, due to microphonics. >> Depends on how much signal he has. I'd expect an engine explosion to >> make lots of signal. > > That also depends on how much gets to the sensor crystal. It can't take > direct exposure to the combustion chamber gasses, for heat and chemical > issues. Thus attenuation, maybe a lot of it, before the sensor crystal > "sees" it.
Our engine in-cylinder pressure sensors are flush with the head, so see the combustion chamber environment directly. I think all they have is a thin metal foil over the sensor material surface. -- _____________________ Mr.CRC crobcBOGUS@REMOVETHISsbcglobal.net SuSE 10.3 Linux 2.6.22.17
Reply by josephkk April 16, 20122012-04-16
On Sun, 15 Apr 2012 14:58:31 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

>On Sun, 15 Apr 2012 23:15:07 +0300, Tauno Voipio ><tauno.voipio@notused.fi.invalid> wrote: > >>On 15.4.12 8:05 , John Larkin wrote: >>> On Sun, 15 Apr 2012 08:10:23 -0700, josephkk >>> <joseph_barrett@sbcglobal.net> wrote: >>> >>>> On Fri, 13 Apr 2012 07:19:40 -0700 (PDT), Geoffrey >>>> <gmortimer2003@yahoo.com> wrote: >>>> >>>>> On Apr 11, 2:49 am, josephkk<joseph_barr...@sbcglobal.net> wrote: >>>>>> On Tue, 3 Apr 2012 07:53:52 -0700 (PDT), Geoffrey >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> <gmortimer2...@yahoo.com> wrote: >>>>>>> Hi there >>>>>> >>>>>>> I have a charge amplifier, used to amplify the signal from a =
piezo
>>>>>>> electric transducer, with 2nF of reference capacitance shunted =
with
>>>>>>> 1GOhm. I need to be able to reset the amplifier, preferably with =
a
>>>>>>> solid state device (the circuit has to be very compact, and =
operate in
>>>>>>> a high-vibration environment). One possibility which comes to =
mind is
>>>>>>> to simultaneously short the amplifier output and input to ground.=
The
>>>>>>> input is the inverting input of the amplifier, and is nominally =
at the
>>>>>>> same ground potential as the non inverting input. I am =
considering the
>>>>>>> use of a mosfet as the shorting switch for the input. When the =
mosfet
>>>>>>> is off, its gate will be at ground potential, as will its drain >>>>>>> (virtual ground) and source. Is there a mechanism whereby a =
leakage
>>>>>>> current could still flow from drain to source? Every nanoampere =
of IDS
>>>>>>> gives 1V of offset at the output, and it should be noted that the >>>>>>> circuit must work at 120 deg C. >>>>>> >>>>>>> Any help appreciated. >>>>>> >>>>>>> Best regards >>>>>>> Geoff >>>>>> >>>>>> As a test engineer at an earlier time i am troubled by the =
conditions you
>>>>>> are subjecting your charge amplifier to. What constraints do you =
have
>>>>>> that you cannot put your charge amplifier in a benign location, =
away from
>>>>>> the heat and vibration? >>>>>> >>>>>> ?-)- Hide quoted text - >>>>>> >>>>>> - Show quoted text - >>>>> >>>>> The amplifier will be placed in the Vee of a motor racing engine, =
the
>>>>> piezo sensor being used to measure the pressure in the combustion >>>>> chamber. It is possible that a solution involving longer cables =
could
>>>>> be found, but there are high levels of EMI due to ignition systems =
and
>>>>> other power electronics. The temperature is a bit of a bother - few >>>>> charge amps are specified at 125 degrees due to the high leakage =
and
>>>>> bias currents at that temperature. >>>> >>>> I was wondering. There is no need to subject the charge amplifier =
to that
>>>> environment. It belongs in the driver compartment. Far less heat, =
and a
>>>> bit less vibration. Of course you are paying about US$18/ft for the >>>> special shielded cable for either placement. (Shake and bake >>>> piezoelectric accelerometer cable from Endevco[, and perhaps Ling or >>>> Umhholz-Dickie].) >>>> >>>> ?-) >>> >>> What's special about piezo cable? Any teflon coax, or semi-hardline >>> for super shielding, would work. He'll probably have lots of signal. >>> >>> >> >>Teflon is not a good idea, due to microphonics. > >Depends on how much signal he has. I'd expect an engine explosion to >make lots of signal.
That also depends on how much gets to the sensor crystal. It can't take direct exposure to the combustion chamber gasses, for heat and chemical issues. Thus attenuation, maybe a lot of it, before the sensor crystal "sees" it. ?-)
Reply by John Larkin April 15, 20122012-04-15
On Sun, 15 Apr 2012 23:15:07 +0300, Tauno Voipio
<tauno.voipio@notused.fi.invalid> wrote:

>On 15.4.12 8:05 , John Larkin wrote: >> On Sun, 15 Apr 2012 08:10:23 -0700, josephkk >> <joseph_barrett@sbcglobal.net> wrote: >> >>> On Fri, 13 Apr 2012 07:19:40 -0700 (PDT), Geoffrey >>> <gmortimer2003@yahoo.com> wrote: >>> >>>> On Apr 11, 2:49 am, josephkk<joseph_barr...@sbcglobal.net> wrote: >>>>> On Tue, 3 Apr 2012 07:53:52 -0700 (PDT), Geoffrey >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> <gmortimer2...@yahoo.com> wrote: >>>>>> Hi there >>>>> >>>>>> I have a charge amplifier, used to amplify the signal from a piezo >>>>>> electric transducer, with 2nF of reference capacitance shunted with >>>>>> 1GOhm. I need to be able to reset the amplifier, preferably with a >>>>>> solid state device (the circuit has to be very compact, and operate in >>>>>> a high-vibration environment). One possibility which comes to mind is >>>>>> to simultaneously short the amplifier output and input to ground. The >>>>>> input is the inverting input of the amplifier, and is nominally at the >>>>>> same ground potential as the non inverting input. I am considering the >>>>>> use of a mosfet as the shorting switch for the input. When the mosfet >>>>>> is off, its gate will be at ground potential, as will its drain >>>>>> (virtual ground) and source. Is there a mechanism whereby a leakage >>>>>> current could still flow from drain to source? Every nanoampere of IDS >>>>>> gives 1V of offset at the output, and it should be noted that the >>>>>> circuit must work at 120 deg C. >>>>> >>>>>> Any help appreciated. >>>>> >>>>>> Best regards >>>>>> Geoff >>>>> >>>>> As a test engineer at an earlier time i am troubled by the conditions you >>>>> are subjecting your charge amplifier to. What constraints do you have >>>>> that you cannot put your charge amplifier in a benign location, away from >>>>> the heat and vibration? >>>>> >>>>> ?-)- Hide quoted text - >>>>> >>>>> - Show quoted text - >>>> >>>> The amplifier will be placed in the Vee of a motor racing engine, the >>>> piezo sensor being used to measure the pressure in the combustion >>>> chamber. It is possible that a solution involving longer cables could >>>> be found, but there are high levels of EMI due to ignition systems and >>>> other power electronics. The temperature is a bit of a bother - few >>>> charge amps are specified at 125 degrees due to the high leakage and >>>> bias currents at that temperature. >>> >>> I was wondering. There is no need to subject the charge amplifier to that >>> environment. It belongs in the driver compartment. Far less heat, and a >>> bit less vibration. Of course you are paying about US$18/ft for the >>> special shielded cable for either placement. (Shake and bake >>> piezoelectric accelerometer cable from Endevco[, and perhaps Ling or >>> Umhholz-Dickie].) >>> >>> ?-) >> >> What's special about piezo cable? Any teflon coax, or semi-hardline >> for super shielding, would work. He'll probably have lots of signal. >> >> > >Teflon is not a good idea, due to microphonics.
Depends on how much signal he has. I'd expect an engine explosion to make lots of signal. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by Tauno Voipio April 15, 20122012-04-15
On 15.4.12 8:05 , John Larkin wrote:
> On Sun, 15 Apr 2012 08:10:23 -0700, josephkk > <joseph_barrett@sbcglobal.net> wrote: > >> On Fri, 13 Apr 2012 07:19:40 -0700 (PDT), Geoffrey >> <gmortimer2003@yahoo.com> wrote: >> >>> On Apr 11, 2:49 am, josephkk<joseph_barr...@sbcglobal.net> wrote: >>>> On Tue, 3 Apr 2012 07:53:52 -0700 (PDT), Geoffrey >>>> >>>> >>>> >>>> >>>> >>>> <gmortimer2...@yahoo.com> wrote: >>>>> Hi there >>>> >>>>> I have a charge amplifier, used to amplify the signal from a piezo >>>>> electric transducer, with 2nF of reference capacitance shunted with >>>>> 1GOhm. I need to be able to reset the amplifier, preferably with a >>>>> solid state device (the circuit has to be very compact, and operate in >>>>> a high-vibration environment). One possibility which comes to mind is >>>>> to simultaneously short the amplifier output and input to ground. The >>>>> input is the inverting input of the amplifier, and is nominally at the >>>>> same ground potential as the non inverting input. I am considering the >>>>> use of a mosfet as the shorting switch for the input. When the mosfet >>>>> is off, its gate will be at ground potential, as will its drain >>>>> (virtual ground) and source. Is there a mechanism whereby a leakage >>>>> current could still flow from drain to source? Every nanoampere of IDS >>>>> gives 1V of offset at the output, and it should be noted that the >>>>> circuit must work at 120 deg C. >>>> >>>>> Any help appreciated. >>>> >>>>> Best regards >>>>> Geoff >>>> >>>> As a test engineer at an earlier time i am troubled by the conditions you >>>> are subjecting your charge amplifier to. What constraints do you have >>>> that you cannot put your charge amplifier in a benign location, away from >>>> the heat and vibration? >>>> >>>> ?-)- Hide quoted text - >>>> >>>> - Show quoted text - >>> >>> The amplifier will be placed in the Vee of a motor racing engine, the >>> piezo sensor being used to measure the pressure in the combustion >>> chamber. It is possible that a solution involving longer cables could >>> be found, but there are high levels of EMI due to ignition systems and >>> other power electronics. The temperature is a bit of a bother - few >>> charge amps are specified at 125 degrees due to the high leakage and >>> bias currents at that temperature. >> >> I was wondering. There is no need to subject the charge amplifier to that >> environment. It belongs in the driver compartment. Far less heat, and a >> bit less vibration. Of course you are paying about US$18/ft for the >> special shielded cable for either placement. (Shake and bake >> piezoelectric accelerometer cable from Endevco[, and perhaps Ling or >> Umhholz-Dickie].) >> >> ?-) > > What's special about piezo cable? Any teflon coax, or semi-hardline > for super shielding, would work. He'll probably have lots of signal. > >
Teflon is not a good idea, due to microphonics.
Reply by John Larkin April 15, 20122012-04-15
On Sun, 15 Apr 2012 08:10:23 -0700, josephkk
<joseph_barrett@sbcglobal.net> wrote:

>On Fri, 13 Apr 2012 07:19:40 -0700 (PDT), Geoffrey ><gmortimer2003@yahoo.com> wrote: > >>On Apr 11, 2:49&#4294967295;am, josephkk <joseph_barr...@sbcglobal.net> wrote: >>> On Tue, 3 Apr 2012 07:53:52 -0700 (PDT), Geoffrey >>> >>> >>> >>> >>> >>> <gmortimer2...@yahoo.com> wrote: >>> >Hi there >>> >>> >I have a charge amplifier, used to amplify the signal from a piezo >>> >electric transducer, with 2nF of reference capacitance shunted with >>> >1GOhm. I need to be able to reset the amplifier, preferably with a >>> >solid state device (the circuit has to be very compact, and operate in >>> >a high-vibration environment). One possibility which comes to mind is >>> >to simultaneously short the amplifier output and input to ground. The >>> >input is the inverting input of the amplifier, and is nominally at the >>> >same ground potential as the non inverting input. I am considering the >>> >use of a mosfet as the shorting switch for the input. When the mosfet >>> >is off, its gate will be at ground potential, as will its drain >>> >(virtual ground) and source. Is there a mechanism whereby a leakage >>> >current could still flow from drain to source? Every nanoampere of IDS >>> >gives 1V of offset at the output, and it should be noted that the >>> >circuit must work at 120 deg C. >>> >>> >Any help appreciated. >>> >>> >Best regards >>> >Geoff >>> >>> As a test engineer at an earlier time i am troubled by the conditions you >>> are subjecting your charge amplifier to. &#4294967295;What constraints do you have >>> that you cannot put your charge amplifier in a benign location, away from >>> the heat and vibration? >>> >>> ?-)- Hide quoted text - >>> >>> - Show quoted text - >> >>The amplifier will be placed in the Vee of a motor racing engine, the >>piezo sensor being used to measure the pressure in the combustion >>chamber. It is possible that a solution involving longer cables could >>be found, but there are high levels of EMI due to ignition systems and >>other power electronics. The temperature is a bit of a bother - few >>charge amps are specified at 125 degrees due to the high leakage and >>bias currents at that temperature. > >I was wondering. There is no need to subject the charge amplifier to that >environment. It belongs in the driver compartment. Far less heat, and a >bit less vibration. Of course you are paying about US$18/ft for the >special shielded cable for either placement. (Shake and bake >piezoelectric accelerometer cable from Endevco[, and perhaps Ling or >Umhholz-Dickie].) > >?-)
What's special about piezo cable? Any teflon coax, or semi-hardline for super shielding, would work. He'll probably have lots of signal. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by josephkk April 15, 20122012-04-15
On Fri, 13 Apr 2012 07:19:40 -0700 (PDT), Geoffrey
<gmortimer2003@yahoo.com> wrote:

>On Apr 11, 2:49=A0am, josephkk <joseph_barr...@sbcglobal.net> wrote: >> On Tue, 3 Apr 2012 07:53:52 -0700 (PDT), Geoffrey >> >> >> >> >> >> <gmortimer2...@yahoo.com> wrote: >> >Hi there >> >> >I have a charge amplifier, used to amplify the signal from a piezo >> >electric transducer, with 2nF of reference capacitance shunted with >> >1GOhm. I need to be able to reset the amplifier, preferably with a >> >solid state device (the circuit has to be very compact, and operate =
in
>> >a high-vibration environment). One possibility which comes to mind is >> >to simultaneously short the amplifier output and input to ground. The >> >input is the inverting input of the amplifier, and is nominally at =
the
>> >same ground potential as the non inverting input. I am considering =
the
>> >use of a mosfet as the shorting switch for the input. When the mosfet >> >is off, its gate will be at ground potential, as will its drain >> >(virtual ground) and source. Is there a mechanism whereby a leakage >> >current could still flow from drain to source? Every nanoampere of =
IDS
>> >gives 1V of offset at the output, and it should be noted that the >> >circuit must work at 120 deg C. >> >> >Any help appreciated. >> >> >Best regards >> >Geoff >> >> As a test engineer at an earlier time i am troubled by the conditions =
you
>> are subjecting your charge amplifier to. =A0What constraints do you =
have
>> that you cannot put your charge amplifier in a benign location, away =
from
>> the heat and vibration? >> >> ?-)- Hide quoted text - >> >> - Show quoted text - > >The amplifier will be placed in the Vee of a motor racing engine, the >piezo sensor being used to measure the pressure in the combustion >chamber. It is possible that a solution involving longer cables could >be found, but there are high levels of EMI due to ignition systems and >other power electronics. The temperature is a bit of a bother - few >charge amps are specified at 125 degrees due to the high leakage and >bias currents at that temperature.
I was wondering. There is no need to subject the charge amplifier to = that environment. It belongs in the driver compartment. Far less heat, and a bit less vibration. Of course you are paying about US$18/ft for the special shielded cable for either placement. (Shake and bake piezoelectric accelerometer cable from Endevco[, and perhaps Ling or Umhholz-Dickie].) ?-)
Reply by John Larkin April 13, 20122012-04-13
On Fri, 13 Apr 2012 07:19:40 -0700 (PDT), Geoffrey
<gmortimer2003@yahoo.com> wrote:

>On Apr 11, 2:49&#4294967295;am, josephkk <joseph_barr...@sbcglobal.net> wrote: >> On Tue, 3 Apr 2012 07:53:52 -0700 (PDT), Geoffrey >> >> >> >> >> >> <gmortimer2...@yahoo.com> wrote: >> >Hi there >> >> >I have a charge amplifier, used to amplify the signal from a piezo >> >electric transducer, with 2nF of reference capacitance shunted with >> >1GOhm. I need to be able to reset the amplifier, preferably with a >> >solid state device (the circuit has to be very compact, and operate in >> >a high-vibration environment). One possibility which comes to mind is >> >to simultaneously short the amplifier output and input to ground. The >> >input is the inverting input of the amplifier, and is nominally at the >> >same ground potential as the non inverting input. I am considering the >> >use of a mosfet as the shorting switch for the input. When the mosfet >> >is off, its gate will be at ground potential, as will its drain >> >(virtual ground) and source. Is there a mechanism whereby a leakage >> >current could still flow from drain to source? Every nanoampere of IDS >> >gives 1V of offset at the output, and it should be noted that the >> >circuit must work at 120 deg C. >> >> >Any help appreciated. >> >> >Best regards >> >Geoff >> >> As a test engineer at an earlier time i am troubled by the conditions you >> are subjecting your charge amplifier to. &#4294967295;What constraints do you have >> that you cannot put your charge amplifier in a benign location, away from >> the heat and vibration? >> >> ?-)- Hide quoted text - >> >> - Show quoted text - > >The amplifier will be placed in the Vee of a motor racing engine, the >piezo sensor being used to measure the pressure in the combustion >chamber. It is possible that a solution involving longer cables could >be found, but there are high levels of EMI due to ignition systems and >other power electronics. The temperature is a bit of a bother - few >charge amps are specified at 125 degrees due to the high leakage and >bias currents at that temperature.
I should think that you'd get a huge signal from that setup. Why not run well-shielded coax to a remote charge amp in a friendlier location? -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by Geoffrey April 13, 20122012-04-13
On Apr 11, 2:49=A0am, josephkk <joseph_barr...@sbcglobal.net> wrote:
> On Tue, 3 Apr 2012 07:53:52 -0700 (PDT), Geoffrey > > > > > > <gmortimer2...@yahoo.com> wrote: > >Hi there > > >I have a charge amplifier, used to amplify the signal from a piezo > >electric transducer, with 2nF of reference capacitance shunted with > >1GOhm. I need to be able to reset the amplifier, preferably with a > >solid state device (the circuit has to be very compact, and operate in > >a high-vibration environment). One possibility which comes to mind is > >to simultaneously short the amplifier output and input to ground. The > >input is the inverting input of the amplifier, and is nominally at the > >same ground potential as the non inverting input. I am considering the > >use of a mosfet as the shorting switch for the input. When the mosfet > >is off, its gate will be at ground potential, as will its drain > >(virtual ground) and source. Is there a mechanism whereby a leakage > >current could still flow from drain to source? Every nanoampere of IDS > >gives 1V of offset at the output, and it should be noted that the > >circuit must work at 120 deg C. > > >Any help appreciated. > > >Best regards > >Geoff > > As a test engineer at an earlier time i am troubled by the conditions you > are subjecting your charge amplifier to. =A0What constraints do you have > that you cannot put your charge amplifier in a benign location, away from > the heat and vibration? > > ?-)- Hide quoted text - > > - Show quoted text -
The amplifier will be placed in the Vee of a motor racing engine, the piezo sensor being used to measure the pressure in the combustion chamber. It is possible that a solution involving longer cables could be found, but there are high levels of EMI due to ignition systems and other power electronics. The temperature is a bit of a bother - few charge amps are specified at 125 degrees due to the high leakage and bias currents at that temperature.
Reply by josephkk April 10, 20122012-04-10
On Tue, 3 Apr 2012 07:53:52 -0700 (PDT), Geoffrey
<gmortimer2003@yahoo.com> wrote:

>Hi there > >I have a charge amplifier, used to amplify the signal from a piezo >electric transducer, with 2nF of reference capacitance shunted with >1GOhm. I need to be able to reset the amplifier, preferably with a >solid state device (the circuit has to be very compact, and operate in >a high-vibration environment). One possibility which comes to mind is >to simultaneously short the amplifier output and input to ground. The >input is the inverting input of the amplifier, and is nominally at the >same ground potential as the non inverting input. I am considering the >use of a mosfet as the shorting switch for the input. When the mosfet >is off, its gate will be at ground potential, as will its drain >(virtual ground) and source. Is there a mechanism whereby a leakage >current could still flow from drain to source? Every nanoampere of IDS >gives 1V of offset at the output, and it should be noted that the >circuit must work at 120 deg C. > >Any help appreciated. > >Best regards >Geoff
As a test engineer at an earlier time i am troubled by the conditions you are subjecting your charge amplifier to. What constraints do you have that you cannot put your charge amplifier in a benign location, away from the heat and vibration? ?-)