>
> On Thu, 19 Aug 1999, Russell McMahon wrote:
>
> > I tried using a Zinc-Air cell as an O2 sensor REALLY roughly (seemed like a
> > cheap way to make a sensor) and cell voltage seemed to be very insensitive
> > to Oxygen concentration (as you suggest it would be). Stored O2 appears to
> > be a major problem.  I'll be trying it again in due course with  a little
> > more finesses (hopefully). We bought a batch of "real" Oxygen sensors but
> > even in 100 volume (I think it was) they cost around $US45 AFAIR. These DO
> > produce a linear pO2 versus Voltage response. Being an electrochemical cell
> > they have a finite lifetime and they drift severely so you need to
> > calibrate them before every use. Fortunately there is an easy cheap and
> > fairly accurate source of 20.8%-Oxygen calibration gas available. (Or, if
> > you want to argue, 20.95 +/- 0.01% - yep, the ranges don't coincide-
> > depends who you listen to :-)).
>
> Before I address the O2 sensor issue, let me first ask if you
> really need one.  If you're looking to do life support
> in a fixed volume container, all you have to do is blow
> a muffin fan through a can of Calcium hydroxide (Sofnolime
> brand is good), and have a demand regulator hooked up
> to a source of 100% O2.  The Co2 goes into the scrubber,
> which drops the pressure inside the environment, and
> causes the demand reg to pump in the appropriate amount
> of O2.  This is what they do in mini-subs.
>
> For the sensors - I did some extensive hyperbaric tests using
> zinc-air cells as oxygen sensors.  My interests were a little
> different, as I was mostly interested in measuring higher
> partial pressures (0-2.0 ATA PPO2).  At any rate, the upshot
> is that they have horrible drift and are not particularly linear.
> They also have a very short life in hyperoxic environments, as
> you might expect.
> If you want to do some playing around with them, use a *small*
> cell (Duracell DA13, as I recall), and put a few hundred ohm load on
> them.  The smaller cells react faster and store less gas internally.
>
> Galvanics are the way to go for O2 sensing.  If you want small,
> Teledyne makes a sensor called the K-1, which is about 3/4 inch
> in diameter and 3/4 inch long.  The calibration issue is real - you
> do need to recalibrate regularly if you want accuracy.
>
> There are also fourescent dye based sensors, which apparently
> work extremely well, but I don't have any experience with those.
>
> Finally, there's paramagnetic O2 sensors.  This is really the
> ultimate O2 sensor, as they never need to be recalibrated and
> never wear out.  Unfortunately, the ones that have no moving
> parts are the size of a Coke can and draw major current.  They're
> also expensive ($2500 as I recall).  The current draw is because
> they've got an internal heater, as apparently the paramagnetic
> effect is very temperature sensitive.
>
> Along these lines, I screwed around with using Hall Effect
> and GMR devices to brew up a cheap paramagnetic O2 sensor,
> but never got too far with that project.
>
> -Will
>
> > decent
> > >pO2 sensors.
> > >
> > >Just looking at their voltage wouldn't work, of course.
> > >The voltage would be something like the log of pO2, a weak function, and
> > >subject to stored O2 every time it got a good exposure.
> > >
> > >But the sensor was run as a current source into a virtual-ground meter
> > input,
> > >with a small diffusive air leak,
> > >the current might be proportional to pO2 with a response time of under a
> > >minute.
> > >
> > >This might be useful for monitoring inert-gas vs oxygen.
> > >I never got around to trying it.
> > >Has anybody tried this or heard of it?
> > >
> > >Jim S
> >

> good luck,
> joe
>
>
> "William M. Smithers" wrote:
> >
> > On Thu, 19 Aug 1999, Russell McMahon wrote:
> >
> > > I tried using a Zinc-Air cell as an O2 sensor REALLY roughly (seemed like
a
> > > cheap way to make a sensor) and cell voltage seemed to be very insensitive
> > > to Oxygen concentration (as you suggest it would be). Stored O2 appears to
> > > be a major problem.  I'll be trying it again in due course with  a little
> > > more finesses (hopefully). We bought a batch of "real" Oxygen sensors but
> > > even in 100 volume (I think it was) they cost around $US45 AFAIR. These DO
> > > produce a linear pO2 versus Voltage response. Being an electrochemical cel
l
> > > they have a finite lifetime and they drift severely so you need to
> > > calibrate them before every use. Fortunately there is an easy cheap and
> > > fairly accurate source of 20.8%-Oxygen calibration gas available. (Or, if
> > > you want to argue, 20.95 +/- 0.01% - yep, the ranges don't coincide-
> > > depends who you listen to :-)).
> >
> > Before I address the O2 sensor issue, let me first ask if you
> > really need one.  If you're looking to do life support
> > in a fixed volume container, all you have to do is blow
> > a muffin fan through a can of Calcium hydroxide (Sofnolime
> > brand is good), and have a demand regulator hooked up
> > to a source of 100% O2.  The Co2 goes into the scrubber,
> > which drops the pressure inside the environment, and
> > causes the demand reg to pump in the appropriate amount
> > of O2.  This is what they do in mini-subs.
> >
> > For the sensors - I did some extensive hyperbaric tests using
> > zinc-air cells as oxygen sensors.  My interests were a little
> > different, as I was mostly interested in measuring higher
> > partial pressures (0-2.0 ATA PPO2).  At any rate, the upshot
> > is that they have horrible drift and are not particularly linear.
> > They also have a very short life in hyperoxic environments, as
> > you might expect.
> > If you want to do some playing around with them, use a *small*
> > cell (Duracell DA13, as I recall), and put a few hundred ohm load on
> > them.  The smaller cells react faster and store less gas internally.
> >
> > Galvanics are the way to go for O2 sensing.  If you want small,
> > Teledyne makes a sensor called the K-1, which is about 3/4 inch
> > in diameter and 3/4 inch long.  The calibration issue is real - you
> > do need to recalibrate regularly if you want accuracy.
> >
> > There are also fourescent dye based sensors, which apparently
> > work extremely well, but I don't have any experience with those.
> >
> > Finally, there's paramagnetic O2 sensors.  This is really the
> > ultimate O2 sensor, as they never need to be recalibrated and
> > never wear out.  Unfortunately, the ones that have no moving
> > parts are the size of a Coke can and draw major current.  They're
> > also expensive ($2500 as I recall).  The current draw is because
> > they've got an internal heater, as apparently the paramagnetic
> > effect is very temperature sensitive.
> >
> > Along these lines, I screwed around with using Hall Effect
> > and GMR devices to brew up a cheap paramagnetic O2 sensor,
> > but never got too far with that project.
> >
> > -Will
> >
> > > decent
> > > >pO2 sensors.
> > > >
> > > >Just looking at their voltage wouldn't work, of course.
> > > >The voltage would be something like the log of pO2, a weak function, and
> > > >subject to stored O2 every time it got a good exposure.
> > > >
> > > >But the sensor was run as a current source into a virtual-ground meter
> > > input,
> > > >with a small diffusive air leak,
> > > >the current might be proportional to pO2 with a response time of under a
> > > >minute.
> > > >
> > > >This might be useful for monitoring inert-gas vs oxygen.
> > > >I never got around to trying it.
> > > >Has anybody tried this or heard of it?
> > > >
> > > >Jim S
> > >
>

> good luck,
> joe
>
>
> "William M. Smithers" wrote:
> >
> > On Thu, 19 Aug 1999, Russell McMahon wrote:
> >
> > > I tried using a Zinc-Air cell as an O2 sensor REALLY roughly (seemed like
a
> > > cheap way to make a sensor) and cell voltage seemed to be very insensitive
> > > to Oxygen concentration (as you suggest it would be). Stored O2 appears to
> > > be a major problem.  I'll be trying it again in due course with  a little
> > > more finesses (hopefully). We bought a batch of "real" Oxygen sensors but
> > > even in 100 volume (I think it was) they cost around $US45 AFAIR. These DO
> > > produce a linear pO2 versus Voltage response. Being an electrochemical cel
l
> > > they have a finite lifetime and they drift severely so you need to
> > > calibrate them before every use. Fortunately there is an easy cheap and
> > > fairly accurate source of 20.8%-Oxygen calibration gas available. (Or, if
> > > you want to argue, 20.95 +/- 0.01% - yep, the ranges don't coincide-
> > > depends who you listen to :-)).
> >
> > Before I address the O2 sensor issue, let me first ask if you
> > really need one.  If you're looking to do life support
> > in a fixed volume container, all you have to do is blow
> > a muffin fan through a can of Calcium hydroxide (Sofnolime
> > brand is good), and have a demand regulator hooked up
> > to a source of 100% O2.  The Co2 goes into the scrubber,
> > which drops the pressure inside the environment, and
> > causes the demand reg to pump in the appropriate amount
> > of O2.  This is what they do in mini-subs.
> >
> > For the sensors - I did some extensive hyperbaric tests using
> > zinc-air cells as oxygen sensors.  My interests were a little
> > different, as I was mostly interested in measuring higher
> > partial pressures (0-2.0 ATA PPO2).  At any rate, the upshot
> > is that they have horrible drift and are not particularly linear.
> > They also have a very short life in hyperoxic environments, as
> > you might expect.
> > If you want to do some playing around with them, use a *small*
> > cell (Duracell DA13, as I recall), and put a few hundred ohm load on
> > them.  The smaller cells react faster and store less gas internally.
> >
> > Galvanics are the way to go for O2 sensing.  If you want small,
> > Teledyne makes a sensor called the K-1, which is about 3/4 inch
> > in diameter and 3/4 inch long.  The calibration issue is real - you
> > do need to recalibrate regularly if you want accuracy.
> >
> > There are also fourescent dye based sensors, which apparently
> > work extremely well, but I don't have any experience with those.
> >
> > Finally, there's paramagnetic O2 sensors.  This is really the
> > ultimate O2 sensor, as they never need to be recalibrated and
> > never wear out.  Unfortunately, the ones that have no moving
> > parts are the size of a Coke can and draw major current.  They're
> > also expensive ($2500 as I recall).  The current draw is because
> > they've got an internal heater, as apparently the paramagnetic
> > effect is very temperature sensitive.
> >
> > Along these lines, I screwed around with using Hall Effect
> > and GMR devices to brew up a cheap paramagnetic O2 sensor,
> > but never got too far with that project.
> >
> > -Will
> >
> > > decent
> > > >pO2 sensors.
> > > >
> > > >Just looking at their voltage wouldn't work, of course.
> > > >The voltage would be something like the log of pO2, a weak function, and
> > > >subject to stored O2 every time it got a good exposure.
> > > >
> > > >But the sensor was run as a current source into a virtual-ground meter
> > > input,
> > > >with a small diffusive air leak,
> > > >the current might be proportional to pO2 with a response time of under a
> > > >minute.
> > > >
> > > >This might be useful for monitoring inert-gas vs oxygen.
> > > >I never got around to trying it.
> > > >Has anybody tried this or heard of it?
> > > >
> > > >Jim S
> > >
>

>
>-Will
>
>
>> good luck,
>> joe
>>
>>
>> "William M. Smithers" wrote:
>> >
>> > On Thu, 19 Aug 1999, Russell McMahon wrote:
>> >
>> > > I tried using a Zinc-Air cell as an O2 sensor REALLY roughly (seemed

>> > > you want to argue, 20.95 +/- 0.01% - yep, the ranges don't coincide-
>> > > depends who you listen to :-)).
>> >
>> > Before I address the O2 sensor issue, let me first ask if you
>> > really need one.  If you're looking to do life support
>> > in a fixed volume container, all you have to do is blow
>> > a muffin fan through a can of Calcium hydroxide (Sofnolime
>> > brand is good), and have a demand regulator hooked up
>> > to a source of 100% O2.  The Co2 goes into the scrubber,
>> > which drops the pressure inside the environment, and
>> > causes the demand reg to pump in the appropriate amount
>> > of O2.  This is what they do in mini-subs.
>> >
>> > For the sensors - I did some extensive hyperbaric tests using
>> > zinc-air cells as oxygen sensors.  My interests were a little
>> > different, as I was mostly interested in measuring higher
>> > partial pressures (0-2.0 ATA PPO2).  At any rate, the upshot
>> > is that they have horrible drift and are not particularly linear.
>> > They also have a very short life in hyperoxic environments, as
>> > you might expect.
>> > If you want to do some playing around with them, use a *small*
>> > cell (Duracell DA13, as I recall), and put a few hundred ohm load on
>> > them.  The smaller cells react faster and store less gas internally.
>> >
>> > Galvanics are the way to go for O2 sensing.  If you want small,
>> > Teledyne makes a sensor called the K-1, which is about 3/4 inch
>> > in diameter and 3/4 inch long.  The calibration issue is real - you
>> > do need to recalibrate regularly if you want accuracy.
>> >
>> > There are also fourescent dye based sensors, which apparently
>> > work extremely well, but I don't have any experience with those.
>> >
>> > Finally, there's paramagnetic O2 sensors.  This is really the
>> > ultimate O2 sensor, as they never need to be recalibrated and
>> > never wear out.  Unfortunately, the ones that have no moving
>> > parts are the size of a Coke can and draw major current.  They're
>> > also expensive ($2500 as I recall).  The current draw is because
>> > they've got an internal heater, as apparently the paramagnetic
>> > effect is very temperature sensitive.
>> >
>> > Along these lines, I screwed around with using Hall Effect
>> > and GMR devices to brew up a cheap paramagnetic O2 sensor,
>> > but never got too far with that project.
>> >
>> > -Will
>> >
>> > > decent
>> > > >pO2 sensors.
>> > > >
>> > > >Just looking at their voltage wouldn't work, of course.
>> > > >The voltage would be something like the log of pO2, a weak

>> > > >minute.
>> > > >
>> > > >This might be useful for monitoring inert-gas vs oxygen.
>> > > >I never got around to trying it.
>> > > >Has anybody tried this or heard of it?
>> > > >
>> > > >Jim S
>> > >
>>
>
>

>
> Dennis
>
>
> >
> >-Will
> >
> >
> >> good luck,
> >> joe
> >>
> >>
> >> "William M. Smithers" wrote:
> >> >
> >> > On Thu, 19 Aug 1999, Russell McMahon wrote:
> >> >
> >> > > I tried using a Zinc-Air cell as an O2 sensor REALLY roughly (seemed
> like a
> >> > > cheap way to make a sensor) and cell voltage seemed to be very
> insensitive
> >> > > to Oxygen concentration (as you suggest it would be). Stored O2
> appears to
> >> > > be a major problem.  I'll be trying it again in due course with  a
> little
> >> > > more finesses (hopefully). We bought a batch of "real" Oxygen
> sensors but
> >> > > even in 100 volume (I think it was) they cost around $US45 AFAIR.
> These DO
> >> > > produce a linear pO2 versus Voltage response. Being an
> electrochemical cell
> >> > > they have a finite lifetime and they drift severely so you need to
> >> > > calibrate them before every use. Fortunately there is an easy cheap and
> >> > > fairly accurate source of 20.8%-Oxygen calibration gas available.
> (Or, if
> >> > > you want to argue, 20.95 +/- 0.01% - yep, the ranges don't coincide-
> >> > > depends who you listen to :-)).
> >> >
> >> > Before I address the O2 sensor issue, let me first ask if you
> >> > really need one.  If you're looking to do life support
> >> > in a fixed volume container, all you have to do is blow
> >> > a muffin fan through a can of Calcium hydroxide (Sofnolime
> >> > brand is good), and have a demand regulator hooked up
> >> > to a source of 100% O2.  The Co2 goes into the scrubber,
> >> > which drops the pressure inside the environment, and
> >> > causes the demand reg to pump in the appropriate amount
> >> > of O2.  This is what they do in mini-subs.
> >> >
> >> > For the sensors - I did some extensive hyperbaric tests using
> >> > zinc-air cells as oxygen sensors.  My interests were a little
> >> > different, as I was mostly interested in measuring higher
> >> > partial pressures (0-2.0 ATA PPO2).  At any rate, the upshot
> >> > is that they have horrible drift and are not particularly linear.
> >> > They also have a very short life in hyperoxic environments, as
> >> > you might expect.
> >> > If you want to do some playing around with them, use a *small*
> >> > cell (Duracell DA13, as I recall), and put a few hundred ohm load on
> >> > them.  The smaller cells react faster and store less gas internally.
> >> >
> >> > Galvanics are the way to go for O2 sensing.  If you want small,
> >> > Teledyne makes a sensor called the K-1, which is about 3/4 inch
> >> > in diameter and 3/4 inch long.  The calibration issue is real - you
> >> > do need to recalibrate regularly if you want accuracy.
> >> >
> >> > There are also fourescent dye based sensors, which apparently
> >> > work extremely well, but I don't have any experience with those.
> >> >
> >> > Finally, there's paramagnetic O2 sensors.  This is really the
> >> > ultimate O2 sensor, as they never need to be recalibrated and
> >> > never wear out.  Unfortunately, the ones that have no moving
> >> > parts are the size of a Coke can and draw major current.  They're
> >> > also expensive ($2500 as I recall).  The current draw is because
> >> > they've got an internal heater, as apparently the paramagnetic
> >> > effect is very temperature sensitive.
> >> >
> >> > Along these lines, I screwed around with using Hall Effect
> >> > and GMR devices to brew up a cheap paramagnetic O2 sensor,
> >> > but never got too far with that project.
> >> >
> >> > -Will
> >> >
> >> > > decent
> >> > > >pO2 sensors.
> >> > > >
> >> > > >Just looking at their voltage wouldn't work, of course.
> >> > > >The voltage would be something like the log of pO2, a weak
> function, and
> >> > > >subject to stored O2 every time it got a good exposure.
> >> > > >
> >> > > >But the sensor was run as a current source into a virtual-ground meter
> >> > > input,
> >> > > >with a small diffusive air leak,
> >> > > >the current might be proportional to pO2 with a response time of
> under a
> >> > > >minute.
> >> > > >
> >> > > >This might be useful for monitoring inert-gas vs oxygen.
> >> > > >I never got around to trying it.
> >> > > >Has anybody tried this or heard of it?
> >> > > >
> >> > > >Jim S
> >> > >
> >>
> >
> >
>