• Researchers achive real time detection of low gas concentrations

    From Jan Panteltje@21:1/5 to All on Mon Jan 13 06:15:45 2025
    Researchers achieve real-time detection of low gas concentrations
    https://www.sciencedaily.com/releases/2025/01/250109125523.htm
    Allowing gas detection and identification in just seconds,
    approach using a coherent control strategy offers promise for
    real-time monitoring in environmental, health and industrial applications Source:
    Optica
    Summary:
    Researchers have developed a method for quickly detecting and identifying
    very low concentrations of gases, which, could form the basis for highly
    sensitive real-time sensors for applications such as environmental monitoring,
    breath analysis and chemical process control.

    Interesting method to stop a quartz tuning fork

    All that said, my MQ type gas sensors work fine:
    https://www.tinytronics.nl/nl/sensoren/lucht/gas
    but those are not so narrow band...

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  • From Bill Sloman@21:1/5 to Jan Panteltje on Tue Jan 14 01:07:41 2025
    On 13/01/2025 5:15 pm, Jan Panteltje wrote:
    Researchers achieve real-time detection of low gas concentrations
    https://www.sciencedaily.com/releases/2025/01/250109125523.htm
    Allowing gas detection and identification in just seconds,
    approach using a coherent control strategy offers promise for
    real-time monitoring in environmental, health and industrial applications Source:
    Optica
    Summary:
    Researchers have developed a method for quickly detecting and identifying
    very low concentrations of gases, which, could form the basis for highly
    sensitive real-time sensors for applications such as environmental monitoring,
    breath analysis and chemical process control.

    Interesting method to stop a quartz tuning fork

    It's a fairly old-fashioned technique - infra-red spectroscopy has been
    around for a whole,and if you want to detect low gas concentrations you
    could always use long-path-length absorbtion cells.

    Ring-down detectors are an interesting variant on that approach.

    The tuning fork detector may be a novel innovation, but it's less
    obvious that is a useful one.

    "Stopping" a high-Q resonator fast is easy enough, but then you have to
    wait until the resonant movement builds up again - unless you have one
    of John Larkin's fast-start resonant devices.

    --
    Bill Sloman, Sydney

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  • From john larkin@21:1/5 to All on Mon Jan 13 08:46:40 2025
    On Tue, 14 Jan 2025 01:07:41 +1100, Bill Sloman <bill.sloman@ieee.org>
    wrote:

    On 13/01/2025 5:15 pm, Jan Panteltje wrote:
    Researchers achieve real-time detection of low gas concentrations
    https://www.sciencedaily.com/releases/2025/01/250109125523.htm
    Allowing gas detection and identification in just seconds,
    approach using a coherent control strategy offers promise for
    real-time monitoring in environmental, health and industrial applications >> Source:
    Optica
    Summary:
    Researchers have developed a method for quickly detecting and identifying
    very low concentrations of gases, which, could form the basis for highly >> sensitive real-time sensors for applications such as environmental monitoring,
    breath analysis and chemical process control.

    Interesting method to stop a quartz tuning fork

    It's a fairly old-fashioned technique - infra-red spectroscopy has been >around for a whole,and if you want to detect low gas concentrations you
    could always use long-path-length absorbtion cells.

    Ring-down detectors are an interesting variant on that approach.

    The tuning fork detector may be a novel innovation, but it's less
    obvious that is a useful one.

    "Stopping" a high-Q resonator fast is easy enough, but then you have to
    wait until the resonant movement builds up again - unless you have one
    of John Larkin's fast-start resonant devices.

    Starting a resonator-based oscillator is trivial, just get the diff
    equation initial conditions right.

    The trick to an instant-start oscillator is really how to stop it,
    totally quench the resonator, so memories of ringing from the previous
    shot doesn't influence the next one.

    HP made one delay generator that used a quartz crystal as the
    triggered resonator. I met the guy who designed that and he was still
    suffering PTSD.

    HP and Tek used triggered delay-line oscillators in many instruments.
    They can be stopped fairly well by terminating both ends.

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  • From Bill Sloman@21:1/5 to john larkin on Tue Jan 14 15:48:13 2025
    On 14/01/2025 3:46 am, john larkin wrote:
    On Tue, 14 Jan 2025 01:07:41 +1100, Bill Sloman <bill.sloman@ieee.org>
    wrote:

    On 13/01/2025 5:15 pm, Jan Panteltje wrote:
    Researchers achieve real-time detection of low gas concentrations
    https://www.sciencedaily.com/releases/2025/01/250109125523.htm
    Allowing gas detection and identification in just seconds,
    approach using a coherent control strategy offers promise for
    real-time monitoring in environmental, health and industrial applications
    Source:
    Optica
    Summary:
    Researchers have developed a method for quickly detecting and identifying >>> very low concentrations of gases, which, could form the basis for highly >>> sensitive real-time sensors for applications such as environmental monitoring,
    breath analysis and chemical process control.

    Interesting method to stop a quartz tuning fork

    It's a fairly old-fashioned technique - infra-red spectroscopy has been
    around for a whole,and if you want to detect low gas concentrations you
    could always use long-path-length absorbtion cells.

    Ring-down detectors are an interesting variant on that approach.

    The tuning fork detector may be a novel innovation, but it's less
    obvious that is a useful one.

    "Stopping" a high-Q resonator fast is easy enough, but then you have to
    wait until the resonant movement builds up again - unless you have one
    of John Larkin's fast-start resonant devices.

    Starting a resonator-based oscillator is trivial, just get the diff
    equation initial conditions right.

    Which turns out to be a less-than-trivial exercise.
    The trick to an instant-start oscillator is really how to stop it,
    totally quench the resonator, so memories of ringing from the previous
    shot doesn't influence the next one.

    They aren't "memories" - in electronic oscillators they are circulating currents in conductive loops, and charges stored on capacitors - and
    those capacitors can be part of a current loop.

    In mechanical resonators, like tuning forks, they are the moving masses.

    If you inject exactly the right amount of energy at the right time, you
    stop the movement, but getting it exactly right isn't trivial either.

    HP made one delay generator that used a quartz crystal as the
    triggered resonator. I met the guy who designed that and he was still suffering PTSD.

    HP and Tek used triggered delay-line oscillators in many instruments.
    They can be stopped fairly well by terminating both ends.

    Except that making a perfect termination isn't trivial either. Even 50R
    coaxial cable isn't exactly 50R. I had a rep try sell me a cable that
    was closer than usual to exactly 50R - it was made by winding the
    insulator onto the centre wire will under closely controlled tension to
    keep outer diameter more nearly precisely correct. We didn't need it.

    --
    Bill Sloman, Sydney

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