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Re: Microphone risk factors

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On 5/13/2017 10:19 AM, Terry Newton wrote:
> On Fri, 12 May 2017 11:02:27 -0700, Don Y wrote:
>
>> For example, when tablets are manufactured (by compressing "powdered
>> granulation"), a common problem is air becoming entrapped in the
>> "powder" as it is compressed.  When the pressure is released, the
>> compressed air causes the tablet to "explode" (the top pops off).
>>
>> This could be sensed audibly by locating a microphone adjacent to the
>> tablets' path of motion and listening to the sound that accompanies the
>> release of the compressive force (heavy filtering but you *know*
>> what the fundamental frequency of the signal is, a priori).
>>
>> But, it would be an impractical environment as the inevitable
>> accumulation of the powdered "granulation" would quickly render the
>> microphone ("acoustical transducer") useless.
>>
>> You'd never encounter this problem in a more traditional microphone
>> application!  :>
>
> Separate the sensor and electronics. Sensor can be a robust piece of
> metal foil etc.

In the above example, a microphone is impractical -- due to other
constraints imposed by the application.  E.g., the tabletting area
has to be "cleanable" to ensure product from "tabletted compound X"
doesn't contaminate "tabletted compound Y" (you wouldn't want
the BABY ASPIRIN that you make in the afternoon to have traces of
the VIAGRA that you made in the morning!  :> )

So, any sensor in the tabletting area has to be cleanable.  Does this
require removing the sensor to clean it "off line"?  Is the later
(re)placement of the sensor critical (you wouldn't want to have to
recalibrate things just because you removed a sensor!)?

Do you have to pot/encapsulate a portion of the sensor to make it
cleanable?  Does this further attenuate the signal you're trying to
sense?

I posed this example to my recording studio friend as he'd seen
one of these pieces of equipment "in action" in the lab on one of
his visits.  The tablet is formed between a pair of stainless steel
"punches" while surrounded by a stainless steel "die" (imagine
putting some powder in a tube and then compressing it *in* the
tube by plunging pegs in each end of the tube; i.e., the tablet is
surrounded by steel as it is being compressed -- several tons of
pressure exerted in a millisecond or three).

You're surrounded by the noise of the mechanism (you're making 35-75
tablets concurrently) and trying to hear a little "pop" that is
muffled inside a steel box -- that is MOVING past your sensor.

The analogy we came up with was mic'ing a kettle drum and recording
its performances -- and, later, trying to decide *if* and *when*
a grain of rice might have been on the membrane (detected by hearing
the rice "bouncing" as the membrane is struck).

Had he a fair bit of experience in that application domain, he would
have realized the dynamic range and sensitivity involved and would
have "waved off" a microphonic solution.

Easier to have a component vendor characterize their components
(e.g., sensors... microphones) than to educate the component vendor
of the varied constraints imposed by the application and HOPE
they can recommend something suitable!  :>

Imagine having potentially dozens of different applications and
having to bring a supplier (or <someone>) up to speed on ALL of
their constraints before they can offer a recommendation vs. letting
THEM educate you on the capabilities/characteristics/liabilities
associated with their "supplies"

(Most folks have experience in very few application domains)

> Or even the material itself. Bounce a laser beam off
> of it to a photocell and "listen" for characteristic "sounds".
> Such a solution would be very inexpensive compared to traditional
> microphone technology and far less subject to the environment.

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Thread

Microphone risk factors Don Y <blockedofcourse@foo.invalid> - 2017-05-10 21:27 -0700
  Re: Microphone risk factors Phil Allison <pallison49@gmail.com> - 2017-05-10 21:39 -0700
  Re: Microphone risk factors jrwalliker@gmail.com - 2017-05-11 07:01 -0700
    Re: Microphone risk factors Don Y <blockedofcourse@foo.invalid> - 2017-05-11 11:06 -0700
      Re: Microphone risk factors piglet <erichpwagner@hotmail.com> - 2017-05-12 09:02 +0100
      Re: Microphone risk factors "Michael Kellett" <nospam@invalid.com> - 2017-05-12 16:02 +0100
        Re: Microphone risk factors Don Y <blockedofcourse@foo.invalid> - 2017-05-12 09:37 -0700
          Re: Microphone risk factors "Michael Kellett" <nospam@invalid.com> - 2017-05-12 18:08 +0100
            Re: Microphone risk factors Don Y <blockedofcourse@foo.invalid> - 2017-05-12 11:02 -0700
              Re: Microphone risk factors Phil Allison <pallison49@gmail.com> - 2017-05-12 17:44 -0700
              Re: Microphone risk factors Terry Newton <nbill@bellsouth.net> - 2017-05-13 17:19 +0000
                Re: Microphone risk factors Don Y <blockedofcourse@foo.invalid> - 2017-05-13 11:57 -0700
                Re: Microphone risk factors Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-13 19:12 +0000
                Re: Microphone risk factors Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-14 08:40 +0000
                Re: Microphone risk factors Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-14 09:17 +0000
                Re: Microphone risk factors Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-14 10:49 +0000
                Re: Microphone risk factors Terry Newton <nbill@bellsouth.net> - 2017-05-13 19:26 +0000
                Re: Microphone risk factors (OT -- long) Don Y <blockedofcourse@foo.invalid> - 2017-05-13 13:37 -0700
            Re: Microphone risk factors "dcaster@krl.org" <dcaster@krl.org> - 2017-05-13 11:06 -0700
              Re: Microphone risk factors Don Y <blockedofcourse@foo.invalid> - 2017-05-13 12:11 -0700
              Re: Microphone risk factors krw@notreal.com - 2017-05-13 20:36 -0400

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