RFI-> need to detect if loudspeaker is working in an environmentalchamber (can't hear it in there!)

[MRS]

Hi all,

I'm performing some high temperature testing in an environmental
chamber on some speakers. The chamber must remain closed during the
duration of the test, so I won't be able to hear if the speakers are
working.

I want to be able to recognize if the speakers have failed (open
circuit). I'm supplying the speakers an output from an amplifier that
is fed with pink noise signal.

Ideally, I'd like to make a circuit that would sense an open load, or
measure the speaker deflection using an accelerometer.

I don't need to monitor quality, just operation, or more precisely,
malfunction.



Any ideas?

 

[Spehro Pefhany]

Hi all,

I'm performing some high temperature testing in an environmental
chamber on some speakers. The chamber must remain closed during the
duration of the test, so I won't be able to hear if the speakers are
working.

I want to be able to recognize if the speakers have failed (open
circuit). I'm supplying the speakers an output from an amplifier that
is fed with pink noise signal.

Ideally, I'd like to make a circuit that would sense an open load, or
measure the speaker deflection using an accelerometer.

I don't need to monitor quality, just operation, or more precisely,
malfunction.



Any ideas?

Any reason you couldn't put a microphone in there?


Best regards,
Spehro Pefhany

 

[MRS]

Any reason you couldn't put a microphone in there?

Best regards,
Spehro Pefhany
--
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Embedded software/hardware/analog  Info for designers:  http://www.speff.com- Hide quoted text -

- Show quoted text -

Thanks for the reply,

well, that would be too easy!! in fact, one of the engineers here
suggested that earlier this morning..


Ideally, since all the thermocouples would be connected to a data acq
card, I was hoping to either include automated sensing or some type of
visual recognition of failure.

We are testing two speakers at one time, and I guess if I had to, the
mic could be mounted right at the transducer.


hmmm....

 

[Joerg]

Thanks for the reply,

well, that would be too easy!! in fact, one of the engineers here
suggested that earlier this morning..


Ideally, since all the thermocouples would be connected to a data acq
card, I was hoping to either include automated sensing or some type of
visual recognition of failure.

We are testing two speakers at one time, and I guess if I had to, the
mic could be mounted right at the transducer.

Switch them on the outside. IOW use one speaker as a microphone once in
a while, then the other, and so on.

 

[John E.]

Switch them on the outside. IOW use one speaker as a microphone once in

a while, then the other, and so on.
Joerg

That seems to me to be the simple, elegant solution: monitor one speaker with
the other. If you find you're not getting output from your "microphone"
speaker, one of the speakers has failed.

 

[Wimpie]

Hi all,

I'm performing some high temperature testing in an environmental
chamber on some speakers. The chamber must remain closed during the
duration of the test, so I won't be able to hear if the speakers are
working.

I want to be able to recognize if the speakers have failed (open
circuit). I'm supplying the speakers an output from an amplifier that
is fed with pink noise signal.

Ideally, I'd like to make a circuit that would sense an open load, or
measure the speaker deflection using an accelerometer.

I don't need to monitor quality, just operation, or more precisely,
malfunction.

Any ideas?

Hello,

When it is an amplifier with a ground return, you may put a small
resistor in series as a current sensor. Now you can calculate the
impedance based on current and driving voltage (at room temperature).
During the "heat" test you can do the same. When you get different
readings (for example over 100 ... 10 kHz), it is likely that your
speaker has been damaged.

Best regards,

Wim
PA3DJS
www.tetech.nl

 

[Ross Herbert]

:Hi all,
:
:I'm performing some high temperature testing in an environmental
:chamber on some speakers. The chamber must remain closed during the
:duration of the test, so I won't be able to hear if the speakers are
:working.
:
:I want to be able to recognize if the speakers have failed (open
:circuit). I'm supplying the speakers an output from an amplifier that
:is fed with pink noise signal.
:
:Ideally, I'd like to make a circuit that would sense an open load, or
:measure the speaker deflection using an accelerometer.
:
:I don't need to monitor quality, just operation, or more precisely,
:malfunction.
:
:
:
:Any ideas?


Unless the speakers you are proposing to use are specifically designed to
operate in a high temperature environent then you could get an extremely
distorted response from the unit under test WITHOUT the voice coil actually
going open circuit. It would therefore be wise to monitor the audio quality so
use of a microphone would be mandatory.

The combination of the different materials and the construction must all be
designed to resist high temperatures while still operating in an undistorted
fashion and continuing to give a long life. Failure of either the voice coil
suspension or adhesive or the diaphragm suspension could mean the speaker is
virtually useless without the voice coil going open circuit. I doubt you will
find all of these characteristics in off-the-shelf speakers designed for the
domestic environment.

High temp speakers are not common, but one company does make a 6" unit which it
claims will operate in close proximity to vehicle exhaust systems.
http://www.motran.com/page10.html

 

[ehsjr]

Hi all,

I'm performing some high temperature testing in an environmental
chamber on some speakers. The chamber must remain closed during the
duration of the test, so I won't be able to hear if the speakers are
working.

I want to be able to recognize if the speakers have failed (open
circuit). I'm supplying the speakers an output from an amplifier that
is fed with pink noise signal.

Ideally, I'd like to make a circuit that would sense an open load, or
measure the speaker deflection using an accelerometer.

I don't need to monitor quality, just operation, or more precisely,
malfunction.



Any ideas?

Depending on amplitude:

----+------[R]-------+------+
| | |
+-[D1]-[R]-[LED]-+ [Speaker]
|
----------------------------+

Or instead of D1, 2 leds antiparallel

Ed

 

[MRS]

:Hi all,
:
:I'm performing some high temperature testing in an environmental
:chamber on some speakers.  The chamber must remain closed during the
:duration of the test, so I won't be able to hear if the speakers are
:working.
:
:I want to be able to recognize if the speakers have failed (open
:circuit).  I'm supplying the speakers an output from an amplifier that
:is fed with pink noise signal.
:
:Ideally, I'd like to make a circuit that would sense an open load, or
:measure the speaker deflection using an accelerometer.
:
:I don't need to monitor quality, just operation, or more precisely,
:malfunction.
:
:
:
:Any ideas?

Unless the speakers you are proposing to use are specifically designed to
operate in a high temperature environent then you could get an extremely
distorted response from the unit under test WITHOUT the voice coil actually
going open circuit. It would therefore be wise to monitor the audio quality so
use of a microphone would be mandatory.

The combination of the different materials and the construction must all be
designed to resist high temperatures while still operating in an undistorted
fashion and continuing to give a long life. Failure of either the voice coil
suspension or adhesive or the diaphragm suspension could mean the speaker is
virtually useless without the voice coil going open circuit. I doubt you will
find all of these characteristics in off-the-shelf speakers designed for the
domestic environment.

High temp speakers are not common, but one company does make a 6" unit which it
claims will operate in close proximity to vehicle exhaust systems.http://www.motran.com/page10.html

They are outdoor speakers, so yes, they need to work at high temp -
there is a Mil spec that covers this up to 49C at a specified RH

The test isn't to verify that the speakers work, we know they work,
it's the protection circuit that needs to be tested.

Thanks for the reply.