Sound Sensors

[ABTechnical]

I hope soeone can help.

I have been given the task of trying to find an ATEX Approved sound sensor. It is to be mounted either inside or outside of a tank that detenators will be exploded inside of. It needs to be ATEX due to the explosive atmosphere (Would have thought that if your exploding detenators then you would do it outside of an atex area but what can I say.) I dont have an actuall Db Value for the explosion but from what i have been told it can make the floor vibrate but not always. Also the tank that will be used isnt going to be pressureised. (To make them explode they are heated to 200 degrees celcius. Can you imagine the pressure inside a tank that is at 200 degrees and then an explosion happens.) If anyone has come across this kind of sensor before I would be greateful if you could let me know where you found it to.

 

[dgallagher]

Check

http://www.casellacel.com

- they offer intrinsically safe sound level meters with datalogging capability.

 

[bogeyman]

Many years ago my department was asked to measure sound pressure levels at the ear of personel firing shoulder launch missiles (I worked for a maker of these nasties then) the firing was carried out in an approved blast chamber with an approximation of a human space model adjacent to the missile launcher. The recording of Spl was taken using a standard battery operated sound level meter driving a chart recorder via long wires from the external meter output of the Spl meter (a Dawe instrument) There was long discussion regarding the intrinsic safety of the meter but for the short period of testing required dispensation was granted to use the meter as it was and fire the store remotely.
To achive an intrinsicaly safe instalation a suitable microphone transformer and zener barrier was offered but the lead time precluded its implimentation.

If the test rig was to have been permanent we would have had

a/ an environmentaly protected measuring dynamic microphone

b/ an intrinsicaly safe isolating microphone transformer and barrier

c/ a screened two core wire from the transformer to a remote monitoring system


We measured about 150 dB at 12" from the missiles rocket motor and it damaged our measuring microphone.

There are charge type sensors available from such companies as Endevco which may be more robust. When these types of transducers were used for shock measurement in explosive device test environments our safety people allowed them to be used without galvanic isolation.