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Electret condenser microphone

microphone sensor sound u6 labview

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3 replies to this topic

#1 ellimac20

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Posted 21 April 2014 - 02:38 AM

I am using the U6 and need to read the output of a ECM such that i can tell when something has gotten louder. Specifically I am tracking the sound cavitation makes as in water. I plan on doing this by running the mic across a pipe where one side has cavitation and the other side of the flow is a free stream. I need to acoustically distinguish between the two. My hypothesis is i will be able to tell from simply the loudness although it only sounds like little crackling but it typical more audible compared to the rest of the flow. So far I have a resistor and capacitor if series on the vs+ and output, and the gnd alone, I am using externally dc supply. So far the graphs is either extreme spastic or the center line of the signal is steadily increasing.  How can I get a graph that i get a readable output from the sensor???? Please help!!! I am new to labjack and only have limited experience with labview.

 

Thanks in Advance



#2 LabJack Support

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Posted 21 April 2014 - 06:48 AM

LJStreamUD would be good software for initial testing.  What sort of signal do you expect from the sensor?  Max/min voltage?  Frequency?



#3 ellimac20

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Posted 21 April 2014 - 09:37 PM

Well here is the data sheet: http://www.cui.com/p...mi-5247tf-k.pdf 

I'm not quite sure the voltage output range. I've hooked it up to a voltmeter and the only setting that made since was AC and it ranged from 0 to about 30 V.



#4 LabJack Support

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Posted 22 April 2014 - 01:54 PM

I think what's happening is that your power source is isolated, and so your readings are floating.

 

My recommendation is to power the chip with DAC0 set to 2.0V, and RL=680Ω.  This will eliminate the need of an external power supply.  Simply configure the startup value of DAC0 to be 2.0V using LJControlPanel to write the value to flash, and it will retain that value every time it is powered on.  If you still want to use an external supply, it's possible to just tie GND of the LabJack device to GND of the power supply, but beware of introducing unintended ground paths.  See the app note on externally powered signals

http://labjack.com/s...powered-signals

 

LJStreamUD should be fast enough to detect an AC signal on the order of kHz, so after the sensor is powered up and you have the output connected to an analog input, run LJStreamUD and see what you get.  Sometimes the output of these electrets is very small, and some pre amplification may be necessary.  Also, at high frequency sounds the sample rate of the U6 may not be fast enough, and the signal will become aliased(not a problem if you're only interested in amplitude).





Also tagged with one or more of these keywords: microphone sensor, sound, u6, labview

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