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Low noise CompactDAQ card for microphone measurements
We use often the NI CompactDAQ 9234 for sound measurements.
Our standard microphones with iepe amplifier have a noise level of about 16 dB(A) and sensitivity of 40...50 mV/Pa.
The noise of the 9234 is about 50μV rms, corresponding to a sound level about 32 dB(A). So we can use this microphones only for measurement above 35 dB(A).
A better version of a card 9234 with 2 ranges 5V and 0.5 V would be very useful. The noise in the lower range should of course not exceed the range of 5...10 μV (12..18 dB(A)).
And many monitoring systems have only one Microphone, so we use only one channel of the 9234.
For this cases would be a lower priced one channel card OK.
A two channel card would be perfect: two channel measurement of one microphone signal in both ranges. The sound level program can measure from 20 dB(A) ... 136 dB peak without range switching.
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