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time domain analysis via onboard microphone on SPEDY-33

Hi,

 

I have attached a screenshot of the time domain waveform graph. If I'm not wrong, the signal displayed is from the onboard microphones of SPEEDY-33 in digitize value. The peak amplitude is 557 and the rms value is 236.23 (and the values look wierd). Hence, how do I convert back to analog input value measured in mV?

 

Please advise.  Thanks!

 

Regards,

Bee Kwang

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Hi,

What is the unit of '557' you have obtained.  Find the output from speedy manuals. Having given the unit of the output obtained it is possible to figure the conversion method.

With regards,
JK
(Certified LabVIEW Developer)
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Are you sure the jumper setting are correct. It looks like you are measuring on a floating analog input, not the microphones. It is just a suggestion 😉


Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
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The SPEEDY-33 User manual did not state much information except that it support either onboard microphone or line-in input via the jumper settings. It support 16-bit A/D and sampling freq of 8, 18,  24, 36 and 48KHz.

 

I guess the "557" should be the digitize value (level) of the "analog volt" measured by the microphone. The maximum given voltage of the  input is given as 600mV.

 

Can I assume that

65535 levels = 600mV

1 level = 600mV / 65535

557 = 557 x (600mV/65535) = 0.005mV?

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Hi guys,

 

I found something new >> http://digital.ni.com/public.nsf/allkb/073133DA607E702A86256FE8007A8D79?OpenDocument 

The link mentioned that the analog output amplitudes from –32,768 to 32,767 (digitize value?) corresponds to approximately ±1.5 volts. This 1.5 volts is refering to the maximum working voltage for analog outputs on page A-1 of the data sheet.

 

If yes, can I make an analogy on the analog input volts amplitude from –32,768 to 32,767 (digitize value?) that is corresponds to approximately ±600m volts  (maxi working input voltage on pg A-1)? Hence, to find the analog input voltage,
 
peak amplitude from graph X (each digitize step value)
= peak amplitude from graph X (1.2/65535)
Thanks!
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BK Lian wrote:

peak amplitude from graph X (each digitize step value)

= peak amplitude from graph X (1.2/65535)
Thanks!

Yes this is correct. Have you tried to hook up your bord to a signal generator. This way you can check if the ADC works as expected



Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)
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Just so anything is not misunderstood. The microphone output level is quite low. So I guess it is a gainstage between the microphones and the ADC. Ni may help you with more info about this


Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)
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Yes the procedure you have got seems to sound right.  But the values are pretty higher since the output from microphones will not be this high.  As said by t06 there should be a gain stage between microphone and ADC .
With regards,
JK
(Certified LabVIEW Developer)
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Yup, previously I've checked with the  NI support engineer, the flow is input sound >> 1)  microphone with buid-in gain >> 2) op-amp >> 3) ADC >> 4) LabVIEW.

 

Hence, the maxi working analog input voltage of 600mV is refering to which stage (before 1 or after 2)?  Also, what is the typical voltage from a microphone?

 

 

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BK Lian wrote:

Yup, previously I've checked with the  NI support engineer, the flow is input sound >> 1)  microphone with buid-in gain >> 2) op-amp >> 3) ADC >> 4) LabVIEW.

 

Hence, the maxi working analog input voltage of 600mV is refering to which stage (before 1 or after 2)?  Also, what is the typical voltage from a microphone?

 

 


 

Actually non of the above. 600mV is the max input level for the analog input channels.


Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)
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