i have to acquire a wrist pulse signal using micriphone, and for that i have used microphone and instrumentation amplifier INA110, i have grounded the negative terminal of microphone and the second terminal is given to 2 pin of INA110 to provide differential signals to amplifier. in order to provide potential to 1 pin i have connected a 1 Mohm potentiometer. But when i am observing results on ossciloscope the signal gets saturated and it is showing constant dc voltage. what should i do eliminate this problem.

 

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i have to acquire a wrist pulse signal using micriphone, and for that i have used microphone and instrumentation amplifier INA110, i have grounded the negative terminal of microphone and the second terminal is given to 2 pin of INA110 to provide differential signals to amplifier. in order to provide potential to 1 pin i have connected a 1 Mohm potentiometer. But when i am observing results on ossciloscope the signal gets saturated and it is showing constant dc voltage. what should i do eliminate this problem.

What kind of microphone do you have?

What is the lowest sound level that the microphone can respond to?

Do you have any type of cone around your microphone to isolate from other sounds and maybe acquire more audio energy.

 

Please post a schematic of your circuit. Without it we cannot know what you are doing.

ak

 

the microphone i have used is condenser microphone of 6 mm dia and is omni directional.

i will post schematic of the circuit soon.

 

Is it actually an electret microphone (i.e. the common, inexpensive type)?

 

yes it is an electret microphone

 

Can you post the schematic today, or are you limited to one post per 24 hours?

 

no its nt lyk dis...i am drawing the schematic and its taking time.

 

The first stage depends very much on your microphone. Here are some sample drawings.

 

thanks...

 

no its nt lyk dis...

Translate please?

 

thanks...one of the circuit diagrams you suggested above worked...and i got good results.

 

i have now acquired the same signal in labview using daq card. and further i want to filter the signal ..what kind of filter should i use.
the sampling rate of the signal is 100 hz. and no of samples read are 300.

 

What frequency range is the signal you're interested in, and what noise is present?

 

no its nt lyk dis...

Translate please?

"No, it's not like this"

 

i m interested in a frequency range below 25 hz.