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Preamplifier for sensor vibration

Roser Torrent
Prodigy 40 points
Other Parts Discussed in Thread: TL084, OPA376
Hi, 

I would like to mount a vibration circuit board for a ground vibration detector. I have searched some types of sensors and I have choosen the following sensors to do some proof:

- Electret condenser microphone

- Piezoelectric microphone

- Accelerometer (Mems)

- Geophone. 

Can you advise me what preamplifier is necessary for this measures? 

I have thought with TL084 or OPA376. What's the better amplifier for the sensors I have choosen?



Thanks for you attention,

Roser

  • 0
    TI__Guru**** 152966 points

    Rosar,

    Those two op op amps are very different. The OPA376 is a low voltage device up to 5.5V and the TL084 needs at least 7V to operate.
    Both have low input current and good bandwidth and either can handle the input sources.

    Regards,
    Ron Michallick

  • 0
    TI__Genius 12325 points

    Hi Roser,

    This is a fairly broad question because the best amplifier for the job is dependent on multiple parameters.  The type of sensor, desired bandwidth, power consumption, size constraints, and temperature span (as well as offset drift over that temperature range) are some of the factors that need to be considered when selecting an amplifier.

    An excellent paper on using electret condensor microphones was written by Precision Analog's own Collin Wells and can be found here (http://www.en-genius.net/site/zones/audiovideoZONE/technical_notes/avt_030110).

    Also, TI has several articles on amplifier considerations when using piezoelectric sensors, one recent example can be found here: http://www.ti.com/lit/an/slyt369/slyt369.pdf

    Geophone's have been a recent topic on the e2e forum and you will find this thread to be particularly useful: http://e2e.ti.com/support/amplifiers/precision_amplifiers/f/14/t/161153.aspx#588384

    Unfortunately there is no single best amplifier for all applications, I recommend you start by selecting a sensor that meets your project requirements in terms of cost, size, sensitivity, etc. and then determine how much amplification is required on the output signal for it to be useable in the following stages (data converter, oscilloscope...). This should give you a reasonable amount of guidance for determining the minimum GBW for your amplifier. Next determine what power supplies do you have available, and is power consumption a major consideration? There is always a tradeoff between noise, bandwidth, and power consumption so you will need to prioritize these factors. As you work through the constraints of your design, you will find that the number of possible candidates for your amplifier gradually shrinks from thousands, to hundreds, to tens, until your left with the best possible candidates for your particular application.

    Hope this helps!

  • 0 in reply to John Caldwell
    Prodigy 40 points 
    Hi Mr John and Mr Ron, 

    Thank you very much for your advices, they are very interesting for our project. I will study what is the best sensor for my circuit. 

    I have been choosing the following sensors to detect ground vibrations.

    -       Electret condenser microphone:  KECG2740PBJ from Kingstate.

    -       Piezoelectric microphone: KPSG-812 from Kingstate.

    -       MEMS Accelerometer: ADXL335 from Analog Devices.

    -       Geophone: SM-24 from Sensor Company.

    If you know these specifics sensors, and you want advise me, I'll be here. 



    In the following days I will try to probe these sensors with their preamplifiers circuits. First, may I'll make to design spice circuits.
    

    Thanks!
    

    

    Roser
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    

	            
                	
	
    
				
		                
                
                
                
                
                
                
        		
		
				
    
			
		
    
		
		 
		
		
     
    
	
    

    
			
    
			
    
		
    

		
    
	
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