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RMS-to-DC for Sound Pressure Level measurement

		
	
				

			

									
					    Valoo
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jan 28, 2016 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
		    			
    
			    
    Hi,
    
 
    I want to measure the RMS value of a microphone's output voltage (to get the SPL value in dB).
    
 
    I see a lot of RMS-to-DC IC seem to do that but I am wondering :
    
 
    At a given moment, if I read the output of the RMS chip (on an ADC), is the RMS (the average/mean part) calculated on the last 10ms ? 100ms ? 1sec ?
    
 
    In other words, I want to read the RMS value every second. So I want it to be representative of the last second that just passed not the last 10ms.
    
 
    How is it related to the "settling time" parameter (if it is) ?
    
 
    Best regards,
    
 
    V.
    
			
    
			
									
		                             
                        
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			








	
	
	
	



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      •  Analog Employees  
      •  Super User  
      
            
						
                            
            
            				
            
                on Jan 29, 2016 2:35 PM
            
            
						
			            		
      
		
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      Hello Valentin,
      
 
      You should post this question in the "Amplifiers" space of the forum. There it will be seen by the proper support people. You should also search EngineerZone for the part number and you will see there are many posts that may answer your question.
      
 
      One other thing to consider is using a SigmaDSP for your application. I do not know what else you plan to do before and after the RMS converter but with a SigmaDSP like the ADAU1761 you would get a pre amp, several inputs and DAC outputs along with the DSP. The DSP can be programmed using SigmaStudio making it relatively easy to program an application. We do have cells (blocks) in the library that does RMS conversion. Then you can continue to process the signal in the DSP to do what you need. So have a look and see if it would work for your intended application.
      
 
      http://www.analog.com/media/en/technical-documentation/data-sheets/ADAU1761.pdf
      
 
      Thanks,
      
 
      Dave T
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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      •  Analog Employees  
      •  Super User  
      
            
						
                            
            
            				
            
                on Jan 29, 2016 2:35 PM
            
            
						
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      Hello Valentin,
      
 
      You should post this question in the "Amplifiers" space of the forum. There it will be seen by the proper support people. You should also search EngineerZone for the part number and you will see there are many posts that may answer your question.
      
 
      One other thing to consider is using a SigmaDSP for your application. I do not know what else you plan to do before and after the RMS converter but with a SigmaDSP like the ADAU1761 you would get a pre amp, several inputs and DAC outputs along with the DSP. The DSP can be programmed using SigmaStudio making it relatively easy to program an application. We do have cells (blocks) in the library that does RMS conversion. Then you can continue to process the signal in the DSP to do what you need. So have a look and see if it would work for your intended application.
      
 
      http://www.analog.com/media/en/technical-documentation/data-sheets/ADAU1761.pdf
      
 
      Thanks,
      
 
      Dave T
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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