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ADXL327 Production
The ADXL327 is a small, low power, complete 3-axis accelerometer with signal conditioned voltage outputs. The product measures acceleration with a minimum...
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ADXL327 on Analog.com

ADXL372 Recommended for New Designs
The ADXL372 is an ultralow power, 3-axis, ±200 g MEMS accelerometer that consumes 22 µA at a 3200 Hz output data rate (ODR). The ADXL372 does not power...
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ADXL372 on Analog.com

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ADXL327 Noise msmts

		
	
				

			

									
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  •  Analog Employees  

			
			
			    	
			                    
                
				                on Jul 8, 2022 
				
			
			
		

		
		                    	    

        	    
Thread Summary

                The user observed noticeable noise power at ~80 Hz on all three axes of the ADXL372 when sampling at 400 Hz and 800 Hz. The final answer confirms this is due to an ASIC bug causing noise tones at 1/5 of the sampling rate. The noise density specification of the ADXL372 accounts for these tones, and the ADXL371 is suggested as a replacement to avoid the issue.
                        	    

                
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Category: Hardware

    		        		            		    
Product Number:  ADXL327 

    		        		    		    

		    		    
		    			

			    
We are using the EVAL-ADXL372Z connected to and powered by ESP32 dev board. SPI rate is 10 MHz. 


The eval board is powered by the ESP32 dev board (which has a AMS1117-3.3 1A LDO, powered by PC’s USB VBUS).


The entire test setup in on the ground, away from any shock/vibration sources.


The sensor is set to Full bandwidth mode and the samples are read through the serial port.


We are experimenting with different sample rates to measure noise performance of the ADXL372. We see noticeable noise power at ~80 Hz (for 400Hz & 800Hz sampling rate) on all three axes in our fft graphs. Do you have any explanation for this noise? Can you suggest some experiments to help us determine the source of this noise?

			

			
									
		                             
                        

    

                                            
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    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Jul 13, 2022 4:52 PM
            
            
						
			            		
    
		
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    Hi, 
    

    Sorry for the late reply. The issue that you describe is due to an ASIC bug. We have identified this "noise tones" appear at 1/5 of the sampling rate, which i think it matches with your observation. The noise density of the ADXL372 is specified so it accounts for this tones. 
    

    This tones cannot be avoided on the ADXL372, but you can use the ADXL371 as replacement. 
    

    I hope this helps, 
    

    Pablo. 
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
						
						
				
				
		
		
    
			
		
    
	
    

    

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