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Question about AD8495



		

			

									
						Kazu
					
							

			
				
									
											
							 		
		        	            							
			
			    	
			                    
                
				                on Jan 31, 2018 
				
			
			
		


				
		

		    		    
		    
		    	
			
Hi All,

 
I have a question about the AD8495. Please take a look at the attachment.

 
I think it is not out of spec, but I would like to know the cause of these variation.

 
Regards,

 
Kazu

								


				
							QuestionaboutAD8495.pdf
					
		

			
						
									
									
						
						
			
			
			
			
		


					

			





	

		
	











	

	

					



			








	
	
	
	



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                                 Analog Employees 
                                
                            
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                on Feb 23, 2018 7:59 AM
            
            
					
    
	
    

		
		
    
					
    Hi Kazu,
    
 
    Yes, that equation is used to correct the nonlinearity and implementing it within the software will get the error down to +/-1.5mV, or less than +/-0.5degC over the 0 to 220degC temp range.   
    
 
    To get this equation, we took the data from the NIST thermocouple table, calculated the expected output voltage of the AD8495 for each temperature over the 0 to 220degC range, and took a 6th order polynomial fit of the data.  The fit is not perfect, so there will be some error between the calculated output voltage from the equation and the output voltage from the table - in this case it is +/-1.5mV.  
    
 
    Regards,
    
 
    Jordyn
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
						
				
				
		
		
    
			
		
    
	
    

    

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													0
							
			
				
									
							        
            
                                                                                                        
      
                            
    • 
                                 Analog Employees 
                                
                            
      • 
                        
     
                                                           			
			                            
                        
                on Feb 23, 2018 7:59 AM
            
            
					
    
	
    

		
		
    
					
    Hi Kazu,
    
 
    Yes, that equation is used to correct the nonlinearity and implementing it within the software will get the error down to +/-1.5mV, or less than +/-0.5degC over the 0 to 220degC temp range.   
    
 
    To get this equation, we took the data from the NIST thermocouple table, calculated the expected output voltage of the AD8495 for each temperature over the 0 to 220degC range, and took a 6th order polynomial fit of the data.  The fit is not perfect, so there will be some error between the calculated output voltage from the equation and the output voltage from the table - in this case it is +/-1.5mV.  
    
 
    Regards,
    
 
    Jordyn
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
						
				
				
		
		
    
			
		
    
	
    

    

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