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AD8494 - remote cold junction sensing

		
	
				

			

									
					    Wallander24
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on Dec 6, 2021 
				
			
			
		

		
		                     
				
        		

		    
		    		    
		    			

			    
Hi, 




I am planning to use the AD8497 K-type thermocoupler amplifier to read temperature. But, the AD8497 will not be any near the thermocoupler cold-junction, in fact, it will be on separate board, becouse of high temperature that i have to measure.There will be significant difference in temperature between actual cold-junction (aprox. 100 celsius).and temperature of the board with AD8497 (max 50 celsius).


My question is, is it possible to compensate this remote cold-junction temperature with this chip, maybe with some RTD sensor near the actual 100 celsius cold-junction of the thermocoupler, which will generate voltage that is applied on the  "REF" pin on AD8497 ? 

Or, is AD9497 not suitable for my case and there is maybe some other chip that you can propose, which will handle this remote cold-junction compensation ? 

Thanks guys, 

Jan 

			

			
									
		                             
                        

    

                                            
                 ad8497
                
                                                    
                 ad8495
                
                                                    
                 thermocoupler
                
                                                    
                 cold junction
                
                                
            

    
    
		


				
				        
        		

			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		


        
        
        
    
					

			





















	

	

					



			


				
	









	
    
	

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    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Jan 3, 2022 7:40 PM
            
            
						
			            		
    
		
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    Hi Jan,
    

    Thanks for reaching out to us.
    Although for the AD8497 since its cold junction compensation feature uses an internal temp sensor, the thermocouple's cold junction and the AD8497 should be kept at the same temperature for best performance.
    

    Since you mentioned that you can put an additional temp sensor (RTD) on the thermocouple's cold junction, have you checked this Circuit Note (https://www.analog.com/media/en/reference-design-documentation/reference-designs/CN0172.pdf ), It's a complete temperature measurement system that uses the ADT7320 as the cold junction reference. You can follow the circuit and connect it directly to the AD7793 for data acquisition or to another instrumentation amplifier for discrete scheme.
    

    I hope this helps.
    Best Regards,
    Dann
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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