Products Mentioned

AD7709 Production
The AD7709 is a complete analog front-end for low frequency measurement applications. The AD7709 contains a 16-bit sigma delta ADC with PGA and can be...
Datasheet
AD7709 on Analog.com

Associated Drivers

  • State Verified Answer
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 75 subscribers
  • Views 983 views
  • Users 0 members are here
Options
Related 

        

            Post
             Go back to editing
        

    

    


    

    









		












	
	
			
	
			
		
	
	
		

		
AD7709 CONVERTER PROBLEM



		

			

									
					    Michael-C-L
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Nov 18, 2013 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hi,
    
 
    i use an ad7709 to measure thermocouple signal, and there is a problem:
    
 
    conditions:
    
 
    1. input channel:AIN1 and AIN2.
    
 
    2. use pseudo-bipolar mode.
    
 
    problems:
    
 
    1. when i operated as follow process:
    
 
         hardware reset (use reset pin ) --> read first data --> read second data --> end
    
 
         then, both datas were wrong.
    
 
    2. when i only read one data,
    
 
         hardware reset --> read first data --> end
    
 
         then, the data was right.
    
 
    so why?
    
 
    and i also have some questions:
    
 
    1. do i need to calibrate the product after manufacture?
    
 
         i read datasheet that, the device is factory-calibrated at final test. however, we will use different voltage reference, is that still ok?
    
 
    2. do i need to care about zero shift?,
    
 
         in most ad converters, this is a serious problem, so is it same with this device?
    
 
    Thanks.
    
									
			        
		
    

				
						
        

    
    Tags: 
                                            
                 Multiplexed A/D Converters
                
                                                    
                 ad7709
                
                                                    
                 Precision A/D Converters
                
                                
            
    
    
    

		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    
















    
	
    
	
    
					



			








	
	
	
	



Parents
	
      
	

    • 
	
      



	
			
		
	



      
	
      
		
      
							
					
      
		
      
			
													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Nov 25, 2013 11:28 AM
            
            
					
      
	
      

		
		
      
					
      Hi,
      
 
      What data are you reading from each channel?
      
 
      When reading two channels the sequence should be:
      
 
        
  
      • Perform a reset
        • 
  
      • Write 0x22 to communications register: This indicates that the next operation is  a write to the filter register
        • 
  
      • Configure filter register: set required output data rate
        • 
 
      
 
      Read first channel:
      
 
        
  
      • Write 0x01 to communications register:  This indicates that the next operation is a write to the configuration register
        • 
  
      • Set channel selection bits(CH2:CH0) in the configurations register to 0b000 to select AIN1 - AINCOM
        • 
  
      • Poll /RDY pin
        • 
  
      • Write 0x43 to communications register:  This indicates that the next operation is a read from the data register
        • 
  
      • Read 16 bit data register
        • 
 
      
 
      Read second channel:
      
 
        
  
      • Write 0x01 to communications register:  This indicates that the next operation is a write to the configuration register
        • 
  
      • Set channel selection bits(CH2:CH0) in the configurations register to 0b001 to select AIN2 - AINCOM
        • 
  
      • Poll /RDY pin
        • 
  
      • Write 0x43 to communications register:  This indicates that the next operation is a read from the data register
        • 
  
      • Read 16 bit data register
        • 
 
      
 
      Was this followed?
      
 
      Since the AD7709 employs chopping and has extremely low offset and gain drift, calibration is not required.
      
 
      The input of the AD7709 performs chopping which removes the offset/zero shifts on the input, thus, there is no need to consider zero shifts.
      
 
      Thanks and Best Regards,
      
 
      Chris
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

      • 

	
    



Reply

      


    • 
	
      



	
			
		
	



      
	
      
		
      
							
					
      
		
      
			
													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Nov 25, 2013 11:28 AM
            
            
					
      
	
      

		
		
      
					
      Hi,
      
 
      What data are you reading from each channel?
      
 
      When reading two channels the sequence should be:
      
 
        
  
      • Perform a reset
        • 
  
      • Write 0x22 to communications register: This indicates that the next operation is  a write to the filter register
        • 
  
      • Configure filter register: set required output data rate
        • 
 
      
 
      Read first channel:
      
 
        
  
      • Write 0x01 to communications register:  This indicates that the next operation is a write to the configuration register
        • 
  
      • Set channel selection bits(CH2:CH0) in the configurations register to 0b000 to select AIN1 - AINCOM
        • 
  
      • Poll /RDY pin
        • 
  
      • Write 0x43 to communications register:  This indicates that the next operation is a read from the data register
        • 
  
      • Read 16 bit data register
        • 
 
      
 
      Read second channel:
      
 
        
  
      • Write 0x01 to communications register:  This indicates that the next operation is a write to the configuration register
        • 
  
      • Set channel selection bits(CH2:CH0) in the configurations register to 0b001 to select AIN2 - AINCOM
        • 
  
      • Poll /RDY pin
        • 
  
      • Write 0x43 to communications register:  This indicates that the next operation is a read from the data register
        • 
  
      • Read 16 bit data register
        • 
 
      
 
      Was this followed?
      
 
      Since the AD7709 employs chopping and has extremely low offset and gain drift, calibration is not required.
      
 
      The input of the AD7709 performs chopping which removes the offset/zero shifts on the input, thus, there is no need to consider zero shifts.
      
 
      Thanks and Best Regards,
      
 
      Chris
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

      • 


    


Children
	
    No Data