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AD5941 Recommended for New Designs
The AD5940 and AD5941 are high precision, low power analog front ends (AFEs) designed for portable applications that require high precision, electrochemical...
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AD5941 on Analog.com

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RTIA, Calibration and Current

		            
		

			

									
					    KeanuDamon
					
							


			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Feb 19, 2024 
				
			
			
		
    
		
     
				
		
    
		    		    
		    
		    		      		            		        
    Category: Software
    
    		        		            		    
    Product Number:  AD5941  
    
    		        		    		    	
			
    Hi, ADI Support.
    

    

    I am having an issue with the AD5941, the problem I am facing is that when changing the RTIA (Gain Resistor) I am getting very different currents. I have noticed a ratio of 0.6 from the currents observed with the 1K and 200 Ohm gain resistors.
    

    

    I am changing the code before initialization, not during the measurement. I have checked the currents with a multimeter and it is approximately the same as when I am using the 200 Ohm gain resistor.
    

    

    Could you give me any insight into why this may be happening?
    

    

    So essentially I would like to know if I should be observing the same current when switching Gain Resistors (RTIA) or should I see a reduction in current when moving to higher Gain resistor?
    

    

    Thanks in advance.
    
									
			        
		
    

				
						
        

    
    Tags: 
                                            
                 software
                
                                                    
                 ad5941
                
                                                    
                 Sensors and MEMS
                
                                                    
                 Electrochemical Sensors
                
                                
            
    
    
    

		
    
			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    
















    
	
    
	
    
					



			








	
	
	
	



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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Feb 20, 2024 8:09 AM
            
                                    
					
      
	
      

		
		
      
					
      Hi,
      

      Input to ADC of AD5491 = input current X RTIA
      

      This ADC input must be within +/-900mV (for PGA gain = 1 or 1.5)
      

      - As long as this input is within allowed range, there won't be any change in current measurement output with change in RTIA value.
      

      - If this input goes out of range (by changing RTIA value), output deviates due to saturation and hence gives different current output value which is not the actual input current value.
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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													0
							
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Feb 20, 2024 8:09 AM
            
                                    
					
      
	
      

		
		
      
					
      Hi,
      

      Input to ADC of AD5491 = input current X RTIA
      

      This ADC input must be within +/-900mV (for PGA gain = 1 or 1.5)
      

      - As long as this input is within allowed range, there won't be any change in current measurement output with change in RTIA value.
      

      - If this input goes out of range (by changing RTIA value), output deviates due to saturation and hence gives different current output value which is not the actual input current value.
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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