Thread Details

  • State Verified Answer
  • Replies 40 replies
  • Subscribers 39 subscribers
  • Views 11366 views
  • Users 0 members are here
Options
Related 

        

            Post
             Go back to editing
        

    

    


    

    









		


















	
	
			
	
			
		
	
	
		

	    
	    
	    		
Three electrode measurement for AD5933?

		
	
				

			

									
					    oscarcot
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on May 19, 2015 
				
			
			
		
    
		
		                    	    
    
        	    
    Thread Summary
    
                The user is using the AD5933 for bioelectrical electrode impedance measurements in a three-electrode configuration. The issue was discontinuities in the Nyquist plot and large errors at low frequencies. The solution involved recalculating the MCLK for each frequency, ensuring the excitation signal was within the ADC range, and adjusting the high-pass filter cutoff frequency to 0.14 Hz. This resulted in continuous and more accurate impedance measurements.
                        	    
    
                
                     AI Generated Content
                
    	    
    
             
				
        		
    
		    
		    		    
		    			
    
			    
    Hi everybody,
    
 
     
    
 
    we're using the AD5933 for bioelectrical electrode impedance measurements. Usually, the electrodes have to be immersed in a saline solution for measuring, and a 2 point measurement (Electrode to Reference electrode) adds unwanted potential offsets to the measurement. For a more accurate measurement, a technique using 3 electrodes is employed:
    
 
     
    
 
    (Fig. 4 from this link)
    
 
    Ralph Group : projects : Fabrication and characterization of graphene electrodes for electrochemistry experiments
    
 
    Figure 4
    
 
    Is there any way to connect the AD5933 in such an arrangement to measure impedance? Do you have any additional suggestions for performing such a measurement?
    
 
     
    
 
    Thanks and Kindest Regards,
    
 
    Oscar Cota
    
			
    
			
									
		                             
                        

    
    
                                            
                 clock and timing
                
                                                    
                 Clocks & Timers
                
                                                    
                 Direct Digital Synthesis (DDS)
                
                                                    
                 ad5933
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			








	
	
	
	



Parents
	
      
	

    • 
	
      



	
		
	
	



      
	
      
		
      
							
					
      
		
      
		    
		    		    
			
				
									
							        
			
			
			
        
            
						
                            
            
            				
            
                on May 29, 2015 8:27 AM
            
            
						
			            		
        
		
										0
					
	
        

		
		
        
		
        
                                
                                                            
        
					
        Hi everybody,
        
 
        I add some extra info I have researched to see if somebody could help us. Here's one schematic of what the lab equipment does to measure electrode impedance. There is a stimulation voltage Vin that generates a current i, which is measured at a TIA. However, Vin is not directly applied to the electrode, but to a control loop that ensures that Vref=Vin. Therefore, Vin is between Vref and Virtual GND (working electrode). The impedance contribution of the counter electrode is thus eliminated.
        
 
        
 
        (Source: E760 - Lectures on Electrodes I - Martin Schüttler . University College London 2009)
        
 
        Do you think such arrangement is feasible with the AD5933?
        
 
        Cheers and Kind Regards,
        
 
        Oscar
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

        • 

	
      



Reply

        


      • 
	
        



	
		
	
	



        
	
        
		
        
							
					
        
		
        
		    
		    		    
			
				
									
							        
			
			
			
          
            
						
                            
            
            				
            
                on May 29, 2015 8:27 AM
            
            
						
			            		
          
		
										0
					
	
          

		
		
          
		
          
                                
                                                            
          
					
          Hi everybody,
          
 
          I add some extra info I have researched to see if somebody could help us. Here's one schematic of what the lab equipment does to measure electrode impedance. There is a stimulation voltage Vin that generates a current i, which is measured at a TIA. However, Vin is not directly applied to the electrode, but to a control loop that ensures that Vref=Vin. Therefore, Vin is between Vref and Virtual GND (working electrode). The impedance contribution of the counter electrode is thus eliminated.
          
 
          
 
          (Source: E760 - Lectures on Electrodes I - Martin Schüttler . University College London 2009)
          
 
          Do you think such arrangement is feasible with the AD5933?
          
 
          Cheers and Kind Regards,
          
 
          Oscar
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
						
				
				
		
		
          
			
		
          
	
          

          

          • 


        


Children
	
        No Data