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Temperature Sensor-RTD-LTC2986



		

			

									
					    Sangeerth_P
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jun 10, 2021 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    Hello 
    

    I am currently using LTC-2986 Board with RTD PT-1000. The RTD is of 2 wire configuration. 
    

     
    

    As seen in this above image, I wanted to connect the RTD between channels 7 & 8 and the R sense resistor between channels 5 & 6.
    

    The channel configuration data I used for Channel number 8, the RTD was 0x79860000 whose binary equivalent is (01111001100001100000000000000000) and 
    

    the channel configuration data that I used for Channel number 6, the Rsense resistor was 0x0xE80FA000 whose binary equivalent is (11101000000011111010000000000000).
    

    I used a 1k ohm resistor for Rsense resistor. 
    

     
    

    My code was working perfectly for Direct ADC Code with few measurable error.
    

    But when i connected the RTD and the Rsense resistor I dont see any values being transferred to the MCU.
    

    I am not sure of the reason. Please help me in this part.
    
								
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	















    
	
    
	
    
					



			


				
	









	
      
	

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      •  Analog Employees  
      
            
			                            
                        
                on Jun 11, 2021 9:44 AM
            
            
					
      
	
      

		
		
      
					
      Hi, 
      

      I just wanted to confirm if you are using DC2531A and accompanying demo software or is it your custom board and software? What did you test on direct adc measurements? 
      

      Regards,
      

      Karen
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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                on Jun 11, 2021 9:59 AM
            
            
												
						in reply to KarenNE
					
									
        
	
        

		
		
        
					
        Hi KarenNE
        

        I am using a NXP Microcontroller.
        

        I set a value in the Regulated Power Supply and was feeding it to one of the ADC Channels and the reading I got in the console window is shown in Fig-2
        

         
        

         
        

        The Direct ADC Code=0 is just to check if I got a integer value. And I was able to get similar outputs for different other values set by the RPS. But when I connect a RTD (2 wire) after connecting a Rsense resistor and changing the Channel configurations, I was not able to get any temperature output and the Results were always zero. I dont know why. Can you please help me in this regard?
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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        •  Analog Employees  
        
            
			                            
                        
                on Jun 11, 2021 4:21 PM
            
            
					
        
	
        

		
		
        
					
        Hi ,
        

            Can you share a wiring diagram? With these channel configurations for a 2-wire RTD you will need to connect CH6 and CH7 with a wire. 
        

            Are you able to put an oscilloscope on the RTD? It would be good to verify that the excitation current is reaching the sensor. 
        

        -Logan
        
			
        

		
		
		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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                on Jun 11, 2021 5:50 PM
            
            
												
						in reply to LoganC
					
									
          
	
          

		
		
          
					
           
          

          I followed this same kind of connection,sir. I dont have an oscilloscope with me. Hence I am not able to see the current waveform. The only difference is I did not use the Capacitors and The value of this Rsense resistor is 1k ohm.
          

          Can you also give an idea on why sensor hard fault may occur?
          
			
          

		
		
		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
						
				
				
		
		
          
			
		
          
	
          

          

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          •  Analog Employees  
          
            
			                            
                        
                on Jun 9, 2022 3:58 PM
            
            
												
						in reply to Sangeerth_P
					
									
          
	
          

		
		
          
					
          Hi   a hard fault is when the sensor is outside of the allowable bounds - for example an open or shorted RTD should produce a hard fault. Similarly if there is a short on the Rsense. 
          

          With the part powered-on but idle, you can measure the components with a multimeter. Measure at the demo board so you are seeing the same connections the part sees.
          

          The Rsense and RTD should read their nominal values. Otherwise you may have a short. 
          

          -Logan
          
			
          

		
		
		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
						
						
				
				
		
		
          
			
		
          
	
          

          

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