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Temperature Sensor-RTD-LTC2986


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.

  • 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? 



  • 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?

  • 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. 


  • 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?

  • 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.