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Temperature Sensor-RTD-LTC2986

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.

  • 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

  • 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. 

    -Logan

  • 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?