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ADS1120EVM: How to connect a 2 wire PTS100 ( OHMS ) RTD to the EVAL board, and configure Gui to get reading

Ahmad Hosseini
Prodigy 20 points
Part Number: ADS1120EVM
Other Parts Discussed in Thread: ADS1120, ADCPRO

Hello,

I would like to see a schematics for how to connect a 100 OHM 2 wire RTD to this EVAL board, and how to configure the Gui to get the temperature reading.

Thanks,

  • 0
    TI__Guru** 112765 points

    Hi Ahmad,

    The instructions for connecting an RTD to the ADS1120EVM is found in section 5.2.3 of the ADS1x20EVM user's guide.

    http://www.ti.com/lit/ug/sbau203/sbau203.pdf

    The 2-wire RTD is connected to the terminal block J2 at positions 2 and 3.  A two-wire RTD requires a jumper between J2.1 and J2.2 as well as between J2.3 and J2.4 to complete the current path through the RTD (see note 3 under Table 7 in the user's guide).  You will also need to place a reference/bias resistor at R3 and REFN0 must be connected to AGND.  The easiest way to accomplish making the ground connection is to place a shorting jumper from J4.9 to J4.7 (which is the header on the board).  Check the schematic at the end of the user's guide for more connection details on the location of the various connections to the connector.

    You must use a proper value for the low-side reference resistor R3 based on the RTD resistance and IDAC current you wish to use.  I would suggest looking at the RTD application example in the ADS1120 datasheet.  You may also find the following document helpful as a basic guide for RTD measurements:

    http://www.ti.com/lit/an/sbaa275/sbaa275.pdf

    As far as the software, unfortunately the ADCPro software will only output codes or voltages.  It does not have provision for making temperature measurements.  You will have to do that in another way.  One method is to save the data to a file and then read into a spreadsheet program such as Excel and make the calculations and conversions there.

    Best regards,

    Bob B