Attached, the schematic.
2. You are perfectly Right.
But, when i use a real resistor (for doing this test i've used a Bourns potentiometer 0-200 ohm) calibrated to 113.994 ohm (using always the same Ohmmeter Fluke 117) the PT100 Measuring device display 36.0 °C (and this is right).
3. I've to obtain the most accurate temperature value shown by my temp. measuring device
If you look the schematic i've disposed 3 Jumper (J1, J2, J3):
- J1, J2 is used to test the behavior connecting B1 to W of each RDAC
- J3 is used to bring to ground one end of the resistor.
J3 was used to test why the Temp. Measuring Devices (not only the one i'm using but also 3/4 different devices) does not recognize the resistor of RDAC.
Our Temp. Measuring Devices use 3 Wire for PT100 reading ( R-R-W) where W is connected to the ground internally of the Meas. Dev.
By connecting the two ground (W with RDAC_L1), the Measuring Device recognize the resistor of rdac.
This bring me to think that the isolation of the RDAC is not too high, or i'm wrong?
Thanks again
David