Daniel, Basically you could do this type of a measurement but there are some issues to keep in mind. There is some error from the REF3030 which would offset the 1.5V that you're setting up with the voltage divider. Also, I would recommend removing R156 and R157. During the calibration, T12 is sourcing 1mA into 2.5kΩ which means that the stack voltage is 2.5V. With AVDD = 3.3V, you have a compliance voltage to the positive supply of 800mV. This is a bit small, and you'll see that the IDAC current will be much less than 1mA. Look at Figure 41 from the datasheet for IDAC voltage compliance. While this figure is for a 5V supply, you'll see that at 800mV of IDAC voltage compliance, with a 1mA IDAC, you're probably going to be near 850uV. If you remove R156 and R157, you won't have this problem. If you need to have them, then make them 500Ω. If the PT1000 is connected to the terminals of 1 and 2 of X160, and the PT1000 is actively measuring a hot temperature, then you may need to make further adjustments. At very hot temperatures the PT1000 will get to 3kΩ or 4kΩ of resistance. That would also increase the stack voltage so that the IDAC output would drop because of the compliance voltage. However, I'm still not clear on what you are trying to measure. Are you just trying to measure a two-wire PT1000? If that's the case, I would just used a ratiometric measurement with a 4kΩ precision resistor as a reference from REFP1 and REFN1. I also don't see why you're using T12 and T13 when you could just send the currents to IEXC1 and IEXC2. I can think of a few different ways to make this measurement, but I'd just like more of a clarification of what exactly you want to measure. Joseph Wu
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