Connecting RTD deactivates Feather

[LateMax2359]

I recently obtained a feather 32u4 for measuring pressures and temperatures. When I connect my 100 Ohm RTD to the 3V pin, the Ground pin, the feather turns off. Thinking it to be a power issue, I threw resistors in series with the 3V pin and the RTD. I've tried 120 Ohm, 240 Ohm, 1 KOhm, and 3 KOhm. With any resistors, the feather no longer deactivates, but it won't collect any data.

For clarification, the RTD is a 3 Pin platinum RTD with a wire not aforementioned connected to A1. My code successfully logs the battery voltage of the circuit, but when it attempts to log the RTD it only writes 0.00 no matter what, that is if the board can even activate.

This issue persists even when using a battery instead of a USB. Any help provided would be greatly appreciated.

[mikeysklar]

Have you used this RTD before successfully on its own?

Usually an amplifier is used with a PT RTD. Is there a reason you are not using the MAX31865?

https://www.adafruit.com/product/3328

[LateMax2359]

We've made sure the RTD works by connecting it to a multimeter measuring the resistance. The resistance does go up & and down according to our calculated temperature.

We're not using an amp because we weren't aware we would need one. Since the RTD is only ~120 Ohms at 20*C, we figured we would still be able to detect the voltage out of the RTD.

[mikeysklar]

For the PT RTD the Adafruit guides strongly recommend the amp. There is not a guide for using them without it.

However, to get that precision and accuracy out of your PT100 RTD you must use an amplifier that is designed to read the low resistance. Better yet, have an amplifier that can automatically adjust and compensate for the resistance of the connecting wires

https://www.adafruit.com/product/3328