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Connecting a 4-wire RTD temperature sensor to MCBSTM32EXL Board

Question asked by swenson.lisa on Nov 22, 2012
Latest reply on Nov 26, 2012 by swenson.lisa
Hi,

I am trying to configure my MCBSTM32EXL board to read from an external temperature sensor. I think I have most the code sorted, including reading from the ADC. However, my knowledge of electronics is weak and I cannot figure how I should be connecting the RTD to the board.

I have a 4-wire RTD sensor. If I understand correctly, these 4 wires constitute two loops; one of which is the "excitation" channel which needs to be connected to pins through which a current is running, and the other is the "channel" channel which needs to be connected to the pin the ADC is going to read. Have I got that right???

Also, I understand that 5V of power is coming in as my power supply via USB from my PC. This is then stepped down to 3.3V on the board. Excuse my naivete, but I connect my scopemeter to some pins and ground and I get 3.31V and nearly nothing when I measure at other pins so, I'm assuming some pins get power and some don't.

So, is it that I'm connecting a red lead to a pin with 3.31V and its white compatriot to ground, and then the other red lead to a pin without power and its white "other half" to ground? And then try to read the upowered pin via the ADC? Can a hurt the RTD by messing around with different connection scenarios?

Thanks in advance for any enlightenment and/or pointing me to any helpful literature.
Lisa

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