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It is. The LM317 has a minimum current draw of either 5mA or 10mA depending on which version. You can't set up a design which only draws 1mA or it will not work right.As I understand it I only want 1ma to the RTD to avoid self heating issues.
The circuit as pictured seems to work. Adjusting the pot I get various ADC readings which IMO would indicate the circuit as pictured works.
BUT I was told that the circuit pertaining to the LM317 is a disaster if referring to the data sheet?
MrDBE said:I guess I was lead down the wrong path on using the LM317?
If you use a 5V regulator IC and the load current does not exceed about 600mA then the 5V will not change.now to figure out a better constant voltage source seeing how the Vcc powering the rest of the circuit may vary some maybe? or just don't worry about it.