How Can I Construct an Excitation Circuit for a 3-Wire RTD?

[OpenLaszlo]

Hi everyone,

Im looking to measure the resistance of a 3-wire RTD using a basic data acquisition system and LabVIEW. My DAQ "box" doesn't have any internal excitation sources, and I realize one is necessary to measure resistance across the RTD element. I'm unsure as to how to construct am excitation circuit that will provide me with the appropriate current (~1 mA) for use with the RTD. Does anyone have any diagrams/links that could help me answer this?

Thanks!

 

[MisterX]

You can make a current source with an op-amp. http://en.wikibooks.org/wiki/Circui...p-amp_inverting_voltage-to-current_converter"

You could use a voltage reference for the input voltage. You should use a low temperature coefficient resistor. You can check the current by measuring the voltage across the resistor (R in the diagram) with the DAQ.