Hi Team,
Customer wants to consult how to use 1pcs ADS124S08 achieve 4 channel of 3-wire RTD measurement ? I see below link application ADS124S08 3-Wire PT100 RTD Measurement Circuit w/ Low-Side Reference and 1 IDAC (Rev. B) (ti.com), which seems cannot achieve 4 channel 3-wire RTD. Do you have any reference guide for us to achieve above demand?
Best,
Stanley
Hi Stanley,
The circuit you provided is a 3-wire RTD measurement using a single IDAC while subtracting the lead resistance with a second measurement. It is possible to adapt this circuit slightly where the lead resistance measurement is measured to a single point. A colleague has put a diagram together to illustrate.
The lead resistance measurement for RTD1 is AIN1 to AINCOM, for RTD2 AIN3 to AINCOM, and so on.
There is also an alternative 3-wire RTD measurement using two IDACs to automatically cancel the lead resistance as given in A Basic Guide to RTD Measurements. Unfortunately due to the number of analog inputs required the circuit requires an external mux as illustrated below for four, 3-wire RTDs.
So there are a couple of options for making four, 3-wire RTD measurements using the ADS124S08.
Best regards,
Bob B
