Other Parts Discussed in Thread: TPD2E1B06
Tool/software: Linux
Hi,
Right now I try to evaluate the ADS1147, but I cannot find a application for ESD, Burst or Surge.
I am specially interessted in the 3 Wire Ratiometric RTD Measurement System.
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Hi Joseph,
thanks for your support. I have tried that already yesterday with series resistance but I would not go higher than 1000 Ohm. In Case of a PT100 you will become a failure of about 50% in the worst case! I have tested the circuit wit a SMAJ5A Diode from STMicro electronic with a leakage current of 1uA it is working pretty fine! I will try to test that this week and if you like i can share with you the results!
Sounds good that you thought the same as I do ;)
Rainer Scalick
Red line = Voltage after serie resistant
Green Line = Voltage after diode
Blue Line = Current inside of the ADS1147
Rainer,
I'm not sure I understand. Did you have a schematic that you weren't able to include in your last post?
For the two-wire RTD measurement, the lead resistance of the RTD will always add an error to the measurement. However, the pcb resistance is probably a very small error. Below is a standard two wire RTD measurement:
The error from the leads will be:
IIDAC * (RLEAD1+RLEAD2)
The only other resistive errors will be the input series resistances (from the input filtering reacting with the analog input current - probably < 10nA). At the input, this may appear as an offset. Similarly, the reference input may have error with the reference input current reacting with the series filter resistances. Because this error involves the reference value, this will appear as a gain error in the measurement.
Joseph Wu