Hi all,
I'm having some troubles while performing a 3-wire RTD measurement with hardware compensation using an ADS1247. During my breadboard experiments to test the circuit I had no problems: I soldered the ADS1247 on a TSSOP to DIP adapter and everything worked well. The only problem was a very intense noise, much more than expected from ADS1247 datasheet, but I think that was caused by breadboard itself (I am a student and this is the first time I work on a low-noise circuit so I don't know exactly what I should expect).
On the contrary when I moved to PCB I had some troubles and, after solving several problems due to bad connections, I still can't measure the RTD because it seems that IDACs stopped working. Is it possible that I burned them, maybe when I connected the resistor to be measured without having a path to ground for the current?(referring to the circuit below, I noticed after several power-ups that the track from pin 1 of Jx2 to Rbias was broken) Or I'm just doing something wrong? This is the acquisition-related part of the circuit:
where J4 represents ADS1247 pins (1 to 10), Rcomp the resistance for hardware compensation and Rbias the resistance for Vref generation. Jx2 is an external connector, to which I connected a 100 ohm resistor between pins 2 and 3 and I short-circuited pins 1 and 2. It isn't showed here but there is a 22 uF electrolytic capacitor between pins 7 and 8.
I'm using PGA = 128, AVDD = 5 V, AVSS = 0 V, IDAC current of 1500 uA.
Thanks in advance.
Mikhail
