Tweet
Right here is where I'd set the damping R:
It's settled at 10us. You could probably sample even at 8us.
It's settled at 10us. You could probably sample even at 8us.
-
-
Better yet:
A little less overshoot. You could sample even at 7us.
Comment
-
I had been thinking the damping resistor is to be set such that the “overshoot” is brought down for a smooth decay.(?) Are you inferring that if the first overshoot is before the sample is taken it’s a don’t care?Comment
-
No, you don't need a smooth decay. In most cases I go for slightly underdamped as in post 17. And you can sample all the way back to the last opamp saturation point if you want. In post 17 that would be 6us. In post 16 the overshoot almost reaches the opamp rail so I would stop there, 7us.Comment
-
Wow I learned something! I totally agree. With 384 ohms with the jig I sample at 6.7uS and it senses a gold ring off the side of the coil at 4”. It senses 1/2” square foil 3” from the center coil. I’d say this is the best I’ve seen it so far. I’m going to leave it here until I try the TVS op amp that TI recommends now in place of the NE5534. Also have new FET coming to try seen recommended here. In any case this is way better than it was!
Comment
-
I also learned something; I wasn't aware an SMPI could sample that low.
For the preamp, I've found the AD797 and LME49990 to work well in the TDI. YMMV.
Comment
Comment