OK, it's been a while since I last posted--between getting parts and traveling, I haven't had much chance to work on this in the last month. I got a 358, an assortment of resistors and capacitors, a 7810, and a 7805, and assembled it all on a breadboard this afternoon. I used a 56K resistor rather than a 50K, but otherwise as directed here. I powered the 358 from the 7805, and the sensor from the 7810. I tied the sensor input and output grounds together.Likely as a result of tying the input and output grounds together, I got some unexpected results. Where previously the output of the sensor was 0 V with 0 psi applied, it became 946 mV. Instead of increasing 1 mV/psi, it increased about 0.5 mV/psi.The output of the 358 was steady at 3.57V. I suspected this was as close to Vcc as its output would go, so I tried powering it from the 7810 instead. The results from that confused me. With 0 psi and an input voltage of 946 mV, the output was 1.834V. With 20 psi and an input voltage of 959 mV, the output was 1.826V. At that point I stopped the test.I understand that this wouldn't meet any kind of certification--this is for an experimental application, so that isn't a problem.