I am trying to buffer an ORP sensor with a gain of 2. See the circuit below. The ORP sensor in water measures about 160 mv. When I connect it to my circuit, the output goes to about 1.4 V. It should be 320 mv. D8 is a dual Schottky diode for op amp protection. C26 is a 16 V ceramic cap & C18 is a 25 V electrolytic cap. When I remove C26 there is no change. What's going on?
View attachment 68774
View attachment 68774