Hello
If you are a person from the future searching the internet because you have a Sensoray 2612 ADC board that is giving erratic results, especially when it is humid or when there is an electric field nearby, I have the following advice for you:
Investigate U12 which is a CMOS logic buffer chip 74HC04. Note that pin
13 and pin 1 are inputs that on my board were left floating. Pin 1 comes from a header JP3 that had no jumper on it. The signal from pin 1 is inverted, goes from pin 2 to pins 3,5,9,11 (tracks under U12), and then the re-inverted signals all go via 100 Ohm resistors to the Fo pins (35) of all the LTC2444 converters. If you put a pull-down (e.g. 100k) on pin 1 of U12, and tie pin 13 to pin 14 on U12, then it should behave itself better. Before I did that, mine would sometimes oscillate at about 70MHz and give silly answers.Also you have my sympathies about the high input current. I had to build an extra board with op-amp buffers to drive the Sensoray 2612, otherwise the input current affected my RTD readings too much. The op-amps needed lots of RF filtering to stop radio signals affecting their offsets. I also had to put chokes in parallel with the 100 Ohm input series resistors on the Sensoray 2612 board, because the input current caused voltage drops. Probably should have started from scratch.
Chris