Can someone here give some pointers on grounding? My adc's are jumping around a bunch. I think the grounding is correct but I like to hear from the experts.

I have a 24 vdc battery source, a 24 vdc to 5 vdc DC/DC converter.

The 24 vdc Battery voltage powers the dc converter module as well as 16 transmitters (sensors). The 5 volt output powers the microprocessor and a couple of other electronic items, and also the loop power for digital inputs.

I have the following grounding scheme:

24 vdc battery common to DC/DC Converter 24 volt common pin, chassis, and to the transmitter common terminal blocks.

5vdc common from DC/DC to Chassis, Processor, and to ADC Common, transmitter common.

Basically, I've taken all commons and tied them together, attached to chassis, and to earth ground.

Transmitter outputs are nice and steady, DC converter outputs are nice and steady with a very small ac on top 20mv from the switching of the dc/dc converter.

Even if I ground all ADC inputs the readings still jump around by 40 mv.

If I disconnect the wiring from the adc inputs to the terminal blocks, the adc calms down and reads zero.

Any pointers?

RIchard