We have pulse signals transmitted from field Flow instrument to Flow computer. But the signal at flow computer is distorted and i doubt the grounding. There is a continuity between Instruments earth and Electrical earth. Is that normal?

 

Unless you have a terminated transmission line of some sort, more or less distortion is a certainty. Most automation gear is heavily filtered and has large noise margins to compensate for (much) less stringent wiring. And since both I&E ultimately go to ground, one can expect continuity, although there may be deliberate or incidental resistance. And as with all rules, there are exceptions. Poking around most automation gear with a scope, one is often surprised that it works at all.

Regards
cww

 

You should be able to read continuity between "Instrument Grounding & Electrical Grounding". You should NOT be able to read any Voltage between "Instrument Grounding & Electrical Grounding".