Equipment grounding methods have evolved over the last 40 or 50 years to the point where the original issues are (mostly) no longer present.
The first widespread commercial applications of data transfer comunications that I am aware of were central computers and data terminals integral to cash registers.
Equipment grounding methods in the 40s and 50s were liable to deterioration. Typically the raceways were used for equipment grounding and the both the old style rigid couplings and to an even greater degree the indent style couplings on EMT were prone to developing high resistance paths. Armoured cable in use before the 50s did not have a grounding conductor. The armour provided a spiral, high resistance ground path with a high reactance due to the spiral. (Due to surface corrosion the current tended to flow around the armour rather than crossing all the joints and flowing in a straight path.
EMT was typically coupled with indent style couplings (illegal in Canada for decades). These were prone to developing high resistance.
Rigid couplings up until I think about the 70s were quite loose. They were designed so that the conduit ends could butt together inside the coupling. Again subject to developing high resistance over time.
When computer based cash registers were introduced to grocery stores, many of the buildings dated back to the 40s and 50s.
Now the data techs made a few mistakes.
1> They did not read the codes which specifically stated that no piece of equipment could depend on a ground connection for proper operation. (Any exceptions did not apply to data loops.)
2> 2> They assumed that any points shown on a drawing as connected to a “ground” symbol were at the same potential. Fine for chassis connections and lab tests, but not realistic in the real world.
1> They assumed that all the grounding systems in the real world were perfect.
2> They used ground as a signal return path to save the cost of an extra wire, or for circuit simplicity. By so doing, they introduced all sorts of resistances and impedances into the signal path.
Now over the last several decades, grounding methods and practice have improved to the point that any circuit grounded in compliance with the codes with a copper conductor is as good or better than any extra grounding conductor imagined by the data people.
An isolated ground that is not connected to the main grounding system can be the source of dangerous voltages in signal circuits. See David’s anecdote and my hypothetical example in previous posts.
IMHO collecting all the instrument and/or data grounds on a dedicated ground bar is good engineering.
Further, connecting this dedicated/isolated ground bar to the system grounding electrodes with a copper jumper size according to the codes is good engineering.
An isolated ground rod, quite ground, tripod ground, etc., is urban legend or folk lore which will cause no harm if properly connected to the system ground, but which may be a potentially lethal hazard if left isolated.
Grounding is NOT about providing a signal path. The purpose of grounding as stated by the codes is to avoid, reduce or eliminate dangerous voltages on the surface of electrical equipment. This may be the source of some of the misunderstandings concerning grounding.
respectfully