yes Potential can be appeared r on the probe tip when floating potential is being measured

Ground is a nebulous concept in electrochemistry. If you are working in a conventional (glass bodied) cell then all the chemical potentials are related to the chemistry in the cell (mixed potential theory) and if there is a ground present (e.g. if the potentiostat you are using has a ground terminated lead) then that ground is just a sink for current and not relevant to any measured potential.

If, however, you are operating in a grounded environment (autoclave, or a sample in the ground) then ground is a complication requiring a floating system to make a measurement. In that case the "ground potential" is just the potential of whichever point in the cell is grounded and its electrochemical potential is still based on the chemistry (often of the metal itself in steady state with the electrolyte around it). If you don't have a floating system to make measurements in that latter case then the current can go to ground through different routes and you can't accurately measure or control the cell.

In either case measuring a potential "relative to ground" does not have intrinsic meaning. You measure potential against something, and if that something is grounded then it is technically vs. ground, but the relevant measure is vs. whatever [mixed] potential value is present at that second electrode (iron in soil, or platinum in sulfuric acid, or Ag/AgCl, or...).

Could you clarify what you mean by a probe tip? What type of probe? Where is it sitting?

The shape of the probe tip is cylindrical and is made of tungsten wire. The tip is inserted in the plasma produced between two electrodes held in parallel-plate configuration. Bottom electrode is connected with ground whereas top electrode is powered with DC power supply.

there would definintely be someground potentia. However to exactly know the value of that potential in your case won't have a meaningful science to it as Jacob Ketter mentioned, and would be difficult.

While you can certainly bias that tip against [ground] in the plasma I'm not sure you can measure its potential. You need a known, stable couple to measure that against and I'm not sure how you could do that in a plasma. Basically what you can know is the voltage (or field effect) not the potential, unless someone knows of some way to establish the potential of/within a plasma.

Thanks for detailed reply, What mean by stable couple, I am not clear about this phrase. Moreover, the question is that whether or not the voltage applied across the electrodes will appear on the probe tip when measuring plasma potential w r to ground. Because cathode is also grounded and so probe tip and cathode will be common.

Yes,