Explain the pressure-measuring device at any point in a fluid in short.

(N/A) An idealized form of a pressure-measuring device is shown in the figure.
It consists of an evacuated chamber with a spring that is calibrated to measure the force acting on the piston.
This device is placed at a point inside the fluid.
The inward force $\Delta F$ exerted by the fluid on the piston is balanced by the outward spring force and is thereby measured.
The pressure $P$ of the fluid acting on the surface of the piston of area $\Delta A$ is given by $P = \frac{\Delta F}{\Delta A}$.
The piston area can be made arbitrarily small. The pressure is then defined in a limiting sense as $P = \lim_{\Delta A \rightarrow 0} \frac{\Delta F}{\Delta A}$.