The ornamental design for a processcontrolinstrument, as shown and described.
FIG. 1 is a perspective view of a process control instrument.
FIG. 2 is a front elevation view thereof.
FIG. 3 is a rear elevation view thereof.
FIG. 4 is a left side elevation view thereof.
FIG. 5 is a right side elevation view thereof.
FIG. 6 is a top plan view thereof.
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a cross-sectional view taken along the line 8-8 in FIG. 2, which omits the internal structure.
The portions of the process control instrument shown in broken lines are for the purpose of showing environmental structure only and form no part of the claimed design. The oblique line shading illustrates translucency.