The ornamental design for a portable testinstrument, substantially as shown and described.
FIG. 1 is a front perspective view of the portable test instrument;
FIG. 2 is a back perspective view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a bottom view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a back view thereof; and,
FIG. 7 is a front view thereof.
The broken lines shown in the figures are for the purpose of illustrating the environmental structure and form no part of the claimed design. The unevenly-spaced broken line at the front end and visible in FIGS. 2-5 illustrate the boundary of the claimed design and form no part thereof.
The right side of the portable test instrument is a mirror image of the left side of the portable test instrument depicted in FIG. 5.
The shade lines in the figures show contour and not surface ornamentation.