The ornamental design for an electrical testinstrument, as shown and described.
FIG. 1 is a bottom-front perspective view of a digital electronic test instrument embodying my new design;
FIG. 2 is a top-front perspective view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a rear elevation view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a left side elevation view thereof; and,
FIG. 8 is a right side elevation view thereof.
The broken lines showing instrument controls, display panel and i/o ports in the figures are for illustrative purposes only and form no part of the claimed design.