The ornamental design for a clampmeter, as shown and described.
FIG. 1 is a front view of an embodiment of a clampmeter.
FIG. 2 is a left side view thereof.
FIG. 3 is a right view thereof.
FIG. 4 is a back view thereof.
FIG. 5 is a top view thereof.
FIG. 6 is a bottom view thereof.
FIG. 7 is a first perspective view thereof.
FIG. 8 is a second perspective view thereof.
FIG. 9 is a third perspective view thereof.
FIG. 10 is a fourth perspective view thereof; and,
FIG. 11 is a fifth perspective view thereof.
The broken line showing of structural features is included for the purpose of illustrating non-claimed subject matter and forms no part of the claimed design.