These tools measure the mean diameter of boreholes. They are used to check the integrity of borehole linings, and where a borehole is unlined to identify zones of washout, breakout or fissures.
For narrower boreholes (<400mm) the 2 or 3 arm calipers give greater resolution than a 4 arm caliper.
2 or 3 Arm Caliper
4 Arm Caliper
|Tool size||1150 x 38 mm||1180 x 80 mm|
|Range||50 – 600mm||100 – 1500mm|