Caliper
Caliper turns up in 2 fields: paper optics, automotive. Here is what it means to the people in each one.
Caliper in paper optics
Thickness of a single sheet of paper, measured under a set pressure and given in micrometers or thousandths of an inch.
Measured with a dead-weight micrometer that clamps the sheet between flat anvils at a defined pressure, caliper is reported in micrometers or in thousandths of an inch, which board makers call points. It sets bulk, stiffness and how a stack feeds and folds. Calendering trades caliper for smoothness and gloss, and caliper loss usually costs opacity at the same time.
"Caliper is down 4 microns since the calender load change, and the folding customer will notice."
Caliper in automotive
The hydraulic clamp in a disc brake system that squeezes the brake pads against the rotor.
The brake caliper is a heavy metal housing that mounts over the brake rotor and contains one or more hydraulic pistons. When the driver presses the brake pedal, brake fluid forces the pistons outward, clamping the brake pads tightly against the spinning rotor to create friction and stop the vehicle. Calipers can be fixed in place with pistons on both sides, or floating with pistons on just one side.
"The right front caliper is seized up completely, which is why your steering wheel shakes when you brake."