Understanding Vernier Caliper Depth Measurement

A vernier caliper is a versatile measuring instrument used to determine the length of objects, the internal diameter of holes, and the depth of cavities or holes. It consists of a main scale and a sliding vernier scale. Different parts are used for different types of measurements.

Parts Involved in Depth Measurement

When measuring the depth of a hole or a slot, the vernier caliper uses a specific part known as the depth measuring blade or depth probe. Let's look at where this part is attached:

• The main scale is fixed to the fixed jaw.
• The vernier scale is marked on a slide that moves along the main scale. This movable slide is called the vernier slide or vernier scale holder.
• The movable jaw is attached to the vernier slide.
• The depth measuring blade is also attached to the vernier slide and extends from the back of the instrument.

How Depth Measurement Works

To measure depth, the fixed jaw is placed on the surface from which the depth is to be measured. The vernier slide, along with the movable jaw and the depth measuring blade, is moved until the end of the depth blade touches the bottom of the hole or cavity. The depth is then read from the main scale and the vernier scale, similar to reading length or internal diameter.

Because the depth measuring blade moves in tandem with the vernier scale and the movable jaw, it must be attached to the part that carries these components. This part is the vernier slide.

Analyzing the Options

Let's consider why the other options are not correct:

• Vernier scale: The vernier scale is the set of markings on the vernier slide. The blade is attached to the slide itself, not just the scale markings.
• Fixed legs: The fixed legs (or jaws) are stationary parts attached to the main scale. The depth blade is a movable part.
• Movable legs: The movable legs (or jaws) are attached to the vernier slide and move with it. While the movable legs and the depth blade move together, the blade's attachment point is specifically the vernier slide (which carries the movable leg). The vernier slide is the more precise answer as it's the primary movable component carrying both the movable jaw and the depth blade.
• Vernier slide: The vernier slide is the movable part of the caliper that carries the vernier scale and the movable jaw. The depth measuring blade is physically attached to the vernier slide, allowing it to extend and retract as the slide moves.

Therefore, the depth measuring part of the vernier caliper is attached to the vernier slide.

Revision Table: Vernier Caliper Parts and Functions

Additional Information: Types of Vernier Caliper Measurements

A standard vernier caliper can typically perform three types of measurements:

• External Measurement: Measuring the outer dimensions (e.g., length, outer diameter) of an object using the main jaws.
• Internal Measurement: Measuring the inner dimensions (e.g., internal diameter of a pipe or hole) using the small jaws at the top.
• Depth Measurement: Measuring the depth of a hole, slot, or recess using the depth measuring blade.

All these measurements rely on the precise movement of the vernier slide along the main scale.