What Is a Depth Gauge?
A depth gauge is a measuring instrument used to measure depth. Unlike digital indicators that measure length based on the retraction of the measuring terminal, a depth gauge uses its base reference plane as the zero point and calculates length based on the extension of the measuring terminal.
Also referred to as a depth micrometer or dips gauge, depth gauges are chosen between analog or digital types depending on the required accuracy and application.
Uses of Depth Gauges
Depth gauges are primarily used in the manufacturing process and quality control of industrial products. As a precision measuring instrument, they are used alongside calipers, micrometers, and height gauges for measuring industrial products on surface plates. These gauges are commonly found in precision measuring rooms and quality control departments in various factories.
Principle of Depth Gauge
A depth gauge measures the distance between its reference surface and the part being measured. It typically has a surface in contact with the reference plane and a measuring element in contact with the part. Depending on the type, the distance is read by a vernier scale, dial gauge, or digital display. Some models, particularly those with dial gauges, come with attachments that allow adjustment of the measuring element’s length for various depths.
Types of Depth Gauges
Depth gauges are broadly categorized into caliper type, micrometer type, and digital indicator type.
1. Caliper Type
Caliper-type depth gauges use a depth bar for measurement, similar to general calipers. Although their accuracy can be limited, they are suitable for measuring grooves and holes that regular vernier calipers cannot reach.
2. Micrometer Type
Micrometer-type depth gauges function like standard micrometers, calculating length through the rotary axis’s feed rate. This type adheres to Abbe’s Law, ensuring higher accuracy as the measuring terminal and instrument scale are aligned.
3. Digital Type
Digital depth gauges, like digital indicators, utilize a linear scale with optical moiré interference fringes. They offer the advantage of calculating average values and feature interchangeable parts such as splice legs to extend the measuring range.
Other Information on Depth Gauge
1. Depth Measurement with Optical Instruments
Optical instruments, like microscopes with autofocus, are used for precise depth measurements. The depth is determined by focusing on the reference plane and the target area, aligning the microscope’s focus direction with the depth direction.
2. Depth Gauge for Hardened and Quenched Layers
Hardened-layer depth gauges measure the depth of surface-hardened layers in steel materials. Traditional methods involved micro-Vickers hardness testing, which was time-consuming and destructive. Modern depth gauges use ultrasonic waves to non-destructively measure the hardened layer’s depth by detecting differences in ultrasonic scattering due to the metallurgical structure inside the material.