height gauge
**Height gauge** is a **precision measuring instrument mounted on a base that slides on a granite surface plate to measure vertical dimensions, step heights, and positional relationships** — combining the flatness reference of a surface plate with the precision of a digital encoder or vernier scale to achieve micrometer-level height measurements for semiconductor equipment component inspection.
**What Is a Height Gauge?**
- **Definition**: A vertical column-mounted measuring instrument with a movable probe or scriber that references from a precision base sitting on a surface plate — measuring heights, step heights, center distances, and geometric features.
- **Resolution**: Digital height gauges achieve 0.001mm (1µm) — vernier models read 0.02mm.
- **Range**: Common models measure 0-350mm, 0-600mm, or 0-1000mm depending on application requirements.
**Why Height Gauges Matter**
- **Precision Reference Measurement**: Height gauges on granite surface plates provide accurate, traceable vertical measurements that handheld tools cannot match.
- **Equipment Component Inspection**: Measuring heights, step dimensions, and positions of chamber components, fixture elements, and tooling.
- **Comparative Measurement**: Zeroing on a master reference then measuring production parts — fast and precise for lot sampling.
- **GD&T Verification**: Measuring position, perpendicularity, and parallelism relationships required by geometric dimensioning and tolerancing on engineering drawings.
**Height Gauge Types**
- **Digital (Electronic)**: Motor-driven or manual with digital encoder display — 0.001mm resolution, data output, and programmable features.
- **Vernier**: Manual operation with vernier scale — fundamental, no electronics, reliable.
- **Dial**: Analog dial readout — easy to read, no batteries.
- **2D Height Gauge**: Dual-axis measurement capability — measures both height and lateral position.
**Common Measurements**
| Measurement | Method | Application |
|-------------|--------|-------------|
| Height | Probe touches top surface, reads from plate | Component height verification |
| Step Height | Measure two surfaces, calculate difference | Shelf, ledge, groove depth |
| Center Height | V-block cradles cylinder, probe touches top | Shaft center height |
| Parallelism | Sweep probe across surface, record variation | Surface flatness to base reference |
| Perpendicularity | Measure feature position at two heights | Column squareness |
**Leading Manufacturers**
- **Mitutoyo**: QM-Height series — motorized digital height gauges with automatic measurement programs and SPC data output.
- **Trimos**: V-series height gauges — Swiss precision with tactile and 2D measurement capability.
- **Tesa (Hexagon)**: Micro-Hite series — compact digital height gauges for inspection rooms.
- **Mahr**: Digimar height measuring instruments for production metrology.
Height gauges are **the precision vertical measurement backbone of semiconductor equipment inspection** — providing traceable, repeatable height and position measurements that incoming inspection, equipment qualification, and maintenance teams rely on for verifying critical component dimensions.