A height gauge can be one of two types of device. The first is simply a device or instrument that measures the height of some object, while the second is a device that automatically marks parts or work pieces at a specific height or point for further attention. A height gauge can also be used to set the height of a desired measurement or the height of a part. They are found in shops, industrial applications, testing and laboratory settings, and even in doctor's offices.
Two main types of height gauges are used. Vernier gauges are purely mechanical in nature with a scale engraved or printed on the device itself, usually on a vertical bar or tower type assembly. A component called a datum slides up and down this vertical bar and may be secured by screws, by clamps, or by other means. The datum usually has an extension that is either aligned with the object or gap to be measured or set to correspond to an indicator that gives a reading on the measurement gauge column.
An electronic or digital height gauge works in much the same way, but the datum is usually a simple electronic digital device and display, often a basic liquid crystal display (LCD) or light emitting diode (LED), that gives the reading corresponding to the position of the datum in relation to the reference or zero point. Both types of height gauges usually have multiple scales or settings for separate measurement conventions, such as decimal and fractional, for both the English and metric systems.
Industrial applications for a height gauge include setting the height for a particular measurement, usually of a part or of a vertical gap in some machinery. Often, the height is set and a scriber is attached to mark a series of parts at the preset height to ensure that a further step in the manufacturing process is carried out on every part in exactly the same position. Height gauges can also be used to set the height for saw blades and other automated tools to ensure precision.
Woodworkers and machinists often use height gauges in their work. Varying degrees of precision are possible, depending on the particular gauge, and machinists will often use models that are capable of very high precision due to the exacting tolerances that are often demanded for machinery and machined parts. A height gauge of another sort may be familiar to anyone who has ever visited a doctor's office and had their height measured, as these devices are common in such places.