Classification of measuring instruments

It refers to a measuring tool that reproduces or provides a given number of one or more known values in a fixed form when used. Such as measuring blocks, square rulers, various curve templates, standard gauges and so on.

2. Limit gauge

Refers to the special inspection tool without scale. Using this tool, the specific dimensions of the inspected workpiece cannot be obtained, but it can be determined whether the inspected workpiece is qualified, such as smooth limit gauge and thread limit gauge.

3. Display measuring instruments

It refers to a measuring instrument that displays numerical values. Its display can be analog (continuous or discontinuous) or digital, it can display multiple values at the same time, and it can also provide records. Such as analog voltmeter, digital frequency meter and micrometer.

4. Measuring system

Refers to a set of measuring instruments and other equipment assembled for specific measurement, and the measuring system may include physical measuring tools. A fixed installation of measuring system is called measuring equipment.

Extended data:

I. Historical development

Scholars and navigators are well aware that if the position of celestial bodies can be accurately measured on the sea surface, then sailors can know their latitudes with certainty. To do this, what is needed is an accurate measuring instrument.

Ptolemy once described the astrolabe (also called the Star Finder). The larger astrolabe is used in the observatory and the smaller one is used in the ship. The use of the astrolabe requires the cooperation of three people-one holds the thumb ring on the astrolabe, one aims at it, and the other reads the results on the dial. When the ship shakes violently, the result is naturally not very accurate. Whenever possible, sailors will go ashore to measure.

Ancient astronomers used the cross scale to measure the latitude of stars, and later sailors also used it in navigation. This instrument consists of a ruler and a cross ruler, the lower end of which is placed in a horizontal position. While observing the celestial body along the ruler, slide the cross ruler until it touches the observed object (sun or star) in your field of vision, and then read the degree on the ruler. This instrument can only be operated by one person.

Both the astrolabe and the cross scale require observers to observe the sun directly. On a clear day, too strong light will make observation impossible. In order to solve this problem, the British captain and navigator john davis invented the back scale. It consists of a ruler and a sliding bar. When observing, the observer first turns his back to the sun, and then slides the crossbar until it casts a shadow on the small dish in front. In this way, observers can observe the horizon.

Second, the instrument index

The concepts of measuring instruments include: accuracy, error, measuring standard equipment, length measurement, angle measurement, shape measurement and traditional optical instruments. Application in precision measurement.

There are two kinds of measuring instruments: contact testing and optical testing (most commonly used at present): general measuring tools and 3D measuring tools (also called coordinate measuring machines). Three-dimensional coordinate measuring machine, also called three-dimensional, can measure many complex spatial dimensions, such as molds and automobile products.

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