What are measuring instruments

Measurement — technical means used in measurements and with normalized metrological properties.

According to their purpose, measuring devices are divided into sample and working ones, and in terms of design and metrological characteristics, they can be similar.

Sample measuring instruments are prohibited to be used for practical measurements, they are intended for checking other measuring instruments on them - both working and sample ones with lower accuracy.

Working measuring instruments have means used for measurements that are not related to the transfer of sizes of physical units «quantities.

You can only be sure of the correct reading of a working meter by checking it with a more accurate sample meter. The inspection of the measuring device, that is, the determination of the errors of the measuring device and the establishment of its suitability for use, is carried out only by the bodies of the metrological service, which have the corresponding permission.

Measuring instruments include measures, measuring instruments, transducers, installations and systems, and measuring accessories.

Measure has a measuring device designed to reproduce a physical quantity of a given size. A measure that reproduces a physical quantity of the same size is called single-valued, and the reproduction of a series of similar quantities of different sizes is called multi-valued. Examples of an unambiguous measure are a normal element (a measure of EMF), a sample coil (a measure of resistance), and an ambiguous measure is a millimeter ruler, an inductance variometer, a variable capacitor, a resistance box.

A measuring transducer is a measuring device designed to generate a signal from measurement information in a form convenient for transmission, further conversion, processing and (or) storage, but not subject to direct perception by an observer.

Measuring transducer — a technical instrument with standard metrological characteristics, used to convert a measured value into another value or measurement signal, convenient for processing, storage, further conversions, indication and transmission. The measuring transducer is either a part of each measuring device (measuring device, sensor) or is used together with each measuring instrument.

According to the place occupied in the measuring circuit, the converters are divided into primary, transmission and intermediate. The input of the primary converter is directly affected by the measured value, and the intermediate one is carried out in the measuring circuit after the primary one. The transmit transducer is used for remote transmission of measurement information and can be primary at the same time.

In order to change the value of one of the quantities acting in the measuring circuit for a certain number of times, without changing its physical nature, scale converters (measuring current transformers, amplifiers, etc.) are used.

Rice. 1. Electrical measuring devices (measuring devices for electrical quantities)

The goal is to generate a measurement information signal in a form available for direct perception by an observer measuring instrument.

The measuring device consists of a number of measuring transducers, communication channels, matching elements, measuring mechanism, which together form a measuring circuit. According to the method of formation of readings, measuring instruments are divided into indicating and recording ones.

An indication gauge only allows reading of the readings. Readings are counted visually on the scale of the meter against which the pointer of the reading device moves, or by the luminous numbers appearing on the reading device in digital indicating devices.

A recording measuring device contains a mechanism for recording the readings. If the device provides for recording the readings in the form of charts, then it is called self-recording.

A measurement setup is a set of functionally combined measuring devices (measures, measuring devices, measuring transducers) and auxiliary devices designed to generate measurement information signals in a form convenient for the direct perception of the observer, and located in one place. As an example, we can cite measuring installations for checking normal elements.

Measuring system Unlike the measuring device, it is designed to generate signals from measurement information in a form convenient for automatic processing, transmission and use in an automatic control system.