10.2.3. Measuring tools and operating mode on them
Measurement is the process of determining a physical quantity using special measurement tools.
Measurement tool is a technical tool designed to determine a physical quantity that reproduces and/or stores a unit of physical quantity whose size is assumed to be unchanged within the established error during the true time interval. Means of measurement have normalized metrological characteristics.
Metrological designation of measuring instruments is divided into:
- on working measuring instruments intended to determine physical quantities in the national economy;
- metrological means of measurement, designed to ensure the uniformity of measurements in the country.
Measuring tools are classified:
- according to the design for measures, measuring instruments, measuring systems, measuring systems, measuring systems;
- by the level of automation to non-automatic, automated, automatic;
- in terms of standardization for standard and non-standard;
- in relation to the measured physical quantity for the main and auxiliary.
Reference - (from the French etalon) is a measurement tool (or a set of measuring instruments) that provides reproduction and/or storage of a unit, as well as transfer of its size to the measuring instruments inferior in the calibration scheme approved as a standard in the prescribed manner.
Measure is a measurement tool designed to reproduce and/or store a physical quantity of one or more specified sizes, whose values are expressed in prescribed units and known with the required accuracy.
The measure can be single-valued, i.e. reproducing a physical quantity of the same size (for example, a plane-parallel measure of a length of 10 mm), and multivalued, reproducing a physical quantity of different sizes (for example, a model ruler, an angular limb).
Measuring Devices is a measurement tool designed to obtain the values of a measured physical quantity within a specified range. Measuring instruments have a device for converting a measured quantity into measurement information accessible for perception. Information is displayed on an analog or digital indicator device on a scale with an arrow, a diagram from which values of a physical quantity can be measured or recorded.
By the nature of the indication of the measured value, the measuring devices are divided into indicating and recording devices; by action - on integrating, summing. Distinguish devices of direct action and devices of comparison.
Measuring installation - a collection of functionally integrated measures, measuring devices, converters and other devices designed to measure, as a rule, several physical quantities.
Measuring system - a set of functionally combined measures, measuring devices, converters, computers and other technical means located at different points of the monitored object in order to measure, as a rule, several physical quantities inherent in the object./p>
Measuring complex - a collection of functionally integrated measuring instruments (measuring devices), auxiliary devices designed to determine physical quantities.
Measurement tools consist of a combination of the following structural elements.
The base of the measuring instrument is a structural element on which all other elements of this measuring instrument are mounted. For example, a barrel of a caliper, a micrometer bracket, a watch-type case, a pendulum frame.
Sensitive element - part of the measuring device that makes contact with the object of measurement and perceives the determined physical size of the object. For example, the measuring sponges of the caliper, a diamond cone on the indenter of the Rockwell device.
Dimension element - a detail of the measuring means, which has its own exact, usually multivalued size, whose value is determined and compared in the measurement process by the size of the measurement object. Say, a bar with a scale of a caliper: it compares the size of the part perceived by the sponges.
Conversion element is an internal mechanism of the measuring means that converts a physical value perceived from the object of measurement to a sensing element into readings on the reading device, available for direct observation and counting. Thus, the gear train in the dial gauge converts small movements of the measuring tip into large movements of the arrow, easily observed on the scale.
Counting device makes it possible to count the readings of the measuring instrument; in most cases, the counting devices consist of a pointer scale, which is a separate stroke, a group of strokes or an arrow. Recently, measurement instruments with digital counting devices have become widespread. These include: the vernier of the caliper, the dial scale of the indicator and the arrow of the hour indicator, the micrometer display with digital indication. Depending on the purpose and principle of operation of a particular measuring instrument in its design, these or other complexes of these devices of elements constituting the structure of a given measuring instrument are used.
Scale - a series of marks, strokes, dots or numbers placed near them, the position of which corresponds to a series of consecutive sizes.
The scale division is - the difference in the values of the values corresponding to the difference of two adjacent scale marks.
The scale range is the range of the scale, bounded by the final and initial scale division.
Measurement range - the range of the measured value, for which the errors of the measuring instrument are normalized.
Limits of Measurement - is the largest and smallest value in the measurement range.
Measuring force - the force with which the sensor affects the surface of the measurement object.
When operating measuring instruments, it is necessary to take into account the types of measurements carried out, the required and possible ranges of measurements, the accuracy of measurements.
The conformity of the measuring means with the requirements must be documented.
The measuring means are regularly calibrated (check the device's divisions) according to the established procedure. If necessary, the instrument setup specialists carry out adjustment of the measuring means, setting up and updating the software.
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