Graduation (instrument)

A scale (plural scales, from the Latin Scalae = ladder, stairway ) is a succession of a number of tick marks on a display surface. The division can be non-uniform or uniform as required. It is used to display a value by means of an index mark. On technical equipment it is usually complemented with numbers and unity, thus enabling the reading of measured values ​​or other output values. Outside the metrology can carry a text explaining various positions.

The standard DIN 1319-2 "Fundamentals of Metrology " uses the term " scale", as well as DIN 43790 "Basic rules for the design of line scales and pointers ."

The alternative to the scale display is in the measurement technique, the digital display ( DIN 1319-2 ).

Basics

Scales are quantitative indication of sizes of fundamental importance in analog technology. While the size "level" of a boiler due to a pointer position as a qualitative statement is "pretty full" possible, " filled to 92% " to specify a scale in addition to the pointer inevitable. In the measurement by means of an analog indicating measuring method is almost always to adjust or reshaped to be measured at a distance or an angle; together with a scale of it is in the reading by humans is a numerical value or measured value ( number of times unit ).

The advantages of the scale display over the digital display are

• The rapid visual detection of the measured value,
• The easy recognition of trends (hiking the pointer ).

On a scale, there is a smooth transition. For example, in a measurement of body size, the display between 1.76 m and 1.77 m can be on the scale of the bar are. In principle, any number of additional digits can be followed at a variable setting. But how much more additional points can be specified depends on the accuracy of the measurement. Both the lack of reproducibility in posture and in the limit given here readability to about 1 mm can be an indication of places under 0,001 m is not responsible in this regard; see also Deviation or Significant digits.

At station clocks conventional design ( with minute hand, but without seconds hand ) does not fail the continuous readability of the scale, but remember that the minute hand will be adjusted only gradually.

Graduation

The magnitude of the difference between the values ​​belonging to two consecutive ticks is called Graduation ( also DIN 1319-2 ). It is expressed in the same units as to-read measurements.

Practical execution of scales

Scales have a graduated scale, which depends on the readability and accuracy required or possible. For ease of reading, the strokes can vary in length or width and are supplemented with a Skalenbezifferung. Often one unit is one of them. Values ​​, the most infinitely adjustable between tick marks are estimated to specify real numbers or measured values ​​within the measurement accuracy. Scale electrical measurement instruments should be conducted in accordance with DIN EN 60051 also a measuring unit symbol, a character class and other important data for use. Case by case basis (see image to the moving iron meter ), the range shall be differentiated and marked by the display area in the image by points on the scale. Manufacturer's instructions for accuracy apply only in the measurement range.

As a read-off is used, for example, a mechanically moving pointer ( for example, when the analog meter ), a light beam ( the mirror galvanometer ), a bar ( the liquid thermometer), a light-emitting point ( the oscilloscope) or the vernier scale graduation on the movable measuring leg of the calipers.

Instead of moving mark before the scale can also be movable with respect to a fixed mark the scale. It is then for example, a printed tape, disc, or provided with markings, movable transparent surface that is projected onto a screen ( Projektionsskale, eg on older laboratory scales and some tube radios ).

With no mechanical movement, can realize economies of scale displays digital -electronic means liquid crystal display.

On many devices ( radio receiver, frequency generators, analog multimeter) there are multiple scales that apply depending on the measuring range or frequency band, for example. You can mechanically switched ( Revolverskale, only the valid scale is visible) or be marked with a luminous display.

Scales may be linear, quadratic, logarithmic or divided by other law. The latter option allows the highlighting of regions of interest with stretched tick intervals or the correction of non-linearities of the corresponding measurement system. Thus, the relevant measuring range parts can be spread by the construction of the measuring equipment eg when moving iron works - the scale is then designed accordingly.

The uniform or linear scale, as it is common knowledge at the meter stick or liquid thermometer is preferred because it is here that appreciate intermediate values ​​between two ticks easiest.

Images of multiple scales with different scale gradients see also analog multimeter.

Accuracy

According to DIN EN 60051, the accuracy of a measuring instrument is defined as the degree of correspondence between the displayed and correct value. The accuracy is a purely qualitative size because at a quantitative indication for a high accuracy, a high value should indicate what is not common. For a quantitative indication of the agreed or normal tolerances are. Devices with high precision have small error limits. These are determined by class characters in electric scale measuring instruments. For a device class 1.5, the margin of error, at best, amounts to 1.5% of full scale value. It applies to both positive and negative variations in measurements.

The deviation due to unavoidable readout inaccuracy contained in the limits of error, so it must be significantly smaller. The reduction of the read- deviation for the inevitable in particular requires a directed perpendicular to the scale look and a thin pointer. This reduction is facilitated by various measures:

• With mirror scale (picture ) by a deposit with a reflective circular arc (vertical reading when the pointer overlaps its mirror image ),
• By a " knife hand " with vertical sheet - pointer tip (vertical reading when the pointer tip appears as narrow as possible ( as " back of the knife " ) )
• The calipers by a vernier
• By additional concurrent scales with finer resolution.

Scales in the digital measurement technology

Digital multimeters are occasionally supplemented addition to the digital display with bar graph display or LCD - vector representation, so that the advantages of scale display are retained (even glance through rapid detection of trends and detection of the measured value ). In place of the estimated uncertainty in the reading of a scale uncertainty occurs due to limited resolution of the stepped display.

The band display shown combines a scale display with a digital measurement, - digital because the display can only change gradually here; see also Digital measurement technology.

• Data acquisition
• Scale