The display described in the art generally to an apparatus for the optical signaling of variable information (conditions and data), in particular measured values . This is how they differ from labels that provide constant information. In the work system , displays represent an interface between people and a technical process or the environment.
A display can have very different designs and be based on different technical implementation. A distinction is made between mechanical , electromechanical and electronic displays . Depending on the type and meaning of the display itself, it can also be subdivided into binary displays , dial displays , number displays and graphic displays . In ergonomics, DIN EN 894-2 differentiates between optical, acoustic and tactile displays.
Designs and technical implementations of displays
In the case of mechanical displays, on the other hand, a distinction is made between continuous and discrete displays .
Examples of continuous mechanical displays:
- Mechanical tachometers convert the speed of a shaft into a proportional angle of a pointer.
- A winding device for a thread combined with a pointer measures how deep a float hanging on the thread has sunk, and thus shows the fill level , u. a. on oil tanks.
- Level indicators or levels for short , as can be found on many rivers, or water or level indicators, e.g. B. on boilers or coffee machines, show by looking directly at the liquid level on a scale, often through a sight glass , the fill level or the water level.
- Liquid thermometer
- Bimetal thermometer
- analog mechanical scales (pointer, moving or projected scale )
- Tuning scale for station selection on radios
Example of discrete mechanical displays:
- Railway shape signals in various designs for instructions such as "drive" and "stop"
- Indicators on fuses indicate a blown fuse element
- mechanical pedometers and odometers ; general: roller counters
- Water meter , gas meter
Continuous electromechanical displays:
- Dial displays
Discrete electromechanical displays:
- Electromechanical counters with dials
- Fall sheet display boards at airports and train stations for texts and times
- Drop flap relay
Electric and electronic displays
Electrically controlled displays without moving parts can be binary displays, numeric displays, but also analog displays ( bar graph display , magic eye ) or images . The term digital display usually means a numeric display.
Technical implementation (examples):
- Signal lamps [light bulbs or light emitting diodes (LEDs), organic light emitting diodes (OLEDs)]
- binary, color change, numeric display or bar graph
- Brightness comparison or flashing at different frequencies
- Liquid crystal displays (LCDs); Character, symbol, number or image display ( smartphones , flat screens )
- Fluorescent displays (VFDs); Character or symbol display, also bar graph displays, magic eye
- Braun tubes ; yx display for picture tubes , oscilloscopes , spectrum analyzers, measuring receivers, display in polar coordinates in radar devices
- Nixie tubes (numeric display)
Common types of control of complex electrical or electromechanical displays are:
- vector-oriented control
- Grid or matrix display
- Segment display ( seven-segment display , fourteen-segment display , binary symbol display )
The screen (also monitor, display, smart display ) is a very universal display instrument. As a Braun tube, it can be controlled in a vector and grid-oriented manner.
Increasingly, liquid crystal screens are used , which are controlled as matrices in a grid.
Projection displays project alphanumeric characters or symbols onto a wall or screen. In the case of alarm clocks with a projection display , a seven-segment display is projected, while u. a. In early mainframes, numeric displays were used that had 10 light bulbs, 10 collimator lenses, gobos 0 ... 9 and 10 appropriately aligned lenses for each digit, so that each digit could be displayed in the same position on a screen. In the past, complex devices such as the Eidophor system were required to project video images ( video projector ) onto large screens . Since the 1990s there have been projection techniques with LCDs or DLPs , called projectors in certain countries .
Displays in measurement technology
In DIN 1319-2, which is fundamental for measuring technology , a distinction is made between scales and numeric displays for “measuring devices with direct output” .
In the case of a measuring device with a scale display, a mark (e.g. a certain point on a physical pointer or a screen pointer, a light pointer (see e.g. also mirror galvanometer ), an edge, the meniscus of a column of liquid) is usually continuous to a point on the scale , or the scale is set to it. For physical pointers, see e.g. B. under analog multimeters , moving coil measuring mechanism .
Scale displays can also be found on a large number of mechanical measuring devices such as scales, calipers ; the latter use a vernier for more precise readability. Mirror scales also have a mirror sector behind the pointer to facilitate vertical reading and thus to avoid parallax errors when reading.
In the case of the band display , a variable number of segments is either discontinuously illuminated or a variable length of the band is set continuously. It can be used for measurement or only for qualitative assessment, see bar graph display or magic eye . The discontinuous tape display works digitally and combines digital technology with the advantages of a dial display.
In the case of a measuring device in which the output variable is a numerical representation of the measured variable quantized in fixed steps, the number (sum) of quantization units or the number (sum) of pulses appear discontinuously in a sequence of digits. The numeric displays differ in the principles of the numeric display. See section Electrical and Electronic Displays . Earlier digit displays used ten discrete, backlit digits per position, which were viewed or projected directly from the light.
Number displays have the disadvantage that trends and the absolute size cannot be recognized at first glance. Therefore, digital multimeters (DMM for short, i.e. those with a numeric display) sometimes also have a fast bar graph display or a pointer element, which, however, also consist of discrete display elements (see picture on the right).
Advantages are e.g. B. the displayability of the measured value over a wide range using variable commas and additionally displayed units of measurement, the clarity of the reading and, with self-lit displays, the good readability in poor lighting conditions.
With the appropriate output technology, ratings can also be included in the advertisement; For example, if a limit value has been exceeded or if there is a risk in the system, a flashing display, additional illuminated signs or changing colors can be used to indicate.
- DIN EN 894–2: 2009–02: Safety of machines - Ergonomic requirements for the design of displays and control elements - Part 2: Displays.