Light knowledge: Our lexicon

Clear explanations of lighting technology terms.
Welcome to our compact lighting encyclopedia!

Current, voltage, power, ...

Current is a fundamental term in physics and describes the flow of electrical charge through a conductor. As a rule, this refers to the electrical current that is driven by electrical voltage. Electric charge carriers, such as electrons, move through the conductor and form a current.

Electricity can occur in two forms: Direct current (DC) and alternating current (AC). In direct current, the electrical charge flows continuously and in one direction, whereas in alternating current, the direction of the current changes periodically. The unit for electric current is the ampere (A).

Direct current (DC)
is an electric current in which the electric charge flows continuously in only one direction. This means that the direction of the current remains constant. A classic example of direct current is the battery. In DC circuits, the polarity (positive or negative) of the current remains unchanged.

Alternating current (AC)
is an electric current in which the direction of the electric charge changes periodically. This means that the current constantly changes direction, typically in the form of a sinusoidal wave. Alternating current is used in households and most industrial applications because it can be transmitted more efficiently over long distances. The power supply from the public grid is alternating current in most countries.

Constant voltage and constant current are two different operating modes used in relation to the power supply or charging of electrical devices or batteries.

Constant current refers to an electrical current that remains constant over a certain period of time and has a constant strength regardless of the load conditions or other external influences. It is a stable current source that maintains a fixed current flow between two points.

Constant current sources are often used in various applications, especially in situations where a constant power supply is required, regardless of the variations in load resistance or load impedance.

A typical application for constant current sources is, for example, the supply of light-emitting diodes (LEDs). LEDs have a specific forward voltage, and a small change in the voltage applied to them can lead to large changes in the current and therefore the brightness. A constant current source ensures that the current through the LED remains constant, regardless of the voltage fluctuation.

A constant current source can also be used in battery charging to ensure a specific charging current regardless of the battery voltage.

It is important to note that a true ideal constant current source does not exist, as this would violate the laws of physics. Instead, a constant current source is usually a current control circuit that keeps the current constant within narrow limits as long as the load is within the specifications of the source.

Electrical resistance is a fundamental property of an electrical component or conductor that indicates the extent to which the flow of electric current is impeded in the material in question. It is measured in ohms(Ω) and is an important parameter in electrical engineering and electronics.

The electrical resistance depends on various factors, such as the length, cross-section and material of the conductor. Basically, the longer the conductor or the smaller its cross-section, the greater the resistance. Different materials have different specific resistance values, which means that some materials conduct electricity better than others.

A high resistance leads to a lower current flow at a given voltage, while a low resistance enables a higher current flow. Resistors are often used in circuits to control the flow of current, to protect components from excessive current or to achieve certain electrical properties. There are fixed resistors with a fixed value and variable resistors whose value can be adjusted to adapt the current flow.

When electric current flows through a conductor (i.e. through materials through which electric current can flow), there is always an electrical voltage between the two ends of the conductor. This is also known as the potential difference. In short, electrical voltage is the electrical charge between two points. It is usually measured in volts (V) and can be generated in various ways: Among other things, through chemical reactions, friction or light. The electrical voltage can be thought of as the “pressure” that drives the current through the conductor. The voltage level depends on the type of material the conductor is made of and the length and diameter of the conductor.

The input voltage is a term used in electrical engineering and refers to the electrical voltage that is applied to the input of an electrical or electronic device or system. It is also usually measured in volts (V).

In electronic circuits or devices, the input voltage serves as the supply voltage that provides the electrical energy required to operate the device properly. The input voltage can come from a power source or a battery, depending on the application.

It is important to note that the input voltage of a device or system is normally limited by specified limits. Exceeding these limit values can lead to malfunctions, damage or even destruction of the appliance. It is therefore important to use the correct input voltage according to the manufacturer’s specifications to ensure safe and efficient operation.

Constant voltage and constant current are two different operating modes used in relation to the power supply or charging of electrical devices or batteries.
Constant voltage refers to an electrical voltage that remains constant over a certain period of time and shows no significant fluctuation or variation. It is a stable voltage source that maintains a fixed potential difference between two points, regardless of the load conditions or other external influences.

Constant voltage is often generated by special electronic devices or power sources, such as power supply units, voltage regulators or battery chargers. These devices are designed to supply a reliable and constant voltage to operate electrical devices or charge batteries without the voltage fluctuating.

The stability of the constant voltage is particularly important when it comes to sensitive electronic components, as a voltage that is too high or too low could cause damage. For this reason, constant voltage sources are widely used in many applications, such as electronics, lighting technology, industrial automation and many other areas.

Electrical power is the amount of electrical energy that is converted, transmitted or consumed in an electrical system per unit of time. It indicates how much electrical work is performed per second and is measured in watts (W).

The rated power is the maximum continuous power at which a power engineering device can be operated without impairing its service life and safety.

This is a fixed value that is normally specified by the manufacturer or in the technical specifications of a product.

The rated power is important to understand the performance of an appliance and to compare it with other appliances. It indicates how much power a product can provide without compromising stability or reliability.

The ambient temperature is the temperature of the air or the surrounding medium in a specific area or room. It is the temperature that prevails at a certain location in the immediate vicinity of objects and living beings. The ambient temperature is usually measured in degrees Celsius (°C) or Fahrenheit (°F).

The ambient temperature can vary greatly and is influenced by various factors such as geographical location, altitude above sea level, time of day, weather, season and human activity.

In lighting technology, it is very important to take the ambient temperature into account, as it can have a significant impact on the performance of electronic devices. The ambient temperature can be an exclusion criterion for the operation of machines and electronic devices.

The luminous flux describes the total amount of light emitted by a light source per second. It therefore measures the brightness of the light, regardless of the direction in which it shines. The unit of luminous flux is lumen (lm). The higher the lumen value, the brighter the light source.

Candela (cd) is the unit for the luminous intensity of a light source in a specific direction. It describes the brightness of light in a particular direction and is often used for directional light sources such as spotlights.

Lux (lx) is the unit for illuminance and indicates how much light falls on a certain surface. It is defined as lumens per square meter (lm/m²). Illuminance is an important parameter for evaluating the brightness and efficiency of LED lighting systems, especially indoors and outdoors.

Kelvin (K) is the unit for the color temperature of light sources. It describes the color of the light emitted by a light source. Low Kelvin values (e.g. 2,700 K) stand for warm white light, while higher Kelvin values (e.g. 5,000 K) stand for cool white or daylight-like light.

The color rendering index, also abbreviated as CRI (Color Rendering Index), is a measure that describes the ability of a light source to reproduce the colors of illuminated objects compared to an ideal or natural light source. It is an important criterion for assessing the quality of color rendering of artificial light sources such as luminaires and lamps.

The CRI is rated on a scale from 0 to 100, where 100 means the best possible color rendering, which corresponds to an ideal light source. Light sources with a CRI value of 80 or higher are considered acceptable for most indoor applications, while values above 90 are considered very good and mean excellent color rendering.

A high CRI value indicates that the light source reproduces a broad spectrum of colors well and thus faithfully represents the natural colors of the illuminated objects. A low CRI value, on the other hand, means that the color rendering is impaired and the colors may appear less vivid or distorted under the lighting.

The CRI rating is particularly important in areas such as interior design, lighting design, photography, art exhibitions, retail stores and other applications where accurate color rendering is critical.

The term half-value angle is widely used in physics and optics and refers to the angle at which the intensity of a particular radiation or other physical quantity falls to half its maximum value.

In optics, the half-value angle is often used in connection with the beam width or the radiation behavior of light sources. If you imagine a light source radiating in a certain direction, then the half-value angle is the angular range in which the intensity of the light has dropped to half of its maximum.

A common example is the half-value angle of light-emitting diodes (LEDs). LEDs often have a directional radiation pattern, and the half-value angle indicates the angle range in which the light has around 50 % of its maximum intensity. This is important to understand and control the illuminance and coverage areas of light sources.

In summary, the half-value angle is an angular measure that indicates how wide the emission of a light source or the propagation of radiation is when the intensity has fallen to half its maximum value.

The uniform glare assessment is a concept from the field of lighting technology and describes a method for assessing the glare caused by light sources. Glare occurs when the human eye is affected by excessively bright light or strong contrasts and the visibility of objects or information is reduced.

The Unified Glare Rating ( UGR) was developed to evaluate and compare glare. The UGR is a key figure based on physiological and psychological studies and enables an assessment of glare from a human perspective.

The UGR scale usually ranges from 10 to 30, with lower values meaning less glare and therefore a better visual environment. For example, a UGR of 10 corresponds to very low glare, while a UGR of 30 indicates strong glare that may be unpleasant or even impair vision.

A uniform glare rating is often used in relation to indoor lighting systems, such as office lighting, classrooms or public spaces, to ensure that the lighting creates a comfortable and ergonomic environment for users and that visual performance is not compromised. It is important to take UGR into account when planning and designing lighting systems to ensure optimum visual performance and visual comfort.

LED knowledge

The development of the LED (Light Emitting Diode) is a fascinating journey through decades of technological progress.
The roots of the LED go back to the early 1900s, when electroluminescence was discovered in semiconductors. However, it was not until 1962 that the American physicist Nick Holonyak Jr. succeeded in developing the first functional LED that emitted red light. In the following years, progress was made in colors, and LEDs also emitted green and blue light.

In the 1970s and 1980s, the efficiency of LEDs improved considerably, enabling them to be used in display panels and digital clocks. Miniaturization led to their use in electronic devices such as pocket calculators and cell phones.

In the 1990s, high-performance LEDs were developed for use in lighting. Efficiency continued to increase and LEDs were increasingly used as a replacement for conventional light bulbs. Over time, they became more energy-efficient and more durable, which helped to promote energy-saving measures.

In the 21st century, LEDs revolutionized the lighting industry by not only saving energy, but also offering a variety of colors and customization options. They have been used in architectural lighting, street lighting, the automotive industry and many other areas.

Today, LEDs are present in almost all areas of life, from consumer electronics to large screens and interior lighting. Their development has helped to reduce energy consumption and improve the quality of life.

A distinction is made between the following LED types:



High Power LED


COB LED stands for “Chip-on-Board Light Emitting Diode”, i.e. a light-emitting diode with a chip on the circuit board. This is a special type of light-emitting diode technology used in the lighting industry. In contrast to conventional LEDs, where each LED chip is mounted individually on a circuit board, with COB LEDs several LED chips are placed directly on a common substrate board and connected to each other.

The advantages of COB LEDs are manifold:

The close arrangement of several LED chips on a small surface results in a higher luminous efficacy, which leads to more efficient light generation. The shared circuit board also helps to better distribute the heat generated, which improves heat dissipation and increases the service life of the LED. As the LED chips are positioned close together, COB technology can lead to a more uniform light distribution, which ensures more homogeneous lighting. In addition, the close arrangement of the LEDs enables a much more compact design, which is particularly advantageous in applications where space is limited. Due to these advantages, COB LEDs are used in many lighting applications.

SMD LED stands for “Surface Mount Device Light Emitting Diode”. This is a special type of light-emitting diode that was developed for surface mounting on printed circuit boards. In contrast to older through-hole LEDs, which are inserted through holes in the circuit board and then soldered, SMD LEDs are soldered directly to the surface of the circuit board.

The main features and advantages of SMD LEDs are

SMD LEDs are generally compact and flat, which saves space on the circuit board and enables the development of thin and lightweight lighting products. As SMD LEDs are mounted directly on the surface of the PCB, they can be assembled more efficiently and automatically in large quantities, which reduces production costs. SMD LEDs also offer uniform light distribution and are versatile due to their design.

SMD LEDs differ in size, luminous efficacy, color temperature and other properties. Popular variants are the 3528 LEDs and the 5050 LEDs. The number sequence indicates the length and width of the LED: 3528 LEDs have a base area of 3.5 x 2.8 mm, 5050 LEDs have a base area of 5.0 x 5.0 mm.

SMD LEDs have become a widely used technology in the modern lighting and electronics industry due to their efficiency, reliability and versatility.

High Power LEDis a special type of light-emitting diode that has a significantly higher output and luminous efficacy than conventional LED models. These LEDs are generally designed for applications where intensive and powerful lighting is required. Compared to standard LEDs, high-power LEDs have a higher light intensity and can emit a considerable amount of light in a specific direction.

The most important features of High Power LEDs are

High Power LEDs can produce a high light intensity, making them ideal for applications that require strong lighting, such as street lighting, floodlights or floodlights.
Despite the higher light output, high-power LEDs are generally more efficient than conventional incandescent or halogen lamps. They convert a large proportion of the electrical energy supplied into light and produce less heat. Nevertheless, the heat generated by high-power LEDs should not be neglected and requires efficient thermal management to ensure the service life and performance of the LEDs.

High Power LEDs are available in various color temperatures, from warm white to cool white or other colors such as red, green or blue. Due to their high output and brightness, high-power LEDs are used in a wide range of applications, including street lighting, industrial lighting, spotlights for stage and event technology, automotive lighting and much more – in short, wherever intensive lighting is required.

As the technology continues to evolve, High Power LEDs are becoming increasingly powerful, energy efficient and versatile, helping to replace conventional lighting solutions in many applications.

DIP LED stands for “Dual In-line Package Light Emitting Diode”. This is an older type of light-emitting diode and is a widely used type of electronic component in which the pins of the component are arranged in two parallel rows so that they can be easily plugged into a circuit board. DIP LEDs are housed in a classic rectangular housing with flattened corners. This housing enables simple mounting on a printed circuit board. They are usually attached to a printed circuit board by through-hole mounting. To do this, the pins of the LED are inserted through holes in the circuit board and then soldered to the back. DIP LEDs are available in various colors, including red, green, blue, yellow, white and more. Each color is generated by the semiconductor materials used. DIP LEDs were commonly used in older electronic devices, display panels, indicator lights and other simple applications before more advanced LED technologies such as SMD (Surface Mount Device) and High Power LEDs became widespread.

Although DIP LEDs are no longer as widespread as they used to be, they are still used in some special applications, especially when through-hole mounting on a PCB is preferred or when older devices or circuits are still in use. However, the advancement of LED technologies has led to more compact, efficient and versatile LED models, such as SMD LEDs and High Power LEDs, which are prevalent in many modern applications.

Dimming light plays a key role in modern lighting technology and offers a wide range of benefits in terms of comfort and energy efficiency. With advances in lighting technology, it is now possible to continuously adjust the brightness of light sources and thus tailor the ambience and atmosphere in interiors.

Dimming light not only enables lighting to be individually adapted to different situations and needs, but also helps to save energy. By reducing the light intensity, power consumption can be significantly lowered, which in turn leads to a longer service life for the light sources and reduces costs.

Dimming the light can also have a calming effect and create a cozy atmosphere. It is therefore not surprising that light dimmers are becoming increasingly popular in residential and commercial premises, as well as in the catering and hotel industries. In this context, smart lighting systems that can be dimmed via app or voice control are also becoming increasingly important.
There are different types of dimmers that have been specially developed for LED luminaires to ensure optimum compatibility and dimming performance. Here we show you the most common dimmer types for LEDs:

Trailing edge phase control dimmers (also known as triac dimmers): Trailing edge phase control dimmers are the most common dimmer types for LED luminaires. They can be found in many households and commercial environments. These dimmers work with alternating current and reduce the power by cutting off the voltage waveform at the leading and trailing edges. It is important to note that not all LEDs are compatible with trailing edge phase dimmers. Some LEDs require a special “dimmable” driver.

In contrast to trailing edge phase control dimmers, leading edge phase control dimmers only cut the voltage waveform at the front of the shaft. This dimmer can be used to achieve smoother dimming for some LED lights.

0 – 10 V dimmers offer an analog dimming option and are mainly used in the commercial/industrial sector. These dimmers supply a control signal of 0 to 10 volts to regulate the brightness. The advantages of the 0 – 10 V dimmers are the simple wiring and the possibility of dimming several lights in a group.

LEDs work with electronic ballasts, the LED drivers. This guarantees constant output values (current or voltage) and the LED module(s) are optimally supplied at all times.
LED modules can be voltage- or current-controlled, whereby components with control gear function can already be integrated on the module board. The more intelligently the control or driver system is designed with the appropriate interfaces, the more adaptable it is to the actual lighting requirements: color control and dimming, for example, make it possible to simulate the course of daylight and thus offer everything for health-oriented lighting.

DALI (Digital Addressable Lighting Interface) is a digital communication protocol used in lighting control. They enable precise and flexible dimming.

PWM dimmers (PWM = pulse width modulation) control the brightness of LEDs by changing the pulse width of the electrical signal. You switch the LED on and off quickly and vary the time it stays on to adjust the brightness.

A potentiometer is an electrical component used in electronics to provide a variable electrical voltage. It consists of a rotatable wiper that slides over a resistor and thus changes the pick-up point on the resistor. This allows the output voltage to be adjusted continuously by moving the wiper to different positions along the resistor. Potentiometers are often used in applications such as volume controls, dimmers or sensor settings to precisely set the desired values.

DMX is another digital communication protocol that is used in professional lighting control, especially in concerts and stage shows. DMX enables precise control of LED luminaires for absolutely synchronized lighting effects.

Before purchasing LED components and dimmers, it is advisable to check their compatibility.

LED modules and LED light engines (=LED modules with integrated ballast) offer outstanding efficiency and durability. Modules usually consist of several LEDs mounted on a carrier and an optical system with wide-angle lenses and reflectors. They are electrically ready for connection.
LED modules are versatile and virtually maintenance-free. They provide white and colored light with good color rendering, are infinitely dimmable and easy to control. Users usually encounter LED modules permanently installed in luminaires; otherwise, installation should be carried out by specialist personnel.
The main distinguishing feature of LED modules is the construction technology.
There are:
– Modules with wired LEDs in through-hole technology
– Modules in SMD technology (Surface Mounted Device)
– Modules with CoB technology (Chip on Board)
– SMD or CoB modules for high-power LEDs (= high-power modules)
If LED modules are used for street lighting, suitable ballasts that meet the requirements should be used. A high degree of protection and overvoltage protection are also important. Special versions have various interfaces for control or additional functions such as luminous flux tracking.

Knowledge about lighting

Reflectors are used to direct the light of a luminaire. They usually have a silver coating so that they can achieve the highest possible light reflection. The design of the reflector also influences the beam angle.

A transformer can increase or decrease alternating electrical voltages. If transformers are used in lighting technology, they convert the mains voltage of 230 volts into an extra-low voltage of 6, 12 or 24 volts.

Light emission is direct and indirect scattered light generated by the artificial lighting of streets, squares and buildings and emitted into the environment. In urban centers in particular, this creates so-called light bells, which displace the natural darkness of the night and can affect the biorhythms of living creatures.

When the brightness changes, the eyes need time to adjust. This adjustment process is called adaptation.
The respective state of adaptation determines the current visual performance. The adaptation process and the associated adaptation time depends on the luminance levels at the beginning and end of the change in brightness.
The adjustment from dark to light takes only seconds. Conversely, it can take many minutes for the eyes to adapt from light to dark, e.g. when leaving a well-lit building into the dark when outdoors.

The lighting level (brightness level) describes the average illuminance in a room or at individual locations.
The lighting level depends on the light emitted by the luminaires and the reflective properties of the surrounding surfaces. This means that the lower the reflectance and the more difficult the visual tasks – e.g. reading, handicrafts or cooking – the higher the illuminance must be in order to achieve a good lighting level.
The term illuminance level is also used when luminance is used as a photometric parameter instead of illuminance, e.g. in street lighting.

Binning is important in the production of LED chips. As tolerances can occur in the industrial production of LED chips within a batch, e.g. in the light color, LEDs are measured and sorted into bins (= pots) depending on the tolerance class.
This “binning” process is particularly important for white LEDs. The selection criteria for binning are the luminous flux (measured in lumens, lm), the color temperature (measured in Kelvin, K9, the color location and the forward voltage (measured in volts, V).
Uniform brightness and light colors are only guaranteed if carefully selected binning groups are used. Good binning is therefore an important quality feature of LED chips. Today, color value deviations are defined with the help of MacAdams ellipses.

Glare can emanate directly from luminaires, light sources or other surfaces with excessive luminance – including windows (direct lighting). Or it is caused by reflections on shiny surfaces (reflected glare).
Both direct and reflected glare reduce visual comfort (psychological glare) and reduce visual performance (physiological glare).
Glare depends on the luminance and size of the light source, its position in relation to the viewer, the brightness of the surroundings and the background.
Glare can be kept to a minimum through the correct shielding and arrangement of luminaires and the selection of light colors and matt surface structure of the room surfaces.
Direct glare can be avoided if the surfaces of luminaires at flat angles have the lowest possible luminance levels and the direct view into the light sources is shielded. Direct glare is assessed according to the UGR (Unified Glare Rating) method; standards specify minimum values for glare protection. Appropriately positioned luminaires and workstations, light entering from the side, matt surfaces in the room and the luminance limitation of the luminaires prevent reflected glare.

Lighting is described as “dynamic” if one or more parameters change during operation – e.g. illuminance, light color or direction of light.
This also includes dynamic color light, generated by LEDs or fluorescent lamps with RGB color mixing. The dynamics are monitored by appropriately programmed control systems.

The socket in a luminaire holds the light source and gives it stability.
The connection is made by the base of the light source. The transfer point for the electricity is also integrated in the socket. Different bases and sockets are used to ensure that conventional lamps are not confused.

Contrast rendition is a criterion for limiting reflected glare.
It is described by the contrast rendering factor (CRF). For the visual task, it defines the ratio of the luminance contrast with given illumination to the luminance contrast with reference illumination.

In electrical engineering, the term converter is used for power converters.
Power converters use electronic components to convert one type of current into another: Alternating current into direct current (rectifier), direct current into alternating current (inverter). Converters that can be operated either as DC or AC converters are called inverters.

Types of protection

Unprotected against the ingress of solid foreign bodies and dust

Protected against solid foreign objects > 50 mm

Protected against solid foreign objects > 12 mm

Protected against solid foreign objects > 2.5 mm

Protected against solid foreign bodies > 1 mm



Unprotected against any ingress of water

Protected against vertical dripping water

Protected against vertically occurring dripping water with an inclination of the housing of up to 15°.

Protected against falling spray water up to 60° against the vertical.

Protected against splashing water on all sides.

Protected against water jets from any angle.

Protected against strong jets of water coming from any angle.

Protected against temporary immersion in water (up to 30 min, up to 1 m).

Protected against permanent immersion in water.

IP20: protected against solid foreign bodies > 12 mm, no protection against the ingress of water

IP44: protected against solid foreign bodies > 1 mm, protected against splashing water from all sides

IP67: dustproof and protected against temporary immersion in water (up to 30 min, up to 1 m)

In protection class 1, electrical appliances must have protective earthing (PE – Protective Earth). In addition to protective earthing, the appliances in protection class 1 have double (reinforced) insulation to provide additional protection against electric shocks. The protective earthing ensures that the electrical current is safely discharged in the event of a fault, thus reducing the risk of electric shock to the user.

Electrical appliances of protection class 2 have no protective earthing. Instead, they rely solely on double insulation to provide adequate protection against electric shock. The insulation prevents live parts from coming into contact with accessible conductive parts.

Protection class 3 is used for appliances that are operated with a safety extra-low voltage. This voltage is so low that it is not normally considered dangerous to humans. Safety is guaranteed by the separation of high-voltage and low-voltage circuits. Typical examples of protection class 3 are low-voltage transformers or battery-operated devices.

In the fascinating world of electrical engineering, test marks and symbols play a central role in ensuring the safety, quality and conformity of electrical devices, components and systems. These visual markings serve as important communication tools that allow technicians, engineers and consumers to quickly grasp relevant information about electrical products. Test marks confirm compliance with specific norms and standards, while symbols are universal pictograms that illustrate the functions and properties of electrical components and devices. Below you will find a small compilation of the most important symbols and test marks.

Symbols and test marks

Protection class I

Protection class II

Protection class III

CE mark:
This product complies with the applicable European directives.

ENEC symbol:
This product complies with the applicable European safety standards.

Meets the requirements of the German Product Safety Act (ProdSG)

Safety extra-low voltage

ROHS mark:
This product complies with the European Directive 2011/65/EU

ROHS mark:
This product complies with the European Directive 2011/65/EU

Quality mark for machines and systems supplied to North America.

TÜV-tested safety

Nemko-tested for electromagnetic compatibility

Products suitable for direct attachment to normally flammable surfaces

MM symbol: Recessed furniture light, surface-mounted and/or recessed in materials with unknown flammability

Safety transformer: short-circuit-proof, output voltage up to a maximum of 50 Vac / 120 Vdc

Independent converter

Subscribe to our newsletter

Exclusive offers, news & information from the world of light straight to your inbox.

Live chat

Do you have any questions? We can clarify your request quickly and easily in our live chat.




Closed on 08.03.24!

We will be closed next Friday due to a company outing to Light & Building.