Désigné également par Alternate ou ON/OFF

Position de l’interrupteur qui reste inchangée quand la force de manoeuvre cesse de s’exercer sur l’organe de manoeuvre de l’interrupteur. S’oppose à Momentané.

Actuation speed refers to the speed with which the user maneuvers a control device, i.e. the speed of mechanical movement between the rest position and the activated position.

👉 It has a direct influence on switching quality, contact bounce,arcing and product life.

Why is this important?

• Action too slow → prolonged arc, increased wear

• Fast, clean action → cleaner, more reliable switching

• Impact on repeatability and electrical performance

Links with other concepts

• Affects switching time

• Influences Contact Bounce

• Depends on mechanical design (snap action, spring, dome)

Backlighting refers to an illumination system integrated behind a symbol, pictogram or surface, making a pushbutton or interface visible in darkness or low light.

👉 It improves legibility, ergonomics and user safety.

In pushbuttons and HMI interfaces

Backlighting can :

• Indicate status (ON/OFF, alarm, availability)

• User guidance (quick location of controls)

• Enhance design (premium effect, increased visibility)

Current technologies

• LED (low power consumption, long life)

• Fixed color or multicolor (RGB)

• Modes: fixed, flashing, dimmable

Backlighting refers to an illumination system integrated behind a symbol, pictogram or surface, making a pushbutton or interface visible in darkness or low light.

👉 It improves legibility, ergonomics and user safety.

In pushbuttons and HMI interfaces

Backlighting can :

• Indicate status (ON/OFF, alarm, availability)

• User guidance (quick location of controls)

• Enhance design (premium effect, increased visibility)

Current technologies

• LED (low power consumption, long life)

• Fixed color or multicolor (RGB)

• Modes: fixed, flashing, dimmable

The CE (Conformité Européenne) mark certifies that a product complies with the essential safety, health and environmental protection requirements laid down by European Union directives and regulations.

👉 It is mandatory to market a product in the European Economic Area (EEA).

What CE marking guarantees

The manufacturer declares that the product :

• Is safe for the user

• Complies with applicable European standards

• Meets electrical safety, EMC and environmental requirements

• Complies with relevant European directives

Current directives (electrical / industrial)

• LVD (Low Voltage Directive) – electrical safety

• EMC – electromagnetic compatibility

• RoHS – hazardous substances

• Machinery Directive – machines

• RED – radio equipment (if applicable)

Important to understand

• CE marking is a self-declaration by the manufacturer (in most cases)

• It involves a technical file and a conformity analysis

• This is not a quality label, but a regulatory requirement

Pushbutton applications / HMI devices

A CE-marked pushbutton complies with European requirements for :

• Electrical safety

• Insulation

• Electromagnetic compatibility

• Authorized materials

Charge électrique dans laquelle le courant initial à la fermeture du contact est plus élevée que le courant permanent.

Charge électrique dans laquelle le courant initial à la fermeture du contact est plus faible que le courant permanent et le courant à l’ouverture plus fort que le courant permanent. L’énergie stockée provoque un arc électrique long et intense.

Charge électrique dans laquelle le courant et la tension sont en phase.

Consumption refers to the amount of electrical energy used by a device during operation.

👉 It depends on voltage, current and operating time.

Surfaces métalliques qui entrent en contact physique pour créer un circuit électrique. Ces surfaces se trouvent sur les contacts mobiles et les sorties (connectique)

Contact Bounce is the mechanical micro-oscillation of electrical contacts as they close or open, causing multiple parasitic switching instead of a single clean changeover.

👉 When a contact closes, it may “shake” for a few milliseconds, generating unwanted electrical pulses.

Why does it happen?

• Mechanical elasticity of lamellas

• Inertia of moving parts

• Vibrations on contact impact

Rebound effects

• False signals (involuntary double-click)

• Logic errors in electronics / microcontrollers

• Accelerated contact wear

• Parasites in control circuits

Order of magnitude

• Typical duration: 1 to 20 ms

• Depends on contact type and actuation speed

Means of limitation

• Snap-action mechanisms

• Electronic filters (debounce)

• Anti-bounce software treatment

Le contact NC (pour Normally Closed) désigne un contact “Normalement Fermé” (NF), c’est à dire qu’au repos le circuit est fermé, le contact entre les deux poles est établi.

Un contact NO est un contact “Normalement Ouvert” (ou Normally Open), c’est à dire qu’au repos le circuit est ouvert, le contact entre les deux poles n’est pas établi.

Normaly Open and Normaly Closed
Acronyme servant à désigner un contact pouvant être à la fois Normalement Ouvert et Normalement Fermé.

Aussi défini par l’acronyme NONF

Il présente de nombreux avantages :

• Fonctionnel : un interrupteur classique possède une entrée et une sortie. Il peut être NO (Normalement ouvert) ou NF (Normalement Fermé).Un interrupteur avec une fonction NONF possède une entrée et 2 sorties, avec par conséquent 2 actions possibles. Une action par défaut lorsqu’il est au repos et une seconde action lorsqu’il est activé.
• Sécuritaire / fonction de redondance : Un interrupteur NONF offre également une fonction de redondance. Il permet de vérifier le bon fonctionnement du système et donc de l’appareil sur lequel il est monté.

Contact resistance is the electrical resistance at the junction point between two conductive contacts when they are closed.

👉 It represents the local electrical loss due to micro-sperities, contact pressure and surface condition.

Why does it exist?

Even if two contacts are metallic :

• They only touch at a few microscopic points

• There may be oxidation, pollution or wear and tear.

• Support force influences conduction quality

Consequences of high Contact resistance

• Local heating (Joule effect)

• Voltage drop

• Accelerated aging

• Risk of welding or failure

Typical order of magnitude

• A few milliohms (mΩ) for quality contacts
  Example: ≤ 50 mΩ on an industrial pushbutton

👉 Link to thermal current: The higher the contact resistance, the greater the heat dissipation.

Corrosion is the progressive degradation of a material (often metal) under the effect of moisture, oxygen or chemical agents, resulting in a loss of mechanical and electrical resistance.

👉 It can cause oxidation, pitting, structural weakening and poor electrical contacts.

Le courant nominal est la valeur maximale de courant qu’un appareil peut supporter en fonctionnement continu, sans surchauffe ni détérioration.

👉 Il correspond à la limite thermique admissible dans des conditions normales d’utilisation.

Concrètement

• Exprimé en ampères (A)

• Défini par le constructeur

• Valable pour une température et une catégorie d’emploi données

À ne pas confondre

• Courant nominal → ce que l’appareil peut supporter en continu

• Pouvoir de coupure → ce qu’il peut interrompre en sécurité

• Courant thermique (Ith) → limite thermique maximale admissible

Exemple

Un bouton poussoir donné pour 10 A nominal peut conduire 10 A en continu, mais ne pourra pas forcément couper 10 A sous charge inductive.

Dans un interrupteur électrique, le courant thermique correspond à la chaleur générée et transférée dans les composants lorsque le courant électrique traverse les contacts et les conducteurs.

Cette chaleur est produite par l’effet Joule : plus le courant est élevé et plus la résistance interne est importante, plus l’interrupteur chauffe.

Origine du courant thermique dans un interrupteur

La chaleur provient principalement de :

• La résistance des contacts électriques

• Les pertes dans les bornes et conducteurs

• Les micro-arcs électriques à l’ouverture/fermeture

• Une mauvaise qualité de contact (oxydation, usure, encrassement)

Pourquoi c’est critique dans un interrupteur ?

Un courant thermique excessif peut provoquer :

• Échauffement des contacts

• Déformation ou fusion des pièces

• Vieillissement accéléré

• Risque d’incendie

• Baisse de la durée de vie électrique

Lien avec le courant nominal

Le courant nominal d’un interrupteur (ex. 10 A, 16 A, 25 A) correspond à la valeur maximale de courant qu’il peut supporter sans dépasser une température critique.

Dielectric strength is the ability of an insulating material to withstand high electrical voltage without piercing or conducting current.

👉 This is the Max voltage that can be withstood before insulation breakdown.

Principle

If the applied voltage exceeds the Dielectric strength :

• Insulation degradation

• An electric arc can occur

• Loss of insulation (potential short-circuit)

Unit

• Expressed in volts (V) or kV/mm (depending on material thickness)

A concrete example

A switch can have a dielectric strength of 2,500 V AC for 1 minute, ensuring that no conduction occurs between terminals and housing.

A pole is an independent electrical path in a switching device (switch, relay, circuit breaker), used to break or make a conductor.

👉 In practice, the number of poles = the number of circuits interrupted simultaneously.

In a switch

• 1-pole switch → single-conductor disconnection

• 2-pole switch → cuts two conductors at the same time (e.g. phase + neutral)

Electrical life is the number of switching cycles a device can perform under electrical load before contact degradation.

👉 One cycle = contact closing + opening, with current applied.

What it actually measures

It reflectswear on electrical contacts due to :

• Electric arc on opening

• Joule effectheating

• Erosion of contact surfaces

• Load type (resistive, inductive, capacitive)

Typical orders of magnitude

• Standard pushbutton under load: 10,000 to 100,000 cycles

• Robust industrial pushbutton: 100,000 to 1,000,000 cycles

• Low load (PLC signal): > 1 million cycles

Highly dependent on

• Current and voltage

• Job category (AC-15, DC-13…)

• Load type

• Actuating speed

Form A refers to a contact configuration term.

Form A refers to a normally open unipolar-unidirectional contact. “1 form A” means that there is one form A contact in the module, “2 form A” means that there are two “form A contacts” in the module, and so on.

Form B refers to a unipolar-unidirectional normally closed contact arrangement. This means that it remains in a closed state (off) without you driving the relay to operate. “1 Form B” means that there is one “Form B contact”, “2 Form B” means that there are two “Form B contacts” in the relay, and so on.

Form C refers to a single-pole-double-throw (SPDT) contact. This means that there is a common point connected to one normally open end and another normally closed contact. “2 Form C” refers to two “Form C contacts”, and so on.

IEC 60529 is the international standard that defines the IP (Ingress Protection) code, used to classify the level of protection of electrical enclosures against dust and water.

👉 It is used to assess thewatertightness and intrusion resistance of electrical and industrial equipment.

IEC 60947 is an international standard that defines the safety, performance and testing requirements for low-voltage switchgear and controlgear, such as switches, circuit-breakers, contactors, relays and pushbuttons.

👉 It ensures that equipment can switch, support and interrupt currents safely in industrial environments.

What IEC 60947 covers

• Switch rating and closing capacity

• Rated current and voltage

• Job categories (AC-15, DC-13…)

• Electrical and mechanical endurance

• Isolation distances

• Dielectric Strengh

• User security

• Environmental testing

Key parts of the standard

👉 For pushbuttons / HMI, the most common is IEC 60947-5-1.

Why it’s crucial in industry

• Ensures electrical safety

• Ensures international compatibility

• Validates resistance to arcs and inductive loads

• Enhance product credibility (catalogs, tenders)

Since 1995, the IK resistance index has been a specific index measuring a product’s mechanical resistance to impact, as defined in European standard EN 62-262.

The IK rating is given on a scale of 0 to 10, depending on the impact energy, which can range from 0 to 20 joules. For example, a device with an IK05 rating can withstand shocks of 0.70 J, i.e., a drop of 0.5 kg from a height of 35 cm. According to the standards, the minimum IK of a device takes into account where it is installed. For example, devices located in kitchens must have a minimum IK02. The IK index is measured by a specific test, using a “Sharpy Sheep”.

Sealing refers to a product’s ability to prevent the infiltration of liquids, dust or contaminants into its housing, in order to preserve its electrical and mechanical functions.

👉 It is generally characterized by an IP (Ingress Protection) rating in accordance with IEC 60529.

Why is it critical?

A good seal guarantees :

• Reliability in harsh conditions (water, oil, dust)

• Product lifetime

• Electrical safety

• Resistance to industrial washing

Examples of pushbuttons / switches

• IP65 → Protected against water jets and dust

• IP67 → Resists temporary immersion

• IP69K → Supports high-pressure cleaning

Typical applications

• Industrial machinery

• Food industry

• Outdoor / humid conditions

• HMI exposed to projections

The insulation class indicates the level of electrical protection of a device against electric shock, depending on the design of its insulation (presence or absence of an earth connection).

👉 It defines how user safety is ensured in the event of a fault.

Main insulation classes

Class I

• Basic insulation + mandatory grounding

• Protection provided by the earth conductor

• Example: metal industrial equipment

Class II (double-insulated)

• Double or reinforced insulation

• No grounding required

• Symbol: double square ⧈

• Very common for compact devices and HMIs

Class III

• Function on safety extra-low voltage (SELV)

• No risk of electric shock

• Example: 24 V DC equipment

Why is this important?

• User security

• IEC / CE compliant

• Correct choice according to installation environment

• Reducing electrical risks

Examples of pushbuttons / switches

• Illuminated pushbutton 24 V → Class III

• Industrial metal enclosure → Class I

• Insulated plastic module → Class II

Insulation resistance measures the ability of a material or electrical device to prevent the passage of current between two conductive parts that should not be in contact.

👉 The higher the insulation resistance, the greater the electrical safety (less current leakage).

What’s it for?

It allows you to check :

• No current leakage

• Insulation quality

• Personal safety

• Equipment reliability

Unit

• Expressed in ohms (Ω), often in MΩ or GΩ

A concrete example

A switch can have an insulation resistance ≥ 100 MΩ, ensuring that no current leaks between the terminals and the housing.

Difference with Dielectric strength

• Insulation resistance → Limits current leakage

• Dielectric strength → Withstands high voltage without breakdown

ISO 13849 is an international standard which defines the safety requirements for machine control systems, assessing their reliability in the event of failure.

👉 Used to measure and certify the safety level of critical functions (emergency stop, safety sensors, interlocks, etc.).

Main objective

Guarantee that safety functions continue to operate correctly, even in the event of a partial failure.

Key concept: Performance Level (PL)

ISO 13849 classifies safety systems into performance levels:

👉 PL d / PL e = high-risk environments

Factors assessed

• System architecture (single channel, dual channel, etc.)

• Redundancy

• Self-diagnostic capability

• Component reliability (MTTFd)

• Diagnostic coverage (DC)

• Resistance to defects

Concrete example (pushbuttons & HMI)

An ISO 13849 PL d-certified emergency stop guarantees :

• Positive contact opening

• Double safety channel

• Fault detection

• Safe behaviour in the event of a breakdown

The category of use defines the type of electrical load that a switching device can control, as well as the electrical constraints during opening and closing (inrush current, arc, inductance, etc.).

👉 This is defined by IEC 60947 and determines the actual current carrying capacity according to use.

Why is this essential?

A device does not carry the same current depending on whether it is switching:

• A resistive load (easy)

• A coil/motor (high inrush current, large arc)

• DC load (arc harder to extinguish)

➡️ Nominal current alone is not enough – the category of use is decisive.

Current categories (control & power)

🔹 AC (alternating current)

👉 AC-15 = coil / contactor control (high inrush current)

🔹 DC (direct current)

👉 DC-13 = DC control of inductive loads (more critical arc)

Concrete example (industrial pushbutton)

A pushbutton can be given for :

• 10 A at AC-1 (single load)

• 3 A at AC-15 (coil control)

• 1 A at DC-13 (DC inductive load)

➡️ Same product, different permissible currents depending on category.

Luminous intensity refers to the amount of light emitted by a source in a given direction, perceived as the level of visible brightness.

👉 It determines how visible a light, pushbutton or backlight is, even in daylight or dark surroundings.

Unit

• Expressed in candela (cd)

• Or, more commonly, millicandela (mcd ) for LEDs

Why it’s important in HMI

Light intensity influences :

• Legibility of indicator lights

• Visibility outdoors or in bright workshops

• Visual comfort (avoid glare)

• State differentiation (normal, alarm, active)

A concrete example

• Low LED: 50-200 mcd → indoors, dark atmosphere

• Standard LED: 300-1,000 mcd → industrial use

• High-brightness LED: > 1,000 mcd → outdoor / daylight

Not to be confused with

• Luminous flux (lumens, lm) → total quantity of light emitted

• Luminance (cd/m²) → perceived brightness of a surface

• LED consumption (mA) → current, not brightness

Luminance measures the perceived brightness of a surface in a given direction.

• Unit: candela per square metre (cd/m²)

• Depends on :

  • The illuminated surface

  • Observation angle

  • The diffuser

• Indicates how bright a surface “looks”.

Example

A lamp with a concentrated diffuser will have a higher luminance and therefore be more visible, even with the same flux.

Luminous flux is the total quantity of light emitted by a source in all directions.

• Unit: lumen (lm)

• Measures overall light output

• Indicates how much light is produced

Example

Two LEDs may have the same luminous flux, but appear more or less bright depending on how they are diffused.

Mechanical life is the number of operating cycles a device can withstand before mechanical degradation, independently of the electrical load.

👉 One cycle = 1 press + 1 release.

What it actually measures

It assesses the robustness of moving parts:

• Springs

• Axes

• Internal mechanisms

• Actuator / plunger

➡️ Excluding electrical contact wear.

Typical orders of magnitude

• Standard pushbutton: 100,000 to 500,000 cycles

• Robust industrial pushbutton: 1 to 5 million cycles

• High-endurance range: > 10 million cycles

Why is this important?

• Long-term reliability

• Reduced maintenance

• High-speed adaptation

• Product quality argument

Temporary position after which the switch returns to its normal position.

Operating temperature is the ambient temperature range within which equipment can operate correctly, safely and without degradation of performance.

👉 Outside this range, the device may malfunction, age prematurely or be damaged.

Why is it critical?

It has a direct influence on :

• Electrical reliability

• Component service life

• Contact stability

• Sealing and plastic materials

• LED behavior

Typical example (industrial pushbuttons)

• -25 °C to +70 °C → standard industrial environment

• -40 °C to +85 °C → harsh environments (outdoor, railway, outdoor)

An output is the terminal or interface through which a control device delivers an electrical signal to an external circuit (PLC, LED, relay, actuator, etc.).

👉 In a pushbutton, the output corresponds to the electrical contacts that transmit the command (or power to an LED).

Examples of pushbuttons / switches

• Contact NO / NC output → signal to a PLC

• LED output → power supply for one LED

• TOR output → relay control

The panel cut-out designates the size and shape of the opening to be made in a panel to install a pushbutton, switch or control device.

👉 It determines the product’s positioning, mechanical fastening andwatertightness.

What the panel cut-out includes

• Diameter or size of opening (e.g. Ø 22 mm, Ø 30 mm)

• Shape: round, square, rectangular

• Tolerances (precision fit)

• Coded pins (anti-rotation notch if required)

• Compatibility with panel thickness

Common examples (industrial pushbuttons)

• Standard pushbutton → Ø 22 mm

• Vandal-proof pushbutton → Ø 19 mm / Ø 22 mm / Ø 25 mm

• HMI console or front panel → manufacturer-specific cut-out

Why is this important?

• Guarantees a clean and safe installation

• Ensures mechanical strength andalignment

• Maintains IP rating

• Facilitates standardization of assemblies

Panel mounting refers to the method of installing a device (pushbutton, switch, indicator, selector) on a front panel or lectern, using a dedicated cut-out, a fastening system and mechanical clamping.

👉 It guarantees mechanical strength,alignment, electrical safety and IP tightness.

Key elements of panel mounting

• Panel cut-out (diameter / standardized shape)

• Permissible panel thickness

• Fastening system: nut, clips, flange

• Gasket (front panel)

• Recommended tightening torque

Common methods

• Nut mounting (industrial standard Ø22 mm, Ø30 mm)

• Clip-on mounting (fast, no tools required)

• Vandal-proof mounting (reinforced clamping, stainless steel face)

Why is this important?

• Ensures robust, durable installation

• Maintains IP protection

• Prevents mechanical play and loosening

• Guarantees a clean, professional finish

Panel thickness refers to the thickness range of the support (sheet metal, front panel, desk) compatible with the installation of a pushbutton, switch or control device.

👉 It is essential for proper fastening, mechanical strength and watertightness (IP).

Why is this important?

Compatible thickness guarantees :

• Correct tightening of nut or fastening system

• Mechanical stability (no play)

• Optimum seal compression

• Installation in compliance with manufacturer’s specifications

Common examples

• Pushbutton Ø22 mm: typical panel thickness = 1 to 6 mm

• Robust vandal-proof pushbutton: up to 8-10 mm depending on model

L’effet piézoélectrique (du grec “Piezein”, appuyer, presser) a été mis en évidence en 1881 par les frères Curie.

Il s’agit de la propriété de certains corps (comme le quartz, topaze, céramique, certains cristaux et polymères) de se polariser électriquement sous l’action d’une force les déformant (effet Direct); réciproquement de se déformer lorsqu’on leur applique un champ électrique (effet Indirect).

Nos boutons sensitifs à technologie piézoélectrique fonctionnent grâce à cette propriété. En savoir plus sur les boutons piezo

Alongside the criteria of robustness, shock resistance, vibration and high temperatures, there’s a decisive variable: the IP protection rating. Whatever the sector of activity (industrial, medical, aeronautics, transport…), all equipment must be protected against the intrusion of solids and liquids.

The protection index (IP) is an international standard of the International Electrotechnical Commission relating to watertightness. This index classifies the level of protection offered by a piece of equipment against the intrusion of solids and liquids. The format of the index, given by standard IEC 60529, is IPXY, where the letters XY are two digits and/or a letter. The numbers indicate compliance with the conditions summarized in the tables below. Where no criteria are met, the number may be replaced by the letter 9.

Typical industrial pushbutton/switch applications

• IP65 → Rain and splash resistant

• IP67 → Resistant to washing and damp environments

• IP69K → High-pressure cleaning (food processing, machinery)

👉 Critical for pushbuttons, emergency stops, HMI, exposed to dust, oil, water or industrial cleaning.

REACH(Registration, Evaluation, Authorisation and Restriction of Chemicals) is a European regulation designed to control the use of chemical substances in order to protect human health and the environment.

👉 It requires manufacturers and importers to identify, assess and limit the hazardous substances present in products.

Main objective

• Identifying substances of concern (SVHC)

• Limit or ban certain harmful chemicals

• Improving materials traceability

• Encouraging safer alternatives

Difference with RoHS

👉 REACH is broader, RoHS more targeted.

Appliance / HMI applications

A REACH-compliant product means that :

• Plastics, gaskets, metals, coatings

• Contain no substances in excess of regulatory thresholds

Redundancy refers to the duplication of a critical component, circuit or function to maintain system operation in the event of failure.

👉 Objective: increase reliability, availability and safety.

Principle

If one element fails, another automatically takes over or detects the fault.

Examples from industry / HMI

• Two EMERGENCY STOP safety contacts

• Double channel in a machine safety circuit

• Two power supplies for one critical system

• Two sensors to validate information (logical voting)

Why is this important?

Redundancy allows :

• Avoid critical breakdowns

• Improve functional safety (ISO 13849, SIL)

• Increase machine availability

• Detect hidden defects

Redundancy types

• Material: lined components

• Functional: dual logic, dual channel

• Time: repeated verification

• Active / passive: backup always active or on standby

RoHS(Restriction of Hazardous Substances) is a European directive that limits the use of hazardous substances in electrical and electronic equipment, in order to reduce environmental impact and health risks.

👉 It is compulsory to sell electrical products in the European Union.

Restricted substances (main)

RoHS limits in particular :

• Lead (Pb)

• Mercury (Hg)

• Cadmium (Cd)

• Hexavalent chromium (Cr⁶⁺)

• PBB / PBDE (flame retardants)

• • phthalates (RoHS 3)

Why it matters (industry / HMI)

RoHS guarantees :

• Safer products for the environment

• Better recyclability

• EU regulatory compliance

• A CSR and commercial argument

Practical application

A RoHS compliant pushbutton means that :

• Welds, plastics and components

• Respect hazardous substance thresholds

Salt spray is a standardized test for assessing a product’s resistance to corrosion in saline atmospheres (marine, industrial, salty roads).

👉 It simulates prolonged exposure to salt, which is very aggressive to metals.

Current standard : IEC 60068-2-11 / ISO 9227

Why it’s important (pushbuttons / HMI / switchgear)

Good corrosion/salt spray resistance guarantees :

• Durability in outdoor or humid environments

• Stability of electrical contacts

• Aesthetic preservation (stainless steel, aluminum, coatings)

• Reliability in harsh conditions

A self-cleaning contact is a contact designed to automatically remove impurities, oxidation and deposits with each operation, thanks to a gentle wiping movement between the conductive surfaces.

👉 Mechanical sliding cleans the contact area and maintains low electrical resistance over time.

Why is this important?

• Improves signal reliability

• Reduces false contacts

• Stabilizes contact resistance

• Extended electrical life

• Essential for low currents (signals, PLC)

Principle

When closing :

• Contact isn’t as simple as that

• They slide lightly over each other, removing the insulating film.

Typical applications

• Industrial pushbuttons

• Low-voltage control circuits

• PLCs, sensors, digital signals

• Dusty or damp environments

Switch rating refers to the ability of an electrical device (switch, circuit breaker, contactor) to interrupt an electrical current safely, without being damaged and without risk to the installation.

👉 This is the maximum current the device can cut, including in the event of an overload or short-circuit.

Why is it critical?

When opening a circuit under load :

• An arc forms between the contacts

• If Switch rating insufficient → contact welding, destruction, fire

Switch rating types

1. On-load switch rating

Ability to cut normal rated current.

2. Short-circuit switch rating

Ability to interrupt a very high fault current (value in kA).

Unit

• Expressed in amperes (A) or kiloamperes (kA)
  Example: Switch rating = 10 kA at 400 V

A concrete example

A switch rated for 16 A but with a switching capacity of 6 kA can :

• Supports 16 A in normal use

• Short-circuit protection up to 6,000 A

Link to standards (IEC)

In industry (IEC 60947) :

• Switch rating is linked to the category of use (AC-15, DC-13, etc.).

• It depends on voltage, load type and power factor.

The switching point is the precise position in the mechanism at which the electrical state of the contact changes (open → closed or closed → open) on actuation.

👉 This is the exact moment when the electrical signal changes, often perceptible by a click or tactile feedback.

In concrete terms

• It is a fraction of the total Travel

• It can be different when pressed and when released (hysteresis).

• It determines precision, repeatability and ease of use.

Example

A pushbutton with :

• Total travel: 4 mm

• Switching point: 2 mm
  → Contact toggles before end of pressure.

Why is this important?

• Clear tactile sensation

• Reduced activation errors

• Improved speed and reliability

• Impact on mechanical life

Switching time is the time required for a contact to change from one electrical state to another (open → closed, or closed → open), from mechanical actuation to signal stabilization.

👉 It generally includes mechanism travel time and, depending on the context, contact bounce time.

What it means in concrete terms

• Delay between pushbutton press and actual signal change

• Speed at which an electrical command is transmitted

Typical orders of magnitude

• Mechanical pushbuttons: 5 to 20 ms

• Fast micro-switches: < 5 ms

• Electromechanical relays: 10 to 50 ms

Why is this important?

• Responsive control systems

• Automation synchronization

• Logic signal accuracy

• Reducing errors in fast electronics

To be distinguished from

• Response time (global system)

• Rebound time (transient instability)

• Actuation speed (user movement)

Tightening torque is the rotational force to be applied to a screw or fastener to ensure correct tightening, without loosening or damage.

👉 It ensures a reliable mechanical connection and, in electrical terms, a stable electrical contact.

Unit

• Newton-meter (N-m)

• Sometimes cN-m or lbf-in

Why it matters (terminals & switchgear)

Correct torque allows :

• Good electrical contact (low resistance)

• Avoid loosening under vibration

• Preventdrivers from being run over

• prevent breakage of terminals or threads

UL (Underwriters Laboratories) and CSA (Canadian Standards Association) are North American certification bodies which guarantee that electrical products meet strict safety, performance and reliability requirements.

👉 These certifications are often essential for selling equipment in the USA and Canada.

UL (United States)

UL certifies that the product :

• Reduces the risk of fire

• Protects against electric shock

• Meets rigorous safety tests

• Complies with American standards (e.g. UL 508, UL 61058, UL 1054)

Typical marking: UL Listed or UL Recognized

CSA (Canada)

CSA certifies compliance with Canadian standards, often aligned with UL.

👉 A product can be UL + CSA (combined certification for North America).

Why it’s important in industry / HMI

• Access to US & Canadian markets

• Increased confidence from OEM and integrator customers

• A frequent requirement in calls for tender

• Strong commercial and regulatory argument

A concrete example

A UL / CSA certified pushbutton can be integrated without restriction into :

• Machines exported to North America

• Industrial electrical cabinets

• Certified OEM equipment

UV resistance refers to the ability of a material or product to withstand the sun’s ultraviolet rays without degrading.

👉 It guarantees that the product will not yellow, become brittle or lose its mechanical or aesthetic properties in outdoor use.

Why is this important?

Good UV resistance allows :

• Preserving color and appearance

• Prevent cracking and premature ageing

• Maintain the strength of plastics and seals

• Guaranteeing outdoor durability

Typical applications

• External pushbuttons

• Industrial outdoor enclosures

• Signage exposed to the sun

• Marine or urban environments

Vibration resistance is the ability of a device to function correctly and durably when subjected to mechanical vibrations, without degrading its electrical or mechanical performance.

👉 It guarantees that the product will not loosen, go out of adjustment or lose reliability in dynamic environments.

Why is this important?

Good vibration resistance enables :

• Avoid false contacts

• Maintain stable contact resistance

• Preserving mechanical life

• Guaranteeing reliability in mobile industrial environments

Environments concerned

• Industrial machinery

• Vehicles / rail

• Machine tools

• Heavy industry

• Installations subject to repetitive shocks

How it’s specified

Often tested to standards (e.g. IEC 60068-2-6) with :

• Frequency range (Hz)

• Acceleration amplitude (g)

• Exposure time

A Form X contact is a forced-break contact, designed to guarantee circuit opening by direct mechanical action, even if the contacts are soldered or glued.

• Contact separation is forced mechanically
• Used in security applications

What’s it for?

The X shape is essential for :

• Emergency stops

• Machine safety circuits

• Critical functions (IEC 60947, ISO 13849)

It ensures that the Contact cannot remain closed in the event of a fault.

Difference from classic shapes

• Form A → NO (Normally Open)

• Form B → NC (Normally Closed)

• Form C → Changeover (NO + NC)

• Form X → Certified positive opening (safety)

A Form Z contact (often called double break) is a changeover contact comparable to Form C, but with physical separation of the NO and NC circuits, and four external connections:

• 2 terminals for normally open (NO) path

• 2 terminals for normally closed path (NC)

Unlike the C form (classic inverter with shared common), the Z form has no single common point: the two circuits are electrically isolated.

What does it actually do?

• Increased galvanic separation

• Enhanced reliability

• Critical industrial applications

• Reduced risk of coupling or common fault