GlobalRelated Contents
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Safety Switches
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Models with Standards Certification
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Glossary of Industrial Automation
Precautions for Correct Use of Safety Switches
Switch Operation
The Switch in actual operation may cause accidents that cannot be foreseen from the design stage. Therefore, the Switch must be practically tested before actual use.
When testing the Switch, be sure to apply the actual load conditions together with the actual operating environment.
All the performance ratings in this catalog are provided under the following conditions unless otherwise specified.
Inductive load:
Lamp load:
Motor load:
A minimum power factor of 0.4 (AC) or a maximum time constant of 7 ms (DC)
An inrush current 10 times higher than the normal current
An inrush current 6 times higher than the normal current
1. Ambient temperature: 5°C to 35°C
2.Ambient humidity: 40% to 70%.
Note:An inductive load causes a problem especially in DC circuitry.
Therefore, it is essential to know the time constants (L/R) of the load.
Mechanical Conditions for Switch Selection
An Actuator suitable for the operating method must be selected.
Ask your OMRON representative for details.
Check the operating speed and switching frequency.
1. If the operating speed is extremely low, switching of the movable contact will become unstable, thus resulting in incorrect contact or contact welding.
2.If the operating speed is extremely high, the Switch may break due to shock. If the switching frequency is high, the switching of the contacts cannot keep up with the switching frequency. Make sure that the switching frequency is within the rated switching frequency.
Do not impose excessive force on the Actuator, otherwise the Actuator may become damaged or not operate correctly.
Make sure that the stroke is set within the suitable range specified for the model, or otherwise the Switch may break.
Electrical Characteristics for Switch Selection
Electrical Conditions
The switching load capacity of the Switch greatly varies between AC and DC. Always be sure to apply the rated load. The control capacity will drastically drop if it is a DC load. This is because a DC load has no current zero-cross point, unlike an AC load. Therefore, if an arc is generated, it may continue comparatively for a long time. Furthermore, the current direction is always the same, which results in contact relocation, whereby the contacts easily stick to each other and do not separate when the surfaces of the contacts are uneven.
If the load is inductive, counter-electromotive voltage will be generated. The higher the voltage is, the higher the generated energy will be, which will increase the abrasion of the contacts and contact relocation load conditions. Be sure to use the Switch within the rated conditions.
If the load is a minute voltage or current load, use a Switch designed for minute loads. The reliability of silver-plated contacts, which are used by standard Switches, will be insufficient if the load is a minute voltage or current load.
Connections
With a Za contact form, do not contact a single Switch to two power supplies that are different in polarity or type.
Power Connection Examples
(Connection of Different Polarities)
Incorrect Power Connection Example
(Connection of Different Power Supplies)
There is a risk of AC and DC mixing.
Do not use a circuit that will short-circuit if a fault occurs, otherwise the charged part may melt and break off.
Application of Switch to a Low-voltage, Low-current Electronic Circuit
1. If bouncing or chattering of the contacts results and causes problems, take the following countermeasures.
(a) Insert an integral circuit.
(b) Suppress the generation of pulses from the contact bouncing or chattering of the contacts so that it is less than the noise margin of the load.
2.Conventional silver-plated contacts are not suitable for this application, in which particularly high reliability is required. Use gold-plated contacts, which are ideal for handling minute voltage or current loads.
3.The contacts of the Switch used for an emergency stop must be normally closed with a positive opening mechanism.
To protect the Switch from damage due to short-circuits, be sure to connect in series a quick-response fuse with a breaking current 1.5 to 2 times larger than the rated current to the Switch. When complying with EN certified ratings, use a 10-A IEC 60269- compliant ｇI or ｇG fuse.
Contact Protection Circuits
Using a contact protection circuit to increase the contact durability, prevent noise, and suppress the generation of carbide or nitric acid.
Be sure to apply the contact protection circuit correctly, otherwise adverse results may occur.
The following tables shows typical examples of contact protection circuits. If the Switch is used in an excessively humid location for switching a load that easily generates arcs, such as an inductive load, the arcs may generate NOx, which will change into HNO3 when it reacts with moisture. Consequently, the internal metal parts may corrode and the Switch may fail. Be sure to select the best contact protection circuit from the following table.
Typical Examples of Contact Protection Circuits
| Circuit example | Applicable current | Features and remarks | Element selection | ||
| AC | DC | ||||
| CR |  | * (Yes) | Yes | * Load impedance must be much smaller than the CR circuit impedance when using the Switch for an AC voltage. | Use the following as guides for C and R values: C: 1 to 0.5 μF per 1 A of contact current (A) R: 0.5 to 1 Ω per 1 V of contact voltage (V) These values depend on various factors, including the load characteristics. Confirm optimum values experimentally. Capacitor C suppresses the discharge when the contacts are opened, while the resistor R limits the current applied when the contacts are closed the next time. Generally, use a capacitor with a low dielectric strength of 200 to 300 V. For applications in an AC circuit, use an AC capacitor (with no polarity). |
 | Yes | Yes | The operating time of the contacts will be increased if the load is a Relay or solenoid. Connecting the CR circuit in parallel to the load is effective when the power supply voltage is 24 or 48 V and in parallel to the contacts when the power supply voltage is 100 to 200 V. | ||
| Diode |  | No | Yes | The energy stored in the coil reaches the coil as current via the diode connected in parallel, and is dissipated as Joule heat by the resistance of the inductive load. This type of circuit increases the release time more than the CR type. | Use a diode having a reverse breakdown voltage of more than 10 times the circuit voltage, and a forward current rating greater than the load current. |
| Diode + Zener diode |  | No | Yes | This circuit effectively shortens the reset time in applications where the release time of a diode circuit is too slow. | Use a Zener diode with a low breakdown voltage. |
| Varistor |  | Yes | Yes | This circuit prevents a high voltage from being applied across the contacts by using the constant-voltage characteristic of a varistor. This circuit also somewhat increases the reset time. Connecting the varistor across the load is effective when the supply voltage is 24 to 48 V, and across the contacts when the supply voltage is 100 to 200 V. | --- |
Do not use the following types of contact protection circuit.
 | This circuit arrangement is very effective for diminishing arcing at the contacts when breaking the circuit. However, since electrical energy is stored in C (capacitor) when the contacts are open, the current from C flows into the contacts when they close. This may lead to contact welding. |  | This circuit arrangement is very useful for diminishing arcing at the contacts when breaking the circuit. However, since the charging current to C flows into the contacts when they are closed, contact welding may occur. |
Although it is thought that switching a DC inductive load is more difficult than a resistive load, an appropriate contact protection circuit can achieve almost the same characteristics.
Using Switches for Microloads
Contact failure may occur if a Switch for a general load is used to switch a microload circuit. Use Switches in the ranges shown in the diagram below. However, even when using microload models within the operating range shown here, if inrush current occurs when the contact is opened or closed, it may increase contact wear and so decrease durability. Therefore, insert a contact protection circuit where necessary. The minimum applicable load is the N-level reference value. This value indicates the malfunction reference level for the reliability level of 60% (λ60) (JIS C5003). The equation, λ60 = 0.5×10−6 / operations indicates that the estimated malfunction rate is less than 1/2,000,000 operations with a reliability level of 60%.
Operating Environment
The Switches are designed for use indoors.
Using a Switch outdoors may cause it to malfunction.
Do not use the Switch submerged in oil or water, or in locations continuously subject to splashes of water. Doing so may result in oil or water entering the Switch interior.
Confirm suitability (applicability) in advance before using the Switch where it would be subject to oil, water, chemicals, or detergents. Contact with any of these may result in contact failure, insulation failure, earth leakage faults, or burning.
Do not use the Switch in the following locations:
*Locations subject to corrosive gases
*Locations subject to severe temperature changes
*Locations subject to high humidity, resulting in condensation
*Locations subject to severe vibration
*Locations subject to cutting chips, dust, or dirt
*Locations subject to high humidity or high temperature
Use protective covers to protect Switches that are not specified as waterproof or airtight whenever they are used in locations subject to splattering or spraying oil or water, or to accumulation of dust or dirt.
Be sure to install the Switch so that the Switch is free from dust or metal powder. The Actuator and the Switch casing must be protected from the accumulation of dust or metal powder.
Do not use the Switch in locations where the Switch is exposed to steam or hot water at a temperature greater than 60°C.
Do not use the Switch under temperatures or other environmental conditions not within the specified ranges. The rated permissible ambient temperature range varies with the model.
If the Switch is exposed to radical temperature changes, the thermal shock may deform the Switch and the Switch may malfunction.
Be sure to protect the Switch with a cover if the Switch is in a location where the Switch may be actuated by mistake or where the Switch is likely cause an accident.
Make sure to install the Switch in locations free of vibration or shock. If vibration or shock is continuously imposed on the Switch, contact failure, malfunction, or decrease in service life may be caused by abrasive powder generated from the internal parts. If excessive vibration or shock is imposed on the Switch, the contacts may malfunction or become damaged.
Do not use the Switch with silver-plated contacts for long periods if the switching frequency of the Switch is comparatively low or the load is minute. Otherwise, sulfuric film will be generated on the contacts and contact failures may result. Use the Switch with goldplated contacts or use a Switch designed for minute loads instead.
Do not use the Switch in locations with corrosive gas, such as sulfuric gas (H2S or SO2), ammonium gas (NH3), nitric gas (HNO3), or chlorine gas (Cl2), or high temperature and humidity. Otherwise, contact failure or corrosion damage may result.
If the Switch is used in locations with silicone gas, arc energy may create silicon dioxide (SiO2) on the contacts and a contact failure may result. If there is silicone oil, silicone sealant, or wire covered with silicone close to the Switch, attach a contact protection circuit to suppress the arcing of the Switch or eliminate the source of silicone gas generation.
Regular Inspection and Replacement
If the Switch is normally closed with low switching frequency (e.g., once or less per day), a reset failure may result due to the deterioration of the parts of the Switch. Regularly inspect the Switch and make sure that the Switch is in good working order.
In addition to the mechanical durability or electrical durability of the Switch described previously, the durability of the Switch may decrease due to the deterioration of each part, especially rubber, resin, and metal. Regularly inspect the Switch and replace any part that has deteriorated to prevent accidents from occurring.
If the Switch is not turned ON and OFF for a long period of time, contact reliability may be reduced due to contact oxidation.
Continuity failure may result in accidents (i.e., the switch may not turn ON due to increased contact resistance.)
Be sure to mount the Switch securely in a clean location to ensure ease of inspection and replacement. The Switch with operation indicator is available, which is ideal if the location is dark or does not allow easy inspection or replacement.
Storage of Switch
When storing the Switch, make sure that the location is free of corrosive gas, such as H2S, SO2, NH3, HNO3, or Cl2, or dust and does not have a high temperature or humidity.
Be sure to inspect the Switch before use if it has been stored for three months or more.
Typical Problems, Probable Causes, and Remedies
| Problem | Probable cause | Remedy | |
| Mechanical failure | 1. The Actuator does not operate. 2. The Actuator does not return. 3. The Actuator has been deformed. 4. The Actuator is worn. 5. The Actuator has been damaged. | The shape of the dog or cam is incorrect. | ・ Change the design of the dog or cam and smooth the contacting surface of the cam. ・ Scrutinize the suitability of the Actuator. (Make sure that the Actuator does not bounce.) |
| The contacting surface of the dog or cam is rough. | |||
| The Actuator in use is not suitable. | |||
| The operating direction of the Actuator is not correct. | |||
| The operation speed is excessively high. | ・ Attach a decelerating device or change the mounting position of the Switch. | ||
| Excessive stroke. | ・ Change the stroke. | ||
| The rubber or grease hardened due to low temperature. | ・ Use a cold-resistive Switch. | ||
| The accumulation of sludge, dust, or cuttings. | ・ Use a drip-proof model or one with high degree of protection. ・ Use a protection cover and change the solvent and materials. | ||
| Dissolution, expansion, or swelling damage to the rubber parts of the driving mechanism. | |||
| There is a large deviation in operating position (with malfunctioning involved). | Damage to and wear and tear of the internal movable spring. | ・ Regularly inspect the Switch. ・ Use a better quality Switch. ・ Tighten the mounting screws securely. Use a mounting board. | |
| Wear and tear of the internal mechanism. | |||
| The loosening of the mounting screws causing the position to be unstable. | |||
| The terminal part wobbles (The mold part has been deformed). | Overheating due to a long soldering time. | ・ Solder the Switch quickly. ・ Change the lead wire according to the carry current and ratings. | |
| The Switch has been connected to and pulled by thick lead wires with excessive force. | |||
| High temperature or thermal shock resulted. | ・ Use a temperature-resistive Switch or change mounting positions. | ||
| Failures related to chemical or physical characteristics | Contact chattering. | Vibration or shock is beyond the rated value. | ・ Attach an anti-vibration mechanism. ・ Attach a rubber circuit to the solenoid. ・ Increase the operating speed (with an accelerating mechanism). |
| Shock has been generated from a device other than the Switch. | |||
| Too-slow operating speed. | |||
| Oil or water penetration. | The sealing part has not been tightened sufficiently. | ・ Use a drip-proof or waterproof Switch. ・ Use the correct connector and cable. | |
| The wrong connector has been selected and does not conform to the cable. | |||
| The wrong Switch has been selected. | |||
| The terminal part is not molded. | |||
| The Switch has been burnt or carbonated due to the penetration of dust or oil. | |||
| Deterioration of the rubber part. | The expansion and dissolution of the rubber caused by solvent or lubricating oil. | ・ Use an oil-resistant rubber or Fluorine Resin bellows. ・ Use a weather-resistant rubber or protective cover. ・ Use a Switch with a metal bellows protective cover. | |
| Cracks due to direct sunlight or ozone. | |||
| Damage to the rubber caused by scattered or heated cuttings. | |||
| Corrosion (rusting or cracks). | The oxidation of metal parts resulted due to corrosive solvent or lubricating oil. | ・ Change the lubricating oil or change mounting positions. ・ Use a crack-resistant material. | |
| The Switch has been operated in a corrosive environment, near the sea, or on board a ship. | |||
| The electrical deterioration of metal parts of the Switch resulted due to the ionization of cooling water or lubricating oil. | |||
| The cracking of alloyed copper due to rapid changes in temperature. | |||
| Failures related to electric characteristics | No actuation. No current breakage. Contact welding. | Inductive interference in the DC circuit. | ・ Add an erasing circuit. |
| Carbon generated on the surface of the contacts due to switching operations. | ・ Use a Switch with a special alloy contact or use a sealed Switch. | ||
| A short-circuit or contact welding due to contact migration. | ・ Reduce the switching frequency or use a Switch with a large switching capacity. | ||
| Contact welding due to an incorrectly connected power source. | ・ Change the circuit design. | ||
| Foreign materials or oil penetrated into the contact area. | ・ Use a protective box. | ||
Other
The standard material for the Switch seal is nitrile rubber (NBR), which has superior resistance to oil. Depending on the type of oil or chemicals in the application environment, however, NBR may deteriorate, e.g., swell or shrink. Confirm performance in advance.
The correct Switch must be selected for the load to ensure contact reliability. Refer to Precautions for microloads in individual product information for details.
Wire the leads as shown in the following diagram.
Correct Wiring
Incorrect Wiring
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