- RFID and magnetic safety switches
- Technology
MN safety door switches: Technology
In manufacturing, there is no such thing as zero risk. Risk can be evaluated and reduced to a tolerable level. “Functional safety” involves determining how much harm a situation can cause and controlling it by means of safety-related devices.
ifm cannot perform risk assessments on applications. We promote RFID technology with the following protection ratings:
- SIL 3
- PL e
IEC 61508 is an international standard for the functional safety of electrical, electronic, and programmable electronic systems. It defines the requirements for the design, operation, and maintenance of systems to achieve a specified Safety Integrity Level (SIL). IEC 61508 serves as the foundational functional safety standard from which many sector-specific standards have been derived.
Functional safety "Umbrella Standard"
- Factory automation & Industrial Machinery:
ISO13849 (PL) Governs the entire safety loop;
IEC 62061 (SIL) Alternative machinery standard to ISO 13849;
ISO 10218 Functional safety requirements for industrial robots and robotic integrations - Device related standards:
IEC 60947-5-3 Requirements for proximity devices with defined behavior under fault conditions (PDDB), such as inductive, magnetic, RFID door switches;
IEC 61496 – 2/3 (Type); Part 2 - Requirements for equipment using active opto-electronic protective devices, covering safety light curtains and grids;
Part 3 - Requirements for active opto-electronic protective devices responsive to diffuse reflection, covering safety laser scanners;
IEC 61131 Programmable controllers (PLCs) functional safety;
IEC 61800-5-2 VFDs functional safety requirements;
IEC 60601-1 Medical and Healthcare devices;
IEC 60335-1 (Annex H) Household smart appliances - Process Industry:
IEC 61511 (SIL) Safety instrumented systems for the process industry sector - Automotive:
ISO 26262 (ASIL) Road vehicles functional safety;
ISO 21448 extension to ISO 26262, SOTIF (Safety of the intended functionality) - Tractors and machinery used in agriculture and forestry:
ISO 25119 / DIN EN 16590 (AgPL) Safety-related parts of control systems - Railways:
EN 50126 (IEC 62278); EN 50128 (IEC 62279); EN 50129 (IEC 62425) - Nuclear Power Plants:
IEC 61513 paired with IEC 61226
| IEC61508 [SIL] |
IEC62061 [SIL CL] |
ISO 13849 [PL] |
ISO 13849 [Category] |
IEC61496 [Type] |
Maximum Allowed PFHd | Risk Profile Safeguarded |
Description |
|---|---|---|---|---|---|---|---|
| SIL 1 | SIL 1 | PL c | Category 2 | Type 2 | < 10 -5 | Low to moderate risk | Basic structures; a single fault will cause the safety function to fail |
| SIL 2 | SIL 2 | PL d | Category 3 | Type 3 | < 10 -6 | Moderate to high risk | Intermittent checks to ensure the safety function is working (periodic diagnostic testing) |
| SIL 3 | SIL 3 | PL d | Category 3 | Type 4 | < 10 -6 | High risk | Redundant hardware; a single fault won’t cause loss of the safety function |
| SIL 4 | SIL 4 | PL e | Category 4 | Type 4 | < 10 -7 | High risk / immediate hazard | Highly redundant; the system withstands accumulation of faults |
SIL CL: Safety Integrity Level Claim Limit, the maximum SIL that a single subsystem component can achieve based on its structural hardware design and software constraints.
In practical terms, regardless of how dependable the rest of the functional safety loop is, this specific part cannot be trusted beyond its SIL CL rating.
SIL: Safety Integrity Level of the entire safety function loop.
Coding of door switches/actuators provide different levels of tamper-resistance and safety.
Uniquely coded actuators
When the actuator leaves the factory, it is permanently paired with a sensor and cannot be modified. Defective products must be replaced as a pair. This is the highest level of coding and is offered in RFID door switches only.
Codable actuators
During installation, the actuator is programmed and assigned to a specific sensor. Actuators can be reprogrammed as necessary and defective products can be replaced individually. This level of coding is offered in RFID door switches only.
Coded actuators
The actuator is not assigned to a specific sensor. All ifm sensors detect each ifm actuator. Defective products can be replaced individually as necessary. This level of coding is offered in both magnetic and RFID door switches.
Both RFID-coded and magnetically-coded safety switches operate without physical contact and are, therefore, maintenance free.
 |
 |
|
| RFID-coded safety switch | Magnetically-coded safety switch | |
|---|---|---|
| Coding level | +++ | + |
| Series connection | +++ *Up to 32 with same safety integrity (Only for codable and uniquely coded sensors!) |
+ *Up to 32 with reduced safety integrity |
| Sensing range | +++ | ++ |
| Display and LED | +++ | - |
| Service life | +++ | ++ *Reed contacts have limited life |
| Cost | + | +++ |
The RFID-coded safety sensor (MN7xxS series) transmits a high-frequency magnetic field with an identification number. The actuator senses the signal and transmits its identification number. The sensor receives the actuator’s identification number and sets the output as shown.
If the two identification numbers match (Fig. 1)
Output = 1 and the door is closed
If the two identification numbers do not match (Fig.2)
Output = 0 and the wrong actuator is detected
Magnetic door switches consist of 2 reed switches. Sensor consists of 2 reed switches.
If the magnetic fields from an actuator are not present (Fig. 1), both reed switches are open.
Output = 0
If the magnetic fields are present (Fig. 2), both reed switches are closed.
Output = 1
Both reed switches must be closed for the output to switch.