Are you looking for answers about what NAMUR sensors are, how they work, and what NAMUR sensors applications are? Now here is the right and comprehensive article for you to learn.
In simple terms, NAMUR output uses the current output signal level to distinguish the switch state. The current is generally very small and is mainly used in explosion-proof occasions. General proximity sensors use voltage high or low level to indicate the presence or absence of an object. The output current is generally large, and a weak spark will be generated during switching, which may cause an explosion.
What is NAMUR?
The NAMUR (Nationale Forschungsgruppe für Automatisierungstechnik) output standard was established by the German Measurement and Control Standards Committee. It was initially proposed by the German proximity sensor manufacturing company Pepperl+Fuchs. Originally a German standard (DIN 19234), it later evolved into a European standard (EN 50227, DIN EN 60947-5-6).
NAMUR sensors working principle
Now let’s take the normally closed NAMUR proximity switch as an example to explain its working principle. Specifically:
- Supply voltage: The sensor requires a direct current voltage of around 8V (typically 8.2V).
- Current signal: Depending on the distance of a metal object approaching the sensor, it generates a current signal ranging from 1.2mA to 2.1mA. The typical switch current value is 1.55mA.
- Signal changes of NAMUR normally closed proximity sensor:
- When the current decreases from high to low or falls below 1.55mA, an output signal change occurs (from 1 to 0, or from NC to NO).
- When the current increases from low to high or reaches 1.75mA, an output signal change occurs (from 0 to 1, or from NO to NC).
NAMUR sensors applications
1. Chemical and petrochemical industries
NAMUR sensors are often used to detect substances in pipelines and tanks, monitor the flow of corrosive or hazardous materials, and ensure process stability and safety. They can also detect leaks and spills, acting as an early warning system to prevent accidents and environmental pollution.
2. Oil and gas industry
In hazardous environments, NAMUR sensors are used to monitor the speed of rotating equipment such as pumps and turbines, as well as the positioning of valves, actuators, and dampers, thereby improving safety and operational efficiency.
3. Wastewater treatment
In wastewater treatment plants, NAMUR sensors optimize the treatment process by measuring the speed of equipment such as agitators, pumps and mixers.
4. Pharmaceutical industry
In the pharmaceutical industry, NAMUR sensors are used to monitor liquid levels, valves, and actuator status. They are resistant to strong cleaning agents used in pharmaceutical production and are suitable for use in cleanroom environments.
5. Food and beverage industry
NAMUR sensors are used in the food and beverage industry to monitor filling processes, detect objects in conveyors and packaging machines. Their non-contact operation enables them to detect material levels without contamination or damage.
6. Factory automation
In manufacturing plants, NAMUR sensors are used to monitor the speed and positioning of product transport, ensuring that components such as conveyors, lifting and feeding systems operate at the required speed and repeatability.
Advantages of NAMUR sensor
- Intrinsic Safety: Since it is designed with low voltage supply and micro-current output, NAMUR output sensors are all intrinsically safe explosion-proof instruments. They are typically used with isolating barriers and can be applied in hazardous locations with explosion-proof requirements.
- Compatibility: The NAMUR signal is the most widely used standard signal for intrinsically safe digital input and frequency input in the world, widely used in the I/O modules of safety barriers and PLC manufacturers.
Comparison between common two wire sensor and NAMUR sensor
Both two-wire common proximity sensors and NAMUR sensors have two wires, but what is the difference between them? Now we list it in the table below so that you can see it clearly:
| Aspect | Common two wire sensor | NAMUR sensor |
|---|---|---|
|
Output type |
Voltage-based, with residual voltage present even in the closed state |
Current-based, with specific current levels (e.g., 1mA when detecting, 3mA when not detecting) |
|
Working voltage |
Typically ranges from 12V to 24V for DC, and can be AC for some models |
Limited to a maximum of 8.2VDC |
|
Safety |
Not intrinsically safe; switching can cause sparks |
Intrinsically safe, minimizing the risk of ignition in hazardous areas |
|
Application |
Suitable for general industrial applications |
Specifically designed for hazardous areas, such as chemical plants, oil refineries, and mining operations |
|
Switching frequency |
Generally suitable for moderate switching frequencies. |
Supports higher switching frequencies than three-wire sensors. |
|
Compatibility |
Works with PLC digital inputs and various industrial control systems. |
Requires a switching amplifier to convert the current signal for PLC compatibility. |
|
Cost |
Lower cost due to simpler design. |
Higher cost due to the need for an external switching amplifier. |
Conclusion
Simply put, NAMUR sensors are designed for explosion-proof scenarios. Unlike common proximity sensors, they use the size of the current to indicate whether an object is within its sensing distance. The current is very small and no sparks are generated during operation.
As one of the premium proximity sensor manufacturers in China, Lorentzzi® can not only produce ordinary proximity sensors with high quality and competitive prices, but also provide NAMUR sensors with high safety performance. If you have other questions or want to get a quote for our proximity sensors, please contact us for free.
