Want to know how far an object has moved on a lead-screw or conveyor?
There are two options: proximity sensors and limit switches.
Since there are two options, you might be wondering: What is the difference between these two products? Which one should I use?
In this article, we will provide you with detailed information, now let’s continue.
What is a proximity sensor?
A proximity sensor is a contactless switch that uses sound, light, and electricity.
For example, when you approach an intelligent street lamp, it will light up automatically without manually touching and turning on the switch to control it.
In addition, proximity sensors can be divided into inductive, capacitive, photoelectric, ultrasonic, and Hall types.
The working principle of inductive proximity sensors is based on electromagnetic induction and eddy currents; capacitive sensors are based on electrostatic fields and capacitance changes; photoelectric sensors are based on optical detection; ultrasonic sensors are based on sound wave flight time; and Hall sensors are based on magnetic field induction.
Among these sensors, inductive and photoelectric sensors are the two most commonly used proximity sensors in the field of industrial control automation.
What is a limit switch?
In contrast, a limit switch is a switch that needs to be touched or pressed to close or open a circuit.
The limit switch is like a foot switch. It can connect or disconnect the circuit through external pressure such as foot pressure.
The figure below is the structure diagram of the limit switch.
Through the structure diagram, we can clearly understand that when external pressure is applied, its normally open contact will close, and if it is a normally closed point, it will be disconnected:
Key differences: proximity sensor vs limit switch
The key differences between proximity switches and limit switches mainly lie in 5 aspects: working principle, life, cost, response time and application.
We will explain them in detail in the following table:
| Item | Proximity Sensor | Limit Switch |
|---|---|---|
|
Working principle |
Objects can be detected without physical contact using methods such as inductive, capacitive, photoelectric, or ultrasonic sensing. |
The switch is triggered by mechanical force, and the detection object should be in contact with the limit switch rod to trigger. |
|
Lifespan |
Longer service life with minimal mechanical wear; ideal for repetitive high-speed operations. |
Due to the tendency of mechanical parts to wear; life is shorter in high cycle applications. |
|
Cost |
Because of the complex production steps and the need for more manual involvement, proximity switches are more expensive than limit switches, generally selling for around $10. |
Since the limit switch has a very simple structure and some can be directly produced by machines, the price of the limit switch is very cheap, and the most common limit switch costs less than US$5.0. |
|
Response time |
Near-instant response (e.g., Lorentzzi inductive proximity sensor response time is only 2 milliseconds). |
Slight delay due to mechanical actuation. |
|
Load capacity |
The proximity sensor has a very low load capacity. It uses a transistor and the output current is only 100-200 mA. |
The limit switch contacts are dry contacts with a load capacity of 2-3 amps and require an external power supply. |
|
Application |
Proximity sensors are ideal for non-contact detection, high-speed automation or hazardous environments such as conveyors, robotic arms, etc. |
The limit switches can be used in door switches, machinery end-stops, elevators etc. |
Can proximity switch replace limit switch?
Proximity switches can indeed replace limit switches in some applications, such as lead-screw motor control and stroke measurement. And the measurement accuracy of proximity switches is higher than that of limit switches.
However, in harsh environments such as high temperature, high humidity or strong electromagnetic interference, the performance of proximity sensors may be affected, reducing their reliability.
In contrast, micro switches are less susceptible to external influences and have higher adaptability.
Even if the operating environment is harsh, the limit switch can still work effectively when an object presses its handle.
On the other hand, proximity switches can be triggered by mistake due to harsh environments, which may lead to misjudgment and serious accidents.
Conclusion
All in all, proximity sensors do have advantages over limit switches in some aspects, but as the saying goes, “there is a reason for existence”, and limit switches also have their own advantages, such as no electromagnetic interference and low price.
Lorentzzi, as one of the leading proximity sensor suppliers in China, can not only provide high-quality proximity sensors, but also provide high-quality suggestions and solutions for your project.
If you are reading this article and plan to purchase proximity sensors from China, please contact us for the latest prices.
