How to choose the appropriate proximity sensor
Proximity sensors allow non-contact detection of objects. Therefore, they are used in many industries, including manufacturing, robotics, semiconductors, and so on. Inductive sensors detect metal objects, while capacitive sensors can detect all other materials. Ultrasonic sensors detect all materials by using sound wave reflection to determine their presence.
Usually, the following steps can help you choose the correct sensor based on your actual application:
Step 1: What is the required sensing distance?
Induction distance refers to the distance between the detection surface of a sensor and the object to be sensed. Kekit lists the corresponding sensing distance for each proximity sensor.
Several key points:
a. Long detection distance:
In many applications, for temperature reasons, keeping the sensor as far away from the detection object as possible is beneficial for the lifespan of the sensor. If the sensor is placed too close to the heat source, it will malfunction faster and require more maintenance.
The use of growth detection distance sensors can achieve larger distances. In many applications, sensors may not be installed close to the object being measured. In this case, a longer sensing distance is required.
Enhanced long-range proximity sensors
In many cases, using long-distance sensors can benefit the lifespan of the sensor. For example, in workplaces with high temperatures, it may not be possible to place ordinary sensors close enough to detectable objects, or more expensive high-temperature sensors may need to be purchased.
High temperature proximity sensor
Another example is in the case of mechanical overshoot. Installing the sensor at a distance from the detection object can eliminate unnecessary contact with the sensor, thereby extending its service life.
The benefits of using long-distance sensors in many applications are obvious. So we can prioritize whether long-distance sensors can save time and money in applications.
b. Properties of the tested material
The detected materials (such as brass, copper, aluminum, steel, etc.) have different detection distances compared to conventional inductive proximity sensors.
Note: If you want to sense non-metallic objects, a capacitive sensor must be used.
If the tested material is frequently changed, it can be considered to choose an inductive sensor with the same detection distance for different metal materials to reduce the cost of replacement and debugging. 
Step 2: How much space is available for installing sensors?
Can the commonly used inductive proximity switches have enough space for installation in your application, or can they be installed just right but cannot make their detection distance appropriate? At this point, you can consider whether the square inductive sensor can meet the installation space requirements of your application. Sometimes special shaped sensors can also be used. 
Step 3: Do we need shielded or unshielded sensors?
Shielded and unshielded sensors are also known as embeddable and non embeddable. Non shielded sensors allow for longer sensing distances, but shielded sensors allow for flush installation.
Step 4: Consider environmental issues.
Inductive sensors will be placed in environments such as underwater, high temperature, continuous oil pollution, welding metal sparks, and metal debris, which will determine the type of sensor you may use. Kekit will list the protection level for each sensor.
For example: IP level
IP65: Prevent live or moving parts, dust, and water spray from any direction.
IP67: Protection against live or moving parts, dust, and immersion in water.
IP68: Prevent live or moving parts, dust, and immersion in water under pressure
IP69K: Prevent high-pressure/steam jet cleaning.
For example, special protection types such as all stainless steel casing and anti metal debris.
Step 5: What is the sensor output connected to?
The required output type (i.e. NPN, PNP, or analog) must be determined. Most PLC products will accept any output. If connected to a solid-state relay, a PNP output is required. 
Step 6: Do I need 2-wire, 3-wire, or 4-wire discrete output?
This to some extent depends on the object that the sensor will connect to.
Do you need analog output?
This depends on the application of the sensor and the object to which the sensor will be connected. The output signal generated by a sensor with analog output is approximately proportional to the distance from the target to the sensor.
If only the presence of the object needs to be detected, there is no need to simulate the output. Please note that many discrete output proximity sensors have an adjustable range of 20-80 mm. This only means that you can set the target distance for detection within that range; This does not mean that you will receive variable output.
Step 7: Determine the output connection type.
Do you want to use a connecting axial cable or a quick plug cable on the sensor?
There are many advantages to using quick plug cables, such as ease of maintenance and replacement; Can be replaced with higher-level link cables, etc
Axial cables also have some advantages:
Cost: The cable has been integrated into the sensor and is included in the price. The plug cable must be purchased separately.
Environmental impact: Due to the cable being sealed in the sensor, the chances of oil, water, or dust infiltrating the sensor are low, which may lead to malfunctions.