Selection and testing of proximity switches

Different types of proximity switches should be selected for different materials of detection objects and different detection distances to achieve high performance-price ratio in the system. Therefore, the following principles should be followed in the selection:

1.1. When the detection object is made of metal material, a high-frequency oscillation type proximity switch should be selected. This type of proximity switch is most sensitive to iron-nickel and A3 steel detection objects.

For aluminum, brass and stainless steel test objects, the detection sensitivity is low.

1.2. When the detection object is non-metallic material, such as wood, paper, plastic, glass and water, a capacitive proximity switch should be selected.

1.3. When metal and non-metal objects need to be detected and controlled at a long distance, photoelectric proximity switches or ultrasonic proximity switches should be used.

1.4. When the detection object is metal, if the detection sensitivity requirement is not high, a low-cost magnetic proximity switch or Hall proximity switch can be selected.

2. Proximity switch technical indicator detection

2.1. Action distance measurement: When the action piece approaches the sensing surface of the proximity switch from the front, the distance that causes the proximity switch to act is the maximum action distance of the proximity switch. The measured data should be within the parameter range of the product.

2.2. Determination of release distance: When the actuating piece leaves the sensing surface of the proximity switch from the front and the switch changes from actuation to release, measure the maximum distance between the actuating piece and the sensing surface.

2.3. Determination of hysteresis H; the absolute value of the difference between the maximum action distance and the release distance.

2.4. Determination of action frequency: Use a speed regulating motor to drive a bakelite disc, fix several steel sheets on the disc, adjust the distance between the switch sensing surface and the action piece to about 80% of the switch action distance, rotate the disc, and make the action piece approach the proximity switch in turn. A speed measuring device is installed on the main shaft of the disc. The switch output signal is shaped and connected to a digital frequency meter. At this time, start the motor and gradually increase the speed. Under the condition that the product of the speed and the action piece is equal to the frequency count, the action frequency of the switch can be directly read by the frequency meter.

MICROSONAR series proximity switch 2.5. Repeatability measurement: Fix the action piece on the gauge, and approach the switch action area from the front of the switch sensing surface from 120% of the switch action distance, and control the movement speed to 0.1mm/s. When the switch is actuated, read the reading on the gauge, then exit the action area to disconnect the switch. Repeat this 10 times, and finally calculate the difference between the maximum and minimum values ​​of the 10 measured values ​​and the average value of the 10 times. The larger difference is the repeatability error.