Proximity switch selection and detection

Proximity switch selection

For different material samples and different detection distances, different types of proximity switches should be selected so that they have a high performance-to-price ratio in the system. Therefore, the following principles should be followed in the selection:

1.1. When the detector is metallic, a high-frequency oscillatory proximity switch should be used. This type of proximity switch is most sensitive to iron-nickel and A3 steels.

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

1.2. When the detector is non-metallic, such as wood, paper, plastic, glass, and water, a capacitive proximity switch should be used.

1.3. Metals and non-metals For long distance detection and control, photoelectric proximity switches or ultrasonic proximity switches should be used.

1.4. When the detection body is metal, if the detection sensitivity is not high, an inexpensive magnetic proximity switch or Hall proximity switch can be selected.

Technical indicators testing

2.1. Determination of operating distance; When the action piece is close to the sensing surface of the proximity switch, the proximity switching action distance is the maximum operating distance of the proximity switch. The measured data should be within the parameters of the product.

2.2. Determination of the release distance; When the action piece moves from the front side away from the sensing surface of the proximity switch and the switch changes from motion to release, the maximum distance the action piece leaves the sensing surface is determined.

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

2.4. Determination of the operating frequency; use a speed-regulating motor to drive the bakelite disc, fix a number of steel pieces on the disc, adjust the distance between the switch sensing surface and the action piece, about 80% of the switching distance, and turn the disc. The action piece is close to the proximity switch. A speed measuring device is installed on the spindle of the disc. The output signal of the switch is shaped and connected to a digital frequency meter. Start the motor at this time, 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 operating frequency of the switch can be directly read by the frequency meter.

2.5. Repeatability determination; The action piece is fixed on the measuring tool, and the motion speed is controlled to be 0.1 mm/s from the switch action distance of 120% of the switch action distance from the front of the switch sensing surface. When the switch is activated, read the reading on the gage and then exit the action zone to turn the switch off. Repeat this 10 times, and finally calculate the difference between the maximum and minimum values ​​of the 10 measurements and the 10 average values. The largest difference is the repeat accuracy error.