When the test body is metal data, high frequency vibration proximity switch should be selected. This type of proximity switch is the most active test for iron, nickel and A3 steel. For aluminium, brass and stainless steel, the test activity is low.

When the test body is non-metallic data, capacitive proximity switches, such as wood, paper, plastic, glass and water, should be selected. When metals and non-metals are to be tested and controlled over a long distance, optoelectronic proximity switch or ultrasonic proximity switch should be selected. When the test body metal but the activity requirement is not high: low-cost magnetic proximity switch or Hall proximity switch can be selected.

Elements for selection of proximity switches:

1. Test distance: mm as unit;

2. Lead-out type, plug-in type and plug-in relay type;

3. Test types: amplifier built-in type and amplifier separated type;

4. Working power supply: DC, AC, DC universal;

5. Output form: Normally open (NO), Normally closed (NC);

6. Shape: round, square and grooved;

7. Test objects: iron, steel, copper, aluminium, plastics, water, paper, etc.

8. Output method: two-line and three-line (NPN, PNP);

9. Shielding and non-shielding;

10. Response frequency: several objects can be tested in one second.