| 摘要 |
The capacitive sensor has a tubular plastic housing (10) which is closed at the front end and which consists of a tubular body (11) and a cup-shaped cap (12). In the cap (12) a pot-shaped sensor electrode (13) and a tubular guard electrode (14) are disposed. The tubular body (11) contains an electronic circuit (20) and a tubular shield electrode (15). The tubular electrodes (14, 15) are impact-resistant metal tubes, preferably of steel, and the pot-shaped sensor electrode (13) is an impact-resistant metal member, likewise preferably of steel. Between the electrodes (13, 14, 15) elastically deformable spacer members (16, 17) are inserted. For assembling the sensor the sensor electrode (13) and the guard electrode (14) with the spacer (16) disposed therebetween are arranged in the cap, and the shield electrode (15) is introduced from the front into the body (11) up to a stop (24) disposed in the body (11). Then, the cap (12) and the body (11) are fitted together and permanently joined to each other by ultrasonic welding. The easily assembled capacitive sensor thus formed is very resistant to shock and impact forces and therefore suitable for use in areas where there is a danger of explosion. |
