Loose contact
A loose contact is a point that unintentionally temporarily interrupts an electrical circuit due to loose plug connections or manufacturing errors, such as cold soldering points , or signs of wear , or at least varies the contact resistance spontaneously.
From electrical appliances with a loose contact in the household u. a. under certain circumstances, there is a considerable risk, since in domestic use they are usually not immediately regarded as defective, but continue to be used with their weaknesses. In the event of a failure, a slight movement of the device can be enough to temporarily close the circuit again. If devices with loose contacts continue to be operated, there may be arcing faults at loose contacts , which can damage the conductors due to heating or lead to cable fires . This is especially true if the line with the loose contact carries higher currents; this is not readily apparent to the layman. Apart from that, the involuntary switching on and off of the circuit in quick succession at a loose contact can cause radio interference . Electrical devices with loose contacts should no longer be operated.
If incandescent lamps occasionally flicker, there may be a loose contact at different contact points, including between two parts of a broken tungsten filament, if they are still in contact with each other due to gravity and electrical forces, but are temporarily moved apart by impact, position variation in relation to gravity or thermal expansion.
Loose contacts in complex electronic devices such as computers can, under certain circumstances, only be discovered with great difficulty, since the interruption of contact does not necessarily result in a total failure, but rather in a sporadic malfunction.
The principle of the carbon microphone is a useful "loose contact".
"Wrong" loose contact
Occasionally a device has no loose contact at all, but a device-side power plug has not been properly inserted, so that no clean permanent contact is made. Mains plugs that cannot be inserted correctly or slip out of their position must be replaced.
literature
- Rudolf Huttary: Successfully repairing household electrics and electronics yourself. 3. Edition. Franzis Verlag GmbH, Poing 2001, ISBN 3-7723-4803-3 .
- Josef Eiselt: Troubleshooting electrical systems and devices. 2nd Edition. Richard Pflaum Verlag KG, Munich 1976, ISBN 3-7905-0243-X .
