Locating device (building services)
A locating device (also line viewfinder , cable locator , timber detector , multi-detector ) is used in the sense of building services, locating non-visible objects within walls , ceilings and floors . These are primarily gas , water or electrical lines , reinforcement bars or stand structures .
Principles:
- Passive electromagnetic induction for conductors through which alternating current flows
- active generation of a magnetic field and testing of the signal response for metals (inductive measurement) ( metal detector )
- active generation of an electric field and testing of the signal response (capacitive measurement); This method can also be used to locate non-metals. ( Bar finder )
- active generation of electromagnetic waves in the radio frequency range and testing of the signal response ( radar ). These devices can also detect filled and empty plastic pipes.
Many devices combine several types of sensors; however, radar location is reserved for professional equipment. Some devices contain several sensors of the same type. As a rule, the devices must be calibrated before use. For this purpose, they are held at a point on the wall or the like that should be free of interfering objects. This is how the device determines the specific values of the wall.
With simpler devices, the type of object you are looking for must be selected before the measurement, and sometimes the wall material as well. Incorrect measurements are possible, depending on the capabilities of the device, on moist substrates (fresh screed, concrete) or building materials with hollow chambers (e.g. hollow bricks). Power lines should have an electrical load applied to them in order to reliably locate them.
The wall is scanned with the device, the sensors measure specific values, the device processes (e.g. with a microcontroller ) the data and reports as soon as a change is detected. The display can acoustically via z. B. beeper or optically via simple lamps to complex liquid crystal screens .
Web links
- The man is himself : tracking devices being tested (PDF; 3.6 MB)
- Elektronik industrie 8/9 2007: Knowing what's behind it [1]