Separable level probes with integrated lightning protection: armed against overvoltage

Hydrostatic level probes are essential for the monitoring and control of environmental engineering equipment such as weirs and sluices. In the event of a lightning strike, potential shifts or increases have a direct effect on the measuring equipment, so that particular importance must be attached to protecting these components. If system failures nevertheless occur during certain overvoltage events, it is important to keep the maintenance effort as low as possible. For both scenarios BD|SENSORS offers a well thought-out solution, which is based on an established device concept of overvoltage protection combined with a simple and time-saving replacement option.


Exemplary for this is the separable level probe LMK 808 with robust, capacitive ceramic sensor, which has a pressure tightness up to 20bar.
On the one hand, it has two-stage overvoltage protection, which protects the sensor signal, signal processing and transmission. While the coarse protection ensures that the overvoltage is limited to 90 V and a pulse current of up to 8,000 A (8 kA) is discharged, the subsequent fine protection reduces the occurring voltage to 36V, acts bipolar and can absorb a pulse power of 1,500W. (To document the performance of the measures, overvoltage tests were carried out in an accredited test laboratory in accordance with EN 61000-4-5. The results show that standard test pulses of 4,000V (4 kV) do not produce any damage).


Secondly, the probe head of the level probe can be separated from the cable section. This means that in the event of damage or servicing, the complex cable does not have to be removed from cable ducts or protective tubes, but only the probe head has to be unscrewed, cleaned and screwed back on, or the spare part fitted. This takes only a few minutes, so that the level probe can be quickly put back into operation and downtimes are kept to a minimum.