Information

www.weg.net
Level Relay (RNW)
32
It is based on the measurement of the electric current of the liquid in the tank by means of a set of submerged electrodes, which
work as liquid presence/absence sensors.
When the system is energized, an alternating current
1)
is applied to the reference electrode. Once the liquid comes into contact
with the electrodes, a path is established for the circulation of electric current between them. An electronic circuit compares the
current and, according to the chosen model, executes the logic that switches the output contacts.
The resistance may vary according to the liquid and the position of the electrodes. in
order to adapt the RNW electronic circuit to the liquid, the sensitivity must be adjusted
through the front dial, which has a graded scale (kΩ).
To perform the sensitivity adjustment, all electrodes must be submersed in the liquid of
the tank, and the dial must be positioned at its anti-clockwise limit (smallest resistance).
With the relay energized, the dial must be turned clockwise (increasing the resistance)
until the relay output switches its contacts and the red LED changes its status. To
confirm the adjustment, the reference electrode must be disconnected and immediately
reconnected. The RNW must return to its previous status of de-energization, and thus
the ideal sensitivity point will be adjusted. If that does not happen, a new adjustment
procedure must be performed.
Output energized
Relay energized
Note: 1) The AC current minimizes the electrolysis and increases the lifespan of the electrodes.
Operation
Sensitivity Adjustment