System Description
The level electrode operation is based on the conductive
measuring principle. The NRG 1...-41.1 is designed for signalling the max. liquid level in electrically conductive liquids.
n One liquid level with one switchpoint
The NRG 1...-41.1 is to be used in conjunction with the
multi-purposed control equipment NRS 1-40.1. The level
data are transferred from the electrode NRG 1...-41.1 to
the control unit via a CAN bus using the CANopen protocol.
Function
The conductivity of the liquid is used to signal the liquid
level. Some liquids are conductive, which means that they
allow an electric current to flow through them. For the safe
functioning of this device a minimum conductivity of the liquid
to be measured is required.
The conductivity measurement method can detect two
conditions: electrode rod submerged or exposed, meaning
switchpoint reached (or exceeded) or not yet reached. Before
installation, the length of the electrode rod must be cut to
the required switching level, e. g. for “Pump off” or “Control
valve closed” or, in case of economiser and air heaters that
are installed close to the steam-generating unit and exposed
to a risk, “Firing/Burner off”.
An additional electrode fully integrated in the system automatically monitors the electrical resistance path between earth
and measuring electrode. As soon as the actual value falls
below the admissible resistance value the protection circuit is
interrupted and cuts off the pump or heat supply to the boiler.
At regular intervals the level electrode NRG 1...-41.1 sends
a data telegram to the switching controller NRS 1-40.1. The
data are transferred via a CAN bus to DIN ISO 11898 using
the CANopen protocol.
