The remote indicator consists of the following components:
- add-on housing with number of probes ordered (EL65 (<=32bar) or EL60 (>32bar)); (min. 5; max. 32 probes)
- measuring unit (MU); fitted on to the add-on housing and fully wired
- control unit (CU) with separate switched-mode power supply unit; for top-hat rail fitting in the distribution cabinet
- display unit (DU) ‒ optional
- various CAN bus connecting cables
Application and function
The electronic remote indicator (EWLI-3B) is used as a water level gauge for steam boilers or tanks with electrically conductive liquid. Depending on the regulations applied the EWLI-3B can also be used as a multi-control system (indicator - limiter - controller).
Recording is carried out by a conductive measuring principle which assumes a minimum conductivity of the liquid.
The measuring unit (MU) can be equipped with up to 32 probes. The distance between the individual probes can be freely determined by the customer – taking into account a minimum distance.
Because of the freely programmable assignment of switch contacts to the probes, any subdivision of the display range can be carried out, e.g. low water level range (LW), working range and high water level range (HW). A subdivision into LLW – LW – working range – HW – HHW is also possible.
Both the measuring unit and the control unit have 2 independent electronic circuits with their own processors. All processors carry out regular self-tests for internal faults in the electronic circuit.
The control unit (CU) processes the signals recorded and controls the downstream functions.
There are seven freely controllable output contacts (SPDT) available. An eighth contact (SPDT) is permanently switched as the signal contact for device error and a ninth contact (SPDT) permanently switched as the water level alarm contact, whereby the probes triggering the alarm (LW and/or HW) can be freely selected.
Here each processor actuates its own relay per contact whereby the output contacts are only switched when both processors signal the normal operating state in agreement. In addition there is a 4mA – 20mA interface as a (virtually) continuous output available. The output is increased per submerged probe by the corresponding proportion (16 mA / number of probes). In the event of an error the output goes to 2 mA.
The programming is carried out via 4 buttons and a 2-row LCD display with 16 characters each.
The EWLI-3B can be optionally supplemented by an additional LED display unit (DU). Here each probe of the measuring module is displayed green or red depending on status (water/steam). Moreover error states can be rapidly and reliably diagnosed with the aid of a 2x7-segment display and 3 status LEDs.
The EWLI-3B complies with EC Directive 2014/68/EU and the applied regulations DIN EN 12952, DIN EN 12953, AD2000 and the ASME boiler code.