Igema FARB2, Инструкция по установке и эксплуатации

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4.2 Function
The FARB2 works in conjunction with IGEMA TDS probes. The measuring current flowing between the
measuring electrode and the cell wall (boiler wall / protection tube) is proportional to the conductivity of
the liquid.
After setting the operating point by entering the current liquid temperature and the conductivity measured
by sampling (reference temperature 25°C), the FARB2 sets the 4..20mA output current and changes it
when the measuring current changes due to conductivity changes of the liquid.
The FABR2 can be operated in two ways (relay output), as:
- TDS limitation
- Switch for TDS control valve
Independent of the use / programming of the relay output, the 4..20mA output with
the current proportional to conductivity is available for control tasks e.g.
continuous TDS control (PLC, PID controller, valve with positioner).
The connection of the relay output defines the function of the unit:
- If the output is integrated in a switch-off / safety circuit, the functionality of FARB2 is based
on the limiting function.
The relay output is active (contacts 3-4 closed) during normal operating condition.
If the limit value is exceeded, the relay opens and closes again when the value falls below
the lower value.
- If the output is connected to a valve control (e.g. opening/closing TDS control valve), the
functionality is on the controller function.
The relay output is inactive during normal operation (3-4 open).
If the limit value is exceeded, the relay is actively energised and can thus switch a valve. The
relay becomes inactive again when the value falls below the lower limit.
The switching points for exceeding the conductivity (upper switching point) and for returning to the
normal state (lower switching point) can be freely selected:
- In this case the respective LED lights up and the change-over output is switched.
If a device error is detected, the change-over contact goes into the de-energised state and the
corresponding LED flashes. The current output goes back to < 2.1mA.
Measuring range and limit values can be freely programmed (see chapter 7.4).
Info