VEGA VEGAMET 407 AFT - Manual (Page 2)

Application
The VEGAMET 407 AF or 407 AFT is a signal con-
ditioning instrument and is used for level propor- tional indication (continuous level measurement).
The VEGAMET 407 AF or 407 AFT consists of:
- plastic housing with plug-in socket (series400)
- electronics
- relay output with floating spdt (fail safe)
- front plate with:
- mains control lamp
- indicating instrument
- signal lamp
- potentiometer for full adjustment
- potentiometer for empty adjustment
- potentiometer for integration time
A measuring system consists of:
- signal conditioning instrument VEGAMET 407 AF
or 407 AFT
- capacitive electrode with oscillator or pressure
sensor with oscillator
Additional indicating instruments and auxiliary level
switches can be connected to the current and
voltage output.
Level measurement with capacitive electrodes
a) non-conductive products
Electrode and container wall form a capacitor.
The level changes the dielectric of the capacitor
and therefore its capacitance.
b) conductive products
The fully insulated electrode and product form a
capacitor. The level changes the size of the
capacitor and therefore its capacitance.
In both cases a level proportional measuring cur-
rent is generated in the oscillator from the capaci-
tance change.
Fault monitoring
The integral fault monitoring detects
-
short-circuit or line break of the connection line
to the transducer
- current value of the connection line < 2,5 mA or
> 23,5 mA (e.g. as well as failures of the elec-
tronics in the transducer)
If one of the above mentioned failures is detected,
the failure LED lights and the output relay de-ener-
gizes, i.e. terminal 16 and 17 are connected
through relays (see electrical connection).
In addition more the output current increases to
approx. 23 mA and the voltage outputs take a
value< 5 V or < 10 V.
Current output
VEGAMET 407 AF
The current output of VEGAMET 407 AF is non-
floating with reference to the sensor input and
voltage output, however is floating with reference to
the mains connection.
VEGAMET 407 AFT
The current output of VEGAMET 407 AFT is float-
ing.
Level measurement with pressure sensors
The diaphragm of the pressure sensor converts the
hydrostatic pressure of the product linear into a
movement. This movement changes the size of a
capacitor.
The respective oscillator generates a level propor-
tional current out of this capacitance change.
The VEGAMET 407 AF or 407 AFT evaluates the
measuring current several times (see page 5).
Integration time
In case of fluctuating product surface it is useful to
smooth the outputs (indication, output 1 - 3), by
adjusting an integration time 0 … 20 sec.
Important note
The period of the integration time orientates on the
filling and emptying time of the vessel, i.e. integra-
tion time
≤
filling / emptying time.
Configuration
Function
2 VEGAMET 407 AF/AFT