Measuring Principle - Endress+Hauser Silopilot FMM20 Operating Instructions Manual

Product description
12
The wiper length (L) depends on the selected maximum nozzle height:
• 225 mm (8.86 in), Ordering code "maximum connection height; wiper", option A or B
• 515 mm (20.28 in), Ordering code "maximum connection height; wiper", option C or D
• 1015 mm (39.96 in), Ordering code "maximum connection height; wiper", option E
or F
3�2

Measuring principle

The FMM works according to a simple measuring principle:
When a measurement starts (manually or automatically), a sensing weight is lowered
by a motor and spring action causes the wiper to be moved slightly out of its end
position. As the weight is lowered, the measuring tape passes over a counting wheel
which sends a pulse to the electronics every 2.5 cm.
When it hits the medium, the freely oscillating motor tilts from its working position,
in which it is held by the weight of the sensing weight, to its rest position. This is
detected by the electronics and the motor is switched off.
The sensing weight is pulled up again and counter pulses are detected once more.
As soon as the sensing weight reaches the measuring device, it causes the wiper to
move to its top position which is detected by the electronics.
The motor is switched off, the measuring cycle is ended and the measured value,
which depends on the configuration, is put out:
- Display value on the LC display
- Current value at the 4-20 mA current output
- Relay switching (e.g. for the "top position" or "measuring" function)
8 Measuring principle of the FMM20
A Sensing weight in the top position
B Sensing weight when lowered (run-down) or raised (run-up)
C Sensing weight on reaching the surface of the medium
Silopilot FMM20
A
B
C
Endress+Hauser
0000000294