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7. If the "Continue" command is issued, the dosed weight is written in the log memory and
the final tolerance check is performed.
8. WP251 jumps to weighing step 0 and waits for further commands.
8.2.3
Operating mode NAWI (non-automatic weighing instrument) - Removal
This operating mode always requires an intervention by the operator, who has to start the
logging of the current weight via a command. This can occur from the HMI touch panel, for
example.
"Removal" means that the product to be weighed is dosed from the scale (for example, a silo
on load cells with discharge valves). In this case, the full scale is tared and the net weight
increases with decreasing gross weight.
In NAWI mode, WP251 also allows a set point to be set, which is then dosed automatically
by the dosing functionality of the module.
The dosing signals "Coarse flow/Fine flow" can be used to directly control the corresponding
dosing elements. After the set point is reached, WP251 jumps to "stopped" state, and the
operator must confirm the dosed weight using the "Continue weighing" command. As a result
of this, the dosed weight is logged and the weighing operation is concluded.
In practice, the execution of dosing in NAWI - Removal mode can be as follows:
1. Scale is filled with sufficient material.
2. PLC sends set point (DR 20) and material parameters (DR 23) to WP251
3. PLC sends "Start" command (e.g. 1101) to WP251
4. WP251 tares (based on setting in DR 25)
5. Coarse/fine dosing phase starts
6. If configured and necessary, post-dosing occurs (DR 22)
7. WP251 jumps to "Stopped" state and waits for "Continue" command (1141) by the
operator
8. If the "Continue" command is issued, the dosed weight is written in the log memory and
the final tolerance check is performed.
9. Emptying signal is set, if necessary (based on setting in DR 25) (weighing step 5)
10.WP251 jumps to weighing step 0 and waits for further commands.
8.2.4
Operating mode AWI (gravimetric filling instrument)
In gravimetric filling mode, WP251 allows a set point to be set, which is then dosed
automatically by the dosing functionality of the module.
The dosing signals "Coarse flow/Fine flow" can be used to directly control the corresponding
dosing elements (e.g. valves). After the set point is reached, WP251 automatically logs the
dosed weight in the log memory, performs a tolerance check (only in checked cycles),
corrects the shut-off points of the dosing signals if necessary (only in checked cycles) and
SIWAREX WP251
Manual, 12/2015, A5E37203357A
Scale parameters and functions
8.2 Weighing steps
59
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