Operating Mode Aci (Automatic Catchweighing Instruments) - Filling - Siemens SIWAREX WP251 Manual

Scale parameters and functions
8.2 Weighing steps
completes the weighing operation autonomously. Optionally, WP251 can also empty the
scale.
In this operating mode, the dosing is controlled by WP251 in a fully-automatic operation. In
contrast to a NAWI scale, logging of the individual dosings by an operator command is not
required (WP251 logs every weighing nevertheless). The scale is therefore tested during
verification to see if the set point setting is always within the legally prescribed limits.
Typically, AWI scales dose continuously in continuous operation, which WP251 also
supports. In this operating mode, the option also exists to define cycles that are not
zeroed/tared and not checked. This increases the throughput of the scale because the
operations that require a standstill do not occur in every cycle.
In practice, the execution of dosing in AWI mode can be as follows:
1. PLC sends set point (DR 20) and material parameters (DR 23) to WP251
2. PLC sends "Start" command (e.g. 1101) to WP251
3. WP251 performs zero setting or tares (based on setting in DR 25) (weighing step 1)
4. Coarse/fine dosing phase starts (weighing step 2)
5. If configured and necessary, post-dosing occurs (DR 22) (weighing step 3)
6. Dosing result is automatically checked and logged (weighing step 4)
7. Scale is emptied, if necessary (based on setting in DR 25) (weighing step 5)
8. WP251 jumps to weighing step 0 and waits for further commands or jumps directly back
to step 1 (continuous operation).
8.2.5 Operating mode AWI (automatic catchweighing instrument) - Filling
In ACI 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, corrects the shut-off points of
the dosing signals if necessary and completes the weighing operation autonomously.
Optionally, WP251 can also empty the scale.
In contrast to NAWI mode, the logging of the dosed single weight is written automatically to
the log memory without an operator intervention.
Dosing in continuous operation is possible.
Here is the basic sequence of dosing in ACI Filling mode:
1. PLC sends set point (DR 20) and material parameters (DR 23) to WP251
2. PLC sends "Start" command (e.g. 1101) to WP251
3. WP251 performs zero setting or tares (based on setting in DR 25) (weighing step 1)
4. Coarse/fine dosing phase starts (weighing step 2)
5. If configured and necessary, post-dosing occurs (DR 22) (weighing step 3)
6. Dosing result is automatically checked and logged (weighing step 4)
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SIWAREX WP251
Manual, 12/2015, A5E37203357A