Weighing Steps; Introduction; Operating Mode Nawi (Non-Automatic Weighing Instrument) - Filling - Siemens SIWAREX WP251 Manual

Scale parameters and functions

8.2 Weighing steps

8.2 Weighing steps
8.2.1

Introduction

Dosing is always executed in steps. These steps involve the same task in each operating
mode and are presented below. The step the scale is currently performing is indicated in the
AWI Status (DR 30 or SIMATIC function block).
Weighing step
0
1
2
3
4
5
8.2.2

Operating mode NAWI (non-automatic weighing instrument) - Filling

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. The material to be weighed is dosed into or onto the scale.
The material to be weighed is placed on a platform weighing machine, for example, and an
entry is made in the log memory of the WP251 by an operator command.
In NAWI mode, WP251 also allows a set point to be set, which the dosing functionality of the
module then automatically doses. Logging of the dosed weight must be initiated by an
operator command and is not an integral component of the automatic weighing cycle.
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 in weighing
step 4, and the operator must confirm the dosed weight using the "Continue weighing"
(1141) command. As a result of this, the dosed weight is logged and the weighing operation
ends or WP251 advances to step 5 for emptying.
In practice, the execution of dosing in NAWI - Filling 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 settings in DR 25)
4. Coarse/fine dosing phase starts
5. If configured and necessary, post-dosing occurs (DR 22)
6. WP251 jumps to "Stopped" state and waits for "Continue" command (1141) by the
operator
58
Function
Scale waits for command
Taring/Zero setting (based on weighing start options from DR 25)
Coarse/Fine phase (based on settings from DR 23)
Post-dosing (based on settings from DR 22)
Checking (based on settings from DR 22)
Emptying (based on settings from DR 25)
SIWAREX WP251
Manual, 12/2015, A5E37203357A