InputFreeze

If the terminal is placed in the freeze state by InputFreeze in the control word, no further analog measured values are relayed to the internal filter. This function is usable, for example, if a filling surge is expected from the application that would unnecessarily overdrive the filters due to the force load. This would result in a certain amount of time elapsing until the filter had settled again. The user himself must determine a sensible InputFreeze time for his filling procedure.

For clarification: temporal control of the InputFreeze and the decision regarding its use must be realized by the user in the PLC, they are not components of the EL3356.

In the following example (recorded with Scope2) impulses on a 15 kg load cell are recorded; the filter is wide open at IIR1 so that steep edges occur in the signal.

Explanation: The weight (A) is shown in blue; the state of the InputFreeze variable, which can be controlled by the PLC program and can be TRUE/FALSE, is shown in red (B). The first two impulses (C) lead to large peak deflections in the signal. After that the following is activated in the PLC program (see example program):

• if the measured value for the last cycle (cycle time 100 µs) has changed by more than 10 g (indicating a sudden load),
• bInputFreeze is set to TRUE for 50 ms by a TOF block on the EL3356

The effect can be seen in (D): The peak load is no longer acknowledged by the EL3356. If it is optimally adapted to the expected force impulse, the EL3356 can measure the current load value without overshoot.