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Scaling logic in 0-100 to 0-4700 in Calc Block?

Happy new year all,.

I have a requirement from operation team for a Cascade loop.

  • Master Loop out: 0 to 100 (as usual)
  • Slave Loop PV: 0 to 4700
  • Slave Loop SP: 0 to 100 (when in cascade mode as usual)

But they need 0 to 4700 Setpoint Range of Slave Loop keeping Slave loop Out 0-100. So question is how to scale 0-100 to 0-4700 in Calculation block if there is no built-in option in DeltaV?

Installed Version is 14.3.1

Let us build success,

Zohaib Jahan

Zohaib Jahan
  • James Beall
    Hi Johan,
    Note that the scale for the SP of a PID block is the same as for the PV of that PID block (PV_SCALE). So, for the slave loop, the SP scale is 0-4700. In DeltaV, the PID/OUT of a DeltaV has a configurable scale, OUT_SCALE. Normally, the PID/OUT_SCALE of the Master loop in a cascade pair of loops is set to the PID/PV_SCALE of the Slave loop. Thus no re-scaling is required for your example. This is normally the desirable configuration for cascade loops.

    In migrations of some older control systems, cascade loops in DeltaV are configured to match the old system that has a non-changable 0-100% scale for the OUT of all PID. I this case, SCALER function blocks are used between the OUT of the Master loop and the SP of the slave loop and between the BKAL_OUT of the Slave loop going to the BKCAL_IN of the Master loop. The SCALER block has in IN_SCALE and an OUT_SCALE to accomondate a linear conversion of units.

    Let me know if you need more details.
    James

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