Response Electronics CL6011B Especificaciones descargar pdf (Pagina 42)

3Ć22 Theory of Operation: Point Processing

Original Ć June 1990CE4.2:CL6211

After the DCP is in automatic mode, the transfer bias value ramps linearly

to zero, which causes a corresponding change in the IVP. In the

previous example, this would cause the IVP to ramp from 60% back

down to the desired value of 50%. The time required for the transfer bias

value to ramp to zero is tunable. A ramp time of zero will cause a bump

in the IVP when the mode is changed from manual to automatic.

When transfer bias ramping is disabled, the normal DCP bias value is

back calculated during a transfer from manual to automatic mode, and

set to a value that will achieve a bumpless transfer. Once the mode

transfer has been completed, the DCP bias value can be changed to any

desired value. Figure 3Ć9 on page 3Ć22 shows the effects of a manual to

automatic mode change on the bias and transfer ramping bias values of

a DCP.

IVP

TBIAS

Old IVP

Desired IVP

60%

50%

100%

10%

Figure 3Ć9. Transfer Bias Ramping

3.3.3.2 Primary Control Algorithm Modifiers

There are several function sequence table functions, such as dead-time

compensation, that act as primary control algorithm (PCA) modifiers.

These functions modify the PCA for specific applications. Descriptions

of these functions follow.

3.3.3.2.1 Dead-time Compensation

The Dead-time Compensation function (DTC) extends the continuous

control capability of a direct control point to include processes having

significant reaction lag time compared to the dominant process time

constant. The DTC function performs a Smith Predictor dead-time

compensation algorithm, which models the process as a first order

process having a gain, a time constant, and a dead-time. A model

process variable value is then calculated, which is passed to the primary

control algorithm as a pseudo-process variable.

The DTC function compensates the process variable in a series of

calculations after alarming has been performed and the actual process

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Response Electronics CL6011B Especificaciones Pagina 42