Marathon Computer AACC 2000 manual Setting the cutback values, Proceed as follows

Marathon Monitors Inc.

Setting the cutback values

The above procedure sets up the parameters for optimum steady state control. If unacceptable levels of overshoot or undershoot occur during start-up, or for large step changes in process variable, then manually set the cutback parameters ‘Lcb’ and ‘Hcb’.

Proceed as follows:

1.Set the low and high cutback values to three proportional bandwidths (that is to say, Lcb = Hcb = 3 x Pb).

2.Note the level of overshoot, or undershoot, that occurs for large atmosphere changes (see the diagrams below).

In example (a) increase ‘Lcb’ by the overshoot value. In example (b) reduce ‘Lcb’ by the undershoot value.

Example (a)

Atmosphere

OvershootSetpoint

Example (b)

Atmosphere

Setpoint

Undershoot

Time

Where the atmosphere approaches setpoint from above, you can set ‘Hcb’ in a similar manner.

AACC 2000 Carbon 57 Nov. 1, 1997