User`s manual

535 User's Manual Chapter 7 97
Applications
interpolated using a straight line relationship between the points. The only
limitation is that the resulting linearization curve must be either ever-increasing
or ever-decreasing.
P. LOAD LINE
Load line is a manual reset superimposed on the automatic reset action.
Adjusting the MAN. RST. tuning constant shifts the controller proportional band
with respect to the setpoint.
When used with a proportional only or proportional/derivative control algorithm,
the MAN. RST. parameter (located in the TUNING menu) is in effect “manual
reset”.
However, when the automatic reset term is present, the reset action gradually
shifts the proportional band to eliminate offset between the setpoint and the
process. In this case, load line provides an initial shift at which the reset action
begins. Load line is adjusted by observing the percent output required to control
the process and then adjusting the load line to that value. This minimizes the
effect of momentary power outages and transients. Load line may also be
adjusted to give the best response when bringing the load to the desired level
from a “cold” start.
Q. SECURITY
The 535 security system is easily customized to fit a system’s needs.
Software Configuration
1. Go to the SECURITY menu.
2. SEC. CODE defines the security password (range from -9999 to 99999).
The rest of the security parameters can be selectively locked out.
3. SP ADJUST prevents the operator from using the
▲▲
▲▲
▲ and
▼▼
▼▼
▼ and keys to
change the setpoint value. It does not prevent the operator from changing
setpoints via the SET PT key.
4. AUTO./MAN. locks out the MANUAL key preventing the operator from
transferring between automatic control and manual control.
100%
50%
0 20% 40% 60% 80% 100%
Controller Output
Process Variable Location (% of Controller Span)
LOAD LINE 20%
LOAD LINE 50%
LOAD LINE 80%
Figure 7.18
Load Line Example
NOTE: SEC CODE does not appear
unless all functions are unlocked.