Honeywell VRX180 Manual De Usuario

Table 4-10   Loop Prompts (continued) 

SP INC SLEW LIMIT & 

SP DEC SLEW LIMIT 

Enter a number 

Working set point slew limits for increasing and decreasing 
slew rates.  (Variable slew limits are available by 
programming a constant's Destination with IS or DS.  See 
Program Constants, Section 4.16.) 

SP LOW LIMIT   & SP 

HIGH LIMIT 

OFF or number 

Limits will be imposed on the working set point value, 
regardless of source. A set point value above or below the 
limits will be entered into the loop at the limit value. OFF entry 
will assume process variable limits.  (Variable limits are 
available by programming a constant's Destination with HS or 
LS.  See Program Constants, Section 4.16.) 

SP1 TRACKING 

SP2, NONE 

A selection of Set point #2 will cause the Set point #1 value to 
be set to the Set point #2 value on a transfer from Set point 
#2 to Set point #1. Set point #1 adjustment may be made 
after the transfer. 

SUPPRESS 

OVERSHOOT 

YES, NO 

This parameter set to YES limits overshoot of the Set point 
(SP) by the Process Variable (PV) after a disturbance in the 
process such as a load or SP change. Through fuzzy logic, 
the working SP of the control loop is dynamically modified by 
the control algorithm to reduce or eliminate overshoot. 

ATTENTION 

Regardless of the setting of this SUPPRESS OVERSHOOT selection, overshoot is not suppressed when the process 
disturbance causes an initial deviation (PV-SP) value between -0.7 and +0.7 engineering units. Consequently, 
overshoot may not be suppressed in applications which require numerically small control loop PV ranges such as 
carbon potential where this range is typically 0.0 to 2.0 engineering units. 

WILD VARIABLE 

 

Enter an analog input (AIn OV) or calculated value (CVn OV) 
parameter that represents a second input signal applied to 
the ratio control loop whose value will be multiplied by the 
RATIO SETPOINT multiplier. The product of this multiplication 
may be specified as the ratio control loop’s working set point 
and can be biased by specifying a RATIO BIAS value. This 
input parameter is referred to as the “WILD VARIABLE” since 
the ratio loop has no control over its value whatsoever. In the 
fuel-air ratio control examples used in RATIO SETPOINT 
AND RATIO BIAS, fuel flow was for all intents and purposes 
the WILD VARIABLE. 
Note that the typical function block diagram one will use to 
represent a ratio control loop is illustrated in Figure 4-1.