Trane PID Control User Manual

®

The throttling range determines the responsiveness of a control system to 
disturbances. The smaller the throttling range, the more responsive the 
control. You cannot directly program the throttling range in Tracer con-
trollers; rather, the throttling range is used to calculate the gains.

Figure 9 shows that as the throttling range increases, the potential error 
becomes larger. When the output is at 0% or 100%, the error is equal to 
one-half of the throttling range. For example, with a 10° throttling range, 
the potential error is 5° from the setpoint (though the error could 
exceed 5°).

Figure 9: Throttling range and error with proportional bias = 50

Gains, which are calculated from the throttling range, determine how fast 
a measured variable moves toward the setpoint. The larger the gains, the 
more aggressive the response. The proportional, integral, and derivative 
calculations each have an associated gain value. The error, the sum of 
past errors, and the change in error are multiplied by their associated 
gains to determine the impact that each has on the output. 

Error

Contro

ller o

u

tpu

t (%)

Throttling range = 10

Throttling range = 4

Throttling range = 20