Precision Digital PD554 - Manual (Page 20)

This parameter establishes reverse (REV) or forward (FWD) activation of the control
outputs. In forward operation, the control outputs will be most active when the PV value is
higher than the SP, as the controller acts to lower the PV. In reverse operation, the control
outputs will be most active when the PV value is lower than the SP value, as the controller
acts to inc rease the PV. The default setting is REV.
This parameter sets a high limit for the levels of the control output. This limits the output
levels based on a percentage of their full scale. Its default setting is 100 (%).
This parameter establishes the percent output transmitted by the control outputs when the
controller is in STOP m ode, or when an error condition occurs such as a PID algorithm
error, A/D error, or open sensor error is detected.
PV
This parameter establishes the cycle time for use with time-proportional PID relay or
voltage pulse control when the outputs are set to HEAT or COOL. The cycle time can be
set from 1 to 300 seconds. Its default setting is 2 seconds.
PV
PV
This parameter sets a low limit for the levels of the control output. This prevents the
outputs from dropping below a certain level based on a percentage of their full scale. Its
default setting is 0 (%). The outputs are limited by both the the low and high limits.
PV
PV
Fig 3: Time-Proportional PID Control Output
3 Sec
CT=10 Sec
5 Sec
Output=50% Output=70% Output=30%
5 Sec 7 Sec 3 Sec 7 Sec
CT=10 Sec CT=10 Sec
Cycle Time (CT) set to 10 seconds
PD550 Series Nova Programmable Process and Temperature Controller Instruction Manual
20