PID Loop Operation
Maintenance
8–3
PID Loop Operation
PID Loop Feature Specifications
Number of loops Selectable, 4 maximum
CPU V-memory needed 32 words (V locations) per loop selected, 64 words if using ramp/soak
PID algorithm Position or Velocity form of the PID equation
Control Output polarity Selectable direct-acting or reverse-acting
Error term curves Selectable as linear, square root of error, and error squared
Loop update rate (time
between PID calculation)
0.05 to 99.99 seconds, user programmable
Minimum loop update rate 0.05 seconds for 1 to 4 loops,
Loop modes Automatic, Manual (operator control), or Cascade control
Ramp/Soak Generator Up to 8 ramp/soak steps (16 segments) per loop with indication of
ramp/soak step number
PV curves Select standard linear, or square-root extract (for flow meter input)
Set Point Limits Specify minimum and maximum setpoint values
Process Variable Limits Specify minimum and maximum Process Variable values
Proportional Gain Specify gains of 0.01 to 99.99
Integrator (Reset) Specify reset time of 0.1 to 999.8 in units of seconds or minutes
Derivative (Rate) Specify the derivative time from 0.01 to 99.99 seconds
Rate Limits Specify derivative gain limiting from 1 to 20
Bumpless Transfer I Automatically initialized bias and setpoint when control switches from
manual to automatic
Bumpless Transfer II Automatically set the bias equal to the control output when control switches
from manual to automatic
Step Bias Provides proportional bias adjustment for large setpoint changes
Anti-windup For position form of PID, this inhibits integrator action when the control
output reaches 0% or 100 % (speeds up loop recovery when output
recovers from saturation)
Error Deadband Specify a tolerance (plus and minus) for the error term (SP–PV), so that no
change in control output value is made
Alarm Feature Specifications
Deadband Specify 0.1% to 5% alarm deadband on all alarms
PV Alarm Points Select PV alarm settings for Low–low, Low, High, and High-high conditions
PV Deviation Specify alarms for two ranges of PV deviation from the setpoint value
Rate of Change Detect when PV exceeds a rate of change limit you specify
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