Section 1
General Information
Programming & Operation 4-21
MN715
Table 4-2 Parameter Block Definitions Level 2
Continued
Block Title
Parameter
Description
PROCESS
CONTROL
Process Feedback
Process Inverse
Setpoint Source
Setpoint Command
Set PT ADJ Limit
At Setpoint Band
Process PROP Gain
Process INT Gain
Process DIFF Gain
Follow I:O Ratio
Follow I:O Out
Encoder Lines
The type of signal used for the process feedback in the PID setpoint control loop.
OFF – The process feedback signal is not inverted (no polarity change).
ON – Causes the process feedback signal to be inverted. Used with reverse acting
processes that use a unipolar signal such as 4-20mA. If “ON”, the PID loop will see a
low value of the process feedback signal as a high feedback signal and a high value of
the process feedback signal as a low feedback signal.
The source input reference signal type to which the process feedback will be compared. If
“Setpoint CMD” is selected, a fixed value that is entered in the setpoint command
parameter (of the Level 2 Process Control block) will be used.
The setpoint value for the PID loop that the control will try to maintain. This is only used
when the setpoint source parameter is set to “Setpoint Command”. Negative
percentage values are ignored in the PID loop if the feedback signal contains only
positive values (such as 0-10VDC).
The maximum frequency correction value to be applied to the motor (in response to the
maximum feedback setpoint error). For example, if the max output frequency is 60 Hz,
the setpoint feedback error is 100% and the setpoint adjustment limit is 20%, the
maximum speed the motor will run in response to the setpoint feedback error is
±
12 Hz.
(60Hz x 20%= 12Hz or a total of 24 Hz total output band-width centered around the
effective setpoint frequency).
The operating band within which the at setpoint opto output is active (turned ON). This
feature indicates when the process is within the desired setpoint range. For example, if
the setpoint source is 0-10VDC and the at setpoint band value is 10%, the at setpoint
opto output will turn on if the process is within (10 x 10% = 1)
±
1VDC of the setpoint.
The PID loop proportional gain.
The PID loop Integral gain.
The PID loop differential gain.
The ratio of the master input to the follower output. Requires the master pulse reference/
isolated pulse follower expansion board. For example, the left number is the master
input rate. The number to the right of the colon is the follower output rate. If you wish
the follower to run twice the speed of the master, a 2:1 ratio is entered. Fractional
ratios such as 0.5:1 are entered as 1:2.
Only used for serial communications. In master/follower configurations this parameter
represents the follower portion of the ratio. The master portion of the ratio is set in the
Follow I:O Ratio parameter.
Note: When using Serial Commands, the Follow I:O Ratio parameter value must be
set using two separate parameters: Follow I:O Ratio and Follow I:O Out. The
follow I:O Ratio sets the Input (Master) part of the ratio and Follow I:O Out
sets the output (Follower) part of the ratio. For example, a 2:1 (input:output)
ratio is set by a Follow I:O Ratio value of 2 and a Follow I:O Out value of 1.
Note: The encoder lines parameter must be defined if a value is entered in the
Follow I:O Ratio parameter.
Only used if an optional master pulse reference/isolated pulse follower expansion board is
installed. Defines the number of pulses per revolution of the master encoder. This
parameter defines the output master pulse rate for a downstream follower drive.
Integrator Clamp
Allows limiting (clamping) of the PID integrator. The clamp is set as a percentage of
maximum motor speed. For example, a setting of 10% (assuming an 1800 RPM motor)
means the integrator will not contribute more than 180 RPM to the total output demand of
the PID loop.
Minimum Speed
Set the minimum demand for the PID output. For example, a setting of 10Hz means the
output demand from the PID will never decrease below this setting (even if the process
error is zero). Minimum speed is active for unipolar as well as bipolar applications.
