535-PROF User's Manual
Chapter 7
109
Applications
Note that when output limits are used, the full output range from -5 to 105% is
available in manual control.
O. RAMP-TO-SETPOINT
The 535 contains a ramp-to-setpoint function that may be used at the user’s
discretion. This function is especially useful in processes where the rate-of-
change of the setpoint must be limited.
When the ramping function is activated, the controller internally establishes a
series of setpoints between the original setpoint and the new
target
setpoint.
These interim setpoints are referred to as the
actual
setpoint . Either setpoint
may be viewed by the user. When the setpoint is ramping, RAMPING will be
shown in the 3rd display when the actual (ramping) setpoint is displayed.
When the target setpoint is being shown, RAMPING will
not
appear. Pressing
the
DISPLAY
key will scroll the 2nd display as follows:
• From the target setpoint to the actual (ramping) setpoint;
• To the deviation from setpoint;
• To the output level; and
• Back to the target setpoint.
Note that when ramping, the deviation indication is with respect to the target
setpoint.
The ramp-to-setpoint function is triggered by one of three conditions:
1. Upon power up, if the 535 powers up in automatic control, then the setpoint
will ramp from the process variable value to the setpoint value at the specified
rate.
2. On a transfer from manual to automatic control the setpoint will ramp from the
process variable value to the setpoint value at the specified rate.
3. On any setpoint change, the setpoint will ramp from the current setpoint to the
new target setpoint. When triggered, the display will automatically change to
indicate the ramping setpoint.
Software Configuration
1. Go to the
PV1 INPUT
menu.
2. Set the
SP RAMP
parameter to the desired rate of change.
P. INPUT LINEARIZATION
Thermocouple and RTD Linearization
For a thermocouple or RTD input, the incoming signal is automatically linearized.
The 535 has lookup tables that it uses to provide an accurate reading of the
temperature being sensed.
Square Root Linearization
Many flow transmitters generate a nonlinear signal corresponding to the flow
being measured. To linearize this signal for use by the 535, the square root of
the signal must be calculated. The 535 has the capability to perform this square
root linearization.
For the first 1% of the input span, the input is treated in a linear fashion. Then it
is a calculated value, using the formula in
Figure 7.17.
