Three Position Step Control Algorithm - Honeywell UDC2800 Product Manual

Chapter 5 - Monitoring and Operating the Controller
Step Operation
3 Change a
value
4 Enter the
value
5 Return to
Normal
Display

Three Position Step Control Algorithm

209
Press
Function key
Increment key or
Decrement key
Function key
Lower Display
key
Introduction
The Three Position Step Control algorithm allows the control of a
valve (or other actuator) with an electric motor driven by two
controller output relays; one to move the motor upscale, the other to
move it downscale, without a feedback slidewire linked to the motor
shaft.
Estimated Motor Position
The Three Position Step control algorithm provides an output display
which is an estimated motor position since there is no slidewire
feedback.
Although this output indication is only accurate to a few percent,
n
it is corrected each time the controller drives the motor to one of
its stops (0 % or 100 %).
It avoids all the control problems associated with the feedback
n
slidewire (wear, dirt, and noise).
When operating in this algorithm, the output display is shown to
n
the nearest percent (that is, no decimal).
See Output Set Up Group for more information.
Result
Enter in the first selection of the selected
Alarm Setpoint
Change any alarm setpoint value.
Enter the value made into memory.
Exit the set up mode, and returns to the main
screen.