Operation
12/00 UDC2300 Controller Product Manual 67
6.11 Three Position Step Control Algorithm
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 (“OT”) which is an
estimated motor position since the motor is not using any feedback.
• Although this output indication is only accurate to a few percent, 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 slidewire (wear, dirt,
and noise).
• When operating in this algorithm, the estimated “OT” display is shown to the nearest
percent (that is, no decimal).
Refer to Subsection 9.4 to set the Motor Travel Time (the time it takes the motor to travel
from 0 % to 100 %).
Motor Position Display
Table 6-14 Procedure for Displaying 3Pstep Motor Position
Step Operation Press Result
1
Access the
Displays
DISPLAY
Until you see:
Upper Display = PV
Lower Display = OT (The estimated motor position in %)
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