Monitoring and Operating the Controller
4.14 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 which is an
estimated motor position since there is no slidewire 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 output display is shown to the nearest percent
(that is, no decimal).
See Motor Travel Time (the time it takes the motor to travel from 0 % to 100 %) in
section 3.8.
Motor Position Display
Table 4-20 Procedure for Displaying 3Pstep Motor Position
Step Operation Press Result
1
Access the
Displays
Lower
Display
Lower
Display
Lower
Display
Until you see:
Upper Display = PV
Lower Display = OT (The estimated motor position in %)
120 UDC3200 Universal Digital Controller Product Manual 12/04
To Next Page
Loading...
