Three Position Step Control Algorithm; Table 4-21 Procedure For Displaying 3Pstep Motor Position - Honeywell UDC2500 Product Manual

Step Operation
3 Change a value
4 Return to Normal
Display

4.15 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).
See Motor Travel Time (the time it takes the motor to travel from 0 % to 100 %) in
section 3.8.
Motor Position Display

Table 4-21 Procedure for Displaying 3Pstep Motor Position

Step Operation
Access the
1
Displays
4/07
Press
Lower Display = A1S1VA = Alarm 1, Setpoint 1
NOTES:
With 3 position step control, alarms set for "output" will
not function.
MAN, RSP, AND FSAF selections do not have setpoint
values.
To change any alarm setpoint value in the upper display.
or
Lower Lower Lower
Display Display Display
Press
Until you see:
Lower Lower Lower
Upper Display = PV
Display Display Display
Lower Display = OT (The estimated motor position in %)
UDC2500 Universal Digital Controller Product Manual
Monitoring and Operating the Controller
Result
A1S2VA = Alarm 1, Setpoint 2
A2S1VA = Alarm 2, Setpoint 1
A2S2VA = Alarm 2, Setpoint 2
Result
113