Appendix A: Definitions - Emerson EIM 2000 Series User Manual

User Manual
84829 Rev. D

Appendix A: Definitions

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Appendix
Command = 4-20mA analog input position command signal generated by remote
control equipment. Same as position command setpoint. Zero and Full-scale
calibrated by user.
Position = 0-5V valve position analog input signal generated by Hall-effect
Position Sensor (HPS). Zero and Full-scale automatically calibrated by controller
based on LSC and LSO valve travel limit switches.
Feedback = 4-20mA analog output signal for feedback of valve position to remote
control equipment. Zero and Full-scale calibrated by user.
Invert = Inverted calibration of 4-20mA command where close position = 20mA,
and open position = 4mA. Feedback is also inverted.
Deadband = Allowable error tolerance to keep valve stopped, i.e. do not turn
on motor control outputs. Deadband cannot be adjusted by the user. Deadband
has a beginning default value based on selected operating mode (motor starter type)
and then controller automatically adjusts the deadband to obtain the best accuracy.
Default deadband based on motor starter type:
a. Futronic II = +/-1.0% deadband
b. Futronic III = +/-0.25% deadband
c. Futronic IV = +/-0.50% deadband
Error = Difference between Command and Position.
Error = Command-Position
If not Invert and Error = Positive then open valve
If not Invert and Error = Negative then close valve
If Invert and Error = Positive then close valve
If Invert and Error = Negative then open valve
Nonlinearity = Difference between analog input and analog output at current
valve position over the full valve operating range.
Close Coast = Difference between Position when the motor is turned off and
Position when the valve stops moving in the close direction. Coast is caused by
both inertia of the motor and latency of Position update due to analog input
filtering. The controller measures close coast to automatically tune control for
maximum accuracy.
Open Coast = Difference between Position when the motor is turned off and
Position when the valve stops moving in the open direction. The controller
measures open coast to automatically tune control for maximum accuracy.
Modulation Delay = Time between when the motor is turned off until the
motor can be started again. This delay prevents excessive number of starts of the
motor, preventing overheating the motor and premature burnout of the reversing
contactor. Modulation delay also prevents valve plugging when the actuator
reverses direction. If a three phase motor is used, the delay time is 2 seconds or
1800 starts per hour. If a single phase, capacitor start, AC motor is used, then the
delay is 12 seconds or 300 starts per hour. The delay between motor control pulses
while the valve is being jogged to position is automatically reduced to one second.
Appendix
March 2013
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