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Milltronics SF 500 - INSTRUCTION MANUAL
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The PID control function of the SF 500 can be configured to operate in several modes.
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controller output: direct acting
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feedback: rate, load or external
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control: local or remote (ratio) setpoint
PID Setup and Tuning
Proper tuning of the control PID terms is essential to system operation and optimum
performance from the feeder. The recommended procedures for tuning the PID control
terms at initial startup are described in this section.
Initial Start Up
Although the default values of the P, I, D, and F terms suit the majority of applications,
some tuning is necessary.
There are several techniques and procedures for tuning conventional PID controllers.
Some work better depending upon the application. We recommend using closed-loop
cycling for the SF 500 integrator/controller for feed rate control. First, tune the P term
while disabling the I and D terms. Then add and tune the I term, and then the D term.
To outline this procedure:
1.
With the P term set to its default value of 0.400, disable the I, D and F terms by
setting them to 0.000.
2.
Enter a feed rate setpoint that is 30% of the designed maximum flow rate.
3.
Start the pre-feeder and observe the time it takes the pre-feeder to reach setpoint.
Observe the oscillation around setpoint.
4.
Adjust the P term accordingly for consistent oscillation and error. Progressively
decrease the P term value if there is too much oscillation and error. Likewise,
increase the value if the error is not consistent and oscillating around the setpoint.
Refer to fig 1, 2, and 3 below.
Notes:
•
Meet Zero and Span criteria
•
Set controller (P400=1) to manual and adjust the output for 0% flow (using the 4
and 8 keys). Material must not flow through flowmeter.
•
Shut off the prefeed to, or ensure that no material is fed into the flowmeter.
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