UM353-1
Operation
March 2003
9-5
Autotuning Considerations:
Process Noise
- could have an effect where the autotuner will not produce periodic valve cycles. The autotuner will
complete an exercise but results may not be satisfactory. This is illustrated in the first autotuning exercise in chart 2
which is the same process as chart 1 but the % HYS was set at 0.5%. If these results occur when the controller %
HYS has been set to A (auto set hysteresis) the controller may be having difficulty deriving a good noise figure and
manual entry of the % HYS parameter should be considered. The % HYS value should be increased to at least
twice the standard deviation value of the noise. In cases where the noise amplitude is extremely large, the filter on
the analog input should be increased to minimize the amplitude of the noise seen by the controller. The value of the
% DEV parameter should be set to at least four time the % HYS value for best results.
Steady State Conditions
- must be established for the process and controller prior to starting an autotune exercise.
The autotuner can be initiated while in manual or auto. Steady state is reached when the present valve signal has
brought the process to its present value, and the setpoint is equal to the process. When not at steady state, valve
cycles will not be symmetrical as illustrated in the second tuning exercise in chart 2 or, as a worse case situation, the
valve may not cycle at all. If the valve is does cycle, although not symmetrically, adequate tuning results will still
be obtained.
Chart 1
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Summary of Contents for Moore 353
Page 2: ...S t o c k C h e c k c o m ...
Page 14: ...Contents UM353 1 xii March 2003 S t o c k C h e c k c o m ...
Page 24: ...Introduction UM353 1 March 2003 1 10 S t o c k C h e c k c o m ...
Page 152: ...LonWorks Communications UM353 1 March 2003 5 4 S t o c k C h e c k c o m ...
Page 164: ...Network Communications UM353 1 6 12 March 2003 S t o c k C h e c k c o m ...
Page 246: ...Operation UM353 1 March 2003 9 8 S t o c k C h e c k c o m ...
Page 254: ...Controller and System Test UM353 1 March 2003 10 8 S t o c k C h e c k c o m ...
Page 282: ...Circuit Description UM353 1 March 2003 13 4 S t o c k C h e c k c o m ...
Page 298: ...Model Designation and Specifications UM353 1 March 2003 14 16 S t o c k C h e c k c o m ...
Page 302: ...Abbreviations And Acronyms UM353 1 15 2 March 2003 S t o c k C h e c k c o m ...
Page 304: ...Warranty UM353 1 W 2 March 2003 S t o c k C h e c k c o m ...