CSZ EZT-570S, Руководство пользователя

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EZT-570S User Manual
75
The
Prop ortional Band is in the units of measurement for the control loop. On temperature for
example, a proportional band of 10 would be 10 degrees. Thus, as the PV drops below set point by 0
to 10 degrees, the output would go from 0 to 100% for full heat.
The Cool ing PB is measured in % of the proportional band with a range 50-300. If cooling action
should be enhanced then decrease the band. If cooling action is too strong then increase the cooling
band. The value of the cooling proportional band is related to the heating proportional band and its
value remains unchanged throughout any auto tuning procedures. Only the proportional band, TI and
TD factors are determined by auto tune.
The cooling proportional band is typically set at a default value of 100% from the factory as chamber
design balances heating and cooling capacities. Under certain conditions however, it may be
necessary to increase the cooling side response when testing live loads that produce a lot of heat.
The
TI and TD values for reset and rate are both entered in seconds and affect both heating and
cooling response. Large values for TI will slow down the control response while smaller values will
speed up the reset action. Having too large of a value can make the chamber sluggish in response to
process changes while too small of a value can cause oscillation.
A larger TD factor can help reduce overshoot; however, it can also make the output respond too
rapidly to small changes in the process and prevent the chamber from every reaching set point. Too
small of a value will usually result in the chamber getting to set point quickly under small process
changes, but may result in greater than desired overshoot.
The adjustment of
Dead Band is more dependent upon system requirements. If more positive values
of dead band (greater dead band) are used, an unwanted cooling action can be avoided but an
excessive overshoot may occur. If more negative values of dead band (greater overlap) are used, an
excessive overshoot can be minimized but an unwanted cooling action may occur.
Dead band is adjustable in the range of -36.0% to 36.0 % of the heating proportional band. A
negative dead band value provides an overlap between heating and cooling in which both outputs are
active. A positive dead band value provides a dead band area in which neither output is active
around set point. This value is rarely used and it is recommended to leave it at the default value of
0.0.