Watlow MLS Manual de usuario descargar pdf (Pagina 115)

Tuning and Control

MLS User’s Guide 103

ANAFAZE also offers the DAC, another optional analog output module

for the MLS. It converts two DZC outputs to two 4-20 mA current

outputs.

Output Digital Filter

The output filter digitally filters the PID control output signal. It has a

range of 0-255 levels, which gives a time constant of 0-127.5 seconds.

Use the output filter if you need to filter out erratic output swings due to

extremely sensitive input signals, like a turbine flow signal or an open

air thermocouple in a dry air gas oven.

The output filter can also enhance PID control. Some processes are very

sensitive and require a high PB, so normal control methods are

ineffective. You can use a smaller PB- and get better control- if you use

the digital filter to reduce the high and low process output swings.

You can also use the filter to reduce output noise when a large derivative

is necessary, or to make badly tuned PID loops and poorly designed

processes behave properly.

Reverse and Direct Action

Reverse action is an output control action in which an increase in the

process variable causes a decrease in the output. Direct action is an

output control action in which an increase in the process variable causes

an increase in the output. Heating applications normally use reverse

action and cooling applications usually use direct action.

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Watlow MLS Manual de usuario Pagina 115