The following is a structure diagram of the STEP3 block:
Behavior of the OUT_POS and OUT_NEG blocks:
If the deviation (DEV = PV - SP) climbs above dev_hl, the logical output OUT_POS is set to 1. If the deviation is less, OUT_POS is then only set to zero if the deviation is less than dev_hl – hyst.
If the deviation is less than dev_ll, the configured output OUT_NEG is set to 1. If the deviation increases again, OUT_NEG is only set to zero if the deviation exceeds dev_ll + hyst.
NOTE: To ensure that the block functions without errors, the outputs OUT_NEG and OUT_POS should not be inverted.
The STEP3 function block has 2 operating modes available according to the value of the MAN_AUTO parameter:
Operating mode
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MAN_AUTO
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Meaning
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Automatic
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1
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The block calculates the outputs OUT_NEG and OUT_POS itself.
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Halt
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0
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The outputs OUT_NEGandOUT_POS will be held at the last calculated value.
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