The ONOFF and ONOFF-E blocks perform “two-position status output” as output signal con- version.
TIP The output tracking of ONOFF-E block can be set on the function block detail builder in related to the settings of output processing. The ONOFF block does not have the capability of output tracking.
SEE
ALSO For more information about the output tracking, refer to:
4.5, “Output Tracking” in the Function Blocks Overview (IM 33K03E21-50E)
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ON/OFF Two-Position Control Computation
▼ ON/OFF Hysteresis
The ON/OFF two-position control computation is a control algorithm of the Two-Position ON/OFF Controller Block (ONOFF and ONOFF-E). This algorithm compares the deviation (En=PVn-SVn) with positive or negative ON/OFF hysteresis and outputs the manipulated out-
put value (MV) by 0 % or 100 % based on the comparison result.
The action of the control algorithm varies with the control action directions.
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Control Algorithm in Direct Action
Performs computation that outputs the manipulated output value (MVn) by 100 % (ON) when
the deviation (En) exceeds the positive ON/OFF hysteresis value, and by 0 % (OFF) when the
deviation falls below the negative ON/OFF hysteresis value.
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Control Algorithm in Reverse Action
Performs computation that outputs the manipulated output value (MVn) by 0 % (OFF) when
the deviation (En) exceeds the positive ON/OFF hysteresis value, and by 100 % (ON) when
the deviation falls below the negative ON/OFF hysteresis value.
Direct action Contact output status Manipulated output value
Reverse action Contact output status Manipulated output value
0 - + Time OFF ON OFF ON OFF ON 100 % 0 % 100 % 0 % 100 % 0 % Deviation (En) ON/OFF hysteresis
Figure 1.8-2 Example of the Two-Position ON/OFF Control Action
Use the Function Block Detail Builder to define the ON/OFF hysteresis value. ON/OFF Hysteresis: Engineering unit data within the PV scale span range.
The default is a value equivalent to 1.0 % of the PV scale span.
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Two-Position Status Output
The ONOFF and ONOFF-E blocks perform two-position status output as output signal conver- sion.
For the 2-position status output, a contact output (1 point) or a internal switch (1 point) desig- nated to the OUT terminal is turned ON and OFF according to the manipulated output value (MV).
The following table shows the relationship between the manipulated output value (MV) and contact output status. Note that the manipulated output value (MV) is always expressed in percentage (%).
Table 1.8-4 Relationship between Manipulated Output Value (MV) and Contact Output
Manipulated output value 0 % 0.1 to 49.9 % 50 to 99.9 % 100 %
Contact output status OFF OFF ON ON
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Data Items - ONOFF, ONOFF-E
Table 1.8-5 Data Items of Two-Position ON/OFF Controller Block (ONOFF or ONOFF-E) (1/2)
Data Item Data Name Entry Permittedor Not (*1) Range Default (*2)
MODE Block mode x --- O/S (MAN)
ALRM Alarm status --- NR
Data Item Data Name Entry Permittedor Not (*1) Range Default (*2)
AF Alarm detection specifica-tion --- 0 AOFS Alarm masking specifica-tion --- 0 PV Process variable Δ (*3) PV engineering unit value SL RAW Raw input data Value in the unit at the con-nection destination --- SUM Totalizer value x Engineering unit value 0 SV Set value Δ (*4) Value in the same engi-neering unit as PV SL CSV Cascade setpoint value x Value in the same engi-neering unit as PV SL RSV Remote setpoint value Δ (*5) Value in the same engi-neering unit as PV SL DV Control deviation value Value in the same engi-neering unit as PV 0 VN Input compensation value x --- 0 MV Manipulated output value Δ (*6) 0 to 100 % 0 % RMV Remote manipulated outputvalue Δ (*7) 0 to 100 % 0 % *1: x: Entry is permitted unconditionally
Blank: Entry is not permitted Δ: Entry is permitted conditionally *2: SL: PV scale low limit
*3: Entry is permitted when the data status is CAL *4: Entry is permitted when the data mode is CAS or RCAS *5: Entry is permitted when the block mode is RCAS *6: Entry is permitted when the block mode is MAN *7: Entry is permitted when the block mode is ROUT
Table 1.8-6 Data Items of Two-Position ON/OFF Controller Block (ONOFF or ONOFF-E) (2/2)
Data Item Data Name Entry Permittedor Not (*1) Range (*2) Default (*2)
HH High - high limit alarm set-point x SL to SH SH LL Low - low limit alarm set-point x SL to SH SL PH High - limit alarm setpoint x SL to SH SH PL Low - limit alarm setpoint x SL to SH SL VL Velocity alarm setpoint x ± (SH - SL) SH - SL PVP Velocity-Reference Sample Value in the same engi-neering unit as PV --- DL Deviation alarm setpoint x ± (SH - SL) SH - SL SVH Setpoint high limit x SL to SH SH SVL Setpoint low limit x SL to SH SL CK Compensation gain x -10.000 to 10.000 1.000 CB Compensation bias x --- 0.000 PMV Preset manipulated outputvalue x 0 to 100 % 0 % PSW Preset MV switch x 0, 1, 2, x 0
Data Item Data Name Entry Permittedor Not (*1) Range (*2) Default (*2)
OPMK Operation mark x 0 to 64 0 UAID User application ID x --- 0 SH PV scale high limit Value in the same engi-neering unit as PV --- SL PV scale low limit Value in the same engi-neering unit as PV --- *1: x: Entry is permitted unconditionally
Blank: Entry is not permitted *2: SH: PV scale high limit
SL: PV scale low limit SEE
ALSO For more information about valid block modes of the ONOFF and ONOFF-E blocks, refer to:
1.9
Three-Position ON/OFF Controller Block
(ONOFF-G), Enhanced Three-Position
ON/OFF Controller Block (ONOFF-GE)
The Three-Position ON/OFF Controller Block (ONOFF-G) performs control by ON and OFF actions via two contact outputs. The Enhanced Three-Position ONOFF Controller Block (ON- OFF-GE) functions the same but have the additional capability to connect to FF faceplate blocks and fieldbus function blocks. Moreover, the output terminals for the two contacts can be defined separately so that the two irrelevant channels can be used.