Lenze DDS Function library Drive Manuel d'utilisateur télécharger pdf (Page 36)

2.2.15 Sample & Hold (L_SH)

Function library LenzeDrive.lib

Analog signal processing

2−26

LenzeDrive.lib EN 1.7

2.2.15 Sample & Hold (L_SH)

This FB can store analog signals. The stored value is also available after mains disconnection.

S & H

L _ S H

n I n _ a

b L o a d _ b

n O u t _ a

n C u r V a l R e t a i n

Fig. 2−28 Sample & Hold (L_SH)

VariableName DataType SignalType VariableType Note

nIn_a Integer analog/velocity VAR_INPUT

bLoad_b Bool binary VAR_INPUT FALSE = store

nOut_a Integer analog/velocity VAR_OUTPUT

nCurValRetain Integer VAR_GLOBAL RETAIN

Function

 By using bLoad_b = TRUE the signal at nIn_a is switched to nOut_a.

 By using bLoad_b = FALSE the last valid value is stored and output at nOut_a. A signal change

at nIn_a does not produce any change at nOut_a.

 Storing in the case of mains disconnection:

– Set bLoad_b = FALSE, when the supply voltage is switched off (either mains/line supply,

DC−bus, or voltage supply of the control terminals).

– Set bLoad_b = FALSE, when the supply voltage is switched on again (either mains/line

supply, DC−bus, or voltage supply of the control terminals).

Store the present output value after power interruption

[ V A R _ G L O B A L R E T A I N ]

S & H

L _ S H

n I n _ a

b L o a d _ b

n O u t _ a

n C u r V a l R e t a i n

Fig. 2−29 Programming to store the present output value after a supply interruption

Inorder to store the latest value at nOut_a after a supply interruption, you must declare a global

variable of type RETAIN (VAR_GLOBAL RETAIN). Link this variable as shown in Fig. 2−29.

 In this variable, the present value is always stored at nOut_a The variable will hold the value

after a supply interruption.

 When the supply is switched on again, the stored value is read into the FB L_SH from the

variable and applied as the starting value.

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Lenze DDS Function library Drive Manuel d'utilisateur Page 36

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