Rockwell-automation T8019 Trusted Process Control Algorithm Software P Manuel d'utilisateur télécharger pdf (Page 8)

Trusted

Process Control Algorithms T8019

Issue 8 Sep 07 PD-T8019 8

1.1. Functions

1.1.1. Square Root Extraction

SQRTX

OUT

MAX

MIN

The Process Variable (PV) is scaled to a value 0…1 according to maximum input value (IP

MAX

) and

minimum input value (IP

MIN

). Out of range values will result in the value being clamped to the range,

i.e. a value greater than maximum input will use the IP

value, similarly a value below the minimum

will use the IP

MIN

value. The square root of the resulting value is then taken and is returned as a

percentage.

i.e.

(

)

(

)

100

IP -IP

IPIP,IPPV,MaxMin

OUT

MINMAX

MINMAXMIN



Note: All inputs (PV, IP

MIN

and IP

MAX

) and the returned value OUT must be real.

If IP

MAX

< IP

MIN

, the function assumes that the values have been reversed and “swap” the values. The

“reversed” error counter is incremented each time the function has to swap the parameters.

If IP

MAX

= IP

MIN

, the function returns a value of zero and increments the “zero divide” error counter to

indicate that a divide by zero error would have occurred.

If PV is not a number (NaN), the function returns a value of zero and increments the “Param” error

counter.

All input range parameters (IP

MIN

and IP

MAX

) must be finite, i.e. not ±infinities or NaNs. Behaviour is not

defined for any other values.

If PV is not a NaN, and an overflow or underflow condition occurs the function returns zero and

increment the corresponding error counter.

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