K_SQRT: Square root

Function description

This function calculates the weighted square root of a numerical value. A division can be defined under which the function issues the value zero.

Taking the square root typically serves to linearize a flow measurement using a throttle device.

and can be configured as additional parameters.

Formula

The function performs the following calculation:

Calculation	Condition

	or

Representation in FBD

Representation:

Representation in LD

Representation:

Representation in IL

Representation:

LD DigitalVariable
K_SQRT WeightingCoefficient, Cutoff
ST OUT

Representation in ST

Representation:

Result := K_SQRT (DigitalVariable, WeightingCoefficient,
                  Cutoff);

Parameter description

Description of input parameters:

Parameter	Data type	Description
DigitalVariable	REAL	Numerical value to process
WeightingCoefficient	REAL	Weighting coefficient
Cutoff	REAL	Division

Description of output parameters:

Parameter	Data type	Description
Result	REAL	Result of the calculation

Runtime error

An error is displayed if a non floating point value is recorded at input or if there is a problem with floating point calculation. In this case the output Result remains unchanged.

NOTE: For a list of all block error codes and values, see Mathematics.

Warning

A warning is given if the Cutoff input is negative. The function block then uses the value 0 for calculation.

EN stands for ENable; it is an optional block input. When the EN input is enabled, an ENO output is set automatically.

If EN = 0, the block is not enabled; its internal program is not executed, and ENO is set to 0.

If EN = 1, the block's internal program is run and ENO is set to 1. If an error occurs, ENO is set to 0.

If the EN input is not connected, it is set automatically to 1.

ENO

ENO stands for Error NOtification; this is the output associated with the optional input EN.

If ENO is set to 0 (because EN = 0 or in case of an execution error):

the status of the function block outputs remains the same as it was during the previous scanning cycle that executed correctly;
the output(s) of the function, as well as the procedures, are set to "0".

REAL

The REAL type is encoded in a 32 bit format.

The possible value ranges are shown in the figure below:

When a result is:

between -1,175494e-38 and 1,175494e-38, it is considered to be a DEN;
less than -3.402824e+38, the symbol -INF (for - infinity) is displayed;
greater than +3.402824e+38, the symbol INF (for + infinity) is displayed;
undefined (square root of a negative number), the symbolNAN is displayed.

NOTE: The IEC 559 standard defines two classes of NAN: the silent NAN (QNAN) and the signaling NAN (SNAN). A QNAN is a NAN with a most significant fraction bit while an SNAN is a NAN without a most significant fraction bit (bit number 22). QNANs can be propagated via most arithmetic operations without throwing an exception. As for SNANs, they generally indicate n invalid operation when they are used as operands in arithmetic operations (see %SW17 and %S18).

NOTE: When a DEN (non-standardized number) is used as an operand, the result is not significant.