GE PACSystems RX7i

Chapter 4. Ladder Diagram (LD) Programming
GFK-2950C February 2018 63
4.1.1 Exponential/Logarithmic Functions
When an exponential or logarithmic function receives power flow, it performs the appropriate
operation on the REAL or LREAL input value(s) and places the result in output Q.
The inverse natural log (EXP)
function raises e to the power
specified by IN.
The Power of X (EXPT) function
raises the value of input IN1 to
the power specified by the value
IN2.
The Base 10 Logarithm (LOG)
function calculates the base 10
logarithm of IN.
The Natural Logarithm (LN)
function calculates the logarithm
of IN.
The power flow output is energized when the function is performed, unless Overflow or one of the
following invalid conditions occurs:
■ IN < 0, for LOG or LN
■ IN1 < 0, for EXPT
■ IN is negative infinity, for EXP
■ IN, IN1, or IN2 is a NaN (Not a Number)
Operands of the Exponential/Logarithmic Functions
Parameter
Description
Allowed Operands
Optional
IN or IN1
For EXP, LOG, and LN, IN contains the REAL or LREAL value
to be operated on.
The EXPT function has two inputs, IN1 and IN2. For EXPT,
IN1 is the base value and IN2 is the exponent.
All except variables
located in %S—%SC
No
IN2 (EXPT)
The REAL or LREAL exponent for EXPT.
All except variables
located in %S—%SC
No
Q
Contains the REAL or LREAL logarithmic/exponential value
of IN or of IN1 and IN2.
All except constants and
variables located in
%S—%SC
No