YOKOGAWA wt3000, Руководство пользователя, Страница: 152 / 384

5-16
IM 760301-01E
The user-defined functions allow you to determine physical values other than those of
the measurement functions by combining operands. The measurement functions that
can be assigned to the efficiency equation (section 5.7) are fixed to power and motor
output. However, by using the user-defined function, an equation consisting of
measurement functions other than power and motor output can be set up to determine
ratios other than efficiency.
• On WT3000s with firmware versions 1.XX or 2.XX, equations (F1 to F20) cannot be
placed inside another equation (F1 to F20).
• On WT3000s with firmware version 3.01 or later, user-defined equations with a
smaller equation number can be used as operands in a user-defined equation. For
example, F1( ) + F2( ) can be defined as an equation for user-defined function F3.
This allows equations that would otherwise exceed 50 characters in length to be
computed. For example, set equations in F1 and F2, and define F3 as F1( )+F2( ) or
F1( )/F2( ). This feature is also convenient when defining multiple equations that
include common operands. For example, set common operands in F1, and define
F4=F3( )/F1( ), F5=F4( )/F1( ). Note that if you enter an equation number that is
greater than equal to its own number, correct results will not be obtained. For
example, if you set user-defined function F3 to F1( )+F3( ) or F1( )+F4( ), the
computed result displays no data [- - - - - - -] or overflow [- OF -].
• On WT3000s with firmware version 4.02 or later, if you set the measurement period to
ASSP (Average for the Synchronous Source Period), regardless of the selected
voltage or current modes, computations for all voltage and current modes (RMS,
MEAN, DC, and RMEAN) can be performed simultaneously.
• Operators
The following operators can be used to create an equation.
Operator Example Description
+, –, *, / U(E1,OR1) – U(E2,OR1) Basic arithmetic of the measurement functions
ABS ABS(P(E1,ORT) + P(E2,ORT)) Absolute value of the measurement function
SQR SQR(I(E1,OR0)) Square of the measurement function
SQRT SQRT(ABS(I(E1,OR3))) Square root of the measurement functions
LOG LOG(U(E1,OR25)) Natural log of the measurement functions
LOG10 LOG10(U(E1,OR25)) Common log of the measurement function
EXP EXP(U(E1,OR12)) Exponent of the measurement function
NEG NEG(U(E1,OR12)) Negation of the measurement function
Number and Type of Characters That Can Be Used in the Equation
• Number of characters
50 characters or less
• Types of characters
Characters that are displayed on the keyboard and spaces
• Equation Examples
When determining the rms value of the harmonic components of the voltage signal of
input element 2.
(Total rms value of the voltage)
2
– (Rms value of the fundamental wave of the voltage)
2
SQRT(SQR(U(E2, ORT)) – SQR(U(E2, OR1)))
Note
If an operand in the equation is undetermined, the computation result displays [-------] (no
data). For example, this occurs if a measurement function of a delta computation is in the
equation, but the delta computation is turned OFF or a measurement function of an element
that is installed is in the equation.
5.4 Setting the User-Defined Function