GW Instek APS-1102 Control Software User Manual - Manual (Page 72)

7 Arbitrary Waveform Editing
59
Embedded constant
Constants shown in Table 7-3 are embedded into "Arbitrary waveform editing tool."
If you use the above stated method to define a constant with the same name as one of the embedded
constants, the definition of that embedded constant is disabled and your definition of values and
formulas become effective.
Table 7-3 Embedded Constant
Expression Meaning Value
pi Circular constant 3.1415926535898
c Speed of light 2.99792458e8
h Planck's constant 6.6260755e-34
k Boltzmann's constant 1.380658e-23
r Euler's constant 0.57721566490153
Function
In formula input section [Y=], provide a formula in Y=f(X) format.
[X] is a value to be changed within the range of the page. For example, if the range in a page is 1000 to
2000, [X] in the formula changes between 1000 to 2000.
The value of [X] in the formula is affected by the unit of horizontal axis ( 7.12.1) which is set on the
unit setting screen.
For example, consider the following cases that a sine wave is provided by a formula like [Y=] [sin(X)].
Radian expression is used for the arguments of the sin() function.
Assume that the unit of horizontal axis is [Address] and the range is from 0 to 4096. Since
4096=2*

*651.8986

, the result of this formula is a sine wave with about 652 waves.
In the case that the unit of horizontal axis is [Time] and the frequency is 500 Hz, the cycle is 2 ms and
2e-3=2*

*0.0003183

. Then the result of this formula is a value that changes just little around 0° of
the sine wave.
In the case that the unit of the vertical axis is [User] and the range is from 0 to 1, 1=2*

*0.1591

.
Then, the result of this formula is a waveform of about 1/6 first half of a sine wave.
To obtain 1 wave of sine wave from the simplest formula, set the unit of the horizontal axis to [User]
and [Min-Max] to 0 to 6.283185.
The value of [Y=] in the formula is affected by the unit of vertical axis ( 7.12.2) which is set on the
system setting screen.
Consider the following cases that a sine wave is provided by a formula like [Y=] [sin(X)]. The value of
sin() function is ±1.
In the case that the unit of a vertical axis is [Data], its range is

32768 to +32767. Therefore, the result
of this formula is a waveform around 0 with very small amplitude.
In the case that the unit of a vertical axis is [ACV] and the amplitude is 20 Vp-p, its range is ±10.
Therefore, the result of this formula is a sine wave of 1/10 of full scale.
In the case that the unit of a vertical axis is [User] and its range is

1 to +1, the result of this formula is
a full scale sine wave.
If the result of calculation exceeds +/

full scale, the waveform clips at +/

full scale.