Stanford Research Systems SR785, Руководство по эксплуатации и программированию

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4-128 User Math Menu
SR785 Dynamic Signal Analyzer
where r =
√
(x
2
+ y
2
) and
θ
= tan
-1
( y/x ). Sqrt computes all angles positive from 0. The
[X/(1-X)]( ) operator is generally used on real arguments only.
The jOmega( ) operator is simply j
ω
and zeroes the real part and fills the imaginary part
with the value of
ω
(2
π
• frequency) at each point in the array. The frequency is
determined by the span of the operand. A measurement operand (FFT(1) or Time(1))
uses the current frequency span. A Trace operand uses the span of the measurement
which is stored in the Trace.
FFT( ) is the windowed FFT operator. These operations switch the X axis type. The
current window chosen in the [Window] menu is used on the operand before the FFT.
FFTu( ) is the un-windowed FFT operator. The uniform window is always used. The
FFT( ) and FFTu( ) operators do not calibrate their results since their operands are not
necessarily input time records. To use a calibrated FFT, use the measurement operand
FFT(1) or FFT(2).
IFFT( ) is the inverse complex FFT operation. This operation switches the X axis type.
d/dx( ) is the derivative operator. The derivative is performed with respect to the X-axis
bin number, not the x-axis values. For example, to convert d/dx( ) to d/df( ) for a linear
frequency display, divide by the frequency spacing of the bins. In the case where the X-
axis is logarithmic, the function needs to correct for d(logx)/dx. The d/dx( ) operator
requires a smoothing aperture or window.
GrpDly( ) is the group delay operator. Group delay is simply d
θ
/d
ω
. Use [Display
Options]<d/dx Window> to set the aperture. This operator yields valid results for any
complex operand which has a frequency x-axis.
AWt( ) is the A-Weighting operator. This filter is a software version of the input A-
Weight filter. BWt( ) and CWt( ) are the software B-Weighting and C-Weighting
operators. The AWt( ), BWt( ), and CWt( ) operators should only be used on operands
with a frequency x-axis. All three filters conform to ANSI Standard S1.4-1983.
Function String
Move the cursor to the function equation window at the top of the screen. Use the knob
to move the highlighted cursor within the equation. <Delete> will delete the highlighted
term. <Operands> and <Operations> will either insert or replace at the cursor. Use
<Insert/Replace> to switch between insert and replace mode.
[<-] (Backspace) deletes the term before the cursor.
Insert/Replace
Toggle between insert and replace mode while editing a User Function equation.
If editing in insert mode, ‘Ins’ appears in the upper right corner of the edit window. If
editing in replace mode, ‘Rep’ appears.