User manual

38
Analysis
multiplied and the impact is damped. The soft menu item
WINDOW allows you to choose from the following window
functions:
HANNING: The Hanning window function is
bell-shaped. In contrast to the Hamming win-
dow function, it is equal to zero at the margin of
the measurement interval. Therefore the noise level is re-
duced in the spectrum and the width of the spectral lines
is increased. This function is useful for a precise amplitude
measurement of a period signal, for instance.
HAMMING: The Hamming window func-
tion is bell-shaped. In contrast to the Hanning
and Blackman window function, it is not equal
to zero at the margin of the measurement interval. There-
fore the height of the noise level in the spectrum is grea-
ter than with the Hanning and Blackman window function
but less than with the square wave window function. How-
ever, the spectral lines not as wide as in other bell-shaped
functions. This function is useful for a precise amplitude
measurement of a period signal, for instance.
BLACKMAN: The Blackman window function
is bell-shaped and its waveform features the
steepest fall-off among the available functions.
Is is zero at both ends of the measurement interval. The
Blackman window function allows you to measure the am-
plitudeswithhighaccuracy.However,itismoredifcult
to determine the frequency due to the wide spectral lines.
This function is useful for a precise amplitude measure-
ment of a period signal, for instance.
RECTANGLE: The rectangle function multiplies
all points by 1. This results in a high frequency
accuracy with narrow spectral lines and incre-
ased noise. This function can be used for pulse
response tests with start and end values of zero.
The menu item Y-SCALING allows you to scale the FFT in
the amplitude logarithmically (dBm / dBV) or linear (V
eff
).
The unit dBm (Decibel-Milliwatt) refers to 1mW. The unit
dBV (Decibel-Volt) refers to 1V
eff
. The displayed values re-
fer to a 50Ω terminating resistor. You can use an external
terminating resistor parallel to the high impedance input.
You can deactivate the FFT function by pressing the soft
menu key FFT OFF or pressing the FFT key on the control
panel again.
9.3 Quick View
Pressing the QUICKVIEW key
10
in the ANALYZE sec-
tion activates several basic automatic measurements. The
QUICK VIEW function allows a quick overview of the typi-
cal signal size. Measurement results are displayed at the
bottom of the screen and with a cursor on the signal. The
followingvemeasurementvaluesaredisplayeddirectlyin
the signal:
❙ Maximum voltage (V
p+
)
❙ Mean voltage (Mean)
❙ Minimum voltage (V
p-
)
❙ Rise time (t
r
)
❙ Fall time (t
f
)
The following ten measurement values are displayed at the
bottom of the screen:
❙ RMS value
Period
❙ Peak to peak voltage
Frequency
❙ Amplitude
Number of positive /slopes
❙ Pos. pulse width
Neg. pulse width
❙ Pos. duty ratio
Neg. duty ratio
Pressing the AUTO MEASURE key allows you to change
the six measurement parameters on the bottom right. You
may undo these changes by choosing RESET or restore
the default setting. Only one channel can be active in the
Quickview mode. All measurements will be performed on
the active channel. Pressing the QUICK VIEW key again
switched off the function.
9.4 PASS/FAIL Test Based on Masks
The Pass/Fail test allows you to evaluate if a signal is located
withindenedlimits.Thislimitsaresetbyaso-calledmask.
If the signal exceeds the mask, there is an error. These er-
rors will be displayed together with successful sweeps and
the total of all sweeps at the bottom of the screen. It is also
possible to perform certain actions if errors are discovered.
Press the QUICKVIEW key
10
in the ANALYZE section of
the control panel and press the soft menu key PASS/FAIL
to activate the mode which opens a menu to set and use
the mask test. Prior to starting the test by pressing the top
soft menu key TEST ON/OFF, it is necessary to generate
or load a mask and to select an action. To generate a new
mask, press the soft menu key NEW MASK. Masks are dis-
played as light gray curves/waveforms on the screen. If a
mask was copied or loaded, you can use menu items to
change the expansion of the signal form and consequently
the limits for the test. In the menu that opens you can use
Fig. 9.9: PASS/FAIL mask test.