XT2640 Operating Manual
13 July 2016
Page 67 of 187
Alternatively you can make a record of the SCOPE VIEW screen by saving an image of it to a graphic file on an external USB drive
attached to the front panel USB port. Note that the trigger configuration and any bandwidth limitation are included on the screen,
enabling these to be included in the recorded image.
Briefly, this is performed by –
1.
Insert the drive into the front panel USB port and wait for it to be READY.
2.
Display the screen to be recorded.
3.
Press the DRIVE INFO area of the screen, the screen shows the file export/import screen.
4.
Press the SCREEN IMAGE button. The screen changes to allowing you to enter a file name.
5.
Enter the desired file name (the extension is automatically provided).
6.
If the file already exists then you are prompted to respond if you wish to overwrite it or not.
7.
The file is then written.
12.11
PERFORMING
EN50564
LOW
POWER
MEASUREMENTS
–
THE
STBY
POWER
SCREEN
The STBY POWER Screen gives you the ability to configure, start/stop, and view the results of low power measurements in
accordance with EN50564:2011. The use of this screen is detailed in section 17.
12.12
PERFORMING
EN61000
‐
3
‐
2
OR
‐
12
ASSESSMENTS
–
THE
ASSESS
EUT
SCREEN
The ASSESS EUT Screen gives you the ability to configure and perform EUT assessments compliant with EN61000‐3‐2 or ‐12. The
use of this screen is detailed in section 18.
12.13
PERFORMING
AND
VIEWING
A
SPECTRUM
ANALYSIS
–
THE
SPECTRUM
SCREEN
This is only available if option H500 is installed and only if the XT2640 is configured for spectrum analysis by the MEAS MODE
setting on the MEAS CONFIG screen.
Normally the XT2640 is used for general power analysis and harmonic analysis purposes, but in some situations it may be desirable
to perform spectrum analysis on the signals instead of harmonic analysis. If option H500 is installed, then this is possible in the
XT2640.
An example of this is for measuring distortion in accordance with some avionics specifications which require a spectral analysis to be
performed with 20Hz resolution for frequencies up to 150kHz (note that this maximum frequency requires W channel types as it is
above the 115kHz upper limit for L, S or A channel types). The XT2640 can be configured to measure the spectrum of all signals at
the same time to this requirement.
Note:
SPECTRUM mode is a single VPA mode; only one VPA can be used in spectrum analysis mode.
You do not have to be viewing the SPECTRUM screen for spectrum data to be measured.
When configured for spectrum analysis, the XT2640 still performs normal power analysis (unchanged) and also harmonic
analysis (but limited to the fundamental component).
The XT2640 is a single measurement DFT based spectrum analyzer not a ‘scanning’ type spectrum analyzer. There are two
phases to a spectrum analysis –
MEASURING. During this phase all signals are sampled and these samples are collected. This phase is one period
of the user set resolution frequency in length (for example if the frequency resolution is set for 1Hz then this
phase takes 1 second).
PROCESSING. After collecting the samples during the MEASURING phase the XT2640 then processes these
samples by DFT analysis to produce the desired spectrum. There is no measurement being performed for
spectrum analysis during this phase. Once this phase is completed the results are available for display (or
exporting to a file) and a new MEASURING phase is started.
There is only a single MEASURING sample collection phase and only a single PROCESSING phase per spectrum
analysis update cycle. The analysis of every spectral point analyzed is performed on the same set of samples in its
entirety so there are no discontinuities in the analyzed results.
12.13.1
CONFIGURING
SPECTRUM
ANALYSIS
Spectrum Analysis is configured by you making the following changes to the normal configuration on the MEAS CONFIG screen –
Set the OPERATING MODE to SPECTRUM
Set the desired SPECTRUM frequency resolution and maximum frequency.
All other settings on that screen are as previously described.
12.13.2
OPTIMISING
CONFIGURATION
FOR
SPECTRUM
MEASUREMENTS
The XT2640 performs both the power analysis and spectral analysis at the same time. In most cases you do not need to consider the
compromises involved in this, but if you wish to perform spectrum analysis with a frequency resolution less than the inverse of the
power analysis measurement period then it should be considered whether to optimize for the spectrum analysis rather than for the
