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132 TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine — 03-04/2013 —TELE-audiovision.com
it was time to throw in the towel and
have a look in the Internet for instruc-
tions. Finding this wasn’t exactly easy
but finally after a tutorial we under-
stood why it didn’t work using the Mi-
croSD card. The firmware is flashed via
the USB port. In order for this to work,
you need DfuSe. This turns out to be
a demo tool to update firmware that
can be downloaded for free from www.
st.com/stonline/stappl/resourceSelec-
tor/app?page=resourceSelector&doct
ype=SW_DEMO&ClassID=1734.
Next the oscilloscope must be start-
ed in Bootloader mode. This is done
by turning on the oscilloscope while
holding down the minus (-) button.
A notification identifying Bootloader
mode appears on the screen and the
DfuSe tool automatically recognizes
the oscilloscope. We recommend that
you first create a backup of the exist-
ing firmware before proceeding. To do
this select “Choose” in the “Upload Ac-
tion” field. Select a name for the file,
for example, “backup.dfu” and click
on “Upload”. Now you can upload al-
ternative firmware at your leisure. We
recommend the “DSO BenF Firmware
v3.61”. This consists of two files, “DSO
BenF APP v3.61.dfu” and “DSO BenF
LIB v3.52.dfu”. Start both of them one
after the other and then restart the
DSO201.
In comparison to a multimeter that
only shows the current voltage level,
an oscilloscope displays the voltage
over a period of time and it makes
analog and digital signal visible. With
a multimeter you can, for example,
check to see if the 14VDC power for an
LNB in horizontal polarization is avail-
able. The 22kHz signal that is used to
switch between an LNB’s low and high
band cannot be seen with a multim-
eter; it’s a square wave signal with a
frequency of 22kHz but with a varying
voltage of less than 1.0 volt. A mul-
timeter would simply continue to dis-
play 14V. An oscilloscope can make a
square wave signal visible and thereby
lets you confirm, for example, if a re-
ceiver is properly producing a 22kHz
signal.
The main feature of an oscilloscope
is its resolution. This describes the fre-
Troubleshooting:
the vertical/lowband
polarization could not
be received from Astra
19.2E. The DSO201
was used to determine
that the multiswitch
was OK
quency that the scope can measure.
Professional analyzers can perform
fast measurements with over 100MHz.
The DSO201 is promoted as having a
bandwidth of 1MHz but this is more of
a marketing value. In reality the band-
width of handheld oscilloscopes should
be reduced by a factor of ten in order
to obtain more realistic values. So how
else would you use the DSO201 in sat-
ellite applications beyond measuring
the 22kHz signal?
As previously mentioned, an os-
cilloscope measures a voltage over
a period of time. This time period is
user-settable, typically from 1µs to 1s
or even longer. This value represents
the time period on the x-axis while the
voltage is represented by the y-axis.
When the end of the x-axis is reached,
the display restarts from the begin-
ning. With analog oscilloscopes with a
CRT, the cathode beam is simply re-
turned to the left side of the screen
and starts moving once again to the
right. Without any additional configu-
ration a very confusing and fidgety
image would be displayed; the return
sweep in the x-axis usually doesn’t
occur at an ideal time for the next
graphic to be offset generated. To
solve this there’s the Trigger function.
This function only allows a new graph-
ic to be generated when the voltage
level reaches a predefined level. With
periodic swings a freeze-frame image
is created. The Trigger function offers
two parameters: the voltage limit val-
ue and the the Trigger type:
- Decreasing
- Increasing
- Single shot
- Continuous
A horizontal marker is raised or low-
ered to mark the voltage level where
the oscilloscope begins a new meas-
urement from the left side of the
screen. The DSO201 can offset the null
point above the x-axis so that signals
that exist before the Trigger point can
be made visible. In order to read the
results, a modern oscilloscope comes
with a Pause function that freezes the
current screen image. Two horizontal
and two vertical markers can then be
placed as needed on the display so
that the voltage and time period can
be read. The calculated minimum and
maximum values along with the delta
value are then displayed. The DSO201