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It’s a computer &
digital oscilloscope
all in one package!
You can control the TDS 7054 with the
touch screen, the front panel controls
or via the mouse. The scope operates
under Windows 98 and any Windows
software can be run on it at the same
time as the scope is being used.
Tektronix TDS7504 Digital
Phosphor Oscilloscope
While many people tend to be blase about
the march of technology, it is difficult not to
be impressed by the latest offering from
Tektronix, the TDS7000 range. These are
Tek’s Digital Phosphor Oscilloscopes, based
on a colour LCD display and having very
high sampling rates.
By LEO SIMPSON
Our review machine was the Tektronix TDS7000, a 500MHz, 5 Gigasample/second, 4-channel oscilloscope
with an amazing range of facilities.
In fact, it is almost possible to ignore
the oscilloscope’s performance while
you familiarise yourself with the com72 Silicon Chip
puter facilities. Did we say computer?
Well, yes. This machine is more of a
computer than oscilloscope.
In fact, the TDS 7000 series can be
regarded as a Windows-based computer which happens to have a very high
performance digital oscilloscope built
into the same box. And rather a big
and heavy box it is, measuring 277mm
high, 483mm wide and 425mm deep
and weighing in at 19kg, which includes the accessory pouch on the top.
It is a Pentium Celeron 500MHz
computer, with a 6GB hard drive, 128
megabytes of RAM, a 3.5-inch 1.44MB
floppy drive and a CD-ROM drive
(rear-mounted). It also has approximately 100KB of non-volatile RAM for
waveform storage (up to two 50,000
point waveforms can be stored).
The TDS 7054 comes loaded with
Windows-98 and virtually any Windows based program can be run on the
machine. The front panel display is
an active-matrix liquid crystal display
(LCD), measur
ing 211mm wide by
158mm high and its display resolution is 640 x 480 pixels. Its contrast
Fig.1: this is a typical screen of the TDS 7054 with two
traces displayed and running at the default sampling rate,
as defined by the timebase setting. Here the timebase is
quite slow at 1ms/div and the sampling rate is relatively
slow too, at 50kS/sec. This defines the resolution of the
waveforms.
Fig.3: Again, same waveforms as in Fig.2 but now all the
amplitude measurement options are shown in the lower
half of the screen. Note that some measurement options
have been selected for both traces.
ratio is 150:1 and the refresh rate is
60Hz. It runs in Windows SVGA highcolor mode (16-bit).
What else has it got? A Creative
SoundBlaster PCI 64V sound card
and a huge array of sockets on the rear
panel. These include two PS-2 sockets
for a keyboard and mouse, a USB (uni
versal serial bus) socket for a mouse,
two video out sockets (SVGA & VGA),
a GPIB (general purpose instrument
bus) socket, a PCMCIA card slot, a
parallel printer port, an RJ-45 ethernet socket (supports 10base-T and
100base-T) and sound card inputs.
The oscilloscope is a 4-channel,
500MHz 5 Gigasample/second digital
Fig.2: Here are the same waveforms as in Fig.1 but now
the sampling rate has been wound up to 5MS/sec and this
shows a lot more resolution. Notice the overshoots on the
lower trace. Also present on this screen are horizontal
cursors and their voltage settings. Note that this shows
buttons at the top instead of the Windows menu bar.
Fig.4: If you don’t want to go through the process of
selecting measurement options for a waveform, you can
do it via the “snap-shot” mode, as shown here for channel
2.
storage Digital Phosphor Oscilloscope
(DPO). DPO is a Tektronix patented
system for showing trace intensity
modulation similar to that inherent
in the CRT phosphor of conventional
analog scopes.
Let’s make a comment on DPO right
at the start. We think it is an awkward
name and one which does not really
do justice to the scope. Sure, it does
show intensity modulation but it is
still not the same as an analog scope
because the traces still show the
quantisation jitter or noise inherent in
any digital scope. At the same time,
it has all the advantages of a very fast
digital scope.
Having criticised the DPO name, we
must say that the real benefit of this
scope is that the sampling rate is not
locked to the timebase as it is in most
other digital scopes. This normally
means that waveforms captured at low
timebase speeds are limited to very
low sample rates. However, we are
getting ahead of matters. Let’s have a
look at the control panel.
Here again, there are major differences between the Tektronix TDS 7000
series and other digital scopes.
For a start, each of the four input
channels has its own vertical sensitivity and position controls, as well as a
button to select an input impedance of
November 2000 73
Fig.5: Same waveforms as in Fig.4 but the timebase and
vertical settings have been changed. This is the snapshot
for channel 1. Note that the timebase is twice as long as
Fig.4 and so the sampling rate is halved.
1MΩ or 50Ω, the latter being selected
when active probes are in use.
Second, the horizontal input also
has its own knobs for timebase, delay
and resolution. Triggering is controlled by an array of buttons plus the
level control. All of these controls are
backed up by indicator lights, so that
no matter what happens, you should
be able to work out the scope settings
by looking at the indicator lights and
the various settings shown on the
LCD screen.
All of this is very important because all functions are settable via the
scope’s touch screen. And when you
touch the screen or use the mouse,
say to change a trigger setting, not
only does it register on the screen
but it also shows on the panel lights,
where applicable. That is a big advance in scope usability. It means that
by looking at the screen readings for
sensitivity, etc and the front panel
lights, you can always get a picture
of what the scope is doing.
On-screen help
Not only that, the TDS 7000 series
has also dispensed with multi-level
on-screen menus. Hooray to that because multi-level menus are hard to
use, particularly if you don’t use the
scope on a regular basis.
Even better, you have on-screen help
for any function selectable on screen,
which means virtually everything.
Better still, you can read the on-screen
help while you use the scope. How? By
using an external SVGA monitor (Ah,
so that’s what the extra VGA socket is
74 Silicon Chip
Fig.6: There are range of options in the display mode,
enabling you to select different coloured traces for each
channel, traditional green, gray, temperature distribution
or spectral distribution.
for). Well actually, as already noted,
there are two video sockets. One is a
VGA socket and it is only used for the
scope display. The SVGA socket, on
the other hand, can be used to display
any Windows application you might
run, such as Word, Excel, Internet
Explorer etc.
For example, when I started doing
this review I used Wordpad on the
second screen, using the keyboard and
mouse in the normal way and then,
if I wanted to change a setting on the
scope, I could move the mouse from
the SVGA screen to the scope screen,
make the setting on a drop-down
menu or button, and then flick back
to the word processor to continue
writing.
Want to write some commentary on
the scope screen to annotate a waveform? Sure, just use the on-screen
keyboard directly, or move the cursor
with the mouse and then type on the
keyboard. Want to save a waveform?
Easy. Decide whether you want the
full screen or just the graticule, hit
Control C and then paste it into
whatever program you want. Or you
can drop it into Windows Paint and
save it as bitmap (.bmp) file. That’s
how all the waveforms shown here
were saved.
Back to the scope now. You can operate it like a Windows program, with
drop-down menus from the task bar at
the top or you can use menu buttons
along the top. Either way, you can
make all settings via the touch screen
or use the mouse, as noted above.
Having used both, I found myself
preferring the mouse at it seems to be
faster and easier, particularly when
selecting from the drop-down menus.
Measurement options
Measurements are easy and highly
flexible. Here, when you touch the
“Measure”, the scope graticule is
vertically compressed so that half
the screen now shows measurement
options. For example, for amplitude
measurements there are 12 options
such as peak-peak, RMS, positive and
negative undershoot.
You can also select which of the
four channels you want to measure
and a total of eight different measurements, enable statistics calculations
on any of the measurements (mean &
standard deviation etc; after all, they
do vary all the time) set up reference
levels, gating and so on. Fig.3 shows
the Measurement screen and you can
see that measurements have been
selected for both channels.
Another screen gives nine time
measurement options such as frequency, period and duty cycle, while
yet another gives another four measurement options and a third screen
gives 12 histogram options.
Maybe you don’t want to go
through all the business of selecting
measurements for each channel. In
that case you simply select “snapshot” and it gives a bunch of measurements for Ch1 or any of the other
three. Fig.5 shows a snapshot group
for Channel 1, while Fig.4 shows a
snapshot group for a similar signal
but on Channel 2.
Fig.7: Quite a few mathematical functions are possible:
Shown here are the four predefined expressions but you
can also define your own as well as the spectral analyses.
We’ve selected Ch1 multiplied by Ch2.
The TDS 7000 also has a mathematics (MATH) mode. This enables you
to display the result of a mathematics
calculation as another trace on the
screen. Four predefined expressions
are available: Ch1 - Ch2, Ch3 - Ch4,
Ch1 x Ch2 and Ch3 x Ch4. You can
also do spectral analyses of waveforms
in both frequency and time domains.
Again, this is where this scope excels
because while the FFT functions are
locked to the sampling rate, they are
not locked to the timebase. So you
can do a more detailed analysis than
would otherwise be possible.
Time did not permit us to delve into
these functions at all but clearly there a
large number of options available and
you can use as many as four different
Fig.8: And here is the result of the Ch1 x Ch2 expression
selected on Fig.7, shown here as the red trace. This can
be very useful when monitoring instantaneous power in a
circuit.
spectral analysers simultaneously.
Nor could we really do justice to all
the other features of this multifaceted
machine. We only had the machine for
a few days and in that time you can
really only gain a brief acquaintance
- you would need weeks to learn and
be really adept with all the functions
and features.
However, in the brief time that we
had the Tektronix TDS 7054 we continually found ourselves being impressed
with its many features and its general
ease of use. This is high praise for the
designers because it is very difficult
to combine very high performance, a
vast range of operating features and
most of all, ease of use.
Still, we’re not sure whether to
regard it as high performance scope
with a Windows computer built in or
a Windows computer which just happens to contain a high performance
scope. Tek
tronix would no doubt
prefer to think of it as the former.
And whether you are in the market for a costly machine such as this
or whether you are just interested
in oscilloscopes, we think the TDS
7000 range is the precursor for digital
scopes of the future - one day they
will all operate under a Windows (or
similar) environment. But the TDS
7000 series does it now!
For further information on product
availability and prices, contact Tek
tronix on (02) 9888 0100 or see their
website at www.tektronix.com SC
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November 2000 75
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