Download Numerical Oscilloscope OX 6152-C

Universitatea POLITEHNICA din Timişoara
Facultatea de Electronică şi Telecomunicaţii
Departamentul Măsurări şi Electronică Optică
www.meo.etc.upt.ro
DIGITAL OSCILLOSCOPE OX 6152-C
1. DIGITAL OSCILLOSCOPE - GENERALITIES
The rapid and ingoing development of electronics and computational techniques has led
to the creation of even more performing measuring instruments. Starting from the analog
oscilloscope there have been developed instruments that integrate circuits and also numerical
functions.
Some digital oscilloscopes contain along the usual circuits of a general use analog
oscilloscope, circuits of connection between the analog and the numerical part (analog to digital
and digital -analog converters) as well as other strictly numeric circuits (storages,
microprocessors). Thus, from the waveform there are taken samples which afterwards are
converted in numbers or codes and then memorized. The samples are again converted in voltages
for the carrying out of the vertical scavenging in order to be displayed on the monitor of the
oscilloscope. Such an oscilloscope has two working topologies: analog when the numeric circuits
are not used and numerical or with storage.
To the most of the digital oscilloscopes the input voltage is converted in numeric format,
the samples are stored, processed and displayed on a screen or transmitted to a computer. The
data can be processed as well after the removal of the signal applied at the oscilloscope input,
transmitted to a computer, or directly printed. The performances of these oscilloscopes depend
mainly on the characteristics of the analog-digital converter.
The digital oscilloscope differs from its analog counterpart in that it “digitizes” or
converts the analog input waveform into a digital signal that is stored in a semiconductor
memory and then converted back into analog form for display on a conventional CRT (CathodeRay Tube). Typical digitizing-scope architecture applies extensive processing power to
waveform acquisition, measurement, and display. A wide variety of plug-in modules are
available for special timing functions and additional channels. The data are displayed most
frequently in the form of individual dots that collectively make up the CRT trace. The vertical
screen position of each dot is given a binary number stored in each memory location, and the
horizontal screen position is derived from the binary address of that memory location. The
number of dots displayed depends on the frequency of the input signal relative to the digitizing
rate, on the memory size and on the rate at which the memory contents are read out. The greater
the frequency of the input signal is with respect to the digitizing rate, the fewer the data points
captured by the oscilloscope memory in a single pass and the fewer the dots available in the
reconstructed waveform.
Digital and analog oscilloscopes each have distinct advantages, but digital scopes are fast
replacing analog scopes because they are more versatile.
2. OSCILLOSCOPE OX 6152-C
This instrument is a digital oscilloscope for laboratory use, intended for the analysis of
the signals encountered in electronics also with a 4,000-count multimeter. The frequency
bandwidth is 150 MHz, with a sampling speed of 1 Gs/s in singular mode and 50 Gs/s in
repetitive mode, also with a 10 bit analog-numeric converter.
The following modes can be used “Multimeter Mode”, “Oscilloscope Mode” and
“Spectrum Analysis Mode”. In this laboratory work we use the “Oscilloscope Mode”,
underlining the specifics of this working mode.
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Universitatea POLITEHNICA din Timişoara
Facultatea de Electronică şi Telecomunicaţii
Departamentul Măsurări şi Electronică Optică
www.meo.etc.upt.ro
The instrument is powered on by a short press of the ON/STANDBY/OFF key. Switch
the instrument to standby (yellow LED flashing inside the key) by one short press. A second
press on the key reactivates the instrument. By a long press (> 3 s) the oscilloscope is powered
off.
A graphical interface similar to a PC's is used to:
-select the advanced functions by means of drop-down menus and the touch-sensitive pad
-act directly on the objects (curves, cursors, etc.) displayed on the screen.
This means that the settings can be modified.
The oscilloscope is designed to operate on a power source delivering 90 to 264 V
(ACrms) at 50 to 60 Hz.
The main control functions are directly accessible using the keys on the front panel and
can be modified using a touch-sensitive pad with the stylus supplied. These can be used for:
selection of menus, validation of functions and movement of symbols appearing on the LCD
screen. The menus at the top of the screen and the submenus selected by the pointer open and are
validated with the stylus. The menus in the curve display area, the command area, the status area
can be opened with the stylus. The stylus can move the symbols displayed in:
1. the main display area: trigger position, position of cursors, reference of the traces
displayed
2. the bargraph: trigger position, position of cursors, position of zoomed area in the
acquisition memory
Place the pointer on the symbol to be moved and keep the stylus pressing
down while you move it to the required position.
It is possible to use the stylus to zoom in the display area: drag to create a rectangle.
The AUTOSET key offers an automatic optimum adjustment on the channels where the
signal is applied. This concerns the following parameters: the coupling, the vertical sensitivity,
the time base, the gradient, the framing and the trigger. The lowest frequency signal is used as
the trigger source. If no trace is detected on the inputs, the autoset will be aborted.
The display elements are presented in figure 1.
Fig. 1. Display elements
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Universitatea POLITEHNICA din Timişoara
Facultatea de Electronică şi Telecomunicaţii
Departamentul Măsurări şi Electronică Optică
www.meo.etc.upt.ro
Up to four signals can be displayed simultaneously on the screen. Two of them are the
input signals CH1 and CH4 and other two can be the result of the mathematical functions Math2
and Math3.
For the displayed signal you can measure the signal parameters using the cursors, or there
are displayed 2 parameters automatically measured (MEASURE menu). The Fast Fourier
Transform for the input signal can be computed and displayed (on a linear or logarithmic scale).
The oscilloscope can be connected directly to a computer, or connected in a network with
computers and other systems. The communication is performed by RS-232 or ETHERNET
interface.
Every function is described in the HELP menu. This menu is on the right corner of the
display.
3. PRACTICAL WORK
3.1. A sinusoidal signal is applied to the input of CH1. From the buttons of the front
panel we execute the necessary adjustments in order to obtain a clear and stable image (time/div,
V/div, triggering). The parameters can be set from the screen as well, from the corresponding
menus. Which is the effect of the button AC/DC/GND?
3.2. We underline the specific functions from menus from the upper side of the screen.
3.3. Measure the parameters of the sinusoidal signal (peak-to-peak voltage, amplitude,
period, frequency) using the cursors (Measure Menu). Then measure and display on the screen
the same parameters using the automatic measuring option.
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Universitatea POLITEHNICA din Timişoara
Facultatea de Electronică şi Telecomunicaţii
Departamentul Măsurări şi Electronică Optică
www.meo.etc.upt.ro
3.4. Apply to the input of CH1 a pulse signal. Measure on the screen the amplitude,
period and the pulse width, using the cursors, then by using the automatic measuring function.
What other parameters can be determined with this function?
3.5. Select the functions from the menu Display. What effect do they have? Select a part
of a signal and visualize it in detail (zoom).
3.6. Use a pulse generator which can generate three signals: synchronization signal
denoted 1, positive and negative pulse signals, denoted 2, respectively 3. Display on the screen
the signals 2 and 3, internally synchronized with 2, then with 3 and finally, externally with 1.
Work in two situations: synchronization on the rising edge, respectively, on falling edge. Draw
the last situation.
3.7. At the inputs CH1 and CH4 we apply the positive and negative pulses from the
previous task. Define the mathematical functions math2= - CH1 and math3=CH1+CH4 and
display all the four signals on the screen. Which other functions can be defined?
3.8. For a sinusoidal signal and then for a rectangular one select the FFT function. For the
displaying FFT, choose a linear scale, then a logarithmic one. What differences can you observe
for the two signals?
3.9. Apply to CH1 a random signal. Save the signal in a file. From the memory, visualize
the saved signal. From memory, bring a second signal for visualization.
3.10. The signal from the internal calibrator is brought to the input by a probe with
attenuation. Measure the peak to peak voltage using the attenuation ratio of 1:1, respectively
10:1. Select the function that allows displaying the same value in both cases.
3.11. Connect the oscilloscope to the computer. Make some remote adjustments using the
SX-METRO application. Make some observations.
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