1 Introduction to TDS 1012 Digital Osciloscope This laboratory exercise is designed as a brief overview of the features of the TDS 1012 digital osciloscope. The osciloscope has long been one of the most important tools in any physics or electronics laboratory. The main purpose of an osciloscope is to display a graph of input voltage on the vertical axis as a function of time on the horizontals axis. As with any graph you need to have the ability to adjust the scale of the vertical and horizontal axis. The VERTICAL and HORIZONTAL sections of the controls alow you to make these adjustments. The osciloscope can display graphs of signals that vary rapidly. This requires a special trigger circuit and the TRIGER controls form a major part of the controls. The trigger has to decide where to "start" the plot. This is usualy set to the point when the voltage reaches a certain value when it is increasing (positive slope) or decreasing (negative slope). The trigger level is shown on the scren as a smal triangle. The digital osciloscope is a recent development, which has added many new features to this important laboratory device. Most of the butons above the VERTICAL and HORIZONTAL controls and to the right of the scren alow the user to make use of these digital features. 2 Introduction: TDS 1012 Digital Osciloscope Read through each section, perform the suggested operations and answer the questions. You can?t break anything so fel fre to explore the controls. The instructions are sketchy, so if you can?t figure something out, ask your instructor. Procedure: 1. Connect the MAIN OUT of the Wavetek Function Generator to channel 1 (CH 1) of the osciloscope and connect the AUX OUT to channel 2 (CH 2). Set the Wavetek to frequency = 1.0 kHz, Vpp = 4.0 volts, function = sine wave, amplitude modulation = OF and DC OFSET = 0. 2. Turn on the osciloscope and pres the AUTOSET button. This makes the necesary adjustments to the osciloscope so you should be able to se the waveforms of a sine wave in channel 1 and a square wave in channel 2. These waveforms are a plot of voltage vs. time with scale information at the bottom of the scren. The scale information is given in units of volts or seconds per division where division refers to the lines on the scren that are about a cm apart. 3. Please note that the AUTOSET button is very useful to get you started, but it changes a number of setings, so it should not be used al of the time. 4. Experiment to determine the efect of the POSITION and VOLTS/DIV knobs for both channel 1 and channel 2. Note that the volts per division for each channel appear at the bottom left of the scren. 5. Pres the CH1 MENU button several times and note that the CH1 waveform is toggled on and of. Presing the CH1 MENU also gives you some input options on the right side of the scren, which can be activated by presing the buttons beside them. Try each of these options. Asignment 1. ? Draw a sketch of the osciloscope scren with the two signals described above. Sketch in the grid lines. Record the volt/div for each signal and time/div at the bottom of the scren. Measure the number of vertical and horizontal divisions (including fractional parts) and determine the amplitude and period for each of the signals. Show the calculations. Coupling ? DC coupling pases both AC and DC components of the signal; AC blocks the DC component and GND (ground) disconnects the input signal. Under "TRIGER" pres the menu button and change the Coupling to AC. Asignment 2 ? Adjust the DC OFSET on the Wavetek to 1.0 volt and look at channel 1 with AC and DC coupling. Describe what happens and why. Return the DC OFSET on the function generator to 0. BW Limit ? limits the bandwidth to reduce display noise. Volts/DIV ? selects the resolution (Coarse or Fine) of the VOLTS/DIV knob. Note the efect of turning the knob when this is set for Coarse and Fine (notice the volts/DIV in the lower left corners of the scren). 3 Probe ? A probe is a special connector that reduces a high voltage to a value that the osciloscope can handle. The Probe option alows you to tel the osciloscope that a special probe is atached. The Probe should be set for 1x in this laboratory since we wil not use special probes. The channel 2 menu works the same as for channel 1. Trigger Control - The function of the trigger control is to set the initial point in time for the waveform to be displayed. Usualy this is a certain rising or faling voltage level on channel 1 or channel 2. If the trigger is not set properly then the display wil be unstable. Experiment with adjustments to the trigger level and notice how the display can move and become unstable. Pres the TRIGER MENU button and experiment with the diferent menu options. Asignment 3 ? Describe what happens when the TRIGER slope is switched from ?rising? to ?falling? and explain why. Horizontal Controls This section controls the horizontal axis, which is time. Notice the efect of turning the POSITION knob and the SEC/DIV knob. It is important to se that the SEC/DIV scale information appears at the bottom-center of the scren. The HORIZONTAL MENU alows you to adjust the window zone (leave it on main) and also selects whether the Trigger Level knob adjusts the trigger level (volts) or hold off time (seconds). The hold off time delays the triggering of the waveform for a fixed amount of time. It is generaly beter to leave this option in the ?level? mode. Special Menus ACQUIRE ? The acquire menu gives various options for smoothing the data. Kep in mind that the Wavetek continuously produces sine and square signals. These signals are converted to a digital value and up to 2500 values are stored and displayed. In the sample mode, the osciloscope records one swep, displays it and then records another. In the Peak Detect mode it overlaps succesive sweps. In the Average mode it averages a number of sweps and displays the average. This is usualy slower. It gives a cleaner waveform, but you can be tricked into thinking the waveform is very stable when it is not. CURSOR ? The cursor menu alows you to make measurements of time or voltage from the waveforms using two cursors, which are controled by the ch1 and ch2 vertical 4 position knobs. Push the CURSOR button, set Type to Voltage and Source to CH 1. Two horizontal cursors appear. Use the cursor controls (CH 1 and CH 2 POSITION knobs) to place the cursors on the top and botom of the sine wave. Note that the voltage levels of cursor 1, cursor 2 and the diference betwen them (Delta) appear to the right of the scren. Asignment 4 ? Use the voltage cursors to determine the Vpp of the sine wave and compare this result with the Vpp that the Wavetek display indicates. Asignment 5 ? Use the time cursors to determine the period of the sine wave. From this value, calculate the frequency of the sine wave and compare with the frequency that the Wavetek display indicates. Show your calculations. MEASURE ? The measure menu instructs the osciloscope to make various direct measurements of the signals. When you select ?SOURCE?, you can choose betwen ch1 and ch2. When you select ?TYPE?, you can select the type of measurement (Vpp, Period, Frequency, etc?) Asignment 6 ? Use the MEASURE menu to measure the period, frequency, and Vpp for the sine wave. Compare your results with the answers of Asignment 4 and 5. DISPLAY ? skip SAVE/RECAL ? This menu alows you to save or recal instrument waveforms or instrument setups (which we wil skip). The saved waveforms are refered to as Reference waveform A or B. To save the waveform of channel 1 as Reference waveform A: select Waveforms, Source = CH1, REF = A, and pres Save. To display a reference waveform, use the lowest button to turn Ref A on. Asignment 7 Save the waveform of the sine wave in Ref A. Then change the frequency range on the Wavetek to 200 HZ, which reduces the frequency of the sine wave by a factor of four. Display the saved waveform (Ref A). Draw a sketch of the active waveform and the stored waveform. Return the frequency range of the Wavetek to 1 kHz. UTILITY ? skip HARDCOPY ? skip. This buton can be used to print display if a suitable printer is atached. RUN/STOP ? Can be used to start or stop the waveform acquisition. 5 Reading Data into the Computer The digital scope at each workstation is connected to the workstation computer. The program Open Choice Desktop controls the reading in of the waveform data from the osciloscope. Follow the steps below to read in the waveform from the Power response procedure. Make a plot of the data (voltage vs. time) in Excel. Print out the graph to turn in with your experimental data. 1. Click on the icon to open the program. 2. Select (click on) Waveform Data Capture 3. Select Instrument: a. Select ASCRL1::INSTR b. Click ok 4. Select channels if needed 5. Click on Get Data 6. Click on Copy to Clipboard 7. Paste into spreadsheet 8. Make a plot of the data: voltage vs. time 9. Label graph properly and print out the plot only 6 Measuring Unknown Signals Name:____________________ Teachscope Model #____________ The Teachscope is a device that generates twelve unknown voltage signals. Try to locate each of the paterns listed below. Start with the easy ones and then look for the more dificult ones. Record in each table the channel you found the signal and then report on the measurements requested for each signal. Be sure to include units. Please note that every Teachscope box is diferent so it is important to record the model number of the box you use. square wave channel number maximum voltage minimum voltage frequency (Hz) sine wave (no offset, 5.4 volts peak-peak) channel number maximum voltage minimum voltage frequency (Hz) sine wave (one half-cycle clipped, no offset) channel number maximum voltage minimum voltage frequency (Hz) cycle clipped (positive or negative) 7 +5 VDC channel number ground (with low level noise spikes) channel number sawtooth (long repetition time, positive ofset) channel number maximum voltage minimum voltage repetition time (secs) Triangle wave (positive offset) channel number maximum voltage minimum voltage frequency (Hz) TL pulse (short duration, long repetition time, ground to positive) channel number amplitude (peak volts) repetition time pulse width (nanoseconds) 8 TL pulse (short duration, long repetition time, negative transition) diferentiated square wave (no offset) channel number amplitude (peak volts) repetition time pulse width (nanoseconds) diferentiated square wave (no offset) channel number maximum voltage minimum voltage frequency (Hz) sine wave channel number maximum voltage minimum voltage frequency (Hz) TL pulse (short duty cycle) channel number maximum voltage minimum voltage frequency (Hz) mary ewell Microsoft Word - Oscope_update.doc
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