Burlington County College INSTRUCTION GUIDE. for the. Hewlett Packard. FUNCTION GENERATOR Model #33120A. and. Tektronix

Transcription

1 v1.2 Burlington County College INSTRUCTION GUIDE for the Hewlett Packard FUNCTION GENERATOR Model #33120A and Tektronix OSCILLOSCOPE Model #MSO2004B Summer 2014

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3 Pg. 3 Scope-Gen Handout_pgs1-8_v1.2_SU14.doc INSTRUCTIONS ON USING THE HEWLETT PACKARD FUNCTION GENERATOR and TEKTRONIX OSCILLOSCOPE Objectives: Each student will: 1. Know the function of the three basic sections of the oscilloscope. 2. Be able to operate the HP 33120A Function Generator and set to the desired frequency and amplitude. 3. To obtain a meaningful display on the Tektronix MSO 2004B Oscilloscope using the instructions provided. 4. Be able to measure AC Voltage levels by counting graticules & Mult. by the Vert. V/Div. scale. 5. Know the use of Ch.1 or Ch.2 Inputs; AC & DC Coupling. 6. Be able to measure the period and Frequency of a sine wave signal by counting graticules & Multiplying by the Horizontal Sec./Div. scale. 7. To measure Voltage, Period & Frequency using the Scope s Measure functions. v1.2 INTRODUCTION: The three most basic types of test equipment that an Electronic Engineer or technician will use in the lab are the: 1. Volt Ohm Meter or Digital Multimeter, 2. Signal Generator or Function Generator, 3. Oscilloscope. The Function Generator produces sine, square and sawtooth AC waveforms whose voltage amplitude and frequency can be adjusted to desired values. An Audio Oscillator is designed to provide a sinewave waveform in the frequency range audible by the human ear. A function generator expands on the audio oscillator by also providing a square wave and triangular waveform with an increased frequency range. Most oscillators and generators require that the output voltage be set by adjusting the generator amplitude control and monitored using a DMM or oscilloscope.

4 Pg. 4 Scope-Gen Handout_pgs1-8_v1.2_SU14.doc The most valuable piece of test equipment is the oscilloscope. VERTICAL SECTION The Vertical Section is basically a voltmeter, NOT like the VOM by deflecting a meter movement, but by graphically by moving a dot on a calibrated vertical scale. DC & AC voltages may be measured on the Calibrated Vertical Scale. However, the rapid changes in AC voltage cause equally rapid changes in the vertical deflection of the dot. Because of the persistence of the oscilloscope phosphor and limitations of the human eye, the rapidly moving dot appears as a vertical line for AC and a dot for DC, if there is no horizontal sweep. By using controls in the vertical section, measurements can be made of a signal s voltage. HORIZONTAL SECTION The Horizontal Sweep causes the dot to move from left to right on the screen in a calibrated time. Note: The generation of the Sawtooth waveforms used to sweep the dot across the screen Horizontally will be covered in the Unit on Capacitance and the Cap RC Time Constant and the LED Flasher Lab (EET 101 & EET 121 only). The Oscilloscope synchronizes the vertical and horizontal dot movements with the trigger controls and presents a graphical waveform of the AC signal. This waveform represents the voltage of a signal with respect to the time in which it occurs. Again, as in the vertical section, by using controls in the horizontal section, measurements may be taken of the time-duration of the waveform or the period. TRIGGER SECTION The Trigger Section has 2 functions. 1. It syncs the scope s H. sweep to the signal to give a stable display. 2. It is used to start the sinewave at the same point on the screen every time. (We normally set the trigger to start on the Left graticule.)

5 Pg. 5 Scope-Gen Handout_pgs1-8_v1.2_SU14.doc Channel 1 LCD Display Channel 2 Ch1 Ch2 Trigger Source 1, 2, Ext. All the controls for the proper operation of our oscilloscope can be accessed from either physical knobs or buttons, located on the front panel - or softkeys with menus displayed on the LCD screen.

6 HP FUNCTION GENERATOR Pg. 6 Scope-Gen Handout_pgs1-8_v1.2_SU14.doc Max frequency out is 15 MHz. Default settings: 100 mvp-p, 1khz Sine Wave with 0 Vdc offset Specifications: For voltage levels on the display to be correct, Generator must drive into a 50 ohm load for a max. of 10 Vp-p out. Therefore use the aluminum box to connect Generator to Load. Most Commonly used Buttons On Upper left Sine Wave Square Wave On Bottom Left Frequency Amplitude Offset STEPS: 1. Select Sine Wave or Square Wave Button on Upper Left side. 2. a. Select Frequency by pressing Freq Button Lower Left side. b. Rotate Knob to change Frequency in 100 Hz increments. c. If it is desired to change the frequency in smaller increments, Press the > button on the lower Right side to move the Blinking Digit to the Right. The Blinking Digit indicates the Frequency increments that rotating the knob will change the Frequency by Note: Do not confuse the commas with the decimal pt. in the displayed frequency. Ex. Default frequency of 1 khz is displayed as 1.000,000,0 khz.

7 Pg. 7 Scope-Gen Handout_pgs1-8_v1.2_SU14.doc 3. Changing the Prefix a. Press the > Key once - after the last blinking digit, the khz. will blink. b. Now Rotating the knob CW will move the decimal pt. to the Right, increasing the frequency by increments of a factor of 10. Ex. 1 khz, 10 khz, 100 khz, 1 MHz, 10 MHz, max. c. If Rotate the knob CCW the decimal point will move to the Left Decreasing the Frequency by increments of a factor of 10. Ex: 1 MHz, 100 khz, 10 khz, 1 khz, 100 Hz, 10 Hz, 1 Hz, 100 mhz, 10 mhz, 1 mhz, and 0.10 mhz NOTE: Watch out for the mhz which is milli Hz., a very Low Frequency not to be confused with MHz (Mega-Hertz) a very High Frequency. NOTE: The < Key at the Bottom Right side does the Same thing as the > Key only moves the blinking digit to the Left instead of Right 4. Select Amplitude: Ampl Changing the Amplitude is similar to method used to change the Frequency. Press the < Key once until the 1 in the 100 mv blinks. Now Rotate the knob CW to increase the voltage in 100 mv increments. Note: The and Keys on the Top Right side serve the same function as the round knob. 5. Set the generator for 8 Vp-p in 100 mv 1KHz.

8 Pg. 8 Scope-Gen Handout_pgs1-8_v1.2_SU14.doc Silver Box The output of the Function Generator is connected via a coaxial cable to an aluminum box (pictured below) mounted below the shelf to the left of the HP Power Supply. Most of your labs will connect to this box (and not directly to the generator) for their input signal. The circuitry inside the box provides two 50 ohm outputs; Vg/1 (or Vg) and Vg/10. Vg/1 is a 1:1 output voltage from the generator. The Vg/10 provides a divide by ten output allowing low input voltages to our labs not available directly from the generator. Some of your labs may use a microphone which has a very low output. The Vg/10 may be used to provide microphone level output signals to test the response of microphone input circuits.

9 Pg. 9 Operating Instructions for the Tektronix MSO 2004B Mixed Signal Oscilloscope Contents Quick Setup - Recalling a previously saved setup. Vertical Section Horizontal Section Trigger Section Save Setup AC Measurements o AC Peak o Period & Frequency Saving a Screen Image to a USB Flash Drive Optional - DC Measurements Optional - Automatic Measurements Optional Automatic Measurements using cursors o Period o AC with DC Offset o Peak voltage, (Vpk, Vo-p)

10 Quick Set Up Pg Press Power ON button at bottom left of scope. Note: Only use the following Quick Setup procedure below to recall a previously stored setup. Do NOT use Auto - Set at this point. 2. Press Menu Button (Top center of Scope) The graphic below illustrates how this document will reference the menu defined buttons below and to the right of the LSD screen. ( Soft buttons explained on pg. 11.) LCD screen soft buttons #A #B #C #D #1 #2 #3 #4 #5 #6 #7 #E

11 Pg Press Recall Setup (LCD #5) 4. Press the LCD #A, B, C, or D associated with a Setup previously stored (see below). (Note the date a particular setup was stored is displayed in the menu. Up to 10 setups can be stored: (Setup1 to Setup10). For EET 101 Press Setup1 (LCD #C) For EET 121 Press Setup2 (LCD #D) For EGR 103 Press more- (LCD #E) then, Press Setup3 (LCD #A) For EET 131 Press more- (LCD #E) then, Press Setup4 (LCD #B) For EET 232 Press more- (LCD #E) then, Press Setup5 (LCD #C)

12 Pg. 12 Initial Setup: To start with a known setup Press Default Setup. From this setup we will make any changes necessary and save the new settings as a custom Saved Setup for your particular course. This oscilloscope makes use of soft buttons or soft-keys - (see below). The function of each of these buttons is not fixed and take on different functions based on the button definition displayed directly above it (or to the left) for the right side buttons. For that reason we identify a particular button, not by it s function, but by it s position. eg. LCD #1 is the left most button below the screen; and LCD #A is the top most button to the right of the screen. LCD screen soft buttons #A #B #C #D #E #1 #2 #3 #4 #5 #6 #7

13 Pg. 13 VERTICAL SECTION Vertical position adjustment Channel activation / menu Vertical scale control Signal Input BNC connector 1. If Ch.1 is not currently active, press Ch.1 button to bring up the menu. 2. Coupling (LCD #1)- Set to DC (Default) Allows DC levels to be displayed & measured. AC coupling removes DC components. GND is used on old Analog Scopes to adjust the vertical position to desired (0V Ref.). 3. Invert. (LCD #2) Set to Off (Default). 4. Bandwidth. (LCD #3) Press LCD #3 to display menu on right of LCD screen. Change to 20MHz. (LCD #B) (Helps to remove noise pulses picked up in lab.) 5. Label. (LCD #4) Default value ok. 6. Probe Setup. (LCD #5) Set to 1X. (Press LCD #C) (or leave at 10X if using a 10X probe). Press Menu Off button to turn-off menus may need to press more than once). 7. More. (LCD #6) Default values are ok.

14 Pg Set Vertical scale (volts/div) to 2.00V The vertical scale value is displayed in lower left the corner of the LCD screen, along with it s associated channel #. 9. Set Ch.1 0V vertical position to center (see fig. below) Repeat Steps 1-9 for Ch.2 but set 0V position of Ch.2 to Bottom Graticule (or second from bottom Graticule.

15 Pg. 15 HORIZONTAL SECTION 1. Connect a BNC to dual banana adapter to the Vg/1 connector of the Silver Box. Connect the BLK terminal of the adapter to the BLK terminal of scope Ch 1 adapter. Connect RED terminal of the adapter to the RED terminal of scope Ch 1 adapter. 2. Adjust the Horiz. scale knob to show 1 to 2 cycles of the waveform. The Horiz. Sweep would be 200µS/div. for a 1KHz. waveform. This setting is displayed on the LCD screen in the Horiz. Info box. (near the bottom center of the screen) 3. Set Horiz. scale to 200 µs/div. 4. Adjust the Horizontal position knob so the trigger point is on the far left graticule.

16 Pg. 16 TRIGGER SECTION 1. Press Menu button under the Trigger label (Right Side of Scope) Trigger menu button 2. Check that Type (LCD #1) is Edge (Default) 3. Check that Source (LCD #2) is 1. (Default) 4. Check that Coupling (LCD #3) 5. Check that Slope (LCD #4) is set to HF Reject (LCD #B) is (rising) (Default) 6. Check that Level (LCD #5) is 0.00V (Default) (Adjustable with Trigger Level control knob. see display may not be = 0V) Trigger Level control 7. Check that Mode (LCD #7) is Auto. (Default) Force Trigger (NEVER PUSH THIS BUTTON!!!) Example of un-triggered waveform (Only one sinewave should be displayed)

17 TRIGGER (cont.) Pg. 17 FilterVu (adjustable low pass filter) Default FilterVu Settings: Noise Filter Off Noise Filter (Foreground) = 70 MHz. Glitch Capture Background: On 1) Push the FilterVu button (it lights up green) 2) Turn Multifunction a knob CCW to change the Noise Filter (Foreground) (LCD #A) to 2.9MHz. from 70MHz. 3) Set Glitch Capture Background (LCD #B) to Off

18 Pg The waveform obtained should look exactly like the one shown above. 2. Note the display on the oscilloscope as you vary the generator frequency. Describe the results observed in your own words. 3. Adjust the gen. amplitude control for 1 khz. sinewave as indicated on the generator display.

19 Pg. 19 To Save Scope Settings: SAVE SETUP 1. Press Save/Recall Menu button (below LCD screen). 2. Press Save Setup (LCD #3) (Activates softkeys menu on right side of LCD.) 2. For EET 101 Press To Setup1 (LCD #C) LCD #: A For EET 121 Press To Setup2 (LCD #D) B C D E LCD #: For EGR 103 Press more- (LCD #E) then, Press To Setup3 (LCD #A) For EET 131 Press more- (LCD #E) then, Press To Setup4 (LCD #B) For EET 232 Press more- (LCD #E) then, Press To Setup5 (LCD #C) A B C D E

20 Pg. 20 AC MEASUREMENTS (A) AC PEAK VOLTAGE MEASUREMENTS: For best accuracy, want as large a sinewave as possible w/o overshooting the LCD display, by adjusting the vertical sensitivity (V/div). The peak voltage can then be determined from: (Vp) = Deflection Peak (# div.) * Vertical Sensitivity (V/div.) To Interpolate between div: Hint: Move Horiz. Position so Top of Sinewave is in Middle of LCD, so can read the sub div. Note: There are 5 sub div. vertically. Each is 0.2 div. Vpk = 3.2 div * 1V/div = 3.2V 0 V Vpk = 6.4 div * 500mV/div = 3.2V 0 V

21 Pg. 21 (B) FREQUENCY MEASUREMENTS The oscilloscope can be used to measure the output frequency of an audio oscillator or function generator using the horizontal sweep rate to determine it s period. Then use the equation: Frequency (F) = 1 / T (period measured in seconds) To measure the Period of the desired waveform: Calculate the number of divisions required to display one complete cycle on the horizontal axis. 1 period (seconds) = T = (# of div for 1 cycle)* [horiz. scale (sec/div)] Note: There are 5 sub div. Horizontally. Each is 0.2 div. Note: For an accurate time or frequency measurement it is best to have between 1 to 2 sinewaves displayed. New Trigger point (relocated from the center) Waveform crosses intersection of Trigger Level (0V) and Trigger point One cycle = 5 div * 200 us/div = 1000 us = 1 ms. F 1/T = 1/1ms = 1000 Hz. one cycle Trigger Level indicator Trigger info: Source Slope Level Freq. Another Example One cycle = 6 div * 200 us/div = 1200us = 1.2 ms. F = 1/T =1/1.2ms = Hz.

22 SAVING A SCREEN IMAGE Pg. 22 This oscilloscope allow you to save a screen image of the displayed waveform, including the vertical, and horizontal settings, as well as any previously set up measurements. Many of the waveform images in this document were saved this way. The function will not, however, save any on-screen menus. The files are relatively small at less than 10kB. To save an image, 1) Plug a USB flash drive into the USB port on the front panel (see graphic below.) No installation is required. 2) Press the Save /Recall - Menu button. 3) Push the Save Screen Image button (LCD #1) 4) File Format (LCD #A).png (a standard graphics format). 5) Make sure Ink Saver in On (LCD #B) (This changes the saved image screen background from black to white) 6) Press OK Save Screen Image (LCD #E) 7) After image has been saved, < 15 sec, remove the USB drive. (No uninstall required.) 8) If Assign (LCD #6) is set to Save to Image, then you just need to press the Save button to save additional images (skipping steps 2 thru 6). A new incrementally numbered file will be created on the USB drive for each image.

23 Pg. 23 OPTIONAL DC Measurements Use the scope to measure dc voltage levels: 1. Press the desired channel ( 1 or 2 ). 2. Set Coupling (LCD #1) to DC (In the AC Coupling mode, a capacitor blocks the DC component from the screen.) 3. Place the scope leads across the unknown DC level and use the following equation to determine the dc level: DC Level (V) = Vertical Deflection (#div.) * Vertical scale (V/div.)

24 Pg. 24 OPTIONAL AUTOMATIC MEASUREMENTS SETUP The MSO2004B can display up to four selected measurements simultaneously. Any four measurements can be displayed from among a list of 30 possible. In addition to selecting a desired measurement, the source for that measurement must also be set if different from the default source. For this setup, we will select the following measurements of the default source - Channel 1: Frequency, Period, Amplitude (Vp-p), High (Vo-p) Note: If 4 measurements are already displayed, one will need to be removed before one is added. In case four are displayed, the procedure to remove a measurement is as follows: 1. Press Measure to display the Measure menu (below). LCD # s Press Remove Measurement (LCD #2)

25 Pg You can remove any selected measurement (LCD #A, B, C, D) or all selected measurement (Remove All) (LCD #E) LCD # s: A B C D E 4. Press Remove All (LCD #E)

26 Pg. 26 ADD MEASUREMENTS 1. Press Add Measurement (LCD #1). Notice Measurements menu on LCD screen. 2. Check that the source is correct, usually 1 (LCD#B) If only one channel is ON, the default source is the active channel. If more than one channel is ON, the source can be selected by turning the Multipurpose knob b. 3. Select the 1 st desired measurement, Frequency, by scrolling up or down the list by turning the Multipurpose knob a until Frequency is highlighted. 4. Press OK Add Measurement (LCD #E) 5. Select the 2 nd desired measurement, Period, by scrolling up or down the list by turning Multipurpose knob a until Period is highlighted. 6. Press OK Add Measurement (LCD #E) 7. Repeat steps 5 & 6 for the 3 rd & 4 th measurements of Amplitude, and High. 8. Alternately, all (30) measurements may be displayed all at once on the screen (obscuring most of the waveform) by selecting Snapshot All Meas. (LCD #E)

27 Pg. 27 Note: If a complete waveform cannot be displayed or is beyond the screen borders, auto measurements cannot be made. In that case a > or < symbol will be displayed before the value in the measurements box. In the graphic above, the vertical scale is too small to allow the entire waveform to be displayed on the screen. To achieve an auto measurement, increase the vertical scale to fit the entire waveform vertically. In the above example less than one cycle is displayed To achieve an auto measurements, increase the horizontal scale to allow at least 1 to 2 cycles to be displayed. Note the ----Hz. Meas. value. Also, the voltage meas. are correct for only the displayed section of the waveform.

28 Pg. 28 OPTIONAL OSCILLOSCOPE MEASUREMENTS USING THE CURSORS PERIOD Press Cursors and turn the Multipurpose a, and b. knobs to adjust the cursors to coincide with a one period interval of the waveform. 1 period The period (T) can be read from the cursor box: 1.01ms AC with DC OFFSET The waveform below is an example of a 1000 Hz. sinewave, 6Vp-p with a +12 Vdc offset. Note that the 0V point has been adjusted to the bottom graticule to allow for the maximum vertical waveform display. Ampl (Vp-p) High (Vmax.) Low (Vmin) 0 V

29 Pg. 29 PEAK VOLTAGE (Vo-p or Vpk) Press the Cursors button a cursor b cursor 0 V Turn Multipurpose a knob to move the vertical a cursor left or right to position the crosshair at the waveform max. Turn Multipurpose b knob to move the vertical b cursor left or right to position the crosshair at the waveform min. Read Vpk in the cursor box. a = 15.1V (~15V). and Vmin in the cursor box. b = 8.96 V (~9V) ( means the difference or change in voltage ) To link the cursors so they move together, press the Select button (notice the LCD box indicates Cursors Linked The Select button will toggle the cursors between being linked and being independent.