leader_lbo-516_delayed_time-base_100_mhz_oscilloscope_operation 电路图.pdf

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TO AVOID ELECTRIC SHOCK, DO NOT PERFORM ANY SERVICING OTHER THAN THAT CONTAINED IN THE OPERATING INSTRUCTIONS UNLESS YOU ARE QUALIFIED TO DO SO. RadioFans.CN 收音机爱 好者资料库 LBO-516 100 MHz DELAYED TIME BASE OSCIILOSCOPE TABLE OF CONTENTS 1. GENERALINFORMATION.1 1-1 INTRODUCTION .1 1-2 SPECIFICATIONS .1 2. OPERATING INSTRUCTIONS.3 2-1 FUNCTION OF CONTROLS, CONNECTORS, AND INDICATORS . 3 2-1-1 Display Block . 3 2-1-2 Vertical Amplifier Block . 4 2-1-3 Sweep and Trigger Blocks . 5 2-1-4 Miscellaneous . 7 2-2 INITIAL OPERATION . 7 2-2-1 Power Connections and Adjustments . 7 2-2-2 Installation . 8 2-2-3 Preliminary Control Settings and Adjustments . 8 2-3 BASIC OPERATING PROCEDURES . 9 2-3-1 Signal Connections . 9 2-3-2 Single-trace Operation .11 2-3-3 Triggering Alternatives .11 2-3-4 Probe Compensation .14 2-3-5 Dual-trace Operation .15 2-3-6 Additive and Differential Operation .16 2-3-7 Triple-trace Operation .17 2-3-8 Four-trace Operation .17 2-3-9 Delayed Timebase Operation .18 2-3-10 Single-shot Operation .20 2-3-11 X-Y Operation .20 2-3-12 Intensity Modulation .20 2-4 MEASUREMENT APPLICATIONS .21 2-4-1 Amplitude Measurements .21 2-4-2 Differential Measurement Techniques .22 2-4-3 Time Interval Measurements .23 2-4-4 Phase Difference Measurements .24 2-4-5 Distortion Comparison .26 2-4-6 Frequency Measurements .27 2-4-7 Risetime Measurements .27 2-4-8 -3dB Bandwidth Measurement .28 1. GENERAL INFORMATION 1-1. INTRODUCTION The LBO-516, shown in Figure 1-1, is a 100 MHz oscilloscope with all of the features normally found on a lab-grade scope: high- fidelity pulse response, stable operation, dual timebase with calibrated sweep delay, flexible triggering facilities, and a bright CRT display with illuminated internal graticule. Moreover, it also has a very unusual feature found on few scopes in any price class: it can simultaneously display up to eight traces from three different input signals! In addition to the two vertical-input channels and their differ- ence signal, the signal used to externally trigger the main timebase can also appear on the CRT display. The alternate sweep mode, which allows the main and delayed timebases to simultaneously sweep the CRT, effectively doubles this four-trace display to an eight-trace display. The comprehensive triggering facilities of the LBO-516 include several features that ease the problem of triggering on complex signals: a variety of frequency-selective coupling filters, a trigger holdoff-control, and a trigger pickoff that alternates between the two vertical channels. 1-2. SPECIFICATIONS Specifications for the model LBO-516 oscilloscope are given in Table 1-1. Table 1-1 SPECIFICATIONS Vertical Amplifiers (Ch. 1 -+5% with Xl0magniflca-tion 1 megohm +-2%, 25 pF +-3 pF Maximum Input Voltage 400 V (DC plus AC peak) 1 Signal Delay Leading edge displayed. Leading edge displayed. CH-1 only, CH-2 only, CH-1 use this as a guide in de- termining whether or not to add the additional 90. 10. The sine-to-angle conversion can be accomplished by using trig tables or a trig calculator. However, if the sine is between 0.1 and 1.0, you can use the Figure 2-21 nomograph. Simply lay a ruler on the nomograph so its edge passes through the cross mark and the number of divisions measured in Step 7 (B dimension). When this is done the edge will also intersect the phase-angle column. 2-4-5 Distortion Comparison The dual-trace feature of the LBO-516 offers a quick method of checking for distortion caused by a signal-processing device (such as an amplifier). To do this, proceed as follows: 1. Connect the output of the signal generator (of frequency suitable to the device under test) to the CH- 1 IN connector (14) and the input of the device under test (DUT). 2. Connect the CH-2 IN connector (15) to the output of the device or its load (see Figure 2-22) 3. Increase the signal to the DUT until the channel 2 trace or an RMS AC voltmeter indicates the desired output level. 4. If the DUT has reversed the phase, press the CH-2 INV pushbutton (19). 26 5. Superimpose the two traces with the vertical POSITION controls (17) and (18), and use the VARIABLE VOLTS/ DIV control (11) of the larger trace to achieve the best trace match. 6. Any uniform horizontal displacement of the traces is simply phase difference (described in paragraph 2-4-4). Any other differences in shape indicate distortion caused by the DUT, such as slew rate or frequency distortion, ringing, etc. 2-4-6 Frequency Measurements When a precise determination of frequency is needed, a frequency counter is obviously the first choice. However, an oscilloscope can be used in either of two ways to measure frequency when a counter is not available, or modulation and/or noise makes the counter unusable. Reciprocal Method. Frequency is the reciprocal of period. Simply measure the period t of the unknown signal as instructed in 2-4-3 Time Interval Measurements, and calculate the frequency f using the formula f = 1/t. If a calculator is available, simply enter the period and press the 1/x key. Period in seconds (S) yields frequency in hertz (Hz); period in milliseconds (mS) yields frequency in kilohertz (kHz); period in microseconds (PS) yields frequency in megahertz (MHz). The accuracy of this tech- nique is limited by the timebase calibration accuracy (see Table of Specifications). Comparison Method. In the frequency-comparison or frequency-ratio method, the unknown frequency is compared to a known frequency (from a calibrated signal generator). The two signals are fed to the oscilloscope operating in its X-Y mode, and the signal generator frequency is varied until a recognizable Lissajous pattern appears. The pattern shape indicates the ratio between the two frequencies. When the generator frequency is multiplied by this ratio, the unknown frequency will be determined. This method is usable for frequencies up to 3 MHz. To measure frequency by the comparison method, proceed as follows: 1. Set up the LBO-516 for X-Y operation (paragraph 2-3-11). 2. Connect the output of a signal generator having accurate frequency calibration to the CH-1 or X IN connector (14). 3. Adjust the CH- 1 VOLTS/DIV switch (10) for about 6 divi- sions horizontal deflection. 4. Connect the signal with the unknown frequency to the CH-2 or Y IN connector (15). 5. Adjust the CH-2 VOLTS/DIV switch (10) for about 6 divi- sions vertical deflection. 6. Vary the frequency of the signal generator until the scope display resembles a circle, an ellipse, or a diagonal line. When this occurs the unknown frequency is the same as the signal generator frequency (which can be read from its dial). The accuracy of this technique depends on the signal generator s calibration accuracy. NOTE: While many other ratios are theoretically possible, drift in either signal frequency makes more complex Lissajous patterns nearly impossible to read. 2-4-7 Risetime Measurement Risetime is the time required for the leading edge of a pulse to rise from 10% to 90% of the total pulse amplitude. Falltime is the time required for the trailing edge of a pulse to drop from 90% of total pulse amplitude to 10%. Risetime and falltime, which may be collectively called transition time, are measured in essentially the same manner. To measure rise and fall time, proceed as follows: 1. Connect the pulse to be measured to the CH- 1 IN connector (14) and set the AC/GND/DC switch (16) to AC. 2. Adjust the A TIME/DIV switch (24) to display about 2 cycles of the pulse. Make certain the associated VARIABLE control (11) is rotated fully clockwise and de-tented in its CAL D position. 3. Center the pulse vertically with the channel 1 vertical POSITION control (17). 4. Adjust the channel 1 VOLTS/DIV switch (10) to make the positive pulse peak exceed the 100% graticule line, and the negative pulse peak exceed the 0% line, then rotate the VARIABLE control (11) counterclockwise until the positive and negative pulse peaks rest exactly on the 100% and 0% graticule lines. (See Figure 2-23). 5. Use the horizontal POSITION (29) and X-FINE (30) controls to shift the trace so the leading edge passes through the intersection of the 10% and central vertical graticule lines. 6. If the risetime is slow compared to the period, no further control manipulations are necessary. If the risetime is fast (leading edge almost vertical), pull the A VARIABLE (X10 MAG) control (26) and reposition the trace as in Step 5. (See Figure 2-23b.) 7. Count the number of horizontal divisions between the central vertical line (10% point) and the intersection of the trace with the 90% line. 8. Multiply the number of divisions counted in Step 7 by the setting of the A TIME/DIV switch to find the measured risetime. If Xl0 magnification was used, divide the TIME/DIV setting by 10. For example, if the A timebase setting in Figure 2-23 was .1/PS (100 KS), the risetime would be 36 nanoseconds (100 KS 10 = 10 KS; 10 KS x 3.6 div = 36 KS). 9. To measure falltime, simply shift the trace horizontally until a trailing edge passes through the 10% and central vertical graticule lines, and repeat Steps 7 and 8. 10. The rise and fall times measured thus far include the 3.5 KS transition times of the LBO-516 (about 5 KS with probe). These errors are negligible if the measured rise and fall times are 20 KS or longer. For shorter transition times, correct the measured rise and fall times using one of the following formulas: 27 2-4-8 - 3 dB Bandwidth Measurement Bandwidth measurement usually involves finding the -3 dB response point in the frequency-response curve of a circuit or device. This can easily be determined without the need for calculations or dB conversions by using the following trick: 1. Connect the output of a constant-amplitude signal generator (of appropriat