HP-185A-Brochure 电路图.pdf
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1、Dual pulse presentation on 185A. Top trace shows pulse from mercury pulser applied to 2N1385 mesa tran- sistor. Bottom trace shows respond- ing turn-on of transistor. Dip in bot- tom trace at start of turn-on results from capacitance. Scape sweep speed 1 millimicrasecond/cm. Analyze mi I I i m icros
2、econd pulses Measure transistor response time Make fractional mil limicrosecond time comparisons Measure diode switching time Determine pulse jitter Make permanent X-Y plots Measure memory-unit switching . . . Measure uhf voltage amplitude _- f 60 nt in the The 185A 500 MC Oscilloscope is a complete
3、ly new instrument that is virtu- ally as simple, convenient and easy to read as conventional broadband oscillo- scopes, yet provides a wealth of fast-circuit information never before available. In such fields as computer and radar research and design, and semiconductor research, the Model 185A is th
4、e first practical, available answer to the pressing need for measuring and viewing millimicrosecond phenomena. It should be emphasized that the 185A is an existing instrument- ready for you now, with bright, clear 5” scope traces that are totally comparable i n information, clarity and usefulness wi
5、th presentations you associate with much lower frequencies. RadioFans.CN 收音机爱 好者资料库 SAMPLING OSCILLOSCOPE 185A is a sampling oscilloscope, whereas most previous oscilloscopes have been broad- band instruments. The sampling technique avoids several inherent limita- tions of the broadband approach whi
6、ch arise in the milli- microsecond region. One of these is the intrinsic sensi- tivity-bandwidth-display-size limitation of cathode ray tubes ; another is the characteristic gain-bandwidth limitation of associated amplifiers. A third critical problem with the broadband approach in the 500 MC band pa
7、ss area is that, frequently, fast pulses or occurrences happen at low repetition rates. This means that the writing rate is not sufficient to pro- vide a bright trace on the cathode ray tube. 185A adroitly sidesteps all these roadblocks by im- mediately translating the input signal to a much lower f
8、requency, through the sampling technique, then pro- ceeding with more conventional signal processing to provide standard oscilloscope operating ease and bright, clear, large-screen presentation. “Sampling” in this application is analogous to strobo- scopic light methodology in that both techniques s
9、imu- late slowing down the “motion” for better visual study -and both depend on repetition to build a faithful image. The first step in building the 185As cathode ray tube picture is to apply a staircase voltage to step the beam across the CRT face. (Figure 1). Next, input voltage samples, each take
10、n from a differing point on the waveform, are fed through the vertical amplifier to the scope face. Now, between the staircase steps, the beam is blanked so that the signal becomes a series of dots. In operation, many dots are present, and the pattern appears continu- ous. (Figure 2). Figure 1 Figur
11、e 2 A basic element of the sampling technique as here ap- plied is the incremental delay of each sampling pulse- such delay insuring that a different or successive portion of the wave is examined each time. i kL j 7 r- -t (-1 _-”i -L -_i L i L- i i - - - I i -: _ _ -A- h L _-L - 2 - _- - _ _ Figure
12、3 Figure 3 illustrates this delay process. Electrically speaking, it operates as follows. A gate is opened for a very brief time and a capacitor charged to a voltage proportional to the instantaneous amplitude of the test signal. The voltage on the capacitor remains after the gate is closed, and is
13、ampli- fied to provide vertical cathode ray tube deflection. OPERATION DESCRIBED In the case of the ($9 185A, the sampling approach is applied in the following manner. So that the entire signal under ex- amination is scanned, each succeed- ing sample is gated El RadioFans.CN 收音机爱 好者资料库 U N I Q U E A
14、 DVA NTAG E S SPECIAL, EASY-TO-USE PROBES An outstanding feature of the 185A is the pair of compact, new-concept probes arranged for easy applica- tion to the circuit under test. The probes provide a high 100,000 ohm input resistance shunted by 3 ppf to virtu- ally eliminate loading to the circuit u
15、nder test. For maxi- mum versatility, the probes may be used with Type N, BNC or other conventional fittings. Calibrated vertical sensitivity controls permit the in- strument to measure a wide range of input levels from 10 to 200 mv/cm. A vernier between steps further in- creases sensitivity to 3 mv
16、/cm. To assure maximum usefulness, the 185A has a variable time delay and a four-range time scale with a six-step scale magnifier. These features permit study of fast pulses in extreme detail and under varied trigger con- ditions. Model 185A syncs with external triggers up to 50 MC, and also provide
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