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\<Id Iii more calibrated sweep speeds to iL

When Heathkit offered the 10-103 oscilloscope kit with its 10 MHz bandwidth and triggered sweep at a price 1 could just argue myself into, i found some precious pennies and quickly sent them off he fore I could change my mind. The re suiting instrument willi its calibrated Vertical attenuator and triggering which proved to he positive beyond the useful response of the vertical amplifier was very satisfactory for my experimenting. The only disappointment was in the limited choice of calibrated horizontal sweep speeds. Seven sweeps in decade steps covered 100 ms/div to O.lju/div. Those of you who are familiar with industrial oscilloscopes will appreciate the restriction this forces on the operator.

Let me illustrate the problem, he horizontal sweep is set at 1 00 s/div. and % of a pulse is displayed.. In order to see the complete pulse you must change the sweep speed and the nearest slower speed is I ms/div-. hi addition to the complete pulse you will also see 6Vi more pulses of the pulse (rain as well. The resolution has been lost. You could use the variable sweep control but then the calibration would be useless for any accurate time measurements. What is needed is a calibrated sweep of 200 jus/dtv. A similar situation arises when three pulses arc displayed at 100 ¿xs/div. and you want to gel maximum detail of one pulse. You need a sweep speed of 50 ¿¿s/div but you only have a sweep speed of 10 jus/div which would display only 3/10 of the pulse.

Adding ten more calibrated sweep speeds may sound like a formidable undertaking but really all you need is one more 10 K£2 1% resistor and a two pole three position switch!

Basic Design

Let us look at the basic sweep circuit in 1 ig. 1 (the designations are Heathkit s) It is a PNP iransistor using a basic characteristic

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