Oscilloscope question

The probe is the "interface" between teh scope and the circuit. The wrong type of connection will either pick up undesired signals, load the signal resistively or capacitively. The latter is signigicant as digital signals are time based and the capacitive load of raw coax cable and alter that timing or worse introduce ringing into the circuit. Scopes are like telescopes, even the cheapest can see Mars, slightly better can see the bands on Mars. Relating the bandwidth to CPU clock is mostly meaningless. The parameters your are mesuring is timing of the waveform and possibly the waveshape. If the bandwidth (and corosponding rise time of the scope amplifiers) is not adaquate you will distort the waveshape and if the timebase(X or horizontal scan time) is either porrly calibrates or cannout go fast enough it may be impossible to determine if a event occurs 450nanoseconds (10^-9) later. Risetime is a measure of how fast the amplifer in a scope can go from 10% to 90%. Usually you want that to be faster than the waveshape you wish to view by more an two and as much as 10 times. Note most TTL have rise times well under 20ns and even some of the older logic families can be very fast rise and fall times. So this is why a 50mhz (465b) scope of better is used. The key here is risetime is the measure used to understand the faithfulness of the reproduction for a given wave shape. An example may be a very fast rise time square wave can end up looking more like a saws teeth when reproduced using a scope with inadaquate risetime in the most extreme case. For the math types 1/risetime+falltime give an approximate repetition rate or frequency 1/40ns=25,000,000 Reptitions/Second. So 2x that is only 50mhz! Also bandwidth and rise time are only related as a scope can have good rise time but limited bandwidth or the reverse. Yes. In both cases there is a requirement to understand electronic basics and what waveforms result from basic circuits. Complex circuits are just many simple ones combined in many ways. Allison