[sdiy] Nicolet Instrument Scope

[RMC]

----- Original Message ----- 
> Thanks. It did help a lot. Both replies did! Fist of all i learned  that i 
> know next to nothing about scopes. The relation between  bandwide and 
> risetime makes sence, but how do i tell what risetime  that scope has from 
> the supplied specs?

You really need to find the exact data for the oscilloscope, but you can 
come up with an approximate value of risetime.

The data you supplied says "digital skop. 12 bit. TPP. úS 1 -  500 og mS 1 - 
500 og S 1 - 200".  I think that means it will have a timebase (x axis) 
which goes as fast as 1 microsecond per division to 500 microseconds per 
division, and then the same for milliseconds and actual seconds.

The fastest time of 1 microseconds corresponds to a frequency of 1 MHz, 
whereby one complete cycle fits inside a division (frequency = 1/time). You 
might be able to see 2 cycles which is 2 MHz but at theta frequency, the 
ability of the scope to digitise the waveform with any accuracy will have 
vanished. It will probably work at 1MHz but not work at (say) 1.1MHz due to 
the way the A to D convertors work.

So, assuming for the sake of being optimistic that 2MHz is the maximum 
frequency, the risetime that you will be able to resolve is 0.35/f = 
0.35/2000000 = 175 nanoseconds.  This is accurate to about 5% I think - have 
a look at those URLs which explain it all a lot better than I can.

1MHz would be able to accurately "see" about 350 nanoseconds - i.e. about a 
third of a microsecond.  Things which change faster than that won't be 
properly displayed on the scope because the electronics associated with the 
scope can't pass the signal fast enough. The electronics if you like is 
acting as a low pass filter.

One thing I forgot to ask - is it dual channel or single channel? I would 
advise you to get a dual channel scope.  Don't bother with it if it is only 
single channel, that's what I reckon.

Cheers

RMC, England