Where do you measure the rise time? When I was in the oldsillyscope
calibration business, we measured rise time of the leading edge of a
square wave as the time between 10% amplitude and 90% amplitude of the
waveform. That makes for a lot less intrepretation of where the rise
begins and where it ends, which you would have to do if you measured 0%
to 100%.
I'm not sure about the latest Tek scopes, but the ones I calibrated have
dashed lines to indicate those points. with the square wave set to cover
six vertical graticule divisions, we measured the rise time from the
lower dashed line (1/2 division up from -3) to the upper dashed line
(1/2 division below +3). This came right out of the Tektronix
calibration procedure manual in the section for checking whether the
scope's vertical rise time met spec. (Yes I know that 0.5 does not
exactly equal 10% of 6, but it is close enough)
DE N6KB
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