digital vertical resolution / vertical sensitivity

hey,

i'm looking for an oscilloscope for audio applications, preferably
digital, so i'm not looking for a huge bandwidth

so i'm looking at the instek gds-806s and similar models,

anyhoo, i have a question about the vertical resolution

it states the vartical resolution is 8 bit, and the vertical
sensitivity is 2mV/Div to 5 V/Div

my question is where typically is the DAC located?

is it after the vertical sensitivity switch in which case at 2 mV /
div i would expect a resolution of

(2mV / DIV )* (no of div) / 2^8 = 0.008 mV * no of div = 0.08 mv with
10 div

similarly at 5 V /div i would expect resolution to be

5/ 256 * no divs =0.2 volts with 10 divs

or is the DAC located before the vertical sensitivty in which case the
resolution is always the same regardless of vertical resolution
setting?

i read that for audio purposes, 16 bit minimum is necessary. Is this
true?

also if anyone could recommend a decent oscope for audio purposes
please let me know. i'd consider a PC / soundcard unit but would rather
a stand alone digital unit.

Thanks

Tom

 

[w2aew]

boonstra171@yahoo.ca wrote:

hey,

i'm looking for an oscilloscope for audio applications, preferably
digital, so i'm not looking for a huge bandwidth

so i'm looking at the instek gds-806s and similar models,

anyhoo, i have a question about the vertical resolution

it states the vartical resolution is 8 bit, and the vertical
sensitivity is 2mV/Div to 5 V/Div

my question is where typically is the DAC located?

is it after the vertical sensitivity switch in which case at 2 mV /
div i would expect a resolution of

(2mV / DIV )* (no of div) / 2^8 = 0.008 mV * no of div = 0.08 mv with
10 div

similarly at 5 V /div i would expect resolution to be

5/ 256 * no divs =0.2 volts with 10 divs

or is the DAC located before the vertical sensitivty in which case the
resolution is always the same regardless of vertical resolution
setting?

i read that for audio purposes, 16 bit minimum is necessary. Is this
true?

also if anyone could recommend a decent oscope for audio purposes
please let me know. i'd consider a PC / soundcard unit but would rather
a stand alone digital unit.

Thanks

Tom

I believe the DAC is typically after the input attenuator and preamp.
The DAC range typically covers the the vertical screen area, plus some
over/under-range. This is why is it always best (from a quantization
error/noise reduction standpoint) to adjust the input attenuator so
that your signal fills most of the screen. This takes the best
advantage of the resolution of the DAC.

Note that most of the better DSOs allow you to do averaging on your
repetitive signals, which allow you to effectively increase the number
of bits of resolution.