Acquiring and Displaying Waveforms
3–34
TDS 500D, TDS 600B, & TDS 700D User Manual
Hi Res Mode. TDS 500D and 700D models only: Hi Res mode averages all
samples taken during an acquisition interval to create a record point. The average
results in a higher-resolution, lower-bandwidth waveform.
A key advantage of Hi Res is its potential for increasing resolution regardless of
the input signal. Table 3–3 and the equations shown below illustrate how you
can obtain up to 15 significant bits with Hi res mode. Note that the resolution
improvements are limited to speeds slower than 100 ns/div. Also, resolutions
above 15 bits are not allowed by internal hardware and computation limitations.
Si = Sampling Interval for TDS 754D = 1 ns
t = Sample Interval =
TimeDiv
Number Of Points/Div
=
5 msDiv
50 PointsDiv
= 100 ns
Nd = Number of points per decimation interval =
Dt
Si
= 100
Resolution Enhancement (bits) =
0.5 LOG
2
(Nd) 3 extra bits
Bits of Resolution = Resolution Enhancement (3 bits) + 8 bits 11 bits
Hi Res mode only works with real-time, noninterpolated sampling. If you set the
time base so fast that it requires real-time interpolation or equivalent-time
sampling, the mode automatically becomes Sample even though the menu
selection will not change.
Table 3–3: Additional resolution bits
Time base speed Bits of resolution
100 ns and faster 8 bits
200 ns to 500 ns 9 bits
1 ms to 2 ms 10 bits
5 ms to 10 ms 11 bits
20 ms to 50 ms 12 bits
100 ms to 200 ms 13 bits
500 ms 14 bits
1 ms and slower 15 bits
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