Measurement Examples For Width A And; Measurement Example For Synchronous In - Tektronix DC5010 Instruction Manual

Operating Instructions-DC 501 0
Ratio B/A
In Ratio B/A mode, the counter measures the number of
events on both channels during the time it takes to accumu-
-'
late the selected number of Channel A events (averaged by
A events). The total number of Channel B events is then
divided by the total number of Channel A events and the
answer displayed without units of time or frequency.
The ratio range is from 1
op8
to 10' . Applying the higher
frequency to Channel B produces a ratio greater than one;
applying the lower frequency to Channel B produces a ratio
less than one. For better resolution, apply the higher fre-
quency signal to Channel B.
Width A a n 4 d Time A
- +
B (Time Interval)
Figure 2-5 illustrates measurements for the WIDTH A
and TlME A
-
B functions. The WIDTH A function mea-
sures the time interval between the first selected positive or
negative edge (+ SLOPE) of the waveform applied to Chan-
nel A and the next opposite polarity edge.
The TlME A
-
B function measures the time interval
between the first selected occurrence
(a
SLOPE) of an
event on Channel A to the first selected occurrence (+
SLOPE) of an event on Channel B. The measurement can
be averaged (AVGS) by the selected number of Channel A
events because there is one Channel B event per Channel A
event
.
, ,
WheneithertheWlDTHA,TlMEA-B,orRISE/FALLA
function is activated, the microprocesor turns on an internal
pseudo-random noise generator that phase modulates the
internal 3.1 25 ns time base, allowing the counter to measure
without error,, input signals that otherwise would be syn-
chronous with its time base. See Fig. 2-5.
Width Width
4
- - - - -
- - -
- - - - - - - - - -
WIDTH A
b
-
-.,
-i
-
- -
-*%,-4k
- - -
---
\ ,
I \
+SLOPE Hysteresis
-SLOPE
Window
A INPUT
1uuUu
TlME A
-
B
I
I
I I
u
k----- Measured Time Interval
I I
(3464-07)3897-05
Fig. 2-5. Measurement examples for WIDTH A and TlME A
+
6.
In Fig. 2-6 the time interval (4.68525 ns, WIDTH A) would
not be measured with a non-modulated time base any more
accurately with averaging than it could have been by making
a single-shot measurement (AVGS
=
0). Using the pseudo-
random phase-modulated clock pulses, and setting the
AVGS switch greater than 1, causes the counter in this ex-
ample to count one clock pulse one-half of the time and two
clock pulses one-half of the time. For example, if AVGS is
set to 10 (10') the total time for the count is at least
l nput Signal
Non rrrodulated
Time Base
Phalse
Modulated
Time Base
Fig. 2-6. Measurement example for synchronous input signals.
REV JUL 1983