
Scans by ArtekMedia © 2007
When performing a versus-chan3 plot, the X-axis scaling of the recording
area is determined by the Channel 3 range setting (rather than by the total
time setting). The Channel 3 range setting is mirrored onto the negative
X-axis. This is shown by the following figure, which shows a recording area
designed for plotting Channel 1 versus Channel 3.
7.0
0.0
III
0
.
0
CHANNEL 3
Calculating Range Settings
FULL SCALE
•
Optimum accuracy of measurements for any selected input channel is
obtained when the channel's
RANGE
is set at the lowest (most sensitive)
value that will allow all data to be plotted without clipping. For ac signals
having
a
median voltage
V.-:I
of zero, this can be achieved by setting
RANGE
equal to the peak signal amplitude (one-half the actual signal range). Sig
nal range may be expressed as
Vmu
-
Vmin•
Hence, the ideal
RANGE
setting
may be obtained by using the
range equation
below.
- Vminl
The following illustration demonstrates how the range setting obtained
using the range equation affects the recording area. The
Vmax
and
Vmin
values for the illustrated signal yield a range setting of 5.0 volts. Using this
setting scales the recording area as shown. Because the range setting is
mirrored above and below the zero point, the entire signal is mapped onto
the recording area as shown.
If a signal having a
nonzero
median voltage is recorded using a range
setting (and no
OFFSET)
calculated using the range equation, an invalid
measurement will result and the plotted signal will be clipped. This is
demonstrated by the subsequent illustration, using signal
A
from previous
examples. When the
RANGE
equation is applied to the
Vmin
and
Vmu
values
for signal
A
and the resulting range setting of 3.25 volts is used, the record
ing area's Y-axis is scaled as shown. Data points for voltages above the
3.25-volt limit are clipped from the resulting plot. Clipping becomes more
pronounced when median signal voltages are displaced (offset) further and
further from zero volts. To obtain accuracy for such signals, the
OFFSET
setup condition should be used in conjunction with
RANGE,
as explained in
the section to follow.
Scaling
the
Axes
for
a
VerslUl-C1um3 MefUJurement
SETUP CONDITIONS
(Ve,sus·Chan3 Recordln�)
RANGE
1
7.0 VO
L
TS
RANGE 3
40.0
MILUVOl TS
Measurement Setup Operations 3-11