SRS Labs SR850 - Manual (Page 91)

4-9
Center value and Trace Units
Trace Offset
and Expand
Indicators
Expd Offst
X
X = 9.7284 mV
±
10.000 e-3 0.0 V
Trace 1
Trace Identifier Trace Definition
Full scale range
BAR GRAPHS
The most commonly used display type is the Bar graph with large numeric readout. This display most closely
resembles a "normal" lock-in. The bar graph display is shown below. The bar graph only occupies half of the
screen, even when the screen format is full height. Thus, it generally makes sense to use the bar graph in
split screen mode and show two bar graphs.
Trace Identifier and Active Display
The bar graph is labelled with a trace identifier
above it. This indicates which trace is being dis-
played. The trace definition is shown next to the
identifier. If this display is the active display, the
trace identifier will be in inverse. When a bar graph
is the active display, the [AUTO SCALE] key will
scale the bar graph. There is no cursor function for
this display. Pressing the [CURSOR] key will not
activate a cursor.
When the trace definition is simple (X, Y, R,
θ
or F)
the trace definition is displayed in the large numer-
ic readout (X=). If the trace is defined as Xn, Yn,
Rn, AI1, AI2, AI3 or AI4, or involves a product or
ratio (A•B/C where either B or C or both are non-
unity), then the large readout simply shows 'T1='
(for Trace 1) instead of the actual parameter(s)
being monitored. The trace definition above the
readout is always displayed fully however.
Bar Range and Center
The graph range and center value are displayed
below the graph. These values are in the units of
the displayed trace.
Bar Scaling
The bar graph scaling can be changed in the
DISPLAY/SCALE menu. Both the center value
and the range can be changed. This allows the bar
graph to expand a portion of the full scale range
around a nominal value. The bar will always be
drawn from the center (nominal value).
For the simple traces, X, Y, and R, changing the
sensitivity will automatically scale the bar graphs
so the range is equal to the sensitivity and zero is
at the center. For other trace definitions, the bar
scaling is not changed when the sensitivity is
changed.
Using [AUTO SCALE] will adjust the range to
make the measured output greater than 40% of
the new range. [AUTO SCALE] always returns the
center to zero.
Rate
The bar graph is updated at a rate of about 7 Hz
while the numeric readout changes at about 2 Hz.
When the data is noisy, the bar graph more accu-
rately shows the "noisiness" while with steady
readings, the numeric display is an accurate
measure of the signal.
Offset and Expand
If the trace being shown is affected by a non-zero
offset or a non-unity expand, then the Offst and
Expd alert indicators are turned on.
Screen Display