Stanford Research Systems SR860 Operation Manual page 90

72 Operation
Offset
Output offsets are reflected in the displays. For example, when the X output is offset to
zero, the displayed value will drop to zero also. This means that the bar graph and
numeric readout both drop to zero. In addition if X is being charted on the graph, its
graph will drop to zero. Any display which is showing a quantity which is affected by a
non-zero offset will display a highlighted Offset indicator within its display.
Ratio
The X, Y, and R may be normalized to an Aux Input voltage. This is called a ratio
measurement. An output ratio is reflected in the displays. The numeric values, bar graphs
and strip charts all reflect the normalized output. Any display which is showing a
quantity which is affected by a ratio will display a highlighted Ratio indicator within its
display.
Expand
Output expands do not increase the displayed numeric values of X, Y or R. Expand
increases the resolution of the displayed X, Y or R numeric value. This is because the
expand function increases the resolution of the output, not the size of the input signal.
The displayed value will show an increased resolution but will continue to display the
original value minus the offset. Any display which is showing a quantity which is
affected by a non-unity expand will display a highlighted Expand indicator within its
display.
Output expands affect the bar graphs. The bar graphs are simply a reflection of the BNC
outputs and as such are expanded to provide more visual resolution.
Output expands do not affect the strip charts. The values being charted are already
floating point numbers with all of the resolution available. The strip charts do reflect the
offsets however.
See the SR860 Basics section for more information.
Output [Select]
This key selects the source for the CH1 (CH2) output BNC. CH1 can select either X or R.
CH2 can select either Y or θ. This also determines which parameter's offset and expand
are adjusted with the [Expand] key and the <Offset> knob.
Output [Expand]
Pressing this key selects the X or R Expand (CH1) or the Y Expand (CH2). Use the
[Select] key to select either X or R (CH1) and Y or θ (CH2). θ cannot be expanded. To
expand phase, expand the value of Y in quadrature.
The expand can be none (×1 or no expand), ×10 or ×100. If the expand is ×10 or ×100,
the corresponding LED will light. The output can never exceed full scale (±10 V) when
expanded. An output expanded beyond full scale will be output overloaded.
SR860 DSP Lock-in Amplifier
Chapter 3