3156B User Manual
Racal Instrument © 2005
WaveCAD 4-11
The 10 MHz Ref sub-group provides selection between internal or
external references. The 3156B has two reference options: Backplane
reference and TCXO. The backplane reference is routed to the VXI
controller. Normal reference is 100ppm however, if an external
reference is applied to the controller, the reference is automatically
routed to all modules that feed off the backplane clock reference. The
TCXO replaces the backplane reference for cases were 1ppm is
sufficient for the application. An external reference input is provided for
applications requiring better accuracy and stability. Click on the
Internal button to select the Internal reference, or the External button
to activate the external reference input.
WARNING
By selecting an external reference you are disabling the
internal reference circuit. If you do not have a 10 MHz
reference connected to the instrument, the output will
generate erroneous frequencies.
Enable
The enable group affects the 3156B only when the operate enable
source is set to software (software is the default enable source). If the
output state is on, clicking on the operate Enable button will stimulate
the output. In some cases, the disable can stop the output. The
various options to enable and disable the output waveforms, using the
enable commands are given in Table 3-2.
The Arbitrary &
Sequence Panel
The Arbitrary & Sequence panel, as shown in Figure 5-5, is invoked by
pressing the ARB button on the Panels bar. Note that if you invoke the
Arbitrary & Sequence Panel from the Panels menu, the 3156B will not
change its output type. On the other hand, if you select the arbitrary,
or the sequenced options from the Main Panel, the 3156B will
immediately change its output to the selected waveform type. The
functional groups in the Arbitrary Waveforms Panel are described
below.
Parameters
The Parameters group contains two parameters for each channel:
Amplitude and Offset. Actually, the values exhibited in this group are
exactly the same as in the Main Panel, so every time you change
amplitude and offset in the Parameters group, the other panels are
updated automatically.
To access the required parameter, click on the parameter name. The
LED next to the required parameter turns on. The value that is
associated with the lit LED is displayed on the digital display. You can
use the dial, keyboard, or the [
↑
] [
↓
} keys to adjust the readout to the
required setting. After you modify the reading, press Execute to
update the 3156B with the new reading.