Manual - 8500A Series Peak Power Meter - Giga-tronics

Series 8500A Peak Power Meters
3.3.5 Graph Mode GPIB Operation
Using the Graph Mode instead of the Peak Mode allows autoscaling of a pulse, and provides you with a
display of the pulse. The Pulse and Marker sub-modes allow automatic timing measurements to be made.
You must first place the PPM in the appropriate sub-mode before using the timing measurement
command.
In the Graph Mode, the PPM can use a plotter to draw the shape of the pulse. In the Cursor sub-mode,
the delay and trigger parameters are written on the plot. The Pulse and Marker sub-modes add the results
of their respective timing measurements.
Delay values used by the instrument (Cursor, Start, and Marker, but not Window) are all displayed and
output relative to the Reference Delay at the time the delays are specified. When the Reference Delay is
changed, it will effect all of the other indicated delay values.
The real timing of the functions described above (relative to the trigger) remains the same, but the
displayed and GPIB output times of these functions are all in relation to the Reference Delay. When the
Reference Delay changes, the other delays change accordingly. For example, if the Cursor Delay was 5 ns
and the Reference Delay was increased by 2 ns, the Cursor Delay would decrease to 3 ns. Therefore,
Reference Delay entries should always be made first. Most applications and measurements will not
require changing the Reference Delay from its default setting of 0.000 nanosecond.
The information to be given next is in ascending order of complexity. All functions that provide results
on an automatic basis will be covered first. This should reduce programming time by allowing the PPM’s
internal software to take care of various tasks such as rise time.
Obviously, there are some types of pulses that cannot easily be measured automatically. If it is required
that algorithms be devised to extract pulse information, the PPM should serve this purpose well by using
the manual commands and functions which will be covered later in this section.
Graph Sub-Mode Selection Commands
GRFA Select Graphic display mode (Cursor sub-mode), channel A.
GRFB Select Graphic display mode (Cursor sub-mode), channel B.
MRKA Select Marker sub-mode display, channel A.
MRKB Select Marker sub-mode display, channel B.
PULA Select Pulse Parameters sub-mode, channel A.
PULB Select Pulse Parameters sub-mode, channel B.
Automatic Functions of the Graph Mode
The following commands will instruct the PPM to automatically carry out a procedure of some kind. In
most cases, only instrument settings are made. In some cases, settings are made and appropriate
information is output to the controller.
When using the PPM’s graphic capabilities, it should be kept in mind that any operations are only
applicable to Pulse measurements. All pulse operations require a trigger of some kind. Therefore, before
attempting GPIB operations it is advised to become familiar with the manual operation of the PPM. To
ensure that the instrument will trigger properly, the Internal Channel A, Internal Channel B, or the
External Trigger function must be selected.
☛ NOTE: Failure to trigger for any pulse operation over the GPIB will result in placing the
PPM in a Waiting for Trigger state.
3-24 Manual No. 20790, Rev C, November 1998
Superceded by Revision D, March 2009