User guide

374 Advanced User Guide
14 GC Output Signals
Digital Signals
The GC outputs digital signals only to an Agilent data system.
The following discussions describe features that impact the data
sent to data systems, not the analog data available to
integrators.
Digital zero
Digital signal outputs respond to the Zero command by
subtracting the signal level at the time of the command from all
future values.
Baseline level shifts
Some run time operations, such as changing signal assignment
or switching a valve, can produce large changes in the signal
baseline position. This can complicate signal processing by
external devices. The GC provides two run table commands to
minimize such problems with digital output—see “Run Time
Programming” on page 14.
Store signal value Saves the value of the signal at the time of
the command.
Signal zero – value Creates a new zero by subtracting the
stored value from the current value of the signal and applies
this zero to all future values.
When these commands surround a baseline- shifting command,
the effect is to bring the new baseline to the previous level, as
shown in the next figure.
The Store signal value event must occur before the event that
shifts the baseline, and the Signal zero – value event must occur
after the baseline has stabilized at the shifted level.