GC Output Signals 7
Advanced Operation Manual 229
Analog Signals
If you use an analog recorder, you may need to adjust the
signal to make it more usable. Zero and Range in the Signal
parameter list do this.
Analog zero
Zero Subtracts value entered from baseline. Press [On/Yes]
to set to current Value or [Off/No] to cancel.
This is used to correct baseline elevation or offsets. A
common application is to correct a baseline shift that occurs
as the result of a valve operation. After zeroing, the analog
output signal is equal to the Value line of the parameter list
minus the Zero setpoint.
Zero can be programmed as a run time event. For details, see
“Run Time Programming” on page 12.
1 Verify that the detector is on and in a ready state.
2 Press [Analog Out 1] or [Analog Out 2].
3 Scroll to Zero.
4 Press [On/Yes] to set Zero at the current signal value,
or
Enter a number between - 500000 and +500000. A value
smaller than the current Zero shifts baseline up.
Analog range
Range Scales data coming from the detector
Range is also referred to as gain, scaling, or sizing. It sizes
the data coming from the detector to the analog signal
circuits to avoid overloading the circuits (clamping). Range
scales all analog signals.
If a chromatogram looks like A or B in the next figure, the
data needs to be scaled (as in C) so that all peaks are
visible on the paper.
Valid setpoints are from 0 to 13 and represent 2
0
(=1) to 2
13
(=8192). Changing a setpoint by 1 changes the height of the
chromatogram by a factor of 2. The following chromatograms
illustrate this. Use the smallest possible value to minimize
integration error.
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