Stanford Research Systems RGA100, Operating Manual And Programming Reference

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Detection Control Commands 6-43
SRS Residual Gas Analyzer
measurement and scanning times due to the reduced bandwidth of the
electrometer and increased averaging.
The NF parameter must be chosen keeping in mind the strong interplay between
detection limit and acquisition speed.
Histogram scans, analog scans, single-mass measurements and total pressure
measurements all share the same value of NF setting during measurements.
Important : The NF parameter is set to its default value when the RGA is turned
on.
It is good practice to readjust the Zero of the ion detector every time the
electometer’’s noise floor setting is changed. This is particularly important if the
new detector settings have not been used in a long time or since the unit was
turned on or recalibrated with the CL command. See the CA command for details
and more recommendations.
RGA Windows note: When using the RGA Windows program to operate the
RGA, the Scan Speed parameter setting available in the Scan Parameter Setups
of the Scan menu is used to set the NF parameter value in the RGA Head
according to the equation:
NF = ScanSpeed - 1.
Parameters:
NFparam, param: 0-7: The parameter represents the noise-floor level desired.
Lower parameter values correspond to lower baseline noise, better detection
limits and increased measurement times.
Please refer to the Electrometer section of the RGA Electronics Control Unit
chapter to obtain detailed information about detection limits and bandwidth
values as a function of NF settings.
NF* : The noise-floor is set to its default value.
Default value: 4.
NF? : Returns the noise-floor setting currently used by the electrometer .
Error checking:
Number parameters must be within the specified range, and be integers.
The absence of a parameter (i. e. NF) is treated as an error.