Stanford Research Systems RGA100, Руководство по эксплуатации и программированию

Страница: 169 / 362

Tuning Commands 6-65
SRS Residual Gas Analyzer
The RGA Head adjusts the DC levels of the quadrupole filter during measurements so
that constant mass resolution is automatically available throughout the entire mass range
of the spectrometer. The bulk of the DC voltage is supplied by a DC power supply whose
output is linearly related to the RF amplitude. The rest of the DC voltage (DC_Tweek) is
provided by the output of an 8 bit digital-to-analog converter (DAC). The firmware uses
two Peak Tuning Parameters : DI (Intercept) and DS (Slope), stored in the non-volatile
memory of the RGA, to calculate the 8 bit settings of the DAC according to the linear
equation:
DAC8 (m) = DS
.
m + DI
where m is the mass in amu, and DAC8(m) is the 8 bit setting at that mass.
The purpose of the Peak Width Tuning Procedure is to determine the values of DI and
DS so that all the peaks in an analog spectrum have the desired peak width (typically 1
amu).
The DS command is used to program the value of the DS peak tuning parameter during
the Peak Width Tuning Procedure. The value is saved in the non-volatile memory of the
RGA Head and used by the firmware to generate DAC8(m) during measurements.
Note to Supervisors : A calibration disable jumper (JP100) available on the circuit board
can be used by a supervisor to block any attempt to modify the value of the DI parameter.
Supervisors may use this feature to prevent accidental changes in the calibration
parameters by inexperienced operators. Setting JP100 will disable peak tuning of the
Head.
Parameters:
DSparam, param: -0.8500 - +0.8500: If Calibration is enabled by the jumper JP100
(See CE Command) the value of DS in non-volatile memory is updated and the internal
scan parameters used to program the DC during scans and single mass measurements are
updated accordingly. RGA100 DS range: -2.5500 - +2.5500
DS* : Use this format to replace the peak tuning parameter with the original factory
setting for DS. The factory value is retrieved from memory, and used as the new
parameter value to excecute the command as above.
DS? : Query. Returns over RS232 the parameter value currently saved in memory.
Error checking:
The absence of a parameter (i. e. DS) is treated as an error in the parameter.
This parameter is protected by an internal jumper (JP100) and a Protection-Violation
error will result if the jumper is in the Calibration Disabled mode (See CE command).
RIparam, param: -86.0000 - +86.0000, *, ?, none
Description : RF_Driver output @ 0 amu (Peak Position Tuning command).
JP100 Jumper protected.
Echo: Query Response.