User`s manual

Programming the RGA ECU 3-21
Technical Reference
The net result is very stable RF/DC levels that are highly insensitive to the operating conditions of the
RGA ECU.
Important: The RF/DC stabilization algorithm (Step 2 above) remains active as long as no new
commands are detected by the RGA ECU. Once a new command is received, stabilization stops, and
the new command is executed.
Use the ML0 command to turn off the RF/DC bias when finished performing measurements and before
quitting the program controlling the RGA.
QMF programming example
ML28 Activate the mass filter and center its pass band at 28 amu
ML42.50 Activate the mass filter and center its pass band at 42.50 amu.
ML0 Deactivate the QMF. (same as MR0 command)
QMF Programming tips
• Take advantage of the stabilization feature of the ML command whenever possible. For
example: Do not send any new commands to the RGA ECU once the QMF has been set to
the specified mass value, or otherwise recall the ML command, whenever practical, to
refresh the QMF RF/DC settings.
• A typical application of the ML command involves monitoring a single mass concentration
looking directly at the linear output of the CDEM anode with a boxcar or transient digitizer.
• Use the ML0 command to turn off the RF/DC bias when finished performing measurements
and before quitting the program controlling the RGA.
• It is good practice to perform an analog scan before using the ML command to assure the
correct tuning (i.e. correct peak locations and widths) of the quadrupole mass filter. Perform
a complete Peak Tuning Procedure as described in the RGA Tuning chapter of this manual
if shifts in the peak locations are observed.
Error Checking the RGA
Several firmware-driven checks automatically test the RGA when the unit is turned on, and
continuously monitor the internal workings of the instrument. A “Background Filament Protection
Mode” is activated when the filament is turned on to protect the delicate filament (and CDEM) from
accidental overpressure. Several commands can be used to trigger hardware tests on the ECU. Any
one of the internal checks just described can detect and report errors, and it is the responsibility of the
user to constantly monitor the RGA ECU for error reports.
There are two ways to detect the presence of errors in the RGA:
1. Visually: Inspecting the red LED’s on the rear panel of the ECU.
2. The Error LED is turned on whenever a hardware problem is detected, and it flashes twice
if a communications error is generated during programming.