SRS Labs QMS 100 Series, Руководство пользователя

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ECU 2-3
Technical Reference
ECU
Independently from the gas handling susbsystem, the ECU completely controls the operation of the
spectrometer, handles its data and transmits it to the computer for analysis and display.
The ECU is a densely packed box of electronics (3”x4”x9”) that connects directly to the probe’s
feedthru-flange and also to a host computer. It includes several regulated power supplies, a built-in
microprocessor, control firmware, and a standard RS232 communications port. It is powered by either
the external 24VDC (@2.5Amps) power supply.
Warning
The ECU does not have any serviceable parts and does not require any routine
maintenance. All calibration procedures should be done using the RS232 interface and
the RGA calibration command set.
During normal operation of the RGA, regulated power supplies built into the ECU set the electron
emission current, the voltage levels on the ionizer electrodes, and the high voltage across the electron
multiplier. RF/DC levels for each mass are also set and regulated by the ECU, based on internal mass
calibration parameters permanently stored in non-volatile memory. A built-in, logarithmic electrometer
detects the ion currents collected by the FC, or electron multiplier, and converts them to voltage signals
that are read by a built in A/D converter. The microprocessor automatically compares those signal
voltages against an internal calibration and calculates the magnitude of the ion currents. The ion currents
are then averaged as needed, offset corrected and transmitted to the host computer over RS232 for
immediate display.
Several built-in checks constantly monitor the operation of the probe and its operating environment. For
example, the filament emission, and the electron multiplier, are immediately turned off in the case of
accidental overpressure.
RS232/DCE/28.8k Connector
Use this connector to interface the RGA to a computer. The RS232 interface connector of the RGA is
configured as a DCE (transmit on pin 3, receive on pin 2) with full RTS/CTS handshaking enabled. Use
a straight through RS232 cable with 9-pin, type D connectors to connect the computer (usually DTE) to
the ECU. The communication parameters are
fixed at: 28,800 baud rate, 8 databits, no parity, 2 stop
bits.
Calibration Lockout
A calibration disable jumper (JP100) can be configured to block any attempt to change the value of the
mass filter settings in the RGA Head. The jumper is located on the top electronics board of the ECU
box, next to the microprocessor chip (i.e. biggest component on the board), and its two settings are
clearly indicated as CAL DIS and CAL EN. Supervisors may use this feature to prevent accidental