Agilent Technologies 1100 Series Reference Manual page 190

6
Introduction to the Variable Wavelength Dector
control circuit is enabled by the processor. Depending on the lamp type the heater voltage
is turned off or kept lower after lamp ignition.
Deuterium Lamp Current Control
The deuterium lamp current control circuit comprises two parts. One part generates an
ignition pulse of 600 VDC for the lamp, resulting in lamp ignition. After ignition this
voltage is disabled. The other part is a constant current source of 320 mA at an operating
voltage of about 85 VDC for stable operating conditions and light emission of the
deuterium lamp.
Igniting the Deuterium Lamp
The deuterium lamp filament is heated for several seconds prior to ignition. The
deuterium lamp current control circuit gives an ignition pulse to the lamp, resulting in
lamp ignition. The filament control circuit disables or lowers the filament voltage
(depending on the lamp type) if the lamp was ignited successfully.
If the deuterium lamp failed to ignite, the whole sequence is repeated after a wait
sequence for cooling down. If the deuterium lamp still does not ignite, an error message
occurs.
Diagnostic A/D Converter
The diagnostic A/D converter senses currents and voltages of the deuterium and
tungsten lamps and converts the analog signals into digital values. The digital values
are transferred via the control bus on the VWM board. When values are outside of the
normal range, an appropriate error message is generated.
Safety Switches
If the rear EPP foam is removed while the instrument is still on, the safety light switches
are activated and the deuterium lamp, the grating drive and the fan are switched off.
188 1100 Series Variable Wavelength Detector Reference Manual