the electric diagram of a Philips HP3111 sunlamp
the infrared/ultraviolet mode selection of  a Philips HP3111 sunlamp
Mode selection of Philips HP3111 sunlamp
The problem that the infrared wavelength
of a single quartz tube heat lamp section
decreased when it was operated as
ballast for the sunlamp, could be
overcome with a diode, assuming that the
sunlamp was designed for AC-operation.
As can be seen in the electric diagram of
the Philips HP3111 sunlamp on display
here, the current in infrared mode would
flow to the quartz tubes during the
positive half of the alternating voltage
only, due to the diode that was connected
in series with the single quartz tube
section. As a result of this configuration
the dissipated energy in the quartz tubes
was almost the same during the
combined- and the infrared mode and
prevented the application of an additional
quartz tube section. The resistor left of
the discharge tube was responsible for
the ignition of the lamp, as will be
explained in the next section of this