QTH lamps and IR emitters should be operated in Current mode in order to prolong lifetime and maintain stable light output throughout the its lifetime. Highly stable light output with minimum ripple for these two light sources is dependent on highly stable current supply to the QTH lamp's filament or the IR emitter. The 68938 is a highly regulated power supply, capable of supplying current with such stability that < 0.4% r.m.s. light ripple achieved when this power supply is also used with an Oriel housing, socket adapter, and power supply cable.

Instantly supplying the maximum current to a QTH lamp or IR emitter can be damaging to the lamp's filament or the emitter. Over time, repeatedly starting a QTH lamp or IR emitter in this fashion can significantly shorten its lifetime. The 68938 has a "soft start" feature, gradually increasing current supply until the user specified current is reached. This allows the user to maximize the lifetime and thus the usage of their QTH lamp/IR emitter.

A safety interlock feature is built in to the power supply. If the door to a lamp housing or output cable is not secured properly while attempting to start the QTH lamp or IR emitter, output current will not be supplied. If the lamp housing door or output cable become unsecured during operation, current supply to the QTH lamp or IR emitter will cease. This feature protects the user from accidental exposure to UV radiation and electrical shock.

For simple configuring and monitoring of power supply output settings, the 68938 has an LED display and OUTPUT ADJUST knob on the front panel. Although this is a constant current supply, the output voltage of the power supply can be momentarily viewed as well.