The standard Model SFA Stereo Microscope Fluorescence Adapter has a simple ON/OFF switch. This is adequate for most customers, who want the maximum excitation intensity so that they see maximum fluorescence from their samples. There are some cases, however, where more control of the lamp output is needed. In some cases users want to be able to fine tune the intensity, and in others they want to be able to turn the excitation light on and off with precise timing, such as for photoactivation or for behavioral experiments. Two options,
DIM and PULSE, add these capabilities.
The DIM option adds a combined switch and dimmer control. When you first turn the unit on it is at full power. As you rotate the switch the intensity decreases, reaching ~30% at the minimum setting. You have finer control in the brighter portion of the adjustment range. We originally added this for an industry customer who had a sample with a fluorescence of interest along with a weaker background fluorescence of the same color. They found that when they decreased the excitation intensity the eye perceived the background fluorescence as decreasing faster than the signal intensity, producing higher contrast.
The PULSE option adds a BNC connector on the rear of the base that accepts a user-supplied voltage input from a computer, function generator, or the like to turn the excitation light on and off. It can be used for precise on/off control, or it can be used as a dimmer by varying the duty cycle of a square wave (
PWM – Pulse Width Modulation).
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