Our human eyes are extremely sensitive to light. Studies have found that we can see as low as a single photon of light. However in our world of electronic media with ever brighter mobile phones and power LEDs we live in kind of sensory overload. To rediscover our eyes amazing capabilities I built the yGauge, a device that emits precisely defined, very low levels of light. Five LEDs with high resistors (in the range of mega-ohm) emit amounts of lights that range from just visible to barely visible. The faint light emitted by the yGauge LEDs can only be seen when well accustomed to the dark and with the device put close to your eye.
The LEDs are referenced against the photo multiplier tube of a Luminometer (Berthold Lumat LB 95019) and individually calibrated. The relative light intensity is marked on the back for each LED (light equivalent unit). The device can be used to reference your eye in the range of the gauge and can even be used to determine the luminosity of a glowing sample such as a bio- or chemoluminescent assays (see long exposure picture with yGauge as reference). It can also be used to test photo detectors sensitivity. And this for the fraction of the price of a luminometer.
The light emitting diodes (LEDs) used for the yGauge are of the type LP T67K from OSRAM. These LED emit light at a wavelength of 562nm, the peak sensitivity of the human eye.
The design files are available here under an open hardware license.
The device ships assembled, tested and calibrated.
CR20 battery not included.