The DALE40 provides continuous measurement of irradiation by simply placing the detection probe under the phototherapy light (fluorescent lamps only). In addition to verifying output power, the DALE40 saves costs by eliminating premature replacement of lamps. Light measurement is according to the percent response given the wavelength characteristics curve. The detector probe, included with the unit, has a wide angle lens which matches the cosine receiving function of human skin. Measurements are taken in µW/cm², with a range of 0-1999. This unit of measurement can be compared directly to other units of measurement.