LEDs have very positive qualities as a light source for photometers:They achieve a very high intensity in a limited spectral range, which enables low-cost optical set-ups. They are very energy-efficient, which ensures a long operating life when battery operated. They have a long service life and usually last the life of the photometer.
However, the semiconductors inside the LEDs react to temperature fluctuations and are subject to changes during their lifetime. These lead to fluctuations in both the emitted wavelength, the spectral bandwidth and the intensity. While intensity fluctuations are still occur by zeroing the instrument can compensate before a measurement, a constant measuring wavelength cannot be achieved without the use of high-quality interference filters.
Only when interference filters are used is it possible to ensure that their analytical methods are reproducible.
All Lovibond® LED photometers use high-quality interference filters with a half-width of approx. 5 nm.