The 521 Series laser wavelength meter from Bristol Instruments is a compact system that provides reliably accurate laser wavelength measurement, intended for scientists and engineers who need to know the absolute wavelength of their laser but not to the highest accuracy available. The 521 Laser Wavelength Meter uses Michelson interferometer-based technology to measure the absolute wavelength of virtually any CW laser to an accuracy of ± 10 ppm. The model 521 uses a Moire scale as a built-in reference. This high-resolution scale provides the continuous calibration necessary to guarantee the accuracy of the wavelength measurement. Two versions of the model 521 are available to satisfy the needs of most experiments. The 521-VIS operates over the wavelength range of 350 to 1100 nm, and the 521-NIR has an operational wavelength range of 500 nm to 1.7 um. A convenient pre-aligned fiber-optic input accepts that laser under test. Instantaneous wavelength information is provided with a measurement rate of 10 Hz, and a USB instrument interface results in automatic laser wavelength reporting and control.