Photometry makes use of several devices and lux meter is one of those. It measures the intensity of light and can be used for various radiation processes to help mankind. Before making any radiating device perfect, it becomes necessary to measure its capability and lux meters can perfectly do that.
However, these devices go through a series of testing processes before being launched into market. This is because if a device has to test and measure something, then its perfection becomes crucial. Many retailers sell such devices but one should buy after researching well about the product and seller.