Example methods are provided to improve placement of an adaptor (210,220) to a mobile computing device (100) to measure a test strip (221) coupled to the adaptor (220) with a camera (104) and a screen (108) on a face of the mobile computing device (100). The method may include displaying a light area on a first portion of the screen (108). The first portion may be adjacent to the camera (104). The light area and the camera (104) may be aligned with a key area of the test strip (221) so that the camera (104) is configured to capture an image of the key area. The method may further include providing first guiding information for a user to place the adaptor (210,220) to the mobile computing device (100) according to a position of the light area on the screen (108).