The smartphone-enabled DMM

The digital multimeter (DMM) is pervasive among technicians, engineers, and do-it-yourselfers. For a very small amount of money, one can obtain an instrument that measures dc and ac voltage, current, and resistance. DMMs have seen modest improvement since the original instruments, with advances in accuracy and improved features due primarily to advances in microelectronic integration. With the advent of smartphones, we see another possibility for advancement in DMMs. The two primary advantages of a smartphone-enabled DMM are compact size due to using the smartphone as the display and the opportunity for customized user interfaces for specific applications. In this article, we develop a prototype pen-style DMM that uses Bluetooth to communicate with an Apple iPhone.