A digital multi-meter (DMM) is described which can be inserted into a peripheral device card expansion slot of a personal digital assistant (PDA) to provide the PDA with DMM functionality. The DMM is configurable by configuration data supplied by application software running on the PDA. Configuration of the DMM may include, for example, setting measurement function and input ranges. The DMM internal circuitry measures input signals, digitizes them and supplies them to the PDA for display and/or storage. This allows for a data acquisition unit which combines a DMM with the computing power of a PDA. The PDA may be programmed to display or store data in a multitude of ways, depending on the requirements of a particular application. The combined DMM and PDA may benefit from various other functions of the PDA, for example wireless communication of data to allow remote data logging.