The 3421A Data Acquisition/Control Unit is an economical system designed for data logging small data acquistion projects. The 3421A scans up to 30 channels, measuring DCV, ACV, 2-wire and 4-wire ohms, frequency, and temperature. It also reads and writes digital information and stores up to 30 analog readings. The standard 3421A comes with an HP-IL interface for battery-powered flexibility or GPIB for more computational power. A choice of up to 3 rear panel installed assemblies allows additional user flexibility. An internal 5.5 digit A/D converter gives 1 microvolt resolution on the 300 millivolt range permitting measurement of thermocouples, strain gauges, and other low-level transducers.