HP 34401A Multimeter, The HP 34401A is a high-performance 6½-digit digital multimeter designed for precision measurements in both bench and system applications. It offers accurate DC and true RMS AC voltage and current measurements, along with resistance, frequency, and continuity testing. With fast measurement speeds, dual display capability, and built-in GPIB and RS-232 interfaces, the HP 34401A provides reliable and versatile operation for calibration labs, R& D, and production environments.