The 2640A and 2645A NetDAQ® Networked Data Acquisition Units are 20-channel front ends that operate in conjunction with NetDAQ Logger for Windows (hereafter known as NetDAQ Logger) to form a data acquisition system. The instruments measure dc volts, ac volts, Ohms, temperature, frequency, and dc current. Temperature measurements use thermocouples or resistance-temperature detectors (RTDs). To measure other parameters, use an appropriate transducer. The instrument also includes ten computed channels for custom calculations based on measured values. The NetDAQ instruments scan the 20 analog channels in sequence and calculate the values for the ten computed channels. Interval timers, alarm conditions, and/or an external signal input can trigger scans. The NetDAQ Logger software configures and controls up to 20 instruments via an Ethernet connection. The software provides the means to view scan data and log it into files. The 2640A and 2645A instruments (Figure 1-1) are identical in operation and appearance, and vary only in emphasis. The 2640A emphasizes precision and supports up to 100 measurements per second, with 5 digits of resolution, .02% accuracy, and 150-volt common mode voltage (300 volts on channels 1 and 11). The 2645A emphasizes increased measurement speed supporting up to 1000 measurements per second, with 4 digits of resolution, 0.04% accuracy, and 50- volt common mode voltage.