The 5790A AC Measurement Standard is a systems instrument that measures ac voltage with the uncertainty of a thermal transfer standard. You control the 5790A’s operation from the front panel or remotely over the serial or IEEE-488 interface. You can operate the 5790A in measurement mode or transfer mode. In measurement mode, the 5790A operates as a digital ac voltmeter with up to 8 digits of resolution. Measurement mode uses an internal dc reference. In transfer mode, you apply an external dc or ac reference source. The 5790A automatically performs switching and calculations, and displays the resulting ac-dc or ac-ac difference on the vacuum fluorescent Control Display. The 5790A covers a voltage range of 700 μν to 1000V (70 mV minimum in transfer mode), and a frequency range of 10 Hz to 1 MHz. A wideband voltage option extends frequency range to 30 MHz. The 5790A is also compatible with Fluke A40 current shunts, which permit you to make ac-dc or ac-ac current transfer measurements up to 20A. Refer to the Specifications for details, A variety of input connections allows you to use the one that best suits your application. There are four sets of input terminals on the 5790A, two 50Ω Type “N” connectors and two sets of five-way binding posts. One 50Ω Type “N” and one set of binding posts is dedicated to the ac measurement and transfer modes. AC or DC voltages can be applied to either input connection, allowing you to perform automated ac-dc transfer measurements. The second Type “N” input connection supports the optional wideband mode, and the SHUNT binding posts are for Fluke A40 Series current shunts. Two patented internal standards contribute the most to the 5790A’s ability to measure rms ac voltage with such low uncertainty. These two standards are a stable and precisely variable dc source similar to the one in the Fluke 5700A Calibrator and a high- performance thermal rms sensor similar to the one in the Fluke 792A AC/DC Transfer Standard. Reference amplifiers establish the accuracy and stability of the internal dc source. A patented 26-bit digital-to-analog converter (dac) provides the 5790A with the ability to precisely vary its internal dc source. This is a pulse-width modulated dac with linearity typically better than 0.2 ppm of full scale. On the ac side, the Fluke rms sensor is similar in principle to a thermal voltage converter (thermocouple), but has faster settling time, low dc reversal error, higher signal-to-noise ratio, and excellent frequency performance.