True RMS voltmeters

Murata has introduced a series of Datel voltmeters that are claimed to overcome the limitations of conventional average-responding AC voltmeters.

The DMS-20RM series can measure the true-RMS value of complex AC voltages and, with an input frequency range of 47 Hz to 1 kHz, is suitable for a wide range of applications including high-end consumer electronics, laboratory instrumentation and other equipment requiring precise AC line monitoring.

The meters can measure and accurately display the true-RMS value of triangle waves, square waves or other irregularly shaped waveforms with a full-scale accuracy of ±0.4%.

Unlike average-responding AC voltmeters, the modules can measure down to 0 V as they use their own integrated, independent power supply that is fully isolated (up to 2 kV) from the input AC signal.

The four-wire series is available with a choice of three input ranges of 20 VAC (with 0.01 V resolution), 200 VAC (0.1 V resolution) or 300 VAC (1 V resolution). Depending on their application, users can choose modules that operate from a supply voltage of either 85 to 264 VAC or 10 to 40 VDC. No external isolation transformers or auxiliary power supply conditioning components are required.

A large 3½-digit 9.4 mm bright red LED display allows easy reading from distances of up to 4 m.