Isolated Energy Metering Chipsets for Polyphase Shunt Meters

ADI's ADE7978, ADE7933, ADE7932, and ADE7923 form a chipset dedicated to measuring three-phase electrical energy using shunts as current sensors.

The ADE7933 and ADE7932 are isolated, three-channel, sigma-delta analog-to-digital converters (Σ-Δ ADCs) for polyphase energy-metering applications that use shunt current sensors. The ADE7923 is a non-isolated, three-channel, Σ-Δ ADC for the neutral line that uses a shunt current sensor. The ADE7932 features two 24-bit ADCs, and the ADE7933 and ADE7923 feature three 24-bit ADCs.

One channel is dedicated to measuring the voltage across the shunt when a shunt is used for current sensing. This channel provides a signal-to-noise ratio (SNR) of 67 dB over a 3.3 kHz signal bandwidth. Up to two additional channels are dedicated to measuring voltages, which are usually sensed using resistor dividers. The unused voltage channels on the neutral ADE7923 can be used for auxiliary voltage measurements. These channels provide an SNR of 75 dB over a 3.3 kHz signal bandwidth. One voltage channel can be used to measure the temperature of the die via an internal sensor.

The ADE7978 is a high-accuracy, three-phase electrical energy measurement IC with serial interfaces and three flexible pulse outputs. The ADE7978 can interface with up to four ADE7933, ADE7932, and ADE7923 devices. The ADE7978 incorporates all the signal processing required to perform total (fundamental and harmonic) active, reactive, and apparent energy measurement and RMS calculations, as well as fundamental only, active and reactive energy measurement and RMS calculations. A fixed-function digital signal processor (DSP) executes this signal processing.