AC Power Analyzers

A power analyzer is a multi-functional measurement instrument that analyzes the electrical power quality of direct current (DC) or alternating current (AC) systems.

A power analyzer optimizes cost and space by combining the capabilities of multiple instruments in a single package. The instruments that it can replace include:

• Power meter: A power analyzer can measure power consumption, efficiency, and power quality.
• Oscilloscope: A power analyzer can capture and display real-time voltage and current waveforms.
• Digital multimeter: A power analyzer can measure instantaneous voltage and current like a multimeter.
• Waveform generator: A power analyzer can generate arbitrary analog waveforms to simulate various electrical conditions.
• Data logger: A power analyzer can record measurement data over time and transfer them to a computer for detailed power analysis.
• Power supplies: Some can work like power supplies to send power to the devices under test (DUTs).
• Electronics loads: Some power analyzers can act as electronic loads to sink current, which is useful when the device being tested is a power supply.

Both power meters and power analyzers are used to characterize power systems. However, power analyzers combine multiple instruments under one package. In a typical test setup, power meters are rarely standalone and often combined with multimeters, waveform generators, oscilloscopes, loads, and data loggers. Power analyzers pack all of them into a single instrument to enable compact, convenient, end-to-end test setups.

Power quality analyzers are categorized based on their AC/DC capabilities as:

• DC power analyzers: They are suitable for analyzing the DC outputs of DC power supplies, DC-DC converters, and AC-DC adapters.
• AC power analyzers: AC power analyzers characterize the outputs of AC power supplies, DC-AC converters, and AC-AC converters. Since AC signals may have DC components, AC power analyzers are typically capable of analyzing DC signals, too. Single-phase analyzers are more common, but three-phase power quality analyzers are also available to verify the overall power quality and individual phase power of three-phase devices.

Power measurements and quality analysis

Power analyzers combine the capabilities of power meters and digital multimeters. They can measure:

• voltages (max, min, average, and peak-to-peak) with high accuracy
  
• current, using current probes such as current transducers, AC/DC current clamps, and shunts
• electrical power in watts
• apparent power (volt-amps)
• reactive power (VAR)
• power factor
• true root-mean-square (RMS) voltage and current, even if your waveform is non-sinusoidal and has DC offsets
• phase angle
• voltage crest factor
• current crest factor
• impedance losses
• energy efficiency

Oscilloscope functions

Power analyzers can act as oscilloscopes with typical scope functions to help diagnose power quality issues. They can:

• Support multiple isolated analog input channels, typically from two to four
  
• Visualize real-time voltage and current waveforms
• Be set to single-shot mode to capture high-speed transients
• Set triggers
• Apply math functions
• Enable AC or DC coupling
• Support floating inputs

For example, the PA2201A IntegraVision AC power analyzer can sample signals at 5 million samples per second with a bandwidth of 2.5 megahertz (MHz).

Some of the features and specifications an engineer should pay attention to depending on the use case:

• AC and DC capabilities: Select a power analyzer that is compatible with the nature of the DUT and the AC/DC nature of its input and output signals.
• Frequencies and harmonics of the signals: Ensure that the bandwidth of the power analyzer is sufficient to capture the harmonics of the signals. As a rule of thumb, the bandwidth should be three to five times the maximum fundamental frequency to capture its higher harmonics and waveform shape accurately. For example, the PA2203A 3-phase AC power analyzer has a 2.5 MHz bandwidth, sufficient for capturing the 400 Hz AC signals used in avionics. Switch-mode power supplies typically operate in tens of kilohertz (kHz), and a power analyzer with about 200kHz bandwidth is sufficient to capture their harmonics.
• High accuracy for digital circuits: For analyzing power supply to sensitive digital circuits like field-programmable gate arrays, use power analyzers with high accuracy and high digits of resolution.
• High-voltage safety features: Verify the tester's safety ratings to ensure that it's designed to handle high voltages and currents. For example, for high-voltage AC power analyzers, look for safety ratings like "1000 V CAT IV," meaning the device can safely handle 1,000 volts and complies with the IEC's CAT IV safety standard.
• Connectivity options for offline analysis: For complicated diagnoses that require a lot of data from the data logger, ensure that the power analyzer has high-speed connectivity options like gigabit ethernet rather than slower options like Bluetooth.
• Calibration: Ensure that the power analyzer's results are accurate and reliable by regular calibration with ISO/IEC 17025 certification.