Power quality meters are essential tools for monitoring and ensuring the reliability of electrical systems. They measure various electrical parameters, including voltage, current, frequency, harmonics and other factors that affect the performance of electrical equipment. When it comes to choosing the right power quality meter, one of the key factors to consider is the accuracy class of the meter. Two of the most common accuracy classes in the industry are Class A and Class S.
What is an Accuracy Class in Power Quality Meters?
Accuracy classes are standardised specifications used to indicate how precise a power quality meter is in measuring electrical parameters. These classes are defined by standards such as IEC (International Electrotechnical Commission) and ANSI (American National Standards Institute), and they help users determine the level of accuracy they can expect from the meter. The higher the class number, the more accurate the measurement.
In the world of power quality monitoring, Class A and Class S meters are designed for different levels of accuracy and understanding their differences is crucial for selecting the right meter for your needs.
Class A Power Quality Meters
Class A meters are designed for general purpose use and are suitable for a wide range of power quality measurement applications. These meters meet the international standard IEC 61000-4-30, which outlines the testing and performance criteria for power quality equipment.
Class A meters are typically used for:
General Power Quality Monitoring:
Class A meters are ideal for assessing overall power quality and identifying common issues such as voltage sags, spikes, transients, harmonic and interruptions.
Regulatory Compliance:
Many organisations use Class A meters to ensure compliance with industry regulations that govern power quality standards.
Routine Energy Audits:
They are commonly used for energy audits, helping businesses and utilities to assess power quality trends over time.
Pictured right: SATEC’s PM180 Class A Power Quality Analyser
Key Features of Class A Meters:
Accuracy:
Class A meters provide sufficient accuracy for most power quality measurements. They generally have a tolerance of ±2% for the measurements they provide.
Frequency Range:
Typically suitable for systems that operate at standard frequencies of 50 or 60 Hz.
Measurement of Common Power Quality Events:
Class A meters are designed to detect and report on common power quality events such as voltage dips, surges and harmonics.
Wide Range of Applications:
Used in industries ranging from manufacturing and utilities to telecommunications and building management systems.
Class S Power Quality Meters
Class S meters, on the other hand, are designed for specialised applications that demand higher levels of accuracy. These meters are often required for advanced diagnostics or when dealing with critical infrastructure.
Class S meters are typically used for:
Precise Power Quality Analysis:
Class S meters are ideal for measuring complex power quality phenomena, such as very fast transients or interactions between harmonics and other disturbances.
Power Quality Investigation and Research:
These meters are often used in research settings or by utilities that are investigating unusual power quality issues or events that need precise, high-resolution measurements.
Forensic Measurements:
Class S meters are essential for forensic analysis in situations where the exact nature and timing of power quality events need to be understood with a high degree of certainty.
Pictured right: The PRO Series – Class A and Class S available
Key Features of Class S Meters:
Superior Accuracy:
Class S meters provide much higher accuracy than Class A meters, with a tolerance of ±1% or better, which is crucial for precise measurements.
Advanced Measurement Capabilities:
These meters are often equipped with specialised features to measure high-frequency disturbances, fast transients and complex waveforms.
More Detailed Data:
Class S meters typically provide much more detailed data for analysis, allowing users to identify subtle power quality issues that Class A meters may miss.
Higher Sampling Rate:
Class S meters often have a higher sampling rate, making them capable of capturing fast transient events that could be overlooked by less sophisticated meters.
Feature
Accuracy
Typical Use
Measurement Range
Sampling Rate
Cost
Regulatory Compliance
Class A
±2% (sufficient for general use)
General power quality monitoring
Common power quality events
Standard
Lower cost
Suitable for basic regulatory needs
Class S
±1% or better (ideal for detailed analysis)
Advanced diagnostics and research
High-frequency disturbances & transient
Higher sampling rate for fast events
Higher cost due to precision
Used for critical compliance or research
When to Choose Class A or Class S?
The choice between Class A and Class S meters depends on the complexity and precision required for your application:
Choose Class A
if you need a meter for general power quality monitoring, such as tracking voltage fluctuations, harmonics and ensuring compliance with standard regulations. These meters are cost-effective and accurate enough for most routine applications.
Choose Class S
if your goal is to conduct advanced power quality analysis, perform detailed investigations or troubleshoot complex and fast power quality disturbances. If you’re dealing with critical systems or need the highest level of accuracy for regulatory compliance, research or diagnostics, Class S meters are the way to go.
Both Class A and Class S power quality meters serve distinct roles in ensuring electrical systems operate efficiently and reliably. Understanding the differences between these accuracy classes will help you make an informed decision when selecting a meter for your application.
Whether you’re looking for a reliable, general-purpose meter or need a highly accurate tool for specialised analysis, SATEC has the perfect power quality meter for your needs. Talk to our team of experts today.
