Name the measurement before the model. Metering energy, tracking demand, sizing a harmonic filter and proving an EN 50160 complaint each need a different instrument class, and only the last one forces IEC 61000-4-30 Class A. Buy the class your decision depends on, not the class your budget prefers.
Specifications come from Circutor product listings for the CVM-B, CVM-A and QNA 600 families, and the requirements from IEC 61000-4-30, IEC 61000-4-7, IEC 61000-4-15 and EN 50160.
Ask what the number will be used for
Three questions settle most of the choice before anyone opens a datasheet.
- What decision does the reading support? Allocating energy cost tolerates a slower update and a wider tolerance. Splitting harmonic responsibility between two parties does not.
- Who has to accept the result? Internal trending accepts almost anything. A network operator, a utility or an auditor asks for the class written into the contract.
- How long must the instrument run unattended? A compliance statistic needs a full week of aggregated data, so memory, communications and clock behaviour are selection criteria.
An analyzer that answers the first question but fails the second produces numbers that look right and cannot be used.
Four goals and the capability each one forces
- Energy and cost allocation. The deciding number is the accuracy class of the whole chain, not the display. Active energy classes 0,2 S and 0,5 S per IEC 62053-22 exist for transformer-operated static meters, and 0,5 S is the usual entry point for sub-metering and internal charging. Reactive and apparent energy should be measured, not derived.
- Demand and load management. You need maximum demand registers over the interval your tariff uses, commonly 15 or 30 minutes, and outputs that act. Two relays and two transistor outputs are enough to run alarms or pulse counters. Without them the analyzer only reports after the peak has passed.
- Harmonics. Total harmonic distortion alone tells you something is wrong, not what to buy. Filter sizing needs the individual orders, so the order range matters. A 31st-order device covers the usual 5th and 7th problems; studies and capacitor bank work often want the 50th order and above.
- Flicker, unbalance and events. Flicker severity, negative-sequence unbalance and voltage dips belong to the same decision, because all three are voltage quality and all three are defined by the same class.
Class A and Class S are different jobs, not two prices
IEC 61000-4-30 (Ed. 3) defines two measurement classes. Class A is the reference class for contractual, statutory and dispute work. Class S is the statistical class for surveys and condition assessment.
If the result may end in a discussion with another party, Class S data will be challenged, and the challenge will be about the instrument.
Match the goal to the class before you match the price
Three recommendations follow from the table rather than a list:
- For internal cost allocation, a 0,5 S panel analyzer is enough. Class A buys accuracy the tariff does not ask for.
- For a harmonic study that will decide a filter, buy Class A. The analyzer costs little against a filter sized on Class S data.
- For a supply complaint or a substation, buy Class A with a calibration certificate and log at least a full week before drawing conclusions.
The Circutor tiers against those goals
Circutor splits the range along the same lines.
- CVM-C and CVM-D families. Panel and DIN rail analyzers for measurement and basic energy, including multi-circuit and DC variants such as the CVM-D41 DC.
- CVM-B50. Panel analyzer, 96 x 96 mm, four measuring channels, harmonics to the 31st order, memory, Modbus TCP/IP over Ethernet or Wi-Fi, two relays, two transistor outputs and four digital inputs.
- CVM-B100 and CVM-B150. The energy tier: active energy accuracy 0,5 S with transformer current input (.../5 A, .../1 A or 250 mA), Modbus RTU or BACnet over RS-485, two relays, two transistor outputs and two digital inputs. The B100 is 96 x 96 mm and the B150 is 144 x 144 mm.
- CVM-A1500. The Class A tier: harmonics to the 63rd order, active energy accuracy 0,2 S, 200 MB of memory, event and waveform recording, a web server with HTML5 and XML, RS-485 and Ethernet, 144 x 144 mm. The CVM-A1500A version adds the IEC 61000-4-30 Class A certification entry and a calibration certificate.
- CVM-A1600 series. Class A analyzers stated against IEC 61000-4-30 (Ed. 3) and the IEC 62586-2 method, with Ethernet, Wi-Fi and RS-485.
- QNA 600. The rack tier for permanent monitoring: Class A, harmonics to the 64th order, 0,5 S energy accuracy, 16 GB of storage, an integrated web server and IEC 61850.
The naming is worth remembering. The higher the letter, the higher the measurement class. ITF marks the transformer current input and FLEX marks Rogowski coils.
The current transformer decides your real accuracy
An analyzer quoted at 0,2 S is only as good as the current signal it receives. A class 1 current transformer feeding a Class A analyzer produces class 1 energy data.
- Match the transformer class to the goal. Class 0,5 and 0,2 S transformers exist for the same reason the analyzer classes do.
- Mind the burden. A high-burden transformer on a long cable run loses accuracy at the low end of the range, which is where standby loads sit.
- Rogowski coils avoid saturation and retrofit quickly, at the price of a different error budget and an integrating input.
- Millivolt inputs suit shunt measurement, mainly in DC and battery systems.
Mistakes that make the data unusable
- Logging for ten minutes and reporting a compliance conclusion. EN 50160 statistics are defined on a week of aggregated values.
- Using Class S data in a dispute. The class is the first thing questioned.
- Ignoring the flagging rule. During a dip, other parameters in the same interval are flagged, and the choice to keep or discard flagged data changes the result.
- Choosing a device with no time synchronisation for long logs. Events without a common time base cannot be correlated with other records.
- Specifying harmonics by THD alone. Two installations with the same THD can need opposite mitigation.
What to write in the RFQ
Send these seven lines and the quotations become comparable:
- Network: voltage level, phases, three-wire or four-wire, nominal current.
- Measurement goal, stated as the decision it supports.
- Required class, cited as IEC 61000-4-30 Class A or Class S, or the energy accuracy class per IEC 62053-22.
- Highest harmonic order needed.
- Current input form and transformer class, including whether the transformers are part of the scope.
- Panel cut-out or DIN rail, and the number of relays, transistor outputs and digital inputs.
- Logging duration, communications protocol and whether a calibration certificate is required.
Where to source it
Circutor builds the range in Spain, covering panel, DIN rail and rack instruments for measurement, energy, protection and permanent power quality monitoring. We supply Circutor devices as a distributor of genuine, brand-new originals. Start at the Circutor brand page or the Circutor catalogue with all 154 models, or narrow to the digital instruments and transducers slice. Analyzer, transformer and accessory part numbers can be quoted on request, and the contact form is the fastest route for a measurement point list.
For related reading, our guide to instrument calibration and traceability covers what a calibration certificate does and does not prove. Browse the brand index, the full product catalogue or the other technical insights.
FAQ
Which class do I need for an EN 50160 study?
Class A, if the result is going to a network operator, a customer or a contract. IEC 61000-4-30 defines Class A for contractual and statutory measurement and Class S for statistical surveys. A survey on your own site can be Class S. Anything that ends in a discussion cannot.
Is Class S good enough for a harmonics investigation?
For troubleshooting a drive or a furnace on your own plant, yes. Class S measures harmonics to the 40th order, which covers the orders that usually cause the problem. As soon as the numbers allocate responsibility between two parties, use Class A, which measures to the 50th order with tighter uncertainty.
How long do I have to log to claim EN 50160 compliance?
One week. The limits are statistics over a week of aggregated values: individual harmonics and unbalance on 10-minute means, flicker on 2-hour Plt intervals, with the usual criterion applied to 95 percent of those values. A ten-minute capture is a snapshot.
Does a Class A analyzer replace a revenue meter?
No. An 0,2 S energy accuracy class gives numbers good enough for sub-metering and internal cost allocation, and Circutor quotes that class for the CVM-A1500 family. Utility billing depends on national metrology approval of the complete metering installation, which is a separate question from the measurement class.
Why does my analyzer disagree with the utility meter?
Usually the current transformers or the metering point, not the analyzer. Check the transformer accuracy class and burden, confirm both devices use the same voltage reference and the same aggregation interval, and compare over the same period with the same time base. A missing time synchronisation shows up as a small but permanent offset.
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