What Is an Energy Analysis Instrument? Power Meters, Wattmeters and Selection
An energy analysis instrument is a portable or benchtop instrument that measures the voltage, current, power, power factor and energy consumption of a device or installation.
An energy analysis instrument is a portable or benchtop measuring instrument that measures the voltage, current, active power (W), apparent power (VA), power factor and energy consumption of a device or installation. Unlike panel-mount power network analyzers that monitor a facility permanently from the panel door, it is connected temporarily at the measuring point.
Types
- Socket-type wattmeter: Plugs into a socket, with the device plugged into it; shows the power and energy of a single-phase device.
- Benchtop power meter: The device under test is supplied through the meter, so current flows through the instrument. Used in production and laboratories to verify a product's power and power factor.
- Three-phase power quality analyzer: Besides voltage, current and power in a three-phase installation, investigates and records problems such as harmonics and imbalance.
Selection criteria
- Number of phases: Socket-type or benchtop for single-phase devices; a three-phase analyzer for three-phase installations.
- Voltage and current range: The benchtop models in the catalog measure up to 600 V and 20 A. As current flows through the meter, the load must stay within this limit. Portable analyzers usually measure current with a clamp, whose range must cover the load.
- Measuring mode and frequency: DC-supplied or rectifier-fed devices need AC, DC and AC+DC modes. The frequency range is 40–70 Hz or 40–400 Hz by model; choose the wide range for 400 Hz equipment.
- Accuracy: Given as a percentage of reading plus a range or digit allowance; for low-power readings such as standby, check the lowest current range.
- Power quality functions: Measurement of harmonics, imbalance and voltage dips, recording time, memory and data transfer.
- Interface: RS-232/RS-485 on the benchtop models serves automated testing and logging.
- Measurement category: The instrument's CAT rating must suit the measuring point: socket circuits CAT II, distribution panels CAT III, the building service entrance CAT IV.
Common mistakes
- Confusing W and VA: With a low power factor, apparent power exceeds active power; consumption is tracked in kWh of active energy.
- Connecting a load above the current limit: Never supply a load beyond the meter's range through a benchtop meter or socket wattmeter.
- Fitting current clamps the wrong way round or on the wrong phase: Power reads negative or wrong; the clamp arrow should point to the load.
Standards
Measuring instrument safety is covered by IEC 61010-1, measurement categories by IEC 61010-2-030. Power quality measurement methods are defined in IEC 61000-4-30; check the manufacturer's documentation for the class an analyzer meets.
Models in the catalog
The Energy Analysis Instruments category lists 5 active models from Unit:
- Three-phase power quality analyzer: UT285C
- Benchtop power meters: UTE9802+, UTE9806+, UTE9811+
- Socket-type wattmeter: UT230B-EU
For permanent panel monitoring see power quality analyzers; for current measurement see multimeters and clamp meters.
Frequently asked questions
Which devices is a socket-type wattmeter suitable for?
Single-phase plug-in devices. Hard-wired or three-phase devices cannot be measured with it.
How long should a power quality measurement last?
Problems may appear only at certain hours or with certain machines running, so measure over a full operating cycle. Assessment of supply voltage under EN 50160 is based on a one-week measurement.
What is the difference between a benchtop power meter and a multimeter?
A multimeter measures voltage and current separately; a power meter measures both at once and calculates active and apparent power, power factor and energy.
How do I get a price?
The price of the UT285C is shown on the product page; the other four models are sold on a quote basis.