WT300E Digital Power Analyzer

The WT300E Series Digital Power Analyzer provides extremely low current measurement capability down to 50 micro-Amps, and a maximum of up to 26 Amps RMS. This instrument is ideal for engineers performing stand-by power measurements, Energy Star®, SPEC Power® and IEC62301 / EN50564 testing, battery charger and other low-level power measurements.

The WT300E's wide range of functions and enhanced specifications allows handling of all the measurement applications from low frequency to high-frequency inverters using a single power meter.

Accuracy with fast display and update rate: 
The WT300E series with the fast display update rate of 100ms, offer’s engineers a short tact time in their testing procedures. The basic accuracy for all input ranges is 0.1% rdg + 0.05% rng (50/60Hz) and DC 0.1% rdg + 0.2% rng.

Simultaneous Measurement:

U/I/P/Freq/Integ(+/-)/Harmonics components/ THD with max. 100ms cycle.

In addition to standard power measurements, the WT300E series measures all DC and AC parameters. Additionally, the WT300E series can measure harmonics and perform integration simultaneously without changing the measurement mode. The accompanying WTViewerFreePlus software can monitor and save the 200 parameters used. 

Auto-ranging function available in selected ranges.

The auto-range function is used to select or change the ranges automatically, within specified ranges. This results in shorter range changing times, allowing more efficient testing.

3 Input Signal Change

Auto Ranging Function For Integration Measurement
Typically, when power meters operate in an integration mode to measure power consumption and standby power, the measuring ranges need to be fixed. However, if the level of the input exceeds the maximum of the selected range, the test will need to be repeated. The WT300E Series has a high-speed automatic ranging capability in integration mode, which removes the need to repeat any test.

Bandwidth: DC and 0.1Hz to 100 kHz (WT310EH is up to 20 kHz for 40A).

Direct Input: Maximum direct input of up to 600V and 20A, or 40A (WT310EH). The wide current input ranges on the WT310E series, give users the option to measure current as low as 50 micro-Amps to as high as 40Arms (WT310EH).

High-speed data update (up to 10 readings per second)

The WT300E Series offers a wide range of communication interfaces such as USB, GP-IB or RS-232 (selectable) and Ethernet Modbus/TCP (Optional)

Wide current input range

WT300E Lineup

  • Wide current input ranges: The WT300E series covers a broad range of current inputs, from few mA up to 40 A rms. Both AC and DC waveforms can be measured.
  • Simultaneous measurement of all parameters: The WT300E can measure all DC and AC parameters. The WT300E series can also measure harmonics and perform integration simultaneously without changing the measurement mode.
  • Fast display and data update rate: The fast display and a maximum data update rate of 100ms on the WT300E series, offers a short tact time in testing procedures. 
  • MAX hold function: The maximum values of RMS/PEAK Voltage & Current, Active Power, Reactive Power and Apparent Power can be held.
  • Line filter and frequency filter capabilities: These filter functions will cut off unnecessary noise & harmonic components for fundamental waveform measurements.

Users therefore have the flexibility to choose a variety of settings according to their application needs e.g. from production lines to engineering test benches. Users can use WTViewerFreePlus software to set up all basic and advanced measurements. Additionally, the numeric values, waveform display* and trend graphs of the measurement data can be displayed and saved.

*Waveform display requires the /G5 Harmonic option

4 Waveform Display WT300E

Connectivity of Modbus/TCP*1 with YOKOGAWA’s recorders and Ethernet*1 with PLC

Digital data measured by the WT series can be acquired by YOKOGAWA’s recorder GP10*2, *3 and GM*2, *3 via Ethernet or Modbus/TCP directly. It is also possible to make use of the GA10*2 data logging software to monitor and record data.

The WT300E series can also be connected with YOKOGAWA’s PLC, FA-M3V*2 using Modbus TCP protocol for production fields.

*1 /C7 Ethernet option is required.
*2 GP10/GM/GA10/FA-M3V are manufactured by Yokogawa Electric Corporation.
*3 /E2 and /MC options are required.

5 Modbu WT300E 1

D/A output for measurement recording

The D/A option is used to output Voltage, Current, Power, and other measured data for recording to data loggers using the +/-5Vdc scaled outputs. 

6 D A Output Measurement Recording WT300E 1

Comparator Mode

This mode will compare measured, computed, and integrated values with previously set determined values by the communication command, and output (from -5V to +5V) determined results by D/A output. 

Automatic Zero Adjustment

The WT300E series compensates for any drift in the zero level by automatically performing a zero adjustment when the input ranges are changed. This is achieved in less than 100 ms and does not require disconnecting wires.

The WT300E Series Power Analyzers are easy to use, cost-effective, and accurate for a wide range of applications, such as production testing, evaluation, and research and development.

For home appliances and office equipment

Production line or QA testing of electric devices

  • Compact half rack mount size helps engineers build smaller test systems with a better return on investment
  • D/A output and Modbus/TCP* functions for data recording
  • Multiple communication interfaces: USB, RS-232 or GP-IB and Ethernet capability

The simultaneous measurement of power consumption parameters such as U, I, P, frequency, power factor and harmonics for production line or QA testing, results in reduced tact times, thereby, reducing time and cost of testing. The D/A outputs and communication interfaces enable data to be remotely and flexibly captured. *“Modbus/TCP” function is available with the Ethernet (/C7) option.

8 Production Line WT300E 1

Development and evaluation tool for home appliances

  • 5mA range allows for small current measurements (WT310E)
  • Auto ranging function during integration mode
  • Range skip (range configuration) function provides the ability to select usable ranges in advance. Auto ranging enables the WT300E series to rapidly adapt to changing input conditions.

The range skip function reduces the transition period between range changes. The WT310E can measure both large and small currents accurately in a single test. This can reduce the total evaluation period or remove the need to use two, rather than one, power meters for the application, thereby saving on capital cost of testing.

3 Input Signal Change

Testing to international standards, such as IEC62301, Energy Star, and SPECpower*1

  • The WT310E has a high measurement resolution of maximum 100 μW under the 5 mA range setting.
  • Simultaneous measurement of normal power parameters, harmonic components, and THD.
  • Dynamic input capability of crest factor maximum 300 (Peak value/minimum effective RMS value)
  • Free PCM software for IEC62301*2 testing

The WT310E together with the Power Consumption Measurement (PCM) software enables users to perform standby power testing in accordance with international standards.
*1 Coming soon
*2 The IEC62301E2.0 is a reference standard in the EN50564: 2011 Directive. This software corresponds to a test method of those two standards.

9 International Standard WT300E 1

Evaluation of large current equipment

  • Direct high current measurements of up to 40Arms without using external sensors (WT310EH)
  • Auto-ranging function for Integration mode.

The WT310EH allows 40 Arms to be directly connected to the input without the requirement to use current clamps or current sensors. This not only provides more precise measurement but also saves on investment costs. The wide current ranges are from 1 A to 40 A and voltage ranges are from 15 V to 600 V.
Users can use it to evaluate special waveform driven devices such as IH cookers and heaters.

10 IH Cooking Heater WT300E 1

For industrial equipment and transportation

Automotive- Battery or DC driven device evaluation

  • Accurate DC measurements: 0.3% total
  • Direct high current measurement of up to 40A without any external current sensor.
  • Charge/Discharge energy measurements for batteries
11 Automotive WT300E 1

Duration testing and efficiency measurement for industrial motors and rotating machinery


The WT300E series provides reliable current integration (Ah) and Energy (Wh) measurements for up to 10,000 hours. The D/A option can be used to transmit these measurements to an external data logger or recorder, such as a ScopeCorder, and monitor and log data along with other parameters, such as temperatures, torque, and rotation speed. The Modbus/TCP communication with /C7 option is used to save and monitor the measurement results of up to 200 channels. YOKOGAWA GA10 data logging software can be used directly to save data along with other parameters such as temperatures, torque and rotation speed by this Modbus/TCP Protocol.
  • Integration measurements over long periods of time
  • Modbus/TCP Protocol for data recording
  • DC, 0.1 Hz to 100 kHz broad bandwidth capability 

13 Durantion Testing WT300E 1
Conformance and evaluation testing of uninterruptible power supplies (UPS)

  • Maximum harmonic order settings for THD calculations
  • Efficiency measurements using a single power meter
  • Average Active Power measurement under integration mode

The WT300E series enables users to conduct conformity tests according to UPS performance testing standards. The WT300E series is used to measure and calculate input & output levels, efficiency, frequency, and THD. The average active power data also provides accurate values of power consumption. This equipment along with the WTViewerFreePlus software helps to simultaneously measure all necessary parameters required to test a UPS, thereby reducing the evaluation time.

14 Confomrance WT300E 1




B9284LK External Sensor Cable

For connection the external input of the WT3000 to the current sensor.
Length: 50cm

758917 DMM Measurement Lead Set

A set of 0.8m long red and black test leads, used in combination with a pair of optional 758922 or 758929 alligator-clip adapters.

705926 Connection Cable for DA4, DA12, Scanner Box (701953)

Applicable for DL850 and WT300 series.

758921 Fork terminal adapter

Adapters for fitting a 4mm banana plug to a fork terminal. Set contains one black and one red clip. 1000 Vrms-CAT II.

758922 Small Alligator-Clip Adapter 300V

Rated at 300 V. Attaches to the 758917 test leads. Sold in pairs.

758923 Spring Hold Safety Terminal Adapter Set

Two adapters in a set (spring-hold type).

758924 BNC to Banana Conversion Adapter

For conversion between BNC and female banana plug
Applicable for DL750/DL750P, SL1000 & SL1400.

758929 Large Alligator Clip Adapter 1000V

Rated at 1000V. Attaches to the 758917 test leads. Sold in pairs.

758931 Screw-Fastened Safety Voltage Terminal Adapter Set

Screw-fastened adapters. Two adapters in a set. 1.5 mm Allen Wrench.

751533-E2 Rack mounting kit

RACK MOUNTING KIT For an EIA-compliant Single-housing Rack

751533-J2 Rack mounting kit

RACK MOUNTING KIT For a JIS-compliant Single-housing Rack

751533-E3 Rack mounting kit

RACK MOUNTING KIT For an EIA-compliant Single-housing Rack

751533-J3 Rack mounting kit

RACK MOUNTING KIT For a JIS-compliant Single-housing Rack

751534-E2 Rack mounting kit

RACK MOUNTING KIT For an EIA-compliant Dual-housing Rack

751534-J2 Rack mounting kit

RACK MOUNTING KIT For a JIS-compliant Dual-housing Rack

751534-E3 Rack mounting kit

RACK MOUNTING KIT For an EIA-compliant Dual-housing Rack

751534-J3 Rack mounting kit

RACK MOUNTING KIT For a JIS-compliant Dual-housing Rack

Application Note
544 KB
Application Note
304 KB

Want to know how green is your Software? Intel® Energy Checker and Yokogawa can help you! The Intel® Energy Checker SDK provides software developers a simple way to measure the energy efficiency (greenness) of their Software by exposing the necessary and basic measurements made by Yokogawa’s highly accurate and reliable Power Analyzers.


Conventionally, measurement of the harmonic distortion required special modes or lengthy data acquisition times which impacted the processing time on manufacturing lines.


Lighting products need to evaluate not only power parameters but also temperature.


In recent years the buzzword “all electric” is becoming popular, which refers to kitchen appliances, water heaters, and other devices in the home all being supplied with electric power.


If a product uses power, then power consumption and power quality measurements must be made as part of product design and test. These measurements are essential to optimize product design, comply with standards and provide nameplate information to customers.
This article will discuss best practices for making these measurements, starting with power measurement basics and proceeding to the types of instruments and associated components typically used to make measurements. The article will conclude with real-world examples, which apply the information imparted earlier in the article to solve practical measurement problems. Although most of us have been exposed to basic power measurement equations, a primer is helpful to summarize this information and to show how it applies to product design and test.

Application Note

Evaluation of vacuum cleaner requires to measure distorted waveform.


In the test of new washing machine, voltage, current, power, and the control signal on the time control panel need to be recorded.


Prevention of global warming has become an issue in recent year, and industry is turning more and more toward stricter energy savings policies and the use of renewable energy.


The precision beaning testing system of the mechanical and electrical engineering company.


The Power Analyzer Accuracy and Basic Uncertainty Calculator can be used to determine the uncertainty in voltage, current, and active power (watts) measurement values for various frequency ranges and wiring systems.

Technical Article
Edition 1

In power measurement, power analyzer accuracy is one of the most important specifications to consider. It is easy to understand the importance of accuracy but to respect its role in power measurements, one must first understand error.

Accuracy is Error

Error is a measurement’s proximity to the true value, a measurement value accepted as standard. True values vary and can include government-mandated standards or manufacturers’ calibration standards. Accuracy is characterized by the amount of error present in the measurement- its proximity to the true value. The cause of error is either random, with no identifiable root cause, or systematic, introduced by components of the measurement system.

Systematic Errors

Systematic errors can categorized as either gross or measurement. Unknowingly created by a user, gross errors occur as a result of improperly configuring or analyzing the results of a measurement system. Engineers working with a power analyzer could cause a gross error by choosing an inappropriate line filter (see Figure 1). 

Figure 1:

Figure 1

Figure 1: Failing to turn on a required line filter could cause a gross error. In this example, the lack of a filter (top image) results in a signal that is difficult to synchronize

The second type of systematic error, measurement error, is introduced by the power instrument or system itself. Measurement errors can be caused by a lack of calibration, limited instrument accuracy, or measurements that have been altered by the measurement system. A shunt resistor used in a power analyzer will introduce a small measurement error due to the change in voltage it introduces to the system.

Once the error type and source are identified, the next step toward precision is to quantify the accuracy.

Accuracy Quantified

Defined previously, accuracy is the difference between a measured value and a true value. This difference can be expressed as an absolute error - an “error band” surrounding the true value. For example, the absolute error for a voltage measurement might be expressed as:

X [Volts] +/- Y [Volts], where X is the true value and Y is the absolute error.

Figure 2:

Figure 2

Figure 2: Error band surrounding a true value

Absolute error is useful because the total accuracy of a components system is equal to the sum of absolute errors. It is common to express absolute error levels in parts per million (PPM), which specifies the accuracy relative to one million.

1 PPM/V = an error band that is +/- 0.000001V

Relative Error

Power analyzer datasheets typically specify voltage, current, and power accuracies as relatively. Relative errors are simply percentages relative to the measurement and to the full-scale range of the input. For example, the WT3000E Power Analyzer specifies a power accuracy of 0.01% f reading +/- 0.03# of range at 60HZ.

Putting it all Together

Before the total system error can be calculated, it is necessary to convert the power analyzer’s relative error to an absolute error.

Total System Error = Σ(Absolute Errors)

Rather than manually converting relative error to absolute error, an uncertainty calculator can be utilized.

Uncertainty Calculator

Entering the following relative errors into the Uncertainty Calculator yields the corresponding absolute error value.

  • Voltage Reading & Range
  • Current Reading & Range
  • Frequency (kHz)
  • Power Factor (between 0 and 1)

Once entered, the Uncertainty Calculator provides the corresponding accuracies:

  • Voltage Uncertainty (Volts)
  • Current Uncertainty (Amps)
  • Power Uncertainty (Watts / Element)
  • Power Uncertainty for 3-phase, 3-wire configuration (Watts)
  • Power Uncertainty for 3-phase, 4-wire configuration (Watts)

Figures 3 and 4 demonstrate how to use Yokogawa’s Uncertainty Calculator. Remember- simply measuring power does not ensure accuracy or precision. If you struggle with accuracy uncertainty, try an Uncertainty Calculator today.

Figure 3:

Figure 3

Figure 3: Simply entering relative errors in the Yellow cells yields the corresponding absolute error values

Figure 4:

Figure 4

Figure 4 - After entering values in the yellow fields, locate the row that corresponds to the appropriate frequency range to read off the absolute uncertainties for voltage, current and power.

Technical Article
Accuracy specifications: Reading it right with range
(Accuracy specifications: Reading it right with range)
Edition 2017

The accuracy of a measurement instrument varies with the range over which a reading is measured.

But what if different manufacturers specify this range differently in their instruments?

This article explores the impact of range definitions on measurement accuracy and how one can be mindful when comparing accuracy across instruments.

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