The WT300 series of digital power meters are the fifth generation of Yokogawa's best-selling compact power meters: instruments that play a key part in ensuring optimum standards of energy efficiency and conservation by measuring the power consumption of electrical equipment. Combining accurate and reliable power measurement over a wide power range with flexibility, ease of use and a choice of communication interfaces, these instruments will help developers, engineers and manufacturers of electrical equipment to ensure that their products comply with emerging IEC and EN standards and increasingly complex and stringent specifications on energy efficiency. They provide ideal measurment solutions for various applications ranging from stand by power measurement to Energy star for various manufacturers such as domestic "white goods", battery chargers, lighting systems.

Model Description
WT310 Single-input element model
WT310HC High current single-input element model
WT332 2-input element model
WT333 3-input element model

The WT300's wide range of funcations and enhanced specifications allows to handle all the measurement applications from low-frequency to high frequency inverters using a single power meter.

Accuracy with fast display and update rate: 
The WT300 series with the fast display and date update rate of Max. 100ms offers the customer a short tact time in their testing procedure. The basic accuracy for all input ranges is 0.1% rdg + 0.1% rng (50/60Hz) and DC 0.1% rdg + 0.2% rng (0.2% + 0.2% for 40A).

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

In addition to standard power measurements, the WT300 offer a wide range of harmonic measurement capabilities, including the ability to carry out simultaneous measurement of normal power parameters such as RMS, mean or DC power along with measurement of harmonics up to the 50th order. As a result, overall measurement times are reduced, allowing users to allocate their effort and time to other tasks.

First in Class:

Auto ranging function available in selected ranges.

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

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First in Industry:

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 WT300 Series has a high speed automatic ranging capability in integration mode, which removes the need to repeat any test.

Bandwidth: DC and 0.5Hz to 100 kHz (WT310HC is up to 20 kHz for 40A).

Direct Input: Maximum direct input up to 600V and 20A, or 40A (incase of WT310HC). The wide current input range gives the customer options to use the WT300 series from as low as 50 micro-Amps to 40Arms.

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

Wide current input range

  • Wide current input ranges: The WT300 series offers a wide range of current inputs from a few mA t
  • Simultaneous measurement of all parameters: The WT300 can measure all DC and AC parameters. The WT300 series can also measure harmonics and perform integration simultaneously without changing the measurement mode. 
  • Fast display and data update rate: The fast display and 100 ms maximum data update rate of the WT300 series offers a short tact time in testing procedures. 0.1% of reading + 0.1% of range (50Hz/60Hz) 
  • 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 capability: These filter functions will cut off unnecessary noise & harmonic components for fundamental waveform measurements.
The WT300 series offers a wide range of communication interfaces such as USB, GP-IB or RS-232 (selectable) and Ethernet (Optional)

Allows users to have the flexibility to choose according to applications needs. Using the WTViewerFreePlus software to set up all kinds of measurements. Additionally, the numeric values, waveform display, and trend graphs of the measurement data can be displayed and saved.

Communication Interface

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 (+/-5Vdc outputs).

DA Output

Two new functions added to D/A output option. (Firmware Ver1.04)

Two new functions, Manual Range Mode and Comparator Mode can be used conveniently with built-in PLC and recorders in production line inspection systems.

Manual Range Mode

The default settings will set D/A output value to rated value of measurement range. In this mode, D/A output can be zoomed in and out on each channel by arbitrarily setting the display value of measurement items when D/A output is either -5V or +5V. For example, if you measure the fluctuating current from 0.6A to 0.8A by 1A current range with D/A output range mode switched to fixed range mode, the D/A output voltage will fluctuate from 3.0V to 4.0V. The D/A zoom function is available for enlarging and observing this fluctuating value. Set the D/A output range mode to manual range mode with minimum value set to 0.6A and the maximum value to 0.8A. Then, when the current value measured is 0.6A, the output will be -5V, and when it’s 0.8A, the output will be 5V.

Comparator Mode

This mode will compare measured, computed, and integrated values with previously set determined value by the communication command, and output (from -5V to +5V) determined results by D/A output. If you are going to use a relay contact output, please prepare the relay and the relay drive circuit.

The upper and lower limit value of Comparator Mode
The following are the D/A output during the Comparator Mode

  • Less than lower limit value. Output: -5 V
  • Greater than lower limit value and less than upper limit value. Output: 0 V
  • Greater than upper limit value. Output: +5 V

* The above 2 modes can only be set by the communication command.
* Both modes can be set for all D/A output items.

Installation Example

The WT300 series power meters 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

-Multiple communication interfaces such as USB, RS-232 or GP-IB and Ethernet capable.

-The compact half rack mount size helps users build smaller test systems with a better return on investment.

-D/A output function for data recording

Development and evaluation tool for home appliances

-5mA range helps small current measurement (WT310)

-Range skip function provides the ability to select usable ranges in advance, while auto ranging adapts rapidly to changing input conditions. [PIC]

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

-The WT310 has a high measurement resolution of Max. 100µW under the 5mA range setting.

-Simultaneous measurement of normal power parameters, harmonic components, and THD.

-Free PCM software for IEC62301 testing

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Evaluation of large current equipment 

-Direct high current measurement up to 40Arms without using external sensors

-Auto ranging function for Integration mode.


For industrial equipment and transportation

Automotive- Battery or DC driven device evaluation

-Accurate DC measurement: 0.3% total

-Direct high current measurement up to 40A without any external current sensor.

-Charge/Discharge energy measurement for batteries

Duration testing and efficiency measurement for industrial motors and rotating machinery

The WT300 series provides reliable current integration (Ah) and Energy (Wh) measurement for up to 10,000 hours. The D/A option is used to save and monitor the measurement results. An external recorder or data logger, such as a ScopeCorder, can be used to save this D/A function data along with other parameters, such as temperatures, torque, and rotation speed.

Current Sensor Input

Conformance and evaluation testing of uninterruptable power supplies (UPS)

-Maximum order setting for THD calculations

-Efficiency measurements using a single power meter

Multiple units for parallel testing of product evaluation of electrical equipment

New version of the WTViewerFreePlus , measurement data can be collected from multiple WT300 units
(same model maximum 4 units).

-Various communication interfaces such as USB, RS-232 or GP-IB and Ethernet are available.
-Data update rate can also be measured simultaneously as fast as 100ms. 
- power parameters can be measured up to the 200 items simultaneously.
-D/A output function for data recording is available.

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Comparison of WT210/230 with WT310/330

  WT310/WT332/WT333 WT310HC WT210/WT230
DC power measurement accuracy 0.1% of reading+0.2% of range 0.3% of reading+0.2% of range 0.3% of reading+0.2% of range
Current range (Crest factor=3)Voltage and current 
basic accuracy
Direct Input 5m/10m/20m/50m/100m/200m/
0.5/1/2/5 /10/20[A]( WT310) 0.5/1/2/5/10/20[A](WT332/WT333
1/2/5/10/20/40[A] 5m/10m/20m/50m/100m/200m/
External current input EX1: 2.5/5/10[V]
EX2: 50m/100m/200m/500m
/1/2[V] (OP.)
EX1: 2.5/5/10[V]
EX2: 50m/100m/200m/500m
/1/2[V] (OP.)
EX1: 2.5/5/10[V]
EX2: 50m/100m/200m[V] (OP.)
Effective input range for voltage & current (CF=3) 1% to 130% 1% to 100% (40A range only) 1% to 130%
Maximum displaying value for voltage & current (CF=3) 1% to 140% 1% to 110% (40A range only) 1% to 140%
Effect of Power Factor (CF=3) 0<PF<1 Power reading x {power reading error + (power range / apparent power reading) + tanφ x (influence when PF = 0)} % Power reading x {power reading error + (power range / apparent power reading) + tanφ x (influence when PF = 0)} % Add the power reading x {tanφ x (influence when PF = 0)}%.
Simultaneous measurement of RMS, Voltage MEAN & DC Yes Yes No
Frequency measurement

2 channels (voltage & current)

2 channels (voltage & current) selected voltage or current (one)
Number of display items 4 items 4 items 3 items
Sampling rate Approximately 100 kS/s Approximately 100 kS/s Approximately 50 kS/s
Harmonic measurement Yes (OP, /G5) Yes (OP, /G5) Yes (OP, /HRM)
THD calculation maximum order setting Yes (OP, 1-50th) Yes (OP, 1-50th) No
Auto ranging of integration Yes Yes No
Communication interface USB Yes Yes NO
GP-IB Yes GP-IB or RS-232 Yes GP-IB or RS-232 Yes (OP) GP-IB or RS-232C
RS-232 Yes RS-232 or GP-IB Yes RS-232 or GP-IB Yes RS-232 or GP-IB
Ethernet Yes (OP) Yes (OP) NO
IEEE standard for GP-IB IEEE488.2 IEEE488.2 IEEE488.1 and IEEE4882.
Comparator function No No Yes
Viewer software Free (included) Free (included) Free (download)