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Introduction to 3 Phase Digital Power Meter

Digital Power Meter (DPM) is a 3-phase AC professional electrical measurement & display device to determine AC electrical parameters including Voltage, Current, Power, Energy, and Power Factor. It can measure up to few thousand amperes and it is always installed in Commercial Electrical Panel for monitoring purpose. Economical DPM could measure all basic electrical parameters while more expensive DPM will have slightly better measurement accuracy, more detail in display and may support Digital / Analog Output for Alarm or signal triggering for protection features. 

Besides measuring high current, DPM can also measure 3 phase Medium Voltage such as 11kV or 33kV electrical system. In order to measure high current, DPM requires Current Transformers (CT) to be installed on each phase while Voltage Transformers (VT) are used to step down voltage to the acceptable range of the DPM. VT rating will have standard rating such as 11000 / 100V which means stepping down from 11kV to 100Vac.

VTs are not required if you are measuring 3 phase Low Voltage such as 400Vac 3 phase. All Low Voltage circuit such as residential, small scale commercial and industry can do direct connection for voltage measurement. Only heavy industrial will have Low Voltage and Medium Voltage (11kV or 33kV) circuits due to large load consumption. It will burn the DPM if Medium Voltage is directly connected to DPM without a VT on each phase. However, a 1A-5A fuse / miniature circuit breaker (MCB) is required for each phase in between measurement point and DPM to have short circuit protection in case of accident or fault happens.  

Multi-purpose 3 Phase Digital Power Meter

Digital Power Meter is a professional monitoring device used to display many important Electrical parameters such as Voltage, Current, Power, Energy, and Power Factor. It supports 3 phase and can measure high voltage and current subject to the applied Current and Voltage Transformers. Grab one at our Aliexpress affiliate link here !!!

Same for current measurement, typical DPM can only measure up to 5A for direct connection measurement. In order to measure higher current, a Current Transformer (CT) is needed. CT also has rating such as 100/5A which means stepping down current from 100A to 5A for DPM measurement. In other words, if the 100/5A CT is used, it can measure current up 100A. At the DPM, we can set the step down ratio of CT & VT so that to multiply and display the actual measurement values. Do not oversized the CT rating by a lot (for example do not get a 200/5A CT to measure a circuit that has only 10A at max or else you will lost the accuracy and resolution.  

Besides the ratio rating of CT & VT, the accuracy class is also depends on the quality of the transformers. Expensive DPM can have high accuracy in measurement only if it is paired with high accuracy class of transformers. Both VT and CT are sold separately and you need each transformer per phase. For example, if you plan to measure 400Vac 3 phase up to 200A, you need 3 CTs of 200/5A while measuring 11kV 150A you need 3 CTs of 150/5A (high voltage type) and 3 VTs of 11000/110V rating.

5A Split-Core Transformers

In order to measure current larger than 5A, a Current Transformer (CT) is needed to be installed per phase. The CTs will step down high measurement current into 5A maximum current to the DPM. Make sure to choose the CT with standard 5A output as typical DPM only could support up to 5A. For example if you want to measure current up to 200A, get CT rating of 200/5A. You can get them at our affiliate link here !!!

Warning ! You may now dealing with high voltage and high power source ! We assumed that you have the basic electrical knowledge and know what you are dealing with. You may need guidance from experienced guys if you are new to electrical work. Safety and Precaution must be always have in mind. We shall not be responsible for anything happening to you.

Energy Meter + Wifi

This is a din rail mounted Single Phase Energy Meter with built in Wifi module allowing the Energy values to be monitored remotely through house’s internet Wifi. Have a look at our affiliate link here !!!

For beginners, I would highly recommend you to get the DPM with the most economic with basic feature such as DPM model YG889E from YiGE. There are already a large number of information in this basic DPM either in total and per phase value:


This DPM could record AC Energy in two direction which is perfect for On-Grid Solar PV Application. The energy export and import are separated rather than displaying a net value. From this we can know the consumption and generation of our Solar PV System. Besides, this DPM has a Modbus RTU communication output port which we can connect to micro-controller including Arduino boards for further data processing such as data logging, alarm triggering for protection purpose and even send data to cloud for online real time monitoring and remote control. We will explain the Modbus RTU communication in detail on my next blog page.

Multi-purpose 3 Phase Digital Power Meter

Digital Power Meter is a professional monitoring device used to display many important Electrical parameters such as Voltage, Current, Power, Energy, and Power Factor. It supports 3 phase and can measure high voltage and current subject to the applied Current and Voltage Transformers. Grab one at our Aliexpress affiliate link here !!!

Before purchasing any components, there are few things you need to check:

  1. Where we plan to install the DPM. Most of the DPM are panel mounted (on the surface of the panel door). All wiring should be covered up for safety reason. We can have the DPM and fuses preinstalled in an enclosure (preferably polymer box) before working on the termination or measurement point.
  2. Be sure to read through the datasheet of the DPM and CT whether can provide the electrical parameter readings that you want and whether they are compatible to each other. Be sure the output of CT is 5A rating for typical DPM.
  3. Get Split-Core transformers instead of solid core for your ease of wiring and to prevent touching existing high current wire. Solid core is suitable for permanent fixture in the panel and disconnection of cable is required to fit it in the CT but not suitable for DIY persons like you and me.
  4. Get fuse or MCBs with suitable size of wires for Voltage measurement. For 0.5mm2 wire you can use 1-3A fuse; for 0.75mm2 wire you can use 3-5A fuse / MCB. Normally all voltage & current sources are taken from Distribution Board of your building and house. For single phase measurement, optionally you can get the voltage source from Wall Outlet Socket. If you are not comfortable to work with electrical, please DO NOT install !!!. 
  5. Know the maximum current rating of your circuit. Getting the undersized CT rating may cause damaged to the DPM and CT while getting the oversize CT rating will sacrifice on accuracy & resolution. 
  6. Wiring the DPM is really easy but have to be precaution as you are dealing with Electricity. First you have to make sure all power source is shutdown before do any wiring. 
  7. After all wiring is done, the final thing to do is the setting of the DPM after the circuits are started up.

NodeMCU micro-controller

The NodeMCU micro-controller is similar to Arduino micro-controller board. It is compatible with Arduino IDE software and is built-in with the ESP8266 module which can be connected to the internet. You can grab some at our affiliate link here !!!  

DPM Settings

There are few things you can set in the DPM:

 Main Display Page

  • You can set the what parameters to be shown on the Main Page of LCD Display. Due to too many parameters, there are few pages to be shown in the display. You can set which page to be the Main Page while you can swap to other pages manually by button. 

Backlight LED 

  • You can have option to turn ON or Turn OFF the LED Backlight of the display for energy saving purpose.

Electrical Network (3 Phase 3 wires / 3 phase 4 wires)

  • 3 Phase 4 Wires refers to 3 Lives + 1 Neutral Cable. This is the electrical network for Low Voltage (400Vac). 3 Phase 3 Wirs only applicable for Medium Voltage (11kV or 33kV that without a neutral cable).

Voltage & Current Select (400V/100V and 5A/1A)

  • For Low Voltage 400Vac, we normally select 400V and 5A input current. Most CT are rated xx/5A while LV we can direct connection for voltage measurement. For Medium Voltage measurement, normally VT and CT rating for Medium Voltage are rated xx/100V and xx/1A.

CT & VT Ratio

  • CT normally rated at xxx/5A. For example 100A/5A has a ratio of 20. In other words, we need to let the DPM knows so that the DPM will magnify the measurement current to 20 times. This is same to VT but VT is not required in LV circuit.

Modbus Address & Baud Rate

  • Modbus Address & Baud Rate is only applicable for Modbus RTU communication if you need to collect data from the DPM to other SCADA or Micro-controllers such as Arduino for futher processing (we will discuss further on my next blog page).

Reset Energy

  • We can reset the accumulative energy back to 0kWh whenever we want.

Digital / Analog Output

  • We can set output alarm signal when under/over voltage/current detected by defining the threshold we want. However the signal output is via Modbus communication and there is no relay for load control.

Fuse with Isolator

Fuse is important to protect a circuit from Overload Current and Short Circuit Current. This is a din rail type of Fuse with removable cartridge for easy fuse replacement. Grab yours at our affiliate link here !!! 

Typical Wiring Diagram:


  1. If you want to monitor only 1 phase, just connected the CT and voltage measurement to input or phase 1.
  2. If measurement is in negative value (for load), you can either swap the CT wires OR change CT measurement direction.

Below I have attached the Step by step setting specifically for YiGe Model : YG889E-3SY. I have also attached the full version of manual (but in chinese version) from the supplier. Kindly take note that different model & brand of DPM may have different setting steps especially Modbus communication register addresses. Be sure to get Manual from supplier before you purchase !!!

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Setting Guide.pdf