Multi-Function Meters for Electrical Power Measurements

Multifunction meters provide digital displays of electrical parameters. A wide range of meters is available from many manufacturers. Multifunction meters have been used since the early 1980's. Their use has increased over time because of the advantages offered by multifunction meters compared with traditional analogue meters. The application for multifunction meters covers a wide range, from low voltage switchboards to HV substations. 

Advantages can include: 

• A large range of electrical parameters measured with a single device
• Power quality parameters can be measured
• Digital Display
• Multifunction
• Compact Display
• Network connectivity options for remote monitoring, Trending and data logging
• Reliability
• Accuracy

In the selection of the meter, care should be exercised to identify both the functions and electrical parameters necessary for the particular application. For example, the application may require the total harmonic distortion (THD) and the harmonic voltages/currents to a certain order e.g. to the 25th harmonic. 

The configuration of the meter will be done by the user and the method will vary according to the manufacturer. Some meters are configured from the front face of the meter, using a keypad. Others are configured using software provided by the manufacturer. If the meter is connected to a data network, there will be additional configuration to get the meter working as part of the network and the testing to prove the data interface.

An important factor to consider is the location of the meter. It is difficult to place the meters in an outdoor location without additional protection. This is because of the IP rating of the meter whether or not the meter can be easily read in sunlight.  An ideal location would be inside an air conditioned switch-room. 

Other features to be checked before selecting a meter include:

• The range voltage and current phases e.g. single-phase, 3-phase 3-wire, 3-phase 4-wire
• The programmable ranges for the voltage transformer (VT) input
• The maximum measurement ranges for kW, kVA, kVAR
• The requirement for the demand measurements e.g. current 15-minute maximum demand
• The programmable units for pulse outputs
• The network connection e.g Modbus RS485, Modbus TCP/IP, Lonworks, Ethernet/IP, etc.
• Internal bridging of current transformer (CT) secondaries within the meter, which could limit the connection of other devices in the CT loop
• DC auxiliary supply voltage, so the communications to the device is maintained if the AC circuits are not energised

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