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Selecting a meter


The ezeio system is compatible with power and energy meters from several manufacturers.

There is no one-size-fits-all solution, but by answering a few key questions you can quickly find a suitable product.

Service and CT's

QUESTION #1 : What is the service voltage?

The power meter needs to connect to the electrical service. For this you will need a qualified electrician installing the meter. All power meters require direct connection to the service. Some meters are limited to a specific voltage range, so you need to know the service voltage to select the correct model.

QUESTION #2 : How many phases, and is there a Neutral?

Residential service in the USA is typically "single split-phase", meaning there are two live conductors and a neutral. Commercial service is typically three-phase, either with a neutral (Wye) or without (Delta). There are meters that work with any service type, while others have different models depending on the service type.

For each measured phase you will need one current transformer. The Neutral wire does not need a current transformer.

QUESTION #3 : How large are the conductors?

Current transformers are available in all shapes and sizes, from 0.2" aperture to large enough to drive a truck through. The outer diameter of the conductor will determine what size you need.

QUESTION #4 : What is the max current?

The current transformers should be selected so they are at their max scale when the service load peaks. This will give you the best accuracy. The fuse size can be used a s guide, but typically the actual max current is significantly less than the fuse, so a smaller CT may be more suitable.

QUESTION #5 : What accuracy is required?

Modern electric power/energy meters are very precise and reliable, but some applications may require more accuracy or traceable calibration. "Revenue Grade" means an accuracy level that matches certain requirements for billing. For most applications standard grade meters are more than sufficient.


The ezeio communicates with the meters either through a pulse signal, or through Modbus.

Pulse meters

Pulse meters are typically a little lower cost, but only provide energy data. They simply emit a pulse for a set amount of energy (for example one pulse for each 100Wh). The ezeio can pick up these pulses and count them, but if the meter is disconnected, the pulses are lost and there is no way to recover the lost data.

The ezeio support up to four (4) pulse meters.

Modbus meters

Modbus / communicating meters can provide much more information than pulse meters. Voltage, Current, Power, Energy, Power factor and per-phase information can all be communicated between the meter and the ezeio. You simply pick the information you are interested in from each meter. Most meters has a permanent counter for energy built in, so even if the communication fails, the meter will continue to monitor and the totals can be read by the ezeio when the communication is restored.

Up to 20 Modbus meters can be read by a single ezeio over a daisy-chained connection.


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Article ID: 6
Category: Power/Energy meters (electric)
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