New ozm3 three-phase version

After a quite busy period of tests and trials, the new version of openzmeter in its three-phase variant is here. Its development is a major step forward towards the reinforcement of the project and we believe that it will allow us to reach a larger number of people.

Following the same philosophy as in single-phase ozm (now called ozm1), the use of ozm3 is not limited by software or hardware, so it can be used in any type of low voltage electrical installations (up to 400V line voltage). We are able now to measure almost any current. This particular characteristic is one of the great new features of the ozm3, since now no shunt resistor is used, but the current is measured through toroidal or Rogowski probes (see the datasheet for characteristics).

Comparison: ozm1 (left), ozm3 (center) and circuit breaker (right)

A lot of improvements have been carried out in the hardware design. The device can measure any three-phase 4-wire system but can also measure 4 single-phase circuits simultaneously. At the software level it is now possible to define virtual analyzers, so that channels can be added or subtracted as in the same way as an oscilloscope. Of course, the original ozm features are still there, and even improved.

  • Extensive system of electricity tariffs that allows country-specific customization.
  • Powerful power quality analyzer.
  • API for developers.
  • High sampling rate
  • Data aggregation
  • Alert system and event management
  • Telegram integration.

We hope you like and enjoy it. Any questions you have the forum at your disposal.

The ozm team.

Upgrade firmware for old oZm versions

The old versions based on Debian images can be upgraded to newest based on OpenWRT. The procedure is simple, but be very careful!. 😛

WARNING: All your information will be lost!!!

  • Uncompress and flash the .img.gz file on a microSD.
  • Power off the ozm and remove the power supply.
  • Extract the NanoPI board from ozm (double check that you’ve removed the power).
  • Insert the microSD into the NanoPI board.
  • Power the NanoPI from a microUSB charger (5V)
  • The update process will start… wait until all LEDs are off (It will take a while).
  • Power off the NanoPI and remove the microSD.
  • Finally, insert the NanoPI board into the ozm and turn the power back on

If everything went well, you can reconfigure the device using Bluetooth access.

Single phase circuits basics

Single-phase alternating current (AC) is a main technology for efficient energy delivery across the world. Among its uses are lighting, low power electric motors or heating. It is characterized by a sinusoidal shape and varies in time so that the same pattern is continuously repeated.

This energy system is characterized by a voltage with the following shape:

In a similar way, the demanded current by a load is typically represented by a sinusoidal function, but its waveform depends on the linearity of the load.

Through the openZmeter analyzer you can observe the waveform of the voltage and the current, as well as their values. A lot of information is provided in the Analysis section and, within its drop-down menu, Voltage or Current items.

In the top right corner of the selected window you can choose how often the data is collected (aggregations) and the timespan. You can also export the collected values to csv format or maximize the graph to carefully analyze the provided values.

On the left side of the window you can see some statistics associated to the voltage signal. The same can be done in the Current section.

Finally, in the lower part of the window, the waveform of the single-phase AC wave can be displayed. You can see the voltage and current signal individually or grouped in the same graph.

For a more detailed explanation please consult our video below.

openZmeter in the press

We are pleased to announce that openZmeter has been noticed by the local mediafor the first time. Five local digital newspapers published about us and our labour at university (Universidad de Almería, Spain).

Our university digital newspaper was the first one to publish an article about openZmeter and, within a week, four more local media were talking about us. Statements like “pioneer electric meter”, “enormous reach and importance”, “revolutionary energy saving method” and “unique in the world” can be found on the articles (links at the end of the page). This has helped our project to gain importance and has boosted our confindece in keeping researching about analizing and metering energy consumption.

The articles mentioned are only aviable in Spanish. For everybody to understand, here is an overview translated to English.


Seven members of the Electric and Hydraulics Ingineering group and Graphic Expression group from Universidad de Almería have published the development of ‘openZmeter’ in various scientific magazines. It’s a low cost advanced electric meter that helps lowering society energy footprint.

Beyond metering electricity consumption it can detect installation malfunctions. This makes openZmeter unique in the world.

It is an open software and hardware device so that any user can build it and modify it within its own resources. No advance knowledge is needed. It’s the first time an equipment like this is publicly available. Private enterprises, public administrations and individual users have now access to this advanced technology. This situation make it possible for the customers to build energy saving strategies and desing more efficient enery consumprion policies.

From an environmental point of view, openZmeter contributes to a proper use of energy. In addition, free software and hardware policy make it easier for everyone to contribute to this project. It helps to speed up openZmetre’s development.

Click on the links below to check the mentioned articles


Gabinete de Comunicación. (8 noviembre, 2019). Investigadores de la UAL crean un contador electrónico avanzado ‘pionero’ en el mundo. Almería, España: UALNEWS (

Noticias de Almería

Martos, Rafael M. (8 noviembre, 2019). Investigadores de la UAL crean un contador electrónico avanzado ‘pionero’ en el mundo. Almería, España: Noticias de #Almería. (

La Gaceta de Almería

Bruma. (8 noviembre, 2019). Investigadores de la UAL crean un contador electrónico avanzado ‘pionero’ en el mundo. Almería, España: La Gaceta de Amería. (


Novapolis. (8 noviembre, 2019). Crean en la UAL un contador electrónico de bajo coste. Almería, España: NOVAPOLIS. (


Gálvez, Gonzalo. (12 noviembre, 2019). Desarrollan en la UAL un nuevo método de ahorro energético revolucionario. Almería, España: AULA MAGNA. (

New version v2.0 released

We are excited to announce the new improved version of oZm v2.0. In this new version, major enhancements have been made to most of the basic modules, resulting in a much more stable and improved system.

Operating system

The first major change has been to switch the operating system from Debian to OpenWRT. This change has been motivated by the improved management of the WiFi module as well as the greater stability in the connection allowed by OpenWRT. Now, oZm takes up much less disk space and the necessary packages are better managed. In previous versions, we have had a lot of problems with the NetworkManager that ships with Debian, which caused a lot of disconnections and crashes. Also, we have found that many modern routers do not adequately support certain Linux systems and this means that the web is not accessible under certain circumstances.

Web redesign

The website has been completely redesigned. It is now more intuitive and better organized. Additional information regarding system properties (RAM, signal strength or temperature) has been added. In addition, some views have been reorganized and new ones have been added.

New Tariff module

One of the important achievements has been the creation of the tariff module. Thanks to this module it is now possible to get the cost of the consumed energy in real time according to the electricity tariff defined by the user. For example, in Spain it is possible to define the typical 2.0DHS tariff (hourly discrimination) for a typical house.

Stay tuned for new enhancements like the three-phase ozm launch!

Paper published in journal Sensors (MDPI)

This is the second specific paper on the openzmeter device. It describes in detail its hardware architecture and provides measurements in a real scenario. Likewise, a comparison is made with commercial and professional devices that reveals the accuracy of the measurements obtained according to international standards.

Cite as:

Viciana, E.; Alcayde, A.; Montoya, F.G.; Baños, R.; Arrabal-Campos, F.M.; Manzano-Agugliaro, F. An Open Hardware Design for Internet of Things Power Quality and Energy Saving Solutions. Sensors. 2019, 19, 627.


An important challenge for our society is the transformation of traditional power systems to a decentralized model based on renewable energy sources. In this new scenario, advanced devices are needed for real-time monitoring and control of the energy flow and power quality (PQ). Ideally, the data collected by Internet of Thing (IoT) sensors should be shared to central cloud systems for online and off-line analysis. In this paper openZmeter (oZm) is presented as an advanced low-cost and open-source hardware device for high-precision energy and power quality measurement in low-voltage power systems. An analog front end (AFE) stage is designed and developed for the acquisition, conditioning, and processing of power signals. This AFE can be stacked on available quadcore embedded ARM boards. The proposed hardware is capable of adapting voltage signals up to 800 V AC/DC and currents up to thousands of amperes using different probes. The oZm device is described as a fully autonomous open-source system for the computation and visualization of PQ events and consumed/generated energy, along with full details of its hardware implementation. It also has the ability to send data to central cloud management systems. Given the small size of the hardware design and considering that it allows measurements under a wide range of operating conditions, oZm can be used both as bulk metering or as metering/submetering device for individual appliances. The design is released as open hardware and therefore is presented to the community as a powerful tool for general usage.

First scientific paper published

The openZmeter team is completely delighted again. Recently, a new scientific article has been published in the prestigious journal Sustainability edited by MDPI. Our Ph.D. Student Eduardo Viciana did a great job and the result is his first international paper entitled “OpenZmeter: An Efficient Low-Cost Energy Smart Meter and Power Quality Analyzer”.  

It is open access and can be found in Please cite it as:

Viciana, E.; Alcayde, A.; Montoya, F.G.; Baños, R.; Arrabal-Campos, F.M.; Zapata-Sierra, A.; Manzano-Agugliaro, F. OpenZmeter: An Efficient Low-Cost Energy Smart Meter and Power Quality Analyzer. Sustainability201810, 4038.


Power quality and energy consumption measurements support providers and energy users with solutions for acquiring and reporting information about the energy supply for residential, commercial, and industrial sectors. In particular, since the average number of electronic devices in homes increases year by year and their sensitivity is very high, it is not only important to monitor the total energy consumption, but also the quality of the power supplied. However, in practice, end-users do not have information about the energy consumption in real-time nor about the quality of the power they receive, because electric energy meters are too expensive and complex to be handled. In order to overcome these inconveniences, an innovative, open source, low-cost, precise, and reliable power and electric energy meter is presented that can be easily installed and managed by any inexperienced user at their own home in urban or rural areas. The system was validated in a real house over a period of two weeks, showing interesting results and findings which validate our proposal.

How to install your oZm in an Electrical Box

Ok, you have just received your brand new openZmeter and it’s time to install it. I must admit it’s not a straightforward task, but it can be done in some few minutes if you put attention. You need a screwdriver and a wire striping tool. Be patient.

Warning: be careful and do it at your own risk.

Some History about oZm (III)

This is the third and final entry about the OpenZmeter project history. You can read the first one here and the second one here.

After the first sketches and designs based on the BBB and own electronics (something homemade… everything is said), there was a step forward in quality with the arrival of Eduardo Viciana to the project. Thanks to his knowledge and experience in microcontrollers, electronics and low-level code, a much more professional approach was taken. oZm was completely redesigned and a new shield based on the micro STM32 was used. This microprocessor has several ADCs that sample the voltage signal. It is also responsible for communication via SPI with the Hall Infineon current sensor TLI4970. The samples obtained in real time are sent via USB to the NanoPi for further processing. The system synchronizes the phase of the voltage and current channel to avoid errors in the energy measurement.

openZmeter v1.2

In its current configuration, the system is able to perform current measurements with an accuracy of 1% and voltage measurements with 0.1%. As an example, the following figures are given:

Sample current waveform

Sample voltage waveform

This is how we close this list of posts related to the historical evolution of the project. Stay tuned for the next news!


También en español!!

Esta es la tercera y última entrada acerca de la historia del proyecto openZmeter. Puedes leer la primera aquí y la segunda aquí.

Tras los primeros bocetos y diseños basados en la BBB y en electrónica propia (algo casera… todo hay que decirlo), se produjo un salto de calidad con la incorporación de Eduardo Viciana al proyecto. Gracias a sus conocimientos y experiencia en microcontroladores, electrónica y código de bajo nivel, se pasó a un enfoque mucho más profesional. Se rediseñó completamente oZm, pasando a utilizar un nuevo escudo basado en el micro STM32. Este micro dispone  de varios ADC que samplean la señal de tensión. También se encarga de la comunicación por SPI con el sensor de corriente de efecto Hall Infineon TLI4970. Las muestras obtenidas en tiempo real son enviadas mediante USB a la NanoPi para su procesamiento. El sistema se encarga de la sincronización de la fase del canal de tensión y de corriente para evitar errores en la medición de energía.

openZmeter v1.2

En su actual formato, el sistema es capaz de realizar mediciones de corriente con precisión del 1% y mediciones de tensión con el 0.1%. Un ejemplo son las figuras siguientes:

Sample current waveform

Sample voltage waveform

Con esta información, cerramos esta lista de posts relacionados con el devenir histórico del proyecto. Estate atento a las próximas novedades!!

Some History about oZm (II)

This is the second entry about the history of the openZmeter project. You can read the first one here.

Once the interface was designed and concept tests were performed, the hardware definition phase began. Initially, and due to limited manpower with advanced knowledge in electronics, it was decided to make use of the Texas Instruments BeagleBone Black (BBB) board. Previously, some sketches were made based on some of Texas Instruments’ ADCs, although they did not happen to materialize. It was 2013 and the project was extended with the collaboration of Javier Clement and Vitaly. It wasn’t until 2015 that the project took off thanks to the collaboration of graduate in electronics Javier Rodríguez. The first designs of the shield on which the BBB would be placed began with him. Initially, a passive network was designed as a resistive divider to measure the voltage as well as a precision shunt resistance to measure the current.

oZm Shield v1 – 2015

We chose the BBB because it was one of the most powerful devices at that time. It also had built-in Linux installed as default, but the most important reason was its two PRU’s microcontrollers with which we could read and manage the voltage and current samples coming from the shield in real time. These PRU’s dumped the information directly into the RAM so that we could perform the necessary electrical calculations without any major problems. As a result of this work, some papers (in Spanish) were presented at the Sarteco 2015 Conference (here the presentation).

The fact is that the prototype was able to measure voltage, but not current due to a design flaw in which the specifications of the INA126 amplifier were not properly taken into account. This helped us to learn some lessons about how complex and delicate electronic design can be!

In the next and last entry, I will talk about the last stage, where a more professional and effective design is performed.


También en español…

Esta es la segunda entrada acerca de la historia del proyecto openZmeter. Puedes leer la primera aquí.

Una vez que se diseñó una interfaz y se realizaron las pruebas de concepto, empezó la fase de definición del hardware. Inicialmente, y debido a los escasos recursos humanos con conocimientos avanzados en electrónica, se decidió hacer uso de de la placa BeagleBone Black (BBB) de Texas Instruments. Previamente, algunos bocetos fueron realizados basados en algunos ADC’s de Texas Instruments, aunque no llegaron a materializarse. Corría el año 2013 y el proyecto se amplió con la colaboración de Javier Clement y Vitaly. No fue hasta 2015 cuando el proyecto tomó un mayor impulso gracias a la colaboración del estudiante de electrónica Javier Rodríguez. Con él empezaron los primeros diseños del escudo sobre el que iría insertada la BBB. Inicialmente, se diseño una red pasiva a modo de divisor resistivo para medir la tensión así como una resistencia shunt de precisión para medir la corriente.

oZm Shield v1 – 2015

Elegimos la BBB porque era uno de los dispositivos más potentes del momento. También tenía Linux instalado de serie, pero el motivo más importante eran sus dos microcontroladores PRU’s con las que podíamos leer y gestionar en tiempo real las muestras de tensión y corriente provinientes del escudo. Estas PRU’s volcaban la información directamente a la RAM de forma que podíamos realizar los cálculos eléctricos necesarios sin mayor tipo de problema. Fruto de este trabajo surgieron algunos papers (en español) como el presentado en las Jornadas Sarteco 2015 (aquí la presentación).

La verdad es que el prototipo llegó a medir tensión, pero nunca corriente debido a un fallo de diseño en el que no tuvimos en cuenta correctamente las especificaciones del amplificador INA126. Esto nos sirvió para aprender ciertas lecciones acerca de lo complejo y delicado que puede ser el diseño electrónico!

En la próxima y última entrada, hablaré de la última fase donde se realiza el diseño actual, mucho más profesional y efectivo.