In 1920 Wilhelm Cremer founded the “Zähler-Eich-und-Reparatur-Anstalt“(Meter-Calibration-and-Repair-Institute) in Königswinter on the Rhine. At that time, calibration was an art that only very few mastered. The meter auditors personally went out and got their first contracts with the utilities in the area. Soon ZERA became known beyond the region for their ingenuity and their penchant for precision.

From service provider for meter calibration, over the years ZERA developed into a highly specialized producer of portable and stationary testing technology for all kinds of electricity meters and instrument transformers. Our solutions have significantly influenced the technological development of testing technology.

In 1950, ZERA developed the first electromechanical error indicator, followed by the electronic testing meter with 0.1% accuracy. At the end of the 90s, ZERA put the first comparator with digital technology and an accuracy of 0.01% on the market. The first primary standard PPCS for metrological institutes was created in 2008. ZERA’s test systems achieved the highest possible accuracy classes that found recognition worldwide.

Starting in 2000, our calibration laboratory received the accreditation from Germany’s National Accreditation Body (today DAkkS) – an approval that metrological laboratories accept worldwide.

Although locally established, ZERA has meanwhile become an internationally operating company: We develop and produce in Germany; however we export over 80 % of our products all over the world.

Precision starts with us. Today we can truly say this. We know that the extraordinary success of the past decades has only been possible thanks to the people that support the company with their knowledge, their ideas and their passion for quality.

Tradition & Quality

As much as the markets have changed over the past 100 years, our corporate values have remained the same: An uncompromising commitment to the highest accuracy and quality, absolute reliability and convincing customer proximity. We know the industry and the needs of our customers from decades of experience. Our engineers and consultants see individual requirements through the eyes of our customers and develop innovative solutions that fit seamlessly into existing processes. Our quality promise Made & Managed in Germany applies not only to our products, but also to our competent advice and qualified service.

We develop and produce in Germany because this is where we find the qualified employees we need – from trainees to engineers. In a climate of appreciation and recognition, many of them have been working in our ranks for decades. 40-year anniversaries are not uncommon. Some families have been with us for generations. In this sense, we are a family business in the truest sense of the word.

We benefit daily from the dedication of our employees and their commitment to our company.

Zera Gruendung 1920 Unternehmensgruendung Reparaturanstalt Business

1920 - Hauptstrasse 392

Establishment of ZERA –
Zähler-Eich- und Reparaturanstalt
Business areas: Maintenance and calibration of meters, repair and sale of repaired meters.

G62 Rotating Watt Hour Meter 1925 5cm Sw

1925 - Rotating watt hour meter

G 63 Rotating Watt Hour Meter 1930

1930 - Rotating watt hour meter

Zera Historie Instandhaltung Eichung Reisende Revisoren


Maintenance and calibration were carried out by traveling inspectors on-site at the customer’s premises.
Repairs were handled out by the workshop in Königswinter.

G 67 Rotating Watt Hour Meter 1942

1942 - Rotating watt hour meter

Zera Historie Pruefraeume

One of the first test facilities at ZERA

Zera Hitorische Pruefraeume History Electric Engineering

View of the historical production facilities

Even before applying the certificate of registration, an initial contract had been concluded with the Emden City Electrical Works to maintain their electricity meters in the grid.

Zera Elektromechanischer Fehlerzeiger Fa3 1951


An electromechanical fault indicator type FA3, used to test dynamic meter. The difference between the set and actual time can be directly read of the dial.

1959 Prüfbank

Meter test bench with wooden housing 1955

G 70 Rotating Watt Hour Meter 1959 5cm

1959 - Rotating watt hour meter

Olympus Digital Camera

1969 Ferraris meter

1969 Ferraris meter, dynamic
Electromechanical meter and register (mechanical drum-type register)

Zera Zaehlerpruefeinrichtung 1970 Historie

Meter test bench 1970

EPZ301- 1972

The first EPZ electronic reference meter was constructed. For the first time, an accuracy of 0.1 % could be achieved. The EPZ301 was installed into test benches as an “uniload substandard meter”. The maximum pulse output frequency with 9000 Hz. This means that errors of meters under test could be measured within shortest test times.

Olympus Digital Camera

1979 Alternating current meter

1979 Alternating current meter, dynamic
Electromechanical meter and register (drum-type register)

Zera Ilmo3 Einphasiger Thermischer Komparator Historie

ILM03 - 1981

A single-phase thermal comparator, for the first time with a measuring accuracy of 0.01% .

Zera Dossam Anlagensteuerung Pc 1990

DOSSAM - 1990

The first purely digital system controls at ZERA, using a PC.

Olympus Digital Camera

1991 Hybrid meter

Hybrid meter
Electronic meter and electromechanical meter (mechanical drum-type register)

Olympus Digital Camera

1994 CT operated meter

CT operated meter, hybrid
Electro-mechanical meter, electronic data processing

Olympus Digital Camera

1996 CT operated meter

CT operated meter, fully electronic, with complex tariff structure

Olympus Digital Camera

Meter test bench 2000

Winsam Editor 2002

WinSAM - 2002

The modular structure of the software allows to be individually and accurately adapted to the meter under test.

Com 3003 Montage Rgb

COM3003 - 2003

The evaluation of the ILM; a highly accurate, three-phase comparator with digital technology.

2004 Mt3000

MT3000 - 2004

First modular system.
Developed in 2002 and received the reddot design award in 2004.

2004 eHZ meter

eHZ meter (industrial meter )
Electromechanical meter and register, highly simplified tariff structure, remote disconnection

Logo Zera India Rgb

ZERA India - 2005

Establishment of a subsidiary in ZERA India 2005

Olympus Digital Camera

2005/2006 AMIS meter

AMIS meter remote disconnection (breaker)

PPCS - 2008

The PPCS has been specially developed for metrological institutes and is used to test other high-precision reference meters or comparators. The PPCS has a measuring accuracy of 0.001 %.

Olympus Digital Camera

2010 EDL meter

EDL meter
EDL21 and EDL40 eHZ or three-point construction

Olympus Digital Camera

WM3000 - 2010

For the first time, different transformer types can be tested with one device.

Zera Basiszaehler

2013 Basiszähler (electrical energy meter)

Com5003 Front Echtewerte 2016

COM5003 - 2016

Comparator with accuracy of 0.005% for the first time

Zerycon Logo Web

Foundation of ZERYCON GmbH 2017

Zera Stm6000 Serie Digitales Messsystem Kommunikation Metrologie Historie

STM6000 series - 2018

First digital measurement system for testing of communication and metrology

Zera Standort Relocation Koenigswinter Gebaeude

New location - 2019

New premises Humboldtstraße
Relocation to new premises in Königswinter-Oberpleis

Zeras S2 Serie Tragbarer Pruefzaehler Zaehlerpruefung Historie

s2 series - 2019

Successor to the MT310 Reference Meter.
Launch of the s2 series – a new generation of portable meter testing.

Smartmeter Mit Gw 2020

2020 Smart Meter Gateway (SMGw)


2021 EMOB32

First test case for testing charging stations/e mobility