KoCoS Blog

Resistance measurement with PROMET - Thanks to Ohm!

After Alessandro Volta created a source that supplied electric current in 1801 with the so-called Volta Column, it was possible to explore the effects of electric current. Many researchers made numerous discoveries and observations, but the mysterious effects of electric current could not be revealed.

It was only through the discoveries and research of Georg Simon Ohm that the facts could be explored. Without his research and without the resulting fundamentals of Ohm's law, the outstanding developments in electrical engineering would not have been possible.

Georg Simon Ohm, born March 16, 1789 in Erlangen, died July 6, 1854 in Munich, was a German physicist.

The decisive measuring instrument for the discovery of Ohm's laws was the torsion balance galvanometer constructed by Ohm. The torsion balance galvanometer consists of a thermocouple (A) in which the ends are kept at different but uniform temperatures (B). A magnetic needle (C) on an adjustable suspension (D) and a device with which the various test conductors (E), i.e. the variable resistance, can be contacted.

If a test conductor is connected so that a current flows, the magnetic needle is deflected. The position is read off a scale. The deflection or the read scale values form a proportional measure for the magnetic effect of the electric current, thus the current intensity.

Ohm was able to deduce the law from these measurements:
I = Uq / (Ri + Rv)
Current = Source Voltage / (Internal Resistance + Variable Resistance)

Ohm published his results in 1826 and initially received little recognition. It was not until 1841 that Ohm received the Copley Medal of the Royal Society of London, which corresponds to today's Nobel Prize, as an award for his work. In 1893, the World Electrical Congress in Chicago gave the designation "Ohm" (sign Omega: Ω) to the unit of electrical resistance.

With Ohm's torsion balance galvanometer, only the first step in the development of resistance measuring instruments is described in this article. The history of resistance measurement shows the changes from the age of early experimenters to today's computer age, i.e. from measuring bridges to the first electronic devices to today's digital measuring systems. Developers always used the latest ideas and systems to make the products more useful and user-friendly. Technological change drove the development of measuring instruments and realized technological advances.


KoCoS is committed to this development and offers a diverse range of resistance measuring instruments with the PROMET series. PROMET precision resistance measuring devices are used to determine low-resistance in the μΩ and mΩ range. With adjustable test currents of up to 600 A in conjunction with a four-wire measuring method, the systems provide measurement results for the highest accuracy requirements. Typical applications are, for example, the determination of the contact resistance of switching devices and the resistance determination on inductive loads such as transformers. The use of state-of-the-art power electronics and the robust design guarantee maximum reliability for mobile use, but also for stationary use in the laboratory and factory.

Do you have questions or additions to the resistance measurement or to our measuring devices? Then contact us via the comment function here on the blog or by mail to info(at)kocos.com.

Reliable operation of all INDEC vacuum inspection systems under the most difficult operating conditions such as vibrations of the conveyor belt.

The vacuum inspection systems of the INDEC series offer our customers a reliable solution for leak testing of jars, bottles and metal cans even under extreme operating conditions. The inspection takes place contact-free as a 100% in-line inspection directly in the production process. An optical sensor detects the vacuum-induced deformation of the lids. Even non-metallic container closures can be inspected. Containers with insufficient vacuum, crooked or missing lids are reliably detected and can be separated fully automatically from the product flow with an ejector. All components are made of stainless steel (1.4404), are resistant to cleaning agents and disinfectants and meet the requirements of protection class IP69K.

How do vibrations of the conveyor affect the reliability of INDEC systems?
We are often confronted by our customers with the question of whether the INDEC systems still function reliably when the conveyor belt is vibrating. This question can be answered with an unequivocal yes.
For this purpose, we would like to refer again to the measuring procedure and the mode of operation of all INDEC systems. The test procedure is based on the determination of the vacuum-induced deformation of the passing container closures. The tightness of the containers is assessed by comparison with a previously “Golden” sample. If a container to be inspected interrupts the light barrier under the sensor head, an infrared light beam is emitted by the sensor head and reflected by the lid of the container.  A sophisticated algorithm calculates the concave shape (yellow curve between the two red arrows, see the figure below measuring principle) of the deformed lid caused by the vacuum in the head space. Depending on the given boundary conditions, vacuum tests are possible from
50 µm deformation or from 150 mbar differential pressure in the headspace to the external pressure.

To illustrate the correct operation of the INDEC models even when the conveyor belt is vibrating, see the following video. From 0:34...0:50 min, artificial vibrations are triggered on the sensor head - analogous to vibrations of the conveyor belt - the INDEC system continues to work correctly in that only when passing the opened bottle marked with the white tape does the signal lamp briefly light up for a container without vacuum.  

Link: cloud.kocos.com/index.php/s/9gkyCKcps5g3rpk

Avoid product recalls even before the goods leave production - with reliable vacuum inspection systems from KoCoS.

A look inside the switchgear chamber "Dynamic Timing" and "Dynamic Resistance

In contrast to evaluation via a simple binary signal, as is the case with high-frequency measurement methods, the use of switchgear test systems ACTAS in combination with resistance measuring devices PROMET allows a well-founded diagnosis of breaker units throughout the entire switching process. The result of the measurement is displayed in the form of a curve in which all events of a switching operation can be seen in detail. An exact assessment of the start of movement and end position of the contacts is thus made possible, even time differences between the movements of the main and resistor contacts become visible.

Evaluation of the breaker unit by means of contact resistance analysis

Regular measurements of the static and dynamic contact resistance allow precise statements to be made about the condition of the entire contact system. Necessary maintenance work can thus be detected at an early stage and downtimes prevented. With the PROMET SE resistance measuring device, contact resistance measurements can be carried out on up to 12 or more interrupters and directly integrated into the overall test sequence. The test current can be set up to a maximum of 200 A. Even very small resistances in the single-digit microohm range can be measured with extremely high accuracy. The measured values are included in the evaluation of the test and output in the test report.

A high contact resistance within a switching device leads to a high power loss, combined with thermal stress and possible destruction of the switching device. Faults, such as high contact resistance due to defective connections, can be detected by measuring the static contact resistance. With the dynamic contact resistance measurement, the resistance curve is determined during a switching operation that can be defined as desired. The measurement allows, for example, conclusions to be drawn about the length and condition of arcing contacts in high-voltage switches.


Any questions or additions to the topic? Then please use the comment function here on the blog or send an email to cstuden(at)kocos.com .

Answer: Nothing! Because when we talk about GOOSE at KoCoS, we usually don’t mean the animal but the network protocol I protection technology. Further answers to the question of what GOOSE is all about and what role the latest ARTES update plays in this context can be found here. 

The IEC 61850 standard of the international Electrotechnical Commission (IEC) describes, among other things, a general transmission protocol for protection and control technology in medium and high voltage substations (station automation). One topic of this series of standards is the “Generic Object Oriented Substation Events”, in short GOOSE messages. 

But what is the significance of these GOOSE messages in a substation? 
In simple terms, GOOSE messages are used to exchange information such as status messages or excitation signals between the IEDs (Intelligent Electronic Devices) of the station. These information are distributed as an Ethernet packets via the process bus of the substation.

With an update to follow in the next few days, the test systems of the 4th ARTES generation can also be integrated into a corresponding environment to evaluate these signals. Thanks to the powerful signal processor of these test systems, they can be connected directly to the process bus, so that the evaluation of GOOSE messages can take place in real time.

Since a large number of GOOSE messages can be present in a network, but only the information of individual ones is of interest for the protection test, the exact structure of the required GOOSE message must be known. For the correct parameterization of ARTES test systems, a relay-specific configuration file is required. This file contains all information regarding the structure of the GOOSE message and its content. The ARTES 5 software analyses the configuration file and the desired signal can be selected. 

After the appropriate parameterization has been carried out, a GOOSE message can perform the same functions as the already used hardware inputs of the ARTES test systems.

Still questions? Then please use the comment function here in the blog or send an e-mail to bfleuth(at)kocos.com

Quality assurance by geometric measurements increasingly becomes important not only in the final inspection. The control of dimensional accuracy is progressively shifting to the beginning of the manufacturing processes in order to detect and minimize rejects at an early stage.
The 3D measuring systems LOTOS are suitable among other applications for the exact measurement of ingots, which represent the beginning of the production process of semiconductor wafers. In order to obtain the optimum yield of wafers from the ingots, a highly accurate geometry determination at the beginning of the manufacturing process is more important than ever.

High-precision measurements of the ingot are critical to the quality and productivity of the wafer cutting process. Only an exact geometry allows to set perfect cuttings.

A solution using mechanical measurements is possible, but very susceptible. The material is very brittle, so mechanical impacts can easily cause micro cracks invisible to the human eye. These lead to wafer breakage in later process steps and thus to cost-intensive rejects.

The advantages of geometry inspection of ingots with LOTOS 3D measuring systems are:

  1. Less waste and scrap of the expensive materials
  2. Optimal utilization of the cross-sectional area of the ingot increases productivity
  3. Contactless measuring method allows a solution without mechanical stress of the material, micro cracks due to mechanical stress are therefore excluded

The following video shows the measurement of an ingot with LOTOS

As well as the scan result as 3D visualization