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Automation in the field of low-resistance measurement is increasingly required in the factory or laboratory. Be it in the automotive/electromobility sector, in the investigation of soldered or welded joints of high-current connections or in a wide variety of other applications.

For special requirements, e.g. for use in test stands, the easy-to-use PROMET PI programming interface is available for control and measurement with the PROMET R300/R600 resistance measuring devices. This can be used in COM/ActiveX-supporting as well as in .NET environments.
By programming the measurement sequence once, it is possible to integrate the PROMET R300 or R600 resistance measuring instruments into the test equipment via the programming interface and to perform measurements automatically.

A driver is installed with the programming interface, via which the connected devices are addressed. Communication between the software/PC and the external PROMET R300/R600 is made possible by the installed ActiveX component. This allows communication via USB or Ethernet interfaces.
As an example, an Excel sheet is used to control the PROMET R300/R600 and to evaluate the measurement results in this description, via which the programmed VBA macros (Visual Basic for Applications) are executed. Programs can be modified and adapted according to the requirements.

The PROMET R300/R600 precision resistance meters are an ideal tool for characterizing components for high current and low resistance due to their four-wire measurement and ability to accurately measure both current and voltage. 
As demonstrated in the article, a resistance measurement system controlled via external software can be easily integrated into an automated application. Using the PROMET R300/R600 resistance measuring instruments to perform such measurements simplifies the test setup, reduces programming time, and enables efficient test sequences.

Further information on the use of the PROMET PI programming interface can be found in the application report PROMET R300/R600 - The intelligent way to measure resistance!

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

Postscript
The EPOS 360 three-phase signal generator can also be integrated into your own test applications in a similar form via the EPOS PI programming interface!

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.

Saving of working time through simultaneous resistance determination at three measuring points

For switchgear in the medium-voltage and high-voltage level, the switchgear standard IEC 62271-1 requires a static resistance measurement of the main circuit in order to exclude an unacceptable heating of the current path.

Traditionally, the measurements are carried out one after the other and individually at each phase. The main circuit is supplied with 100 A direct current and the voltage drop is measured. If the measured value, i.e. the voltage drop is within the specified limits, the test is passed and the results can be recorded/stored. This measuring procedure is time-consuming as the three phases are tested one after the other.

To increase productivity and improve reliability, the measuring method for resistance and voltage drop measurement can be optimized with the PROMET R300 or R600.

The PROMET R300/R600 resistance measurement systems are equipped with three voltage measurement inputs, allowing parallel measurement at three measuring points, for example to measure the resistance of three main contacts statically.

 

In order to perform a simultaneous measurement of three main contacts, the test objects must be connected in series and provided with a test current connection. Since a four-wire measurement is carried out, it is important to ensure that the voltage connections are between the high current connections and that they are connected exactly at the points where the resistance is to be determined.

Connection example for a measurement on three test objects connected in series, e.g. three interrupter units.

In stand-alone mode, the three static resistance results with the measurement details (actual test current and voltage drop, measurement ranges etc.) can be stored in the measurement device.

 

The data stored in the device can be read out and managed with an easy-to-use PROMET software. The clearly displayed measurement results can also be output in a PDF test report or exported as CSV data.

The described simultaneous measuring method for the acquisition of three resistances thus saves working, changeover and measuring time!

As a further automation option, PROMET R300/R600 are equipped with interfaces for connection to the ACTAS 2.60 switchgear testing software. Resistance measurement can be conveniently integrated via the ACTAS test software. Even without an additional ACTAS test system, automated test sequences and a comprehensive analysis of the test results can be carried out without any problems.

 

The method is not only applicable in switchgear testing, but also in applications such as e.g. in the field of e-mobility, where several resistors have to be detected at the same time.

If you have further questions, please leave a comment or contact us directly.

Use of the Kelvin test probes KP 200 together with PROMET R300/R600

The KP 200 Kelvin test probes were developed for safe and easy resistance measurement at measuring points which are difficult to access. The test probe pair is equipped with spring-loaded high-current and voltage contacts for the determination of low-resistance according to the four-wire method for a test current of up to 200 A.

 

Can the test probes be used together with the PROMET R300 or R600 resistance meters?

The PROMET R300/R600 are designed with 13 mm high current sockets for the connection of 50 or 70 mm² high current cables. With the reducers 13/9 from 13 mm to 9 mm socket/plug diameter, it is possible to connect high-current cables with a smaller cross-section and 9 mm plugs or sockets to the PROMET R300/R600, such as the CS 205 cable set (2 x 5 m , 25 mm²).
With these cables it is now possible to use the KP 200 Kelvin test probes with the PROMET R300 or R600.

 

Furthermore, a measuring mode for the safe use of the KP 200 Kelvin test probes has been implemented in the stand-alone operation of the PROMET R300/R600 (from firmware version FWP 1.5).
According to the maximum load of the KP 200 Kelvin test probes, the current output in this mode is limited to 200 A.

If the measurement has started actively, the measuring device waits in this measuring mode for the test probes to be placed on the test object. A measurement is only carried out when the test probes are reliably and completely contacted (voltage and current contact). That is, the test current is output, the best measuring ranges are determined and the resistance value is measured. The measurement is carried out automatically with the shortest possible measurement time.

In order to simplify the use of the test probes on site, the current status of a measurement is also signaled by means of the LED status display and an acoustic signal.
The measurement result now remains on the display until the test probes are removed and the next measurement process is activated by placing the test probes. The resistance measurement results are displayed in a table and the results can be viewed before they can be saved.

With this sophisticated functionality, safe and automated operation of the KP 200 Kelvin test probes together with the PROMET R300/R600 resistance measuring devices is possible.

If you have further questions, please leave a comment or contact us directly.