2023-12-28 07:30:10
LNE has developed the first instrument capable of characterizing high voltage pulses of up to 500 kilovolts, and whose rise times are only a few nanoseconds. To guarantee the traceability of the measurement, the device is calibrated and calibrated to the international system of units.
High pulsed powers are a technology for generating very high electrical voltages, which can reach several thousand volts, in the form of extremely short pulses, ranging from a few milliseconds to a few nanoseconds. This process is for example used to test the resistance of devices to lightning. Until now, there was no metrology to characterize high voltage pulses of up to 500 kV (kilovolts), with rise times of only a few nanoseconds. The LNE (National Metrology and Testing Laboratory) has just developed the first instrument capable of carrying out these measurements.
“For manufacturers, it is important to be able to generate a wave that rises and falls as cleanly as possible so that it can be used efficiently, declares Pierre-Jean Janin, head of the low frequency department at LNE. For this, this wave must have no oscillation, no crackling and no double peak. To obtain this quality of impulse, it is necessary to control it, and to control it, it is necessary to measure it using measuring tools which are calibrated and calibrated to the international system of units. »
The main part of this new measuring system consists of a voltage divider. Since there is no instrument capable of directly measuring high voltage, this divider has the function of attenuating the signal, and can, for example, reduce a voltage of 500 kV to just 10 volts. An oscilloscope, positioned at the output, then measures this voltage. The challenge in developing this new measurement system was to manufacture the most precise divider possible, capable of dividing a voltage without distorting the signal.
“To design our tool, we first carried out electro-magnetic and mechanical modeling work, specifies Pierre-Jean Janin. Next, we looked for precision companies capable of bonding the parts to each other with a very thin layer, only a few micrometers thick, and made of materials with very particular properties and characteristics. Finally, tests were carried out with voltages reaching several hundred kV, while ensuring that they were not destructive. All of this work is very complex and took us four years to develop. »
High voltage pulses increasingly used in multiple fields
In addition to measuring a very short signal of only a few nanoseconds, this new device has the particularity of being connected to the international system of units (SI), which is a first in the world. Other measuring instruments already offer this guarantee of traceability, but only for pulses ranging from milliseconds to microseconds. This new instrument is transportable to characterize pulsed wave generators as well as voltage dividers. Manufacturers and research laboratories will thus be able to benefit from the guarantee of traceability on all their types of pulses, providing them with precision and security. Since the generation of pulses requires energy, this measuring instrument will also ensure that you do not use more energy than necessary and will therefore limit any waste.
Pulsed waves are historically used in the military field to detect mines in the ground and assess their depth. The briefer and faster the impulse, the lower the risk of not identifying them. They also find applications in the space sector and are the source of high frequency signals from satellites. In the food industry, many pasteurization, sterilization and food preservation processes also use this pulse wave technology.
In the medical field, this process is used in particular to treat cancers. “Radiotherapy basically uses high voltage waves which are produced by a generator and then transformed into X-rays, continues Pierre-Jean Janin. The cleaner the high voltage pulse, the more precise and localized the rays will be in order to kill cancer cells, while avoiding spillover onto healthy cells. It is therefore important to calibrate the equipment used to perfectly control the shape of the wave. »
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