Quantum sensors

Quantum sensors: going with the flow

Quantum sensors are already creating concrete added value in industrial application, faster than any other quantum tech­nology. They use the electron spin of alkali atoms to make even the smallest magnetic fields visible. Quantum-based technology can be used to mea­sure the magnetic fields of sub­stances that would be invisible to conventional measurement technologies, for example. Leonhard Schmieder from the Fraunhofer Institute for Phys­ical Measurement Techniques IPM in Freiburg came up with a specific application scenario for measuring the flow inside pipes. Wherever industrial processes involve liquids flowing through pipes, the flow needs to be measured in order to ensure a smooth process. There are already proven solutions on the market to do this, but they have critical drawbacks. They might not work reliably if air or other gases are present, or they might depend on the conductivity of the substance. Some are costly and time-consuming to incorporate into the pipe, while others come into direct contact with the substance being measured.

“Our method offers especially significant advantages in areas where an accurate, contact-free or non-invasive solution is important,” Schmieder explains. “That includes fuels, soap solutions, oils, coolants and even foods and liquid hydrogen.” The only requirement is that the sub­stance must contain bound hydrogen, as its nuclear spin provides strong signals for measurement purposes. It is also found almost everywhere. To read the signals, Schmieder and his team use “optically pumped” magne­tometers, which are used for their unmatched sensitiv­ity in applications such as magnetoencephalography, which measures the magnetic fields produced by elec­trical currents in the brain. The liquid is first magnetized and then marked by disrupting the magnetic field. These magnetic markings are then logged through travel time measurement. The magnetic measurement technology needed to do this fits into a tiny box about the size of a sugar cube placed on the outside of the pipe. The “sugar cube” senses the tiny magnetic changes, even through steel and plastic.

This patented new approach also offers further possibilities. “With our method, we can not only measure the flow rate but also capture other valuable in­formation that could not be logged on a touchless basis be­fore now,” Schmieder explains. “For example, flow profile detec­tion would be conceivable, or multi-phase flow measurement, say if you want to measure oil, water and gas at the same time.” Another advantage is that plans call for the measurement unit not only to be able to be installed in a permanent location but also to serve as a mobile moni­toring tool. This feature could be used to check flow quality at specific points and visualize any deposits forming inside the pipe. “These new possibilities could radically reshape the way liquids are monitored in industry,” Schmieder says with conviction.