Coffee is one of the world’s most consumed drinks, which is why it is no surprise that so many coffee machines can be found where people live and work. Coffee from bean-to-cup machines is enjoyed most often.

Bean-to-cup coffee machines are devices which can produce a range of coffee types completely automatically. A fully automatic machine comprises a grinder, an instant water heater, a pump and a brewing assembly. In addition to making coffee, some bean-to-cup machines are equipped with extra modules which use steam to heat up and foam milk.

The grinder has the task of producing freshly ground powder from whole coffee beans. A mobile piston then transports this to the brewing chamber which is part of the brewing assembly and therefore the heart of the machine. The instant water heater is responsible for heating up the water that is going to be used.

A pump is connected to this which transports the hot water. The coffee grounds and the hot water are combined within the brewing assembly. In order to produce the coffee, the coffee grounds are first pre-brewed, where they are moistened with a small quantity of water at low pressure and swell up, allowing the flavours to be released.

Then, the chosen quantity of hot water is forced at high pressure through the layer of swollen coffee grounds and a highly concentrated coffee is produced. The light cream foam on the surface of the coffee comes from the coffee oils released through this process.

No pressure, no coffee

Pressure is essential for an aromatic coffee. Within the brewing assembly and during coffee production, specific pressure is used in most bean-to-cup machines. In order to create this pressure, it is paramount that the built-in pump carrying the hot water into the brewing chamber produces a high pressure itself. The reason for this is that the pressure reduces over the course of the process.

In order to guarantee this system, it is necessary to install sensors. The sensors do more than measure the steam pressure – they also regulate the temperature of the water. A sensor is also required to prevent overpressure. Should overpressure occur, a valve is switched allowing the steam to escape.

Swiss manufacturer, Rex-Royal AG makes these bean-to-cup coffee machines and continuously develops new products and technologies for perfect coffee. Rex-Royal has sourced pressure transducers from Keller’s 21C series for their S300 model range.

Alongside the pressures described above, these pressure transducers also measure and control the temperature of the milk heated to make latte macchiato and cappuccino coffees. With Rex-Royal’s professional coffee machines, the perfectly brewed coffee is no longer out of reach.



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