Technical Principles
1ª review – UK 12 – 2020
12
A10. Volumetric counter
Its function is to measure the quantity of water that is pumped
for the elaboration of the espresso coffee
A blade inside it spins boosted by the water flow. Two magnets
on the blades activate a terminal locate on the counter cap. The
three terminals on the cap are positive, negative (5V cc) and the
_П_ (square signal symbol). If it is measured between negative
and _П_ when water is pumped through the counter it will be
gotten the voltage difference 0V and 5V. In a digital tester it will
be shown 2.5V which indicates that the counter is working well.
A11. Water pump
E1. By-pass
E2. Non return
When an espresso coffee is elaborated, the water pressure needed is quite high to be able to
pass through the compressed ground coffee in the infusion element. This resistance the coffee
offers makes the water pressure in the boiler increase up to a pressure of 9 Kg/cm². At this
pressure the by-pass opens allowing a small amount of water to return; sufficient to prevent
the water pressure from going over the 9 Kg/cm².
The by-pass is a small hole covered with a ball that is held in place by a spring. This spring will
hold a pressure of 9 Kg/cm², but over this pressure it compresses and allows the water to
pass.
The pressure of 9 Kg/cm² is considered the ideal for elaborating espresso coffee.
When the instant beverages are elaborated, there is no resistance offered and so during there
elaboration the water pump works at lower pressures than when elaborating espresso coffee.
The pump has an non return valve that prevents the return of water from the boiler.
Technical characteristics:
Voltage
230 Vdc
Power
48 w
Working pressure
9 Kg/cm²
