Schaerer Ambiente 2 Service Manual

Chapter 3 Functional descriptions
SMSO-2-02.03- 15.07.03 49
3.2.14 Level probe
The level probe controls the water level in the steam genera-
tor. To ensure that there is always enough steam available,
the water level in the steam generator must not be allowed to
rise above a certain level.
Conductance
Due to its mineral and metal content water conducts electric
current. These low levels of elements causes the water to
have electrolytic properties (movement of ions under the ef-
fects of an electric field). This electrolytic conductance can be
measured in a similar way to the conductance of a metal con-
ductor.
These characteristics of water can be used to check the level
inside steam generators. The level of an electrically conduc-
tive medium in a metal container is signalled by means of an
insulated electrode placed inside the metal container (level
probe) and a conductance amplifier (part of the unit control
system).
If the water does not touch the electrode, the resistance be-
tween the container wall and the electrode is very high, if the
water is touching the electrode, the resistance reduces. These
changes in resistance are analysed by the conductance ampli-
fier and the feed valve is triggered accordingly.
Function
The level probe is built into the steam generator. It is electri-
cally insulated by insulation tubing to just a few millimetres
from the tip and as far as the flat plug connector. The negative
potential (GND) is placed on the steam generator and a posi-
tive voltage from the control system on the level probe. If the
water level reaches the tip of the level probe, current is able to
pass through the water. The unit control system analyses the
signal and closes the feed valve to the steam generator. As
soon as the water level goes down, the flow of current through
the probe is interrupted. The signal stops and the unit control
system opens the feed valve. To ensure that this type of circuit
operates correctly, the water must have a minimum conduc-
tance of 100 µS.
Level probe
1 Level probe
2 Insulation
3 Clamping ring
4 Union nut
5 Connection sleeve
6 Steam element
7 Water
8 Steam
9 GND connection
10 White ring
11 Seal
Level probe for the SO-2: This illustration shows the level probe for the steam element at actual size.
Indicator: white ring at the plug connector
Drawing symbol Illustration

Schaerer Ambiente 2 Specifications

General

Brand	Schaerer
Model	Ambiente 2
Category	Coffee Maker
Language	English