10.1.5 Water Sensor
The water sensor is used to monitor the liquid level change.
Appearance
The liquid-level sensor adopted by Huawei is a kind of plug-in spacing liquid-level sensor. This
sensor is of the current type. When the sensor enters the liquid, the power supply forms an
injection current to the signal end so as to monitor the liquid level change.
shows the water sensor.
Figure 10-4
Water sensor
77+1
2700+20
1
8
Unit: mm
Principles
shows the electrical principles of the water sensor.
Figure 10-5
Electrical principles of the water sensor
R1
R2
D2
D1
Red
White
Green
Solid-state
liquid-level
sensing
head
The water sensor is a three-wire interface.
l
Green wire: When no liquid contacts the solid-state liquid-level sensing head, the output
(green wire) is less than 80uA.
l
Red wire: When the measured liquid contacts the solid-state liquid-level sensing head, the
output end absorbs the current 10 mA to 15 mA against the power end (red wire). The solid-
state liquid-level sensing head adopts the infrared photoelectricity theory. When the
detected liquid contacts the sensing head, the light path is changed, and the infrared
receiving point is in the stop state. In this way, the reverser is inverted, and outputs the low-
level absorbing current.
l
White wire: The white wire is the ground cable.
UA5000 Universal Access Unit
Environment Monitoring
10 Sensors
Issue 01 (2012-08-17)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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