8
Liquid Leakage Sensor Amplifier with Disconnection Detection Function
K7L-AT50D/-AT50D-S
Operation
■
Disconnection Detection Function
Operation While Monitoring for Liquid
Leakage
•
Short-wave signals (2.5 VAC, 3.75 Hz) for liquid leakage detection
are output from terminal 4 of the K7L.
•
When there is no liquid leakage, the liquid leakage detection sig-
nals that are output are interrupted by the Terminator and the core
of the Sensing Band will form an open loop.
Operation at Liquid Leakage Detection
•
When liquid leakage occurs within the sensing range, the liquid
leakage detection signals output from terminal 4 are input to termi-
nal 2 through the leaked liquid.
•
The voltage of the input signals will vary with the resistance of the
leaked liquid. This voltage is compared with the detection level set
at the K7L.
•
As a result of the comparison, if the K7L determines that liquid
leakage has occurred, the K7L’s output LED will light, and the liquid
detection output will either turn ON or OFF.
Operation While Monitoring for
Disconnection
•
Output of disconnection detection signals starts within 2 s of power
being supplied to the K7L and is repeated at 7-s intervals.
•
Disconnection signals are DC signals of 10 V max. that are output
for approximately 200 ms. During this time, the K7L is in disconnec-
tion monitoring mode, i.e. it monitors for disconnections only and
the liquid leakage detection signals are stopped.
•
If there is no disconnection, the disconnection detection signals
(10 VDC) that are output pass through the Terminator and return to
the K7L. The K7L takes this as normal, i.e., there is no disconnec-
tion.
Operation at Disconnection Detection
•
If there is a disconnection, the signals will be interrupted at the
place where the disconnection occurred, and will not return to the
K7L.
•
If the signals do not return when the K7L is in disconnection moni-
toring mode, it will determine that a disconnection has occurred.
The output indicator will flash, and the disconnection output will
turn ON/OFF depending on the position of the DIP switch (right).
Note: 1.
Disconnection detection is only performed between terminals 2 and 4. Therefore, be sure to connect the Sensing Band between terminals
2 and 4.
2.
The K7L will switch from liquid leakage detection to disconnection detection if either of the following conditions occur while liquid leakage
is detected.
•
Disconnection occurs between the K7L and the place where liquid is leaked.
•
While liquid leakage is detected, disconnection occurs between the place where liquid is leaked and the Terminator (F03-20T) and,
subsequently, the leaked liquid is removed (e.g., wiped up or dried).
3.
During disconnection detection, liquid leakage will not be detected. Once disconnection has been detected, reset the power supply to
stop disconnection detection.
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Block Diagram for External Connections
K7L
2.5 VAC (3.75 Hz)
Signals interrupted by
Terminator.
K7L
K7L
10 VDC max., 200 ms
Disconnection detection signals
are not interrupted by the Termi-
nator and return to the K7L.
Signals are interrupted where the
disconnection occurred.
K7L
Open-collector output
100 mA at
30 VDC max.
(Bottom view)
K7L-AT50D
Signal
transmission
Level input 1
Level input 2
Liquid leakage
detection output
Disconnection
detection output
Common
OUT+
BURN OUT+
COM-
12 to 24 VDC
Connecting cable
(0.2 mm
2
min.)
F03-20 Terminal Block
Sensing Band
F03-20T Terminator