Purpose
The waste tank continuous level sensor calculates the amount of waste in the tanks. This data is only for indications that show on the cabin area control panels (CACP) and cabin system control panels (CSCP).
Physical Description
The waste tank continuous level sensor is a capacitance-type pressure sensor. The sensor has these components:
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Remote diaphragm
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Capillary tube
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Electrical connector J3
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Sensor module.
Wires connect the electrical connector to the logic control module (LCM).
Location
The continuous level sensors are in the bulk cargo compartment, behind the left side wall. There is a sensor for each waste tank. The sensor module is in the drain line below the tank. The remote diaphragm is in the vent line above the tank. The capillary tube goes from the remote diaphragm to the remote sensor.
Functional Description
The remote diaphragm and the capillary tube find the pressure of the air in the tank. The sensor finds the difference between the air pressure in the tank and the liquid in the drain line. It uses the difference to calculate the amount of waste in the tanks.
Training Information Point
You use the (LCM) to do a zero adjustment when you install a continuous level sensor.
You can test the operation of the sensor with the LCM or with an all test through the cabin services system (CSS).
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General
The logic control module (LCM) gives information about the amount of waste in the waste tanks to the cabin services system. The LCM does not let the vacuum waste system operate for the lavatories connected to a waste tank that is full.
There are three LCMs, one for each tank. It also has BITE for itself, the point level sensors, and the continuous level sensor.
Physical Description
The LCM has four electrical connections. Three are for the sensors and one connects the LCM to the airplane wiring. The LCM also has a three-position switch.
It has five lights:
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Sensor J1, red
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Sensor J2, red
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Sensor J3, red
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Tank full, red
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Power on, green.
The first two lights are for the point level sensors. The third is for the continuous level sensor.
Location
The LCMs attach to the support fitting inboard of each waste tank.
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Operation
To do a test of the LCM, first push the switch down. All five lights come on. When you release the switch the lights go off.
Next, push up on the switch. All five lights come on. If any light stays on when you release the switch, that sensor fails the test.
When you do an ALL TEST from the CSCP, the LCM does a test of the sensors and the LCM circuit.
See the cabin services system section for more information about the ALL TEST (SECTION 23-39).
After you replace a continuous level sensor, you must do an auto zero adjustment of the LCM. You use the three-position switch to do an auto zero adjustment.
When a sensor detects that the tank is full, the associated sensor light on the LCM will come on. The tank full light turns on if any of these conditions occur:
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The two point level sensor detect the tank is full
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The two point level sensors fail
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One point level sensor fails or is fouled and the other point level sensor detects the tank is full
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The continuous level sensor detects the tank is almost full.
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If any of the sensors are failed or the point level sensors are fouled, the light for that sensor will flash on the LCM. If the LCM fails, the tank full light flashes.
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General
The continuous level sensor sends data about the quantity of waste in the tanks to the LCM. The LCM sends the data to the cabin services system (CSS). The cabin area control panels (CACPs) (not shown) and the cabin system control panel (CSCP) (not shown) in the CSS show the waste tank level information.
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