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MAINTENANCE MANUAL

FQIS Tank Units
Figure 2 (Sheet 2)

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MAINTENANCE MANUAL

RIGHT MAIN TANK COMPENSATOR SEE

(EXAMPLE)
A
FQIS Compensator
Figure 3

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MAINTENANCE MANUAL

TERMINAL BLOCK
LEFT MAIN TANK DENSITOMETER
SEE A
ARROW TO SHOW THE UP DIRECTION
TERMINAL POST
(EXAMPLE)

CENTER TANK DENSITOMETER
SEE A
DENSITOMETER (EXAMPLE)
A
FQIS Densitometer
Figure 4

RIGHT MAIN TANK DENSITOMETER
SEE A
HOUSING
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MAINTENANCE MANUAL

 (2)  
The densitometer is installed at the bottom of the fuel tank, aft of the compensator. A tank wiring harness attaches to each densitometer. The tank wiring harness for the densitometer goes through the rear spar.

 (3)  
The densitometer contains a nickel alloy, wiring-wrapped, vibrating spool, an excitation coil, a sensing coil, and eight calibration resistors, all installed in a cylindrical, vented housing. The vents in the housing let fuel go into the housing to cover the spool and let air escape.

 (4)  
The processor sends an AC signal through a coil to excite the spool, which then vibrates. The processor reads the frequency of the vibration and changes the frequency of the excitation signal until the spool vibrates at its maximum frequency. The maximum "resonant" frequency is a function of the fuel density only. The processor calculates the fuel density from the resonant frequency.

 (5)  
The densitometer also gives a check on the specific gravity data from the compensator. This increases the accuracy of the FQIS.
　
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