Optical Level Gauging System
Design Concept of Optical Level Gauging System
Optical Level Gauging system is an optical sensor measuring level of fluidsystem. This system uses optical refraction. In air, light coming out fromilluminators goes back to receiver because of complete reflection of prism.
In liquid, the light passes the prism and does not reach to receiver.
Photocells including illuminator, receiver and prism are put vertically togenerate signal depending on liquid level.

Photo CellPrism

Illuminator
ReceiverThis gauge has matrix circuit and it lights illuminators with pulse offset
repeatedly. Based on current value of photo receiver, height of liquid levelis detected. Benefits of this method are;- More than 100 pcs illuminators and receivers can be controlled onlywith 5 lead wires.
- Illuminators are lighted one by one to save current consumption.
- Time of the illumination is short and it results longer lifetime ofilluminators.
This Optical Level Gauging system is explosion proof type and passed
DO-160 explosion proof test, and can be used for fuel level measurementin fuel tank.
This system does not have any movable parts. Therefore, there is no riskof jamming of movable parts and wear. Illuminators ad receivers are in 2lines, and monitor each line. Because of the 2 lines, illuminator andreceiver failure can be detected by built in test. Even if one line would notwork, another line can keep liquid level detection as redundancy. If
sloshing would be concerned, level signal outputs can be averaged withfunction of output signal delay. As option, prism cover is available forsplash and illuminated condition.
Even frost would be put on prism, liquid level can be measured.
Processor Unit CPU calculates liquid quantity with signal of Level Gaugeand signal from density sensor. Filter of Processor Unit reduces EMI noise
to protect Level Gauge.
Liquid quantity data is transmitted to airplane (Avionics) through ARNIC429
serial communication.

Level Gauge

Processor Unit

Strong Points

1 Low Installation Cost
2 Easy Calibration
3 Easy MaintenanceInstallation of a Compensator is not required for the “Optical Level Gauge”.

The “Optical Level Gauge” does not require temperature calibration required for capacitance type.

⑴ Since the “Optical Level Gauge” measure the liquid level itself, there is no temperature dependence,and there is no change in measured value over time, therefore no need to calibrate.

⑵ The digital built-in-test can quickly identify the location of any faulty cable or sensor. This reduces thecost of maintenance and support associated with troubleshooting and replacing failed sensor.

Optical Level Gauging System
Processor Unit
SignalLevel Gauge

ARINC429

Airplane (Avionics)

SignalDensity Sensor

New Development Item

Specifications
No.

Item1Sensing Length

846 mm (Customizing)

2Temperature

Level Gauge and Processor Unit
Operational / Storage : -54 °C to 71 °C3System Accuracy± 1 % at full scale

4Input Power

28 VDC
Processor Unit : 4 W max (Measured value : 200 mA /1probe)

5Connection Number

Max. 10 Level Gauges / Processor Unit

6Mass

Level Gauge：1.5 kg max
Processor Unit：1.0 kg max

7

Applicable Fluids

MIL-DTL-5624, Grade JP-4
MIL-DTL-83133E, Grade JP-8
MIL-DTL-5624, Grade JP-5
JET-A / JET-A1 ATSM D-1655
Applicable for kerosene, light oil, gasoline and water

8MTBF

Level Gauge : 100,000 Hr min
Processor Unit : 50,000 Hr min

9Qualifications

TSO C55a, DO-160, DO-178 (preliminary review)

Specifications

TEL: +81-265-21-1814 FAX：+81-265-56-4108
https://www.tamagawa-seiki.com/
ʼ20.04
T12-1724