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Automotive Applications of Level Sensors
Group: Calcium δEric Black
Daniel Carter
Introduction
• Level sensors are not only used in Industrial and Chemical Applications
• Common household items use them as well
• These sensors range from simple mechanical devices to electronic or radiating tools
Level Sensors on Cars
• Cars contain two of the main kinds of level sensors– Float sensor– Visual sensor
• The float sensor is found in the gas tank, whereas there are a few visual sensors under the hood of the car
Gas Tank Float Sensor
• Initially, the float is at top of tank• The attached wiper is closer to negative side of terminal
– Less resistance– More current– Hotter Heating coil– Pulls Bimetallic strip so dashboard gauge displays full
Gas Tank Float Sensor
• As fuel leaves tank, float lowers• Wiper moves further down resistor
– More resistence– Less current– Coil cools– Strip pulls with contracting metal
Gas Tank Float Sensor
• Finally, after float hits bottom of tank, wiper is pulled to far right– Highest resistance– Lowest current– Coolest heating coil– Strip pulled gauge to empty
Gas Tank Float Sensor
• Pros:– Relatively simple mechanical design– Good for estimating level of fuel
• Cons:– Inaccurate when:
• Tank is completely full• Tank is near empty
– Doesn’t measure precise tank volume
Level Gauges Under the Hood
• Under the hood of a car, there are ways to check the level of various other fluids– Oil– Transmission– Coolant / Antifreeze– Windshield washer fluid
• These are checked using visual level gauges
Dipsticks
• Dipstick is inserted into engine
• Then removed with oil residue on tip
• Tip is marked with “full” and “add oil” markings
• Checking transmission fluid is similar
• Similary to the fuel tank float meter:– Good for estimating fluid
level– Not a precise measurement
of volume
Container Markings
• Small tanks under the hood containing windshield washer fluid and coolant have markings on the sides
• Only good for level estimation• Can’t measure precise fluid volume