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