# A in the height of the float

A potentiometer or potential divider is a device, which can be used to measure certain type of data. It consists of a moving contact, which can pass along a surface of high resistance. When it does this the resistant output changes and as a result this can be used to measure things, such as distances or angles, as long as the device can be applied to either a rotary potentiometer or liner potentiometer. Current I = V/R V=voltage R= resistance I have researched that radio and hi-fi systems rely on potentiometers to adjust volume levels.

On an old radio there is often a scratchy sounds as you turn the volume knob. This is because the signal from the radios is controlled by tapping off part of it with a sliding contact moving along the surface of high resistance. It works by having the signal from the radio – a varying potential difference – across the whole resistance, but the signal to the speaker is then taken from across only a part of the whole resistance. The scratchy noise on an old radio may come from dirt on the surface of high resistance, which briefly spoils the contact as the slider moves.

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Really top quality hi-fi equipment sometimes uses a chain of fixed resistors in between gold-plated contacts to beat the noise problem Another use for these devises is in car fuel gauges. In a car the fuel gauge doesn’t actually measure the amount of fuel in the tank. Instead, it measures the level of fuel in a tank. A fuel gauge can use a potential divider to detect the position of the float. When petrol is used up the float goes down. As this happens the tilting arm turns and the sliding contact inside the potential divider that it is attached to moves.

As a result the output of the potential divider changes and the signal goes to the fuel gauge to tell the drive that fuel is running low. Car fuel tanks are often built into complicated shapes to fit into spaces within the car. As a result the change in the height of the float with not be directly proportional to the amount of petrol still in the tank. This is known as a non-linear calibration. Aim For this project we had to devise a sensor, which would enable us to measure something. With my experiment I plan to use a rotary potentiometer to measure the angle at which an object is leaning.

To do this I plan to connect an arm to a rotary potentiometer to act as a leaver like in the fuel gauge, however instead of a float I plan to attach a weight. If the rotary potentiometer is fixed to a leaning object then due to gravity acting on the weight the arm will swing to the lowest point, which would make in perpendicular to the floor. This should then in turn move the sliding contact within the rotary potentiometer and change the reading given. As a result I should be able to work out the angle at which the chair will fall over.