Physics Coursework: Strain Gauge
Aim:
To design, make, test and evaluate a strain gauge sensor. The sensor has to detect how the change in strain on a wire affects the voltage across the wire.
Reasoning behind aim:
I have chosen the strain gauge because it is Interesting as well as challenging. The strain gauge presents many different variables and complications, which will help me to understand the meaning of strain and stress.
Theory:
I have used various resources, including books, CD-ROM's and the Internet to come to this conclusion of the Wheatstone bridge.
The Wheatstone bridge circuit in its simplest form (Diagram shown) consists of four resistive elements, or bridge arms (R1, R2, R3, R4), connected in a series-parallel arrangement, and a voltage source(E). The electrical connections where pairs of bridge arms are joined to the wires from the voltage source are referred to as input corners of the bridge. In my experiment R4 will be a weak wire strand and R1, R2, R3 123? resistors. A differential output voltage (eo) is measured at the two remaining bridge corners, referred to as output or signal corners.
With Mathematical proof, it can be shown that if the arms resistance's are chosen such that the bridge is resistively symmetrical about an imaginary line drawn through the bridge output corners e.g. between [R1, R2 and R3, R4]. Therefore differential output voltage (eo) will be identically zero regardless of the value of the supply voltage. In this condition, the bridge is resistively balanced. If the bridge is not in balance, a differential voltage will be present at the output corners of the bridge, and the magnitude of this output voltage will be proportional to the amount of unbalance.
Hypothesis:
As the wire is stretched due to increasing weight applied, the resistance will increase proportionally. As the resistance increases the voltage and amperage across the wire will also increase.
Justification:
As the length of the wire increases, so do the chances for the electrons to collide with a positive ion. The chances increase because there is a bigger distance for the electrons to travel. A rule is that energy is always given out from a collision in the form of heat. Therefore the voltage and amperage will have to increase to provide the electrons enough energy to pass through the wire.
List Of Required Equipment:
* Wires
* 3x 123? resistors
* 1metre length of very fine wire
* µamp meter
* µvolt meter
* 12volt battery pack
Aim:
To design, make, test and evaluate a strain gauge sensor. The sensor has to detect how the change in strain on a wire affects the voltage across the wire.
Reasoning behind aim:
I have chosen the strain gauge because it is Interesting as well as challenging. The strain gauge presents many different variables and complications, which will help me to understand the meaning of strain and stress.
Theory:
I have used various resources, including books, CD-ROM's and the Internet to come to this conclusion of the Wheatstone bridge.
The Wheatstone bridge circuit in its simplest form (Diagram shown) consists of four resistive elements, or bridge arms (R1, R2, R3, R4), connected in a series-parallel arrangement, and a voltage source(E). The electrical connections where pairs of bridge arms are joined to the wires from the voltage source are referred to as input corners of the bridge. In my experiment R4 will be a weak wire strand and R1, R2, R3 123? resistors. A differential output voltage (eo) is measured at the two remaining bridge corners, referred to as output or signal corners.
With Mathematical proof, it can be shown that if the arms resistance's are chosen such that the bridge is resistively symmetrical about an imaginary line drawn through the bridge output corners e.g. between [R1, R2 and R3, R4]. Therefore differential output voltage (eo) will be identically zero regardless of the value of the supply voltage. In this condition, the bridge is resistively balanced. If the bridge is not in balance, a differential voltage will be present at the output corners of the bridge, and the magnitude of this output voltage will be proportional to the amount of unbalance.
Hypothesis:
As the wire is stretched due to increasing weight applied, the resistance will increase proportionally. As the resistance increases the voltage and amperage across the wire will also increase.
Justification:
As the length of the wire increases, so do the chances for the electrons to collide with a positive ion. The chances increase because there is a bigger distance for the electrons to travel. A rule is that energy is always given out from a collision in the form of heat. Therefore the voltage and amperage will have to increase to provide the electrons enough energy to pass through the wire.
List Of Required Equipment:
* Wires
* 3x 123? resistors
* 1metre length of very fine wire
* µamp meter
* µvolt meter
* 12volt battery pack
