Wheatstone bridge

Purpose

Used to increase sensitivity

Setup

Consists of:

• 1 source of electrical potential (i.e. battery)
• 1 galvanometer
• 4 resistors
  * 2 x constant (R1 and R2)
  * 1 x variable (R3)
  * 1 x unknown (R4)

Usage

Calibration involves adjusting the variable until it produces null deflection of the galvanometer
* i.e. R1/R2 = R3/R4
* --> no current through galvanometer

Often designed so that when pressure changes, resistance of 2 resistors on opposite sides will increase and the resistance of the other 2 will decrease
--> deflection produced in galvanometer will be maximised
* i.e. higher sensitivity