Higher Physics

Electricity and Electronics - Activity 22

The differential amplifier used to monitor light level

Aim - To investigate the use of a differential amplifier with a Wheatstone Bridge to monitor light level.     Instructions
The two potential dividers  R1,R2   and  R3, R3  are connected as a Wheatstone Bridge circuit. Any out of balance potential difference from the Wheatstone Bridge is applied across the inputs of the Op-Amp.  The output of the Op-Amp is therefore proportional to the change in resistance of the LDR caused by the change in light level.
  • Click the arrows to move the lamp left and right in 5 cm steps.  
  • Record the output voltages as the lamp is moved.

 

  • Plot a graph of output voltage against distance from the LDR.

 

 

Copyright Physics Support Materials 2000