H Exp – Electricity and Electronics 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, R₄ 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.

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