Published:2011/5/10 8:32:00 Author:Christina | Keyword: Electrical bridge | From:SeekIC
The Electrical bridge circuit is as shown:
The E-bridge is composed of the phototube PC1, R1, R2 and R3, the operational amplifier 741's differential input port connects to the middle-point of the E-bridge's two arms.
When the PC1 has no light, the e-bridge is balance, the output of 741 is 0. When the PC1 has light, the e-bridge is out of balance, the electric potential of 741 output port is proportional to the brightness, the header indicates the corresponding brightness value.
The bridge balance adjustment step: first you need to cover the photocell, then adjust R5 to the maximum value, and adjust R3 to make the meter indicates to zero. Then decrease the value of R5 to make the pointer deviation from zero, and adjust R3 to make the meter indicates to zero. Repeat this process and you can get the maximum sensitivity. The dotted line showns the 0.1uF decoupling capacitor.
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