Light Column Voltmeter

Title 

To design a Light Column Voltmeter by using operation amplifier.

Theory

An operational amplifier is a direct-coupled high amplifier usually consisting of one or more differential amplifiers and usually followed by a level translator and an output stage. The output stage is generally a push-pull complementary-symmetry pair. An operational amplifier is available as a single integrated circuit package.

 

The operational amplifier is a versatile device that can be used to amplify dc as well as ac input signals and was originally designed for performing mathematically operations such as addition, subtraction, multiplication and integration.

 Light column voltmeter displays a column of light whose height is proportional to voltage. Manufacturers of audio and medical equipment may replace analog meter panels with light column voltmeters because they are easier to read at a distance. A light column voltmeter is constructed in the circuit of Fig- 2. 

Required instrument

1.      Electronics workbench software                 

2.      Operation amplifier(5*1)

3.      Resistor(6*1)     

4.      Diode(5*1)     

5.      LED(5*1)                          

            6.   Voltage source  

Circuit diagram  

                                                                   Fig 02: Light column voltmeter

 Simulation result

R₆ is adjusted so that 2mA flows through the equal resistor divider network R₁ to R₅ . Five separate

reference voltages are established in 2-V steps from 2V to 10V.

 

When E_i =0V or is less than 1-V, the outputs of all op amps are at –V_sat . The silicon diodes protect the light-emitting diodes against excessive reverse bias voltage. When E_i is increased

 E_i=1-V & E=10 then any LED cannot light;      E_i=2-V& E=10 then LED₁ can light;

E_i=3-V& E=10 then LED₁ can light;                   E_i=4-V& E=10 then LED₁ & LED₂ can light;

E_i=5-V& E=10 then LED₁ & LED₂ can light;      E_i=6-V& E=10 then LED₁ to LED₃ can light;

E_i=7-V& E=10 then LED₁ to LED₃ can light;     E_i=8-V& E=10 then LED₁ to LED₄ can light;

E_i=9-V& E=10 then LED₁ to LED₄ can light;   E_i=10-V& E=10 then LED₁ to LED₅ can light;

The 220-Ω output resistors divert heat away from the op-amp.

Conclusion

In this system we can measure the water level in a tank, gas density in a gar or octant level of a filing station.

In this system, when E<E_i then all LED also light. But only in proper voltage the LED can light. That a demerit of the system. The op-amp sometime gives more voltage & sometime gives low voltage than the input voltage.