Bridge circuits
8 likes2,897 views
The document discusses different types of bridge circuits. It describes the Wheatstone bridge, which converts variations in resistance into variations in voltage. When balanced, the output voltage is zero, but any change in a resistive element results in an unbalanced condition and a non-zero output voltage. It also discusses AC bridges for detecting changes in inductance and capacitance. Examples are provided for calculating voltage offset in a Wheatstone bridge and determining constants of an arm in an AC bridge. Finally, it briefly mentions comparison bridges for measuring unknown capacitance or inductance compared to known values, and the Maxwell bridge for measuring inductance in terms of a known capacitance.
Bridge circuits
- 1. Bridge Circuits Dr. Ashraf Saleem Dr. Ashraf Saleem 1
- 2. Bridge Circuits g Wheatstone Bridge: The primary application of this g p y pp bridge in signal conditioning is to convert variations of resistance into variation of voltage Dr. Ashraf Saleem 2
- 3. Wheatstone Bridge g VO will equal zero. In this situation, the bridge is said to be BALANCED. Any change in any resistive element will result in an UNBALANCED condition, hence VO will be non-zero. , Dr. Ashraf Saleem 3
- 4. Wheatstone Bridge g If we replace R3 with an active strain gauge, RG, which will vary b ∆R when pressure i applied (th arrow ill by h is li d (the through the resistor shows that it has a variable value), then Dr. Ashraf Saleem 4
- 5. Example 1: p The resistors in a bridge are given by R1=R2=R3=120Ω and R4=121Ω. If the supply is 10V Find the voltage offset? 10V. Dr. Ashraf Saleem 5
- 6. AC Bridges g AC bridges are used mainly to detect changes in inductance and/or capacitance At balance condition Dr. Ashraf Saleem 6
- 7. Example 2: p An ac bridge is in balance with the following constants: arm AB, R = 200 Ω in series with L = 15 9 mH ; arm BC R = 15.9 BC, 300 Ω in series with C = 0.265 µF; arm CD,unknown; CD unknown; arm DA = 450 Ω The DA, Ω. oscillator frequency is 1 kHz. Find the constants of arm CDCD. Dr. Ashraf Saleem 7
- 8. Comparison Bridge: Capacitance p g p Measure an unknown capacitance by comparing it with a p y p g Known capacitance. Dr. Ashraf Saleem 8
- 9. Comparison Bridge: Inductance p g Measure an unknown inductance by comparing it with a y p g Known inductance. Dr. Ashraf Saleem 9
- 10. Maxwell Bridge g Measure an unknown inductance in terms of a known capacitance Dr. Ashraf Saleem 10