In the context of measurement and instrumentation, a bridge circuit is often used to measure various physical quantities like resistance, capacitance, or inductance. One of the most common types of bridge circuits is the Wheatstone bridge, which is used to measure an unknown electrical resistance by balancing the bridge.
The general equation for bridge balance in a Wheatstone bridge circuit is given by:
1
⋅
4
=
2
⋅
3
R
1
⋅R
4
=R
2
⋅R
3
Where:
1
R
1
= Resistance of one leg of the bridge (known resistance)
2
R
2
= Resistance of another leg of the bridge (known resistance)
3
R
3
= Resistance of the third leg of the bridge (unknown resistance)
4
R
4
= Resistance of the fourth leg of the bridge (unknown resistance)
For the bridge to be balanced, the ratio of the known resistances (
1
/
2
R
1
/R
2
) must be equal to the ratio of the unknown resistances (
3
/
4
R
3
/R
4
). This balance is usually detected using a null indicator, such as a galvanometer or a digital voltmeter, and the unknown resistance (
3
R
3
) can be calculated using the known resistances (
1
,
2
R
1
,R
2
) and the balanced condition equation.
It's important to note that different bridge circuits might have variations in their balance equations, depending on the specific configuration and purpose of the bridge. The Wheatstone bridge is just one example, and other types of bridge circuits (e.g., Kelvin bridge, Maxwell bridge, etc.) may have different balance equations.
Always refer to the specific bridge circuit you are working with to ensure you are using the correct balance equation for that particular configuration.