Wheatstone Bridge | Working, Examples, Applications

Wheatstone Bridge |
Wheatstone Bridge |

Have you wondered how electronics experts precisely measure unknown electrical resistances? Wheatstone bridges, basic yet clever circuits, hold the key. You’ve undoubtedly seen it in science class but never understood it. We’ll explain the basics clearly. The Wheatstone bridge will be second nature to you after reading this article.

What’s the Wheatstone Bridge?

An electrical circuit called a Wheatstone Bridge measures unknown resistances accurately. It uses the balanced bridge circuit technique to compare the resistances in each arm. The bridge usually has four resistive arms, a power source, and a galvanometer. When the bridge is balanced, the potential difference across the galvanometer is zero, the unknown resistance can be determined from the other arms’ resistances. This bridge arrangement measures resistance precisely and is commonly utilized in practical applications.

How Works

Squarely connected four resistors form the Wheatstone bridge. Two resistors have known resistances, two unknown. Current flows via resistors when the bridge is voltaged. Adjust the unknown resistances until the voltage between the branch midpoints is zero. Currently, the bridge is “balanced.”

After balancing, you can use known resistances to find unknown resistances. Simple formula to compute unknown resistance:

R1/R2 = R3/R4

R1 and R2 are known, R3 and R4 are unknown.

R4 is 150 ohms if R1 is 100 and R2 is 50 and the bridge balances at R3 is 75.

Resistance and sensor outputs in circuits can be measured precisely with the Wheatstone bridge. This instrument is essential in many technological gadgets.

Common uses include:

Strain gauges measure resistance to determine force.

•Thermistors—measure temperature by resistance change.

Potentiometers are adjustable resistors that null the bridge.

When used with oscillators, can measure unknown inductance and capacitance.

Wheatstone bridges are simple circuits with many precision measuring applications. When you utilize a gauge, sensor, or meter, a Wheatstone bridge may be working quietly!

How Do Wheatstone Bridges Work?

The Wheatstone bridge is a clever circuit for measuring unknown component resistance. Step-by-step, we’ll explain it.

Balance the bridge

Four diamond-shaped resistors comprise the Wheatstone bridge. R1 and R2 are known resistors on one side. Another side includes Rx, an unknown resistor, and R3, a known one.Voltage and galvanometer are applied to the diamond’s edges and midpoints. Rx can be estimated from the other resistor values with the bridge “balanced” (no galvanometer current).

Finding equilibrium

R1 is altered while R2 remains constant to balance the bridge. Bridge balance occurs when the galvanometer reads zero. At this point, R1/R2 = Rx/R3. The unknown value Rx can be calculated from this ratio and R1, R2, and R3.

If R1 = 100 ohms, R2 = 50, and R3 = 10, and the bridge is balanced when R1 is 120, then:

R1/R2 = 120/50 = 2.4 Rx/R3 = 2.4 * 10 = 24 ohms

Thus, the unknown resistor Rx is 24 ohms.

Application in real life

The Wheatstone bridge is often used to test circuit resistance, capacitance, inductance, and impedance. Specific uses include:

Strain gauge sensor resistance measurements
Verifying new component resistance values
Resistance detection for circuit troubleshooting
Using internal resistance to monitor battery levels

Many electrical engineers and technicians use the Wheatstone bridge because of its simple but clever design. I hope this clarifies how this useful item works!

Wheatstone Bridge Circuit

The Wheatstone bridge balances two bridge circuit legs, one of which contains the unknown component, to measure electrical resistance. Its simple design and great precision make it helpful for testing circuit resistance.

Basic Wheatstone bridge circuits have four known resistors, one unknown resistor, a voltmeter, and a DC current source.The square’s middle voltmeter measures the potential difference between the sides.

A balanced bridge has a zero voltmeter. This happens when the legs’ resistance ratio is equal. Use the other resistors’ values to compute the unknown resistance.

Simple Wheatstone bridge circuit diagram:

Circuit Diagram

R1 | R2 V | R4 | Rx (Unknown Resistance) R3

R1, R2, R3, and R4 have known resistances. The potential difference is measured by the voltmeter (V) between R2 and R4. Balance the bridge by adjusting R1 and R3, then calculate Rx using the other resistors.

Due to its simple and attractive design, the Wheatstone bridge measures resistance precisely. Many electrical measuring tools and sensors use it for reliable measurements. Understanding this basic circuit will simplify many electrical ideas and gadgets.

Examples of Wheatstone Bridge Use

Many practical applications show the Wheatstone bridge’s value. Some examples:

The strain gauge

A thin wire in strain gauges changes resistance when stretched or squeezed. Measurements of object forces are widespread. One Wheatstone bridge arm contains the strain gauge. Changes in strain gauge wire resistance unbalance the bridge. Measure the voltage difference to calculate strain and force.

Temp sensor

The resistance of a wire in resistance temperature detectors can alter with temperature. RTD resistance changes with temperature, unbalancing the bridge. Measure the voltage differential to ascertain temperature.

Potentiometer

A potentiometer controls voltage with a variable resistance. Adjusting the variable resistor of a Wheatstone bridge with a potentiometer unbalances it. Measure the voltage difference to set the potentiometer. Potentiometers regulate volume knobs, dimmer switches, and tuners.

The Wheatstone bridge’s resistance measuring accuracy makes it helpful for various sensor and measurement applications. While basic, this circuit has led to enormous advances in instrumentation and control systems.

Steps to Use a Wheatstone Bridge

Steps to use a Wheatstone bridge:

Gather needed parts

Basic Wheatstone bridge setup requires:

Four resistance-known resistors
A voltage source
Galvanometers detect tiny currents.
Connect resistors

  • One bridge arm is formed by connecting two resistors in series. Form the adjacent arm by seriesing the other two resistors.
  • Join arms to create a diamond.
  • Create a diamond by connecting the ends of each arm.
  • Voltage source attached
  • Connect galvanometer.
  • Connect the galvanometer to the other arm ends.

Balance the bridge

Adjust the resistance settings until the galvanometer reads zero to balance the bridge.Adjusting the other resistances lets you find an unknown arm resistance after balancing. When the galvanometer displays zero again, you matched the unknown resistance.

Examples and uses

Wheatstone bridges assess strain and resistance. A beam strain gauge can quantify minor length variations that effect resistance and bridge balance. Bridge rebalancing estimates strain and resistance.

Weight, blood pressure, and stress/strain analysis employ wheatstone bridges. The Wheatstone bridge is simple but necessary for precise measurements.

Conclusion

So there’s the Wheatstone bridge explained. The premise is simple despite appearances. A simple but powerful circuit can measure resistance with a few resistors and a battery. In physics labs or field debugging circuits, the Wheatstone bridge illustrates that simple tools can be useful. Don’t be afraid of diamond-and-arrow diagrams. You now understand that black box and how to calculate the unknown resistance. The Wheatstone bridge, designed 180 years ago, is still significant in high-tech. Impressive for a four-resistor circuit!

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