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- An unbalanced Wheatstone bridge cannot be solved using simple series and parallel circuit analysis because the resistors are connected in a complex configuration. This section provides a step-by-step walkthrough demonstrating how to solve an unbalanced Wheatstone bridge using the mesh current method (also known as the loop current method).
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The Wheatstone Bridge equation required to give the value of the unknown resistance, R X at balance is given as: Where resistors, R 1 and R 2 are known or preset values. Example No1. The following unbalanced Wheatstone Bridge is constructed. Calculate the output voltage across points C and D and the value of resistor R 4 required to balance the ...
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- I-V Characteristic Curves
- Unbalanced Wheatstone Bridge
- Step 1: Identify and Label The Current Loops
- Step 2: Label The Voltage Drop Polarities
- Step 3: Apply Kirchhoff’s Voltage Law to Each Loop
- Step 4: Solve The Simultaneous Equations For Unknown Currents
- Step 5: Redraw The Mesh Currents and Determine The Branch Currents
- Step 6: Calculate The Voltage Drops
- Using Spice to Verify Our Voltage Calculations
- Mesh Current Method For An Unbalanced Wheatstone Bridge Review
- Related Content
First, let’s determine the voltages and currentsfor the unbalanced Wheatstone bridge circuit of Figure 1. Since the ratios of R1 / R4 and R2 / R5 are not equal, there will be a voltage across the resistor, R3, and some amount of current through it. As discussed at the beginning of this chapter on network analysis theorems, this type of circuit is i...
The first step in the mesh current method is to draw just enough mesh currents to account for all components in the circuit. Looking at our bridge circuit, it should be obvious where to place two of these current loops, as shown in Figure 2. The directions of these mesh currents, of course, are arbitrary. However, two mesh currents are insufficient...
Now, we must label the resistor voltage drop polarities, following each current direction (Figure 4).
Next, let’s generate a KVL equation for the top loop of the bridge, starting from the top node and tracing it in a clockwise direction. This results in the following equations: R2I1+R3(I1+I2)+R1(I1−I3)==0VR2I1+R3(I1+I2)+R1(I1−I3)==0V 50I1+100(I1+I2)+150(I1−I3)=0V50I1+100(I1+I2)+150(I1−I3)=0V In this equation, we represent the current through each r...
Now we have three simultaneous equations that we can solve using any method we prefer: 300I1+100I2−150I3=0V300I1+100I2−150I3=0V 100I1+650I2+300I3=0V100I1+650I2+300I3=0V −150I1+300I2+450I3=24V−150I1+300I2+450I3=24V First off, we will use GNU Octave, an open-source Matlab clone, to solve these equations. We can enter the resistor coefficients into a ...
The negative values for currents I1 and I3 indicate that our assumed current directions were in the wrong direction. For I3, it makes intuitive sense because the current would have to flow out of the only power source in our circuit. Thus, the actual loop current directions and the directions resistor are shown in Figure 5. From here, we can calcul...
Finally, we can calculate the voltage drops across each resistor: VR1=IR1R1=(0.042299)⋅(150)=6.3448VVR1=IR1R1=(0.042299)⋅(150)=6.3448V VR2=IR2R5=(0.093793)⋅(50)=4.6897VVR2=IR2R5=(0.093793)⋅(50)=4.6897V VR3=IR3R5=(0.016552)⋅(100)=1.6552VVR3=IR3R5=(0.016552)⋅(100)=1.6552V VR4=IR4R5=(0.058851)⋅(300)=17.6553VVR4=IR4R5=(0.058851)⋅(300)=17.6553V VR5=IR5R...
Next, to confirm the accuracy of our voltage calculations, we can use a SPICE simulationusing the circuit of Figure 6.
Using the mesh current method, we were able to solve for the currents and voltages in an unbalanced Wheatstone bridge. The three simultaneous KVL equations with three unknown loop currents were solved using GNU Octave. We then validated our results using SPICE circuit simulation software.
Below you can find additional resources concerning mesh current analysis and Wheatstone bridge circuits: Calculators: 1. Wheatstone Bridge Calculator 2. Ohm's Law Calculator 3. Parallel Resistor Calculator Worksheets: 1. DC Bridge Circuit Worksheet 2. DC Mesh Current Analysis Worksheet 3. AC Network Analysis Worksheet 4. Ohm's Law Worksheet 5. Kirc...
Apr 2, 2024 · The circuit below shows a Wheatstone bridge where the unknown resistor is replaced with a strain gauge. Due to the external force, the resistance of the strain gauge changes and as a result, the bridge becomes unbalanced. The output voltage can be calibrated to display the changes in strain.
This is an unbalanced wheat stone bridge. Lets find the correct value of R4 for which it becomes a balanced wheat stone bridge. R1 / R2 = R3 / R4. R4 = ( (R2 / R1) x R3) = (100Ω / 50Ω) x 40Ω = 80 ohms “Ω”. If R4 = 80 ohms, our circuit will become a balanced wheat stone bridge.
What is the Wheatstone Bridge Principle? The Wheatstone bridge works on the principle of null deflection, i.e. the ratio of their resistances is equal, and no current flows through the circuit. Under normal conditions, the bridge is in an unbalanced condition where current flows through the galvanometer. The bridge is said to be balanced when ...
- 49 min
- What is Wheatstone Bridge?Wheatstone bridge, also known as the resistance bridge, calculates the unknown resistance by balancing two legs of the bridge circuit. One leg incl...
- What is the Wheatstone Bridge Principle?The Wheatstone bridge works on the principle of null deflection, i.e. the ratio of their resistances are equal and no current flows through the cir...
- When is the Wheatstone Bridge balanced?A Wheatstone bridge is said to be in a balanced condition when no current flows through the galvanometer. This condition can be achieved by adjusti...
- What are the limitations of Wheatstone Bridge?For low resistance measurement, the resistance of the leads and contacts becomes significant and introduces an error.
If the bridge is unbalanced, the direction of the current indicates whether R2 is too high or too low. At the point of balance, Detecting zero current with a galvanometer can be done to extremely high precision. Therefore, if R1, R2, and R3 are known to high precision, then Rx can be measured to high precision.
Aug 31, 2023 · Wheatstone bridge is an electrical circuit measuring unknown electrical resistances with high precision. It can be accomplished by balancing two legs of a bridge circuit, with one leg consisting of the unknown component.
