Calculating Wheatstone Bridge with R1=600, R2=R3=R4=400, V Supply=10V

In summary, the conversation discusses a problem with calculating the voltage output (Vout) for a Wheatstone bridge circuit. The given values include resistance values, a steel bar with a specific diameter and modulus, and a load applied. The formula for Vout is mentioned, as well as the relationship between stress and tensile strain. The conversation also mentions the use of a sensitive galvanometer and a bridge setting to measure the strain gauge resistor. Ultimately, the conversation asks for help with solving the problem.
  • #1
if r1 has value of 600 and r2=r3=r4=400 ohms. supply voltage is 10v.
im getting the wrong answer and do not know how.

im using [(R4R2 - R3R1) / (R1+R4)(R2+R3)] * VS

i get an answer of [160000 - 240000 / (1000)(800)] * 10 = [-80000 / 80000] * 10 = -1ohm

but this is the incorrect answer. where am i going wrong?
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  • #2
Your Wheatstone bridge is not balanced. You cannot have r1=600 and r2=r3=r4=400 ohms. Check all your resistances.
  • #3
Since you supplied us with all four resistance values I'm assuming that you're looking for the voltage across the bridge. If that is the case then your formula is incorrect. Check Wikipedia.
  • #4
I think you have the right answer but the wrong units. Assuming you are looking for the voltage between the junctions at the centre of the bridge.

One side of the bridge must have two equal resistors (both 400 ohms) so the voltage must be half the supply voltage. 5 v

The other side must have a 600 and a 400 ohm resistor. So, it must have 4/10 of the supply voltage at the junction. 4 v

So there must be 1 volt difference between the two junctions. Polarity depends on how you measure it.
  • #6
Wheatstone bridges are designed to use a sensitive galvanometer across the two junctions at the center of the bridge, and to zero the current thru the galvanometer using the bridge. If you are using a 120 ohm strain gauge, then you want (for example) three 400 ohm resistors, and a 280 ohm setting on the bridge in series with the strain gauge. Even better if you can use three 120 ohm resistors, because then you can get a direct reading of the strain gauge resistor on the bridge setting..
  • #7
hi all, could you possibly help me with this problem?

R1 and R2 are 2 guages with resistance of 100 ohm.
A steel bar has diameter 45mm and modulus of steel bar is 170GN/m^2 and gauge factor of 2. How would I calculate Vout when a load of 35kN is applied?

i know what the Vout formula is and stress = tensile strain x YM.



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1. How do I calculate the output voltage of the Wheatstone Bridge?

The output voltage of a Wheatstone Bridge can be calculated using the formula Vout = (R2/R1)(Vs), where R2 and R1 are the resistances of the two arms of the bridge and Vs is the supply voltage. In this case, the output voltage would be Vout = (400/600)(10V) = 6.67V.

2. How do I determine the balance condition of the Wheatstone Bridge?

The Wheatstone Bridge is said to be in balance when the voltage across the bridge is equal to zero. This can be achieved by adjusting the resistance of one of the arms until the voltage across the bridge is zero. In this case, the balance condition would be when R2/R1 = R4/R3 = 400/600 = 2/3.

3. What is the significance of the resistances used in this Wheatstone Bridge configuration?

The resistances used in this configuration determine the sensitivity and range of the Wheatstone Bridge. In this case, the equal resistances of 400 ohms in R2, R3, and R4 provide a balanced condition at a ratio of 2:3, which allows for more accurate measurements.

4. What are some potential sources of error in calculating the Wheatstone Bridge?

Some potential sources of error in calculating the Wheatstone Bridge include variations in the actual resistance values, temperature changes, and imperfections in the bridge circuit or measurement equipment. It is important to use precise and calibrated components and to consider and compensate for any potential sources of error.

5. Can this Wheatstone Bridge configuration be used in other applications?

Yes, this configuration can be used in various applications such as strain gauge measurements, temperature sensors, and resistance measurements. It is a versatile circuit that can be modified by changing the values of the resistors or using different types of sensors. It is commonly used in scientific and industrial applications for precise measurements.

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