Wheatstone bridge output voltage

[Jimbo bob]

Hi everyone ,

I had a go at the first part of the wheatstone bridge question of the attachment and I got a "zero offset" output voltage of 0. However, some of my friends tell me that my answer is not right and I am not going to be able to go through it with them because I cannot get in touch with them soon enough. I cannot see what is wrong with my method, So, I would appreciate it if anyone could confirm or reject my answer.

 

[Arouse1973]

Do you think you might need to include the resistance of the wires connecting the strain gauges?
Adam

 

[Jimbo bob]

Do you think you might need to include the resistance of the wires connecting the strain gauges?
Adam

I believe that those wires that you are talking about are the lead wires (i.e. "leads") mentioned in the question. Moreover, I am not given any information about the resistace of the wires, except for the lead wires. Considering that in non of the examples which were solved in the classroom an arbitrary wire resistance was assuemed at any point, I doubt that I need to assume any either.
But under the given information, do you think my answer is correct?

 

[Arouse1973]

The resistance of the wires is in the question. This will effect the balance of the bridge don't you think?
Adam

 

[Gryd3]

The resistance of the wires is in the question. This will effect the balance of the bridge don't you think?
Adam

This would.. but the setup on either side of the bridge is the same.
The question read that the strain guages are connected to two pairs of 40 ft leads. I read that as R3, and R4, each having their own 40' lead.
Even with a high wire resistance, both sides should always remain balanced.

I've been tinkering with a project using a wheatstone bridge and a single strain guage... the result is me needing to use additional wire to compensate for the wire's resistance.... I should have bought two, it would have made things a little simpler.

 

[Jimbo bob]

This would.. but the setup on either side of the bridge is the same.
The question read that the strain guages are connected to two pairs of 40 ft leads. I read that as R3, and R4, each having their own 40' lead.
Even with a high wire resistance, both sides should always remain balanced.

I've been tinkering with a project using a wheatstone bridge and a single strain guage... the result is me needing to use additional wire to compensate for the wire's resistance.... I should have bought two, it would have made things a little simpler.

What you say, makes sense. Thanks a lot everyone. I really appreciate your help.

 

[Arouse1973]

Yes correct valid point.
Adam