What does the equation used in a magnetostrictive system do?

[mathisp64]

Hey, I have a magnetostrictive system that measures the the tensile and compressive forces on an output shaft. It does so through the use of an excited primary coil which saturates a ferromagnetic sleeve. The torsional forces are sensed by secondary coils and converted to DC.

My question is: the designer processes the two DC inputs by calculating the difference between the two inputs and then dividing by the sum of the two inputs. What does this equation do?

Have googled it to death and cannot find a description of this equation.

Thanks,

Phil

 

[jsgruszynski]

Hey, I have a magnetostrictive system that measures the the tensile and compressive forces on an output shaft. It does so through the use of an excited primary coil which saturates a ferromagnetic sleeve. The torsional forces are sensed by secondary coils and converted to DC.

My question is: the designer processes the two DC inputs by calculating the difference between the two inputs and then dividing by the sum of the two inputs. What does this equation do?

Have googled it to death and cannot find a description of this equation.

Thanks,

Phil

I'm assuming it's something like this (see Figure 6-5, a screen down):

http://www.omega.com/literature/transactions/volume3/force3.html

Notice the "Wheatstone Bridge" configuration of the magnetostriction sensors/resistors

http://en.wikipedia.org/wiki/Wheatstone_bridge#Derivation

The relation between output voltage and bias voltage as a function of bridge unknown leg value sounds something like the equation you are talking about (how you describe it doesn't sound quite right but I bet I'm close).

 

[mathisp64]

Thanks,

The circuit that you referenced, only full wave rectification occurs prior to the Wheatstone. One post on the homework page stated that the formula that I posted was a percentage of unbalance equation. I can't speak to the accuracy of this statement, but it sure seems applicable in this case.

Thanks very much, for taking the time to reply.

Phil