Question

3. Describe a scenario where driving a bridge circuit with a constant cur- rent source is more advantageous than driving the circuit with a constant voltage source.

Answer 1

One of the major application of Wheatstone bridge circuit is to measure the value of resistor without an accurate reference voltage. In the above bridge circuit output voltage

The equation can be simplified if the values of all the resistors are equal

When all the four elements are active and consider when increases and decreases with increasing intensity of the measuring property output voltage becomes

which is linear and easy to use for calculations.

When only one active element is there, this relationship becomes , which is a non linear realtionship. The non linearity is predictable.

When the bridge has two active elements, which have identical response and will be more effective when these resistors are at diagonal positions of the bridge, same type sensing elements can be used in the two locations. The output equation in this case is which is again non linear relationship. This non linearity can be removed if constant current source is applied rather than constant voltage source.

Now the equation becomes hence a linear relationship is optained and it is easy to do calculations.