What is the Wheatstone Bridge and Load Cell Circuit

 

What is the Wheatstone Bridge?

Whenever the change in the resistance of strain gauge takes place, it is displayed as an electrical output. But, have you ever wondered, how the resistance change of a strain gauge is measured?

A load cell works only when the strain gauge has some change in its resistance and, we use the Wheatstone Bridge to measure this change.

Load Cell Circuit

Load cell circuit is also known as a Wheatstone Bridge Circuit.

Let us assume that a load cell sensor has four internal strain gauges i.e. A, B, C, and D as shown in the image above.

The input voltage supplied by a signal conditioner or digital display is attached to the two opposite corners of the bridge i.e. C and D whereas, the output voltage is measured by joining the A and B resistors to the signal side of the digital display.

When no load is applied to the load cell (Load=0), the circuit is said to be balanced. As soon as the load is applied to it, the strain gauge resistors will witness a change in its resistance, thereby, altering the voltage flowing through the circuit.

Hence, the voltage across A and B will change which will be displayed as the weight on the readout unit or the digital display.

The output of the Wheatstone bridge or a load cell is an analogue data which is converted to readable units using an interpreter.