Full bridge

Force measuring bolts are provided with a so-called full bridge.
The full bridge is a voltage-fed deflection resistance measuring bridge that is suitable for measuring changes in resistance. It consists of a resistance network in which the bridge voltage is measured and the resistance is calculated from this and is particularly suitable for sensors, as all resistors function as sensor resistances, i.e. they are variable, and therefore have a very high sensitivity and compensation for the change in resistance due to temperature influences .
A classic full bridge circuit with four resistors is shown in the following figure.

It consists of a DC voltage source across which 𝑈0 drops, the bridge across which 𝑈𝐵 drops and the four sensor resistors 𝑅1.4=𝑅−Δ𝑅 and 𝑅2.3=𝑅+Δ𝑅, which have a difference in sign due to being in the same or opposite direction to one another.

The bridge voltage is calculated according to equation 4.2. As a full bridge with four sensor resistors, it can be simplified to equation 4.3. The change in the output variable (𝑈𝐵) when the input variable (𝑅) changes is described by the sensitivity 𝐸 with Equation 4.4. For 𝑈𝐵 according to Equation 4.3, the sensitivity of a full bridge is calculated in Equation 4.5. In comparison with the other bridges, it can be seen that the sensitivity is twice as high as the half bridge and four times as high as the quarter bridge.