Effect of the resistance of conductors on the sensitivity and calibration of bridge circuits

Conclusions

• 1. The sensitivity of the bridge circuit depends to a great extent on the ratio of the lead-in conductor and transducer resistances. Thus, the sensitivity will be reduced by the order of 20–30% for R_c/R=0.1. It is necessary, in setting up for testing, to analyze the degree to which the sensitivity is reduced and to find the possibility for its partial compensation by raising the supply source voltage.

• 2. In working out the test results it is necessary to take into account that an overestimation of calibration signals leads to an underestimation of measured deformations (voltages). Thus, an error of 44%, dangerous for the design of the set, is produced by R_c/R=0.1. In practical strain-gauge measurements with low-resistance transducers (3–15 Ω) instances occur when R_c/R=0.2, which raises the calibration signal by 96%, i.e., the voltage calculated from this signal will amount to almost one-half of its actual value.

• 3. It should be noted that the above distortion of the calibration signal can also occur with high-resistance transducers (100–200 Ω). In this event the error in the dangerous direction amounts to 10–20%.