Comparing the effect of lead and switch resistances on voltage- and current-fed strain-gage circuits

Strain gages are passive measuring elements and therefore require an electrical input to operate.

Strain gages are passive measuring elements and therefore require an electrical input to operate. The two main measuring circuits in use today are current-fed circuits and voltage-fed bridge circuits. This article describes both types and discusses their advantages and disadvantages.

The author also introduces a new bridge circuit which permits error-free measurement with strain gages in quarter-, half-, and full-bridge circuits by not allowing lead or contact resistance at selector switches to falsify readings. The new circuit permits the use of single strain gages with long leads.