Multiplexed strain gauge bridge

A load measuring system, comprising:

• Dc circuit means for producing across its output terminals a DC signal of amplitude dependent upon a load supported by a load-support member;
• time division multiplexing means connected across said output terminals of said DC circuit means for producing an alternating voltage of amplitude substantially equal to said load dependent DC signal amplitude;
• high gain, AC coupled amplifier means for amplifying said alternating voltage;
• demultiplexing means responsive to the amplitude of said amplified alternating voltage for producing an amplified version of said load dependent DC voltage;
• and
• means responsive to said amplified load dependent DC voltage for providing an indication of said load.

A load measuring system, comprising:

• a DC energized bridge having first and second output terminals and arms including strain gauge means, said arms being connected to said output terminals, said bridge being energizable for producing a DC output voltage across said first and second bridge output terminals and dependent upon a load supported by a load support member;
• a high gain, AC coupled amplifier having an input terminal and an output terminal;
• multiplexing means actuable for switching said first and second bridge output terminals alternately to said input terminal of said AC coupled amplifier at a preselected frequency, so that said AC coupled amplifier alternatingly amplifies the voltage levels at said first and second output terminals of said bridge;
• load means having first and second terminals and responsive to the difference between voltage levels applied alternatively to said first and second terminals;
• demultiplexing means actuable at said frequency and in synchronism with said multiplexing means for transferring amplified versions of said voltage levels at said first and second bridge output terminals from the output terminal of said AC coupled amplifier alternately to respective ones of said terminals of said load means;
• whereby to produce across first and second terminals of said load means a DC signal which is an amplification of said DC output voltage of said DC bridge.