Resistance bridge transducer conditioning circuit

Claim 2

A signal conditioning circuit for a resistance bridge transducer comprising a voltage regulated power supply connected to supply DC power to the excitation terminals of said bridge transducer, amplifier means connected to the signal output terminals of said bridge transducer, a bridge calibration resistor, and a calibration select circuit for selectively connecting said calibration resistor into and out of parallel relationship with one arm of said resistance bridge transducer said calibration select circuit comprising a field effect transistor connected in series with said calibration resistor between two adjacent resistance bridge tranducer terminals, and an operational amplifier connected to turn said field effect transistor on and off in response to positive and negative DC control signals.

Claim 3

A signal conditioning circuit for a resistance bridge transducer as defined in claim 1 wherein said calibration select circuit comprises said field effect transistor, the source electrode thereof being connected through said calibration resistor to one resistance bridge transducer terminal and the drain electrode thereof being connected to an adjacent resistance bridge transducer terminal, said operational amplifier having first and second inputs and an output, first, second, third, fourth, fifth and sixth resistors, a capacitor, and a calibration select circuit actuating trigger, the output of said operational amplifier being connected through said first resistor to the gate electrode of said field effect transistor, said second resistor being connected between the gate electrode and the source electrode of said field effect transistor, said third resistor being connected between the output and the first input of said operational amplifier, said fourth resistor being connected between the first input of said operational amplifier and ground, said fifth resistor being connected between the second input of said operational amplifier and said actuating trigger, said sixth resistor being connected between the second input of said operational amplifier and one resistance bridge transducer excitation terminal, said capacitor being connected between said second input of said operational amplifier and ground, and said actuating trigger being switchable between positive and negative power supply source terminals.