Signal conditioner front-end

A signal conditioner front-end comprising:

• a differential input inverting amplifier having input terminals for transducer SIGNAL HI and SIGNAL LO, .+-.15 VDC, -15 VDC, and COMMON;
• and output terminals for SIGNAL OUTPUT and COMMON:
• first, second, and third operational amplifiers each having terminals for inverting and noninverting inputs, +15 VDC, -15 VDC and output;
• the .+-.15 VDC terminal of each of said operational amplifiers connected to the +15 VDC input terminals of said differential amplifier,
• the -15 VDC terminal of each of said operational amplifiers connected to the -15 VDC input terminal of said differential amplifier,
• the output terminal is connected to the inverting input terminal of each of said first and second operational amplifiers;
• and
• the SIGNAL HI input terminal of said differential amplifier is connected to the noninverting input terminal of said first operational amplifier,
• the output terminal of said third operational amplifier is connected to the SIGNAL OUTPUT terminal of said differential amplifier,
• a first resistive divider comprising first and second series connected matched resistors connected between the output terminals of said first and third operational amplifiers with the junction of said first and second resistors connected to the inverting input terminal of said third operational amplifier;
• a second resistive divider comprising third and fourth series connected matched resistors connected between the output terminal of said second operational amplifier and the COMMON input terminal of said differential amplifier with the junction of said third and fourth resistors connected to the noninverting input terminal of said third operational amplifier;
• an excitation voltage selector circuit comprising output terminals for + EXCITATION, - EXCITATION, and COMMON;
• the +15 VDC input terminal of said differential amplifier is connected to the + EXCITATION output terminal of said selector circuit,
• the COMMON input terminal of said differential amplifier is connected to the COMMON output terminal of said selector circuit,
• said excitation voltage selector circuit further including switching means having a normally open contact terminal, a normally closed contact terminal and a wiper terminal,
• the wiper terminal of said switching means is connected to the -EXCITATION output terminal of said selector circuit,
• the normally closed contact terminal of said switching means is connected to the -15 VDC input terminal of said differential amplifier;
• and
• a Zener diode connected between the normally closed and normally open contact terminals of said switching means.