Measurement amplifier for small direct voltages

Claim 1

A MEASUREMENT AMPLIFIER CIRCUIT FOR MEASURING SMALL D.C. VOLTAGES, COMPRISING TWO-WAY SWITCHING MEANS CONSTITUTING A CONVERTER, MEANS FOR APPLYING THE D.C. VOLTAGE TO BE MEASURED TO THE CONVERTER AND THEREBY CONVERTING IT INTO AN A.C. VOLTAGE, AN AMPLIFIER, MEANS FOR APPLYING THE A.C. VOLTAGE OUTPUT OF THE CONVERTER TO THE AMPLIFIER, TWO-WAY SWITCHING MEANS CONSTITUTING A RECTIFIER, MEANS FOR APPLYINGTHE AMPLIFIER OUTPUT TO THE RECTIFIER, MEANS FOR OPERRASTING THE CONVERTER SWITCHING MEANS AND THE RECTIFIER SWITCHING MEANS IN SYNCHORNISM WITH ONE ANOTHER, A MEASURING INSTRUMENT, FILTER MEANS, MEANS FOR APPLYING THE RECTIFIER OUTPUT TO THE MEASURING INSTRUMENT IN CIRCUIT WITH SUCH FILTER MEANS AND FEEDING BACK FROM COOPERATING WITH THE FILTER MEANS AND FEEDNG BACK FRM THE RECTIFIER OUTPUT TO THE INPUT SIDE OF THE AMPLIFIER, AND A MIXED A.C.-D.C. FEED-BACK CIRCUIT FEEDING BACK FROM THE AMPLFIIER OUTPUT THROUGH THE RECTIFIER SWITCHING MEANS AND THROUGH THE CONVERTER SWITCHING MEANS TO THE INPUT OF THE AMPLIFIER.