Electrical moisture sensing device

• US 3,197,699 A
• Filed: 03/05/1964
• Issued: 07/27/1965
• Est. Priority Date: 03/05/1964
• Status: Expired due to Term

• Current Assignee: Storm Johansen Knud Harald
• Original Assignee: Storm Johansen Knud Harald
• Inventors: STORM JOHANSEN KNUD HARALD
• Application Number:
  US04/349,639
• Time in Patent Office: 509 Days
• US Class Current: 324/694
• CPC Class Codes: G01N 25/64 using electric temperature-responsive elements

Claims

1. IN AN ELECTRICAL MOISTURE SENSING DEVICE, AN ELECTRICAL CIRCUIT COMPRISING, A FULL-WAVE BRIDGE RECTIFIER HAVING TWO SETS OF ALTERNATE JUNCTIONS COMPRISING A SET OF A.-C. JUNCTIONS AND A SET OF D.-C. JUNCTIONS, A LOAD RESISTOR CONNECTED BETWEEN SAID D.-C. JUNCTIONS, AN A.-C. SOURCE CONNECTED ACROSS SAID BRIDGE RECTIFIER TO SAID A.-C. JUNCTIONS FOR APPLYING A SUBSTANTIALLY CONSTANT A.-C. VOLTAGE TO SAID BRIDGE RECTIFIER, A CURRENT-CONDUCTING MOISTURE SENSOR CAPABLE OF ABSORBING MOISTURE AND HAVING THE CHARACTERISTIC OF VARYING IN CONDUCTIVITY PROPORTIONATELY TO THE MOISTURE ABSORBED AND CONNECTED TO ONE OF SAID A.-C. JUNCTIONS IN SERIES WITH SAID A.-C. SOURCE FOR DEVELOPING A D.-C. VOLTAGE CORRESPONDING TO A RECTIFIED A.-C. VOLTAGE APPLIED TO SAID BRIDGE RECTIFIER AND VARIABLY PROPORTIONATE TO THE CONDUCTIVITY OF SAID SENSOR, AN ADJUSTABLE D.-C. SOURCE CONNECTED TO SAID BRIDGE RECTIFIER FOR APPLYING A KNOWN SECOND D.-C. VOLTAGE TO SAID BRIDGE RECTIFIER OF A POLARITY OPPOSITE TO THE POLARITY OF SAID FIRST D.-C. VOLTAGE TO DEVELOP A DIFFERENCE VOLTAGE BETWEEN SAID FIRST AND SECOND D.-C. VOLTAGES AND REPRESENTATIVE OF THE CHANGE IN CONDUCTIVITY OF SAID SENSOR, AND VOLTAGE-RESPONSIVE MEANS CONNECTED TO SAID BRIDGE RECTIFIER TO RESPOND TO SAID DIFFERENCE VOLTAGE, AND MEANS FOR SUPERIMPOSING AN A.-C. VOLTAGE ON SAID ADJUSTABLE D.-C. SOURCE TO IMPROVE THE ACCURACY, AND SENSITIVITY OF THE DIFFERENTIAL VALUES.