Hematocrit meter

• US 3,250,987 A
• Filed: 01/04/1963
• Issued: 05/10/1966
• Est. Priority Date: 12/24/1959
• Status: Expired due to Term

• Current Assignee: Herman P. Schwan, Robert H. Okada
• Original Assignee: Herman P. Schwan, Robert H. Okada
• Inventors: Okada, Robert H., Schwan, Herman P.
• Application Number:
  US04/249,524
• Time in Patent Office: 1,222 Days
• US Class Current: 324/443
• CPC Class Codes: A61B 5/150022 for capillary blood or interstitial fluid
• CPC Class Codes: A61B 5/150099 by negative pressure, other than vacuum extraction into a syringe by pulling on the piston rod or into pre-evacuated tubes
• CPC Class Codes: G01N 15/0656 using electric, e.g. electrostatic methods or magnetic methods by investigating individual particles G01N15/1031, G01N15/12
• CPC Class Codes: G01N 33/49 Blood chemical methods for determining blood cell populations G01N33/5094; chemical analysis of blood groups or blood types G01N33/80

Claims

1. AN ELECTRONIC INSTRUMENT FOR MEASURING CHARACTERISTICS OF BLOOD COMPRISING IN COMBINATION, AN OSCILLATOR CIRCUIT, A BRIDGE CIRCUIT COUPLED TO THE OSCILATOR CIRCUIT INCLUDING A TEMPERATURE RESPONSIVE DEVICE IN ONE BRIDGE ARM AND A PAIR OF CONDUCTIVITY SENSING CONNECTIONS IN ANOTHER BRIDGE ARM, SAID TEMPERATURE RESPONSIVE DEVICE BEING CALIBRATED TO CORRECT BRIDGE CIRCUIT BALANCE FOR CHANGES IN BLOOD CONDUCTIVITY AT DIFFERENT TEMPERATURES, A HOLLOW BLOOD CELL UNIT HAVING A PAIR OF ELECTRODES SPACED APART TO CONTACT A BLOOD SAMPLE IN SAID CELL UNIT AND OF SUCH ELECTRICALLY CONDUCTIVE MATERIAL TO REDUCE ANY POLARIZATION IMPEDANCE ERROR IN THE PRESENCE OF BLOOD BETWEEN THE ELECTRODES AT THE PARTICULAR OSCILLATOR FREQUENCY CHOSEN, SAID BLOOD CELL UNIT FORMING A BLOOD SAMPLE CHAMBER IN THE INTERIOR THEREOF ARRANGED BETWEEN THE ELECTRODES FOR HOLDING A FIXED VOLUME OF ABOUT .02 CUBIC CENTIMETERS OF BLOOD, MEANS FOR FILLING THE PORTION OF SAID CHAMBER BETWEEN THE ELECTRODES WITH A BLOOD SAMPLE FROM A FINGER PRICK, MEANS DISPLAYING THE BRIDGE CIRCUIT UNBALANCE IN CALIBRATED SCALE READINGS INDICATING THE NORMALLY ENCOUNTERED PERCENTAGE VOLUME OF RED CELLS IN WHOLE BLOOD, AND MEANS FOR CONNECTING SAID BLOOD CELL UNIT TO THE PAIR OF CONDUCTIVITY SENSING CONNECTIONS IN THE BRIDGE CIRCUIT TO PRODUCE A CONDUCTIVITY READING FOR A BLOOD SAMPLE CONTAINED IN SAID CHAMBER.