×

Blood warming apparatus with digital display and monitoring circuit

  • US 4,314,143 A
  • Filed: 06/29/1979
  • Issued: 02/02/1982
  • Est. Priority Date: 06/29/1979
  • Status: Expired due to Term
First Claim
Patent Images

1. Fluid warming apparatus for heating a refrigerated fluid such as blood to a predetermined nominal temperature, comprising:

  • a housing defining a heating chamber for the fluidmeans including at least one electric heater element operable from an applied electric current in thermal communication with the fluid in said heating chamber for heating the fluid as it passes through the chamber;

    control circuit means responsive to the output temperature of the fluid for generating a heater control signal;

    switch circuit means electrically connected between said heating element and a source of electrical current, and responsive to said heater control signal, for controlling the application of current to said heating element to maintain the fluid at said predetermined nominal temperature;

    temperature sensing means for generating an analog output signal indicative of the output temperature of said fluid, said temperature sensing means including an output terminal, a constant current source, a thermistor in thermal communication with said fluid at the output of said heating chamber, and first and second resistances;

    said constant current source being connected to one terminal of said thermistor and being connected to a plane of reference potential through said first resistance;

    said output terminal being coupled to said other terminal of said thermistor and being connected to said plane of reference potential through said second resistance, the sum of said first and second resistances being selected to substantially linearize the temperature-voltage characteristic of said analog output signal at said output terminal over a predetermined temperature range, the ratio of said resistances being selected to provide a desired voltage level on said output terminal at a selected temperature within said operating range; and

    temperature display means coupled to said output terminal and linearly responsive to said analog output signal for producing an output display indicative of the output temperature of the fluid.

View all claims
  • 0 Assignments
Timeline View
Assignment View
    ×
    ×