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Make up air controller for use with fume hood systems

  • US 4,773,311 A
  • Filed: 11/24/1986
  • Issued: 09/27/1988
  • Est. Priority Date: 11/24/1986
  • Status: Expired due to Fees
First Claim
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1. Apparatus for controlling the volume of make-up air supplied to an area in which is located a fume hood having an exhaust volume which varies as the fume hood sash is opened and closed comprising:

  • transducer means, responsive to the fume hood sash position, for providing an output signal representative of the area of the sash opening;

    make-up air control means, connected to an air supply and responsive to a make-up air command signal, for providing a make-up air flow the volume of which is determined by the make-up air command signal, anda make-up air controller for providing the make-up air command signal, including;

    means for mu1tiplying the transducer means output signal by a scale factor to provide a scaled output signal;

    offset means, responsive to the scaled output signal, for subtracting therefrom a signal representative of a desired air flow volume differential between the fume hood exhaust volume and the make-up air volume to provide an output signal representative of a resulting make-up air volume; and

    means, responsive to the offset means output signal, for applying a make-up air command signal to the make-up air control means so as to produce a make-up air flow the volume of which equals said resulting make-up air volume.

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