×

Two-wire level measuring instrument

  • US 4,851,831 A
  • Filed: 05/29/1984
  • Issued: 07/25/1989
  • Est. Priority Date: 05/13/1981
  • Status: Expired due to Fees
First Claim
Patent Images

1. Apparatus for indicating a level of a dielectric material within a vessel at a first location, said apparatus comprising:

  • a first probe means for location within said vessel, said first probe means being adapted to provide a first analog signal representative of a dielectric constant of said material,a second probe means for location within said vessel, said second probe means adapted to provide a second analog signal indicative of a net capacity of said material;

    transmitter means located at said first location and electrically connected to said first and second probe means, said transmitter means comprising means for dividing said first analog signal provided by said first probe means into said second analog signal provided by said second probe means to produce a third analog signal indicative of said level of dielectric material within said vessel and means for transmitting said third analog signal;

    a two-wire cable electrically connected to said transmitter means, said transmitter means transmitting said third analog signal over said two-wire cable;

    power supply means at a second location remote from said first location, said power supply means electrically connected to said two-wire cable;

    said power supply means transmitting power over said two-wire cable to said transmitter means; and

    receiver means at said second location, said receiver means electrically connected to said two-wire cable, said receiver means comprising means for receiving said third analog signal indicative of said level over said two-wire cable from said transmitter means and indicator means for indicating said level;

    wherein said dividing means comprises;

    integrator means for generating a voltage signal;

    voltage supply means for supplying an initial voltage to said integrator means;

    means for supplying said first analog signal to said integrator means for a first period of time T dependent on said dielectric constant of said material to integrate said first analog signal;

    means for supplying said second analog signal to said integrator means for a second period of time equal to said time T to integrate said second analog signal;

    analog switching means connected to said integrator means for switching from said means for supplying said first analog signal to said means for supplying said second analog signal after said first analog signal has been supplied to said integrator means for said first period of time;

    whereby a ratio of said voltage signal generated by said integrator means to said initial voltage signal is indicative of said level within said vessel.

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