Apparatus for providing an indication of fluid flow through a fluid metering device

• US 4,462,263 A
• Filed: 01/15/1982
• Issued: 07/31/1984
• Est. Priority Date: 01/15/1982
• Status: Expired due to Term

• Current Assignee: F.S. Brainard & Co.
• Original Assignee: F.S. Brainard & Co.
• Inventors: Bash, Ignatius F.
• Primary Examiner(s): Swisher, S. Clement
• Assistant Examiner(s): TUMM, BRIAN
• Application Number:
  US06/339,294
• Time in Patent Office: 928 Days
• Field of Search: 73/861.77, 73/861.78, 324/173, 324/174, 336/110
• US Class Current: 73/861.77
• CPC Class Codes: G01F 1/115 with magnetic or electromagnetic coupling to the indicating device

Abstract

A flow metering device includes a very sensitive sensor and detection unit for accurately measuring the flow of fluids such as water through a meter housing. At least two excitation windings are wound around a toroidal core of magnetic material having a non-linear characteristic. The excitation windings are connected in series to an AC source in such a way that the magnetic effects of the windings are additive. A pair of pickup windings are also wound around the core but in series-opposition fashion. The output of the pickup windings is fed to a detector unit including a negative feedback amplifier, rectifier diodes and a summing network. The apparatus is so sensitive that it can accurately detect the movement of an internal magnetic rotor through the rotor housing while rejecting other sources of possible interference.

Claims

1. An apparatus for providing an indication of fluid flow through a fluid metering device of the type in which the motion of an internal permanent magnet in a housing is related to fluid flow through the fluid metering device, said apparatus comprising:

(a) excitation means for providing an AC excitation current, said excitation means including an operational amplifier having an inverting input and a non-inverting input and an output, an NPN bipolar transistor and a PNP bipolar transistor having their bases connected together to the output of said operational amplifier and their emitters connected together so as to provide a greater excitation current, automatic gain control means for providing constant AC voltage amplitude to the junction of the emitters of said bipolar transistors, a feed back means from said bipolar transistors to said inverting input of said operational amplifier, and a source of DC current connected to said non-inverting input of said operational amplifier;

(b) a core of magnetic material having a substantially non-linear characteristic;

(c) at least two excitation windings connected to said excitation means and wound in series on said core such that their magnetic effect is additive and wherein the output of said bipolar transistor emitters is coupled to said excitation windings;

(d) at least two pick-up windings connected to each other in series and wound in such a fashion that they are in magnetic opposition to each other; and

,

(e) detection means, electrically connected to said pick-up windings for producing an output signal proportional to the flow of fluid through the fluid metering device,

wherein said magnetic core, said excitation windings and said pick-up windings comprise a sensor which is mountable external of the housing for the internal permanent magnet.

2. An apparatus for providing an indication of fluid flow through a fluid metering device of the type in which the motion of an internal permanent magnet in a housing is related to fluid flow through the fluid metering device, said apparatus comprising:

(a) excitation means for providing an AC current, said excitation means including an operational amplifier having an inverting input and a non-inverting input and an output, an NPN bipolar transistor and a PNP bipolar transistor having their bases connected together to the output of said operational amplifier and their emitters connected together so as to provide a greater output excitation current, automatic gain control means for providing constant AC voltage amplitude to the junction of the emitters of said bipolar transistors, a feedback means from said bipolar transistors to said inverting input of said operational amplifier, and a source of DC current connected to said non-inverting input of said operational amplifier;

(b) a core of magnetic material having a substantially non-linear characteristic;

(c) at least two excitation windings connected to said excitation means and wound in series on said core such that their magnetic effect is additive, and wherein the output of said bi-polar transistor emitters is coupled to said excitation windings;

(d) at least two pick-up windings connected to each other in series and wound in such a fashion that they are in magnetic opposition to each other; and

,

(e) detection means, electrically connected to said pick-up windings for producing an output signal proportional to the flow of fluid through the fluid metering device, said detection means including a pair of semi-conductor diodes connected to said pick-up windings, a pair of series connected capacitors connected to said semi-conductor diodes;

summing means for combining voltages appearing across said capacitors, means for storing the output of said summing means, and a negative feed back amplifier means connected between said pick-up windings and said semi-conductor diodes for amplifying the output from said pick-up windings,

wherein said magnetic core, said excitation windings and said pick-up windings comprise a sensor which is mountable external of the housing for the internal permanent magnet.

3. The apparatus of claim 2 wherein said automatic gain control means includes a variable resistor to adjust the amplitude of the AC voltage produced by said excitation means.

4. The apparatus of claim 3 further including:

coupling means attached to said core to assist in the detection of said permanent magnet through said housing.