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Example vibrating helical spring sensors and methods to operate the same are disclosed. A disclosed example apparatus includes a housing, a helical spring held in tension, a flowline to expose the helical spring to a fluid, a magnet to expose the helical spring to a magnetic field, and a wire to ele

Example vibrating helical spring sensors and methods to operate the same are disclosed. A disclosed example apparatus includes a housing, a helical spring held in tension, a flowline to expose the helical spring to a fluid, a magnet to expose the helical spring to a magnetic field, and a wire to electrically conduct an actuating current through the helical spring to displace the helical spring.

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1. An apparatus comprising: a housing;a helical spring held in tension;a flowline to expose the helical spring to a fluid;a magnet to expose the helical spring to a magnetic field, wherein the magnetic field radiates radially from an axis of the helical spring; anda wire to electrically conduct an a

1. An apparatus comprising: a housing;a helical spring held in tension;a flowline to expose the helical spring to a fluid;a magnet to expose the helical spring to a magnetic field, wherein the magnetic field radiates radially from an axis of the helical spring; anda wire to electrically conduct an actuating current through the helical spring to displace the helical spring. 2. An apparatus as defined in claim 1, wherein the helical spring comprises electrically conductive wire. 3. An apparatus as defined in claim 1, wherein the helical spring comprises at least one of Tungsten or a Tungsten alloy. 4. An apparatus as defined in claim 1, wherein the helical spring and the housing have a substantially similar thermal expansion coefficient. 5. An apparatus as defined in claim 1, wherein the helical spring is to vibrate in response to the actuating current and the magnetic field. 6. An apparatus as defined in claim 1, further comprising a sensor to detect an electromotive force (emf) voltage induced by displacement of the helical spring. 7. An apparatus as defined in claim 1, further comprising an analysis module to estimate a viscosity of the fluid based an electromotive force (emf) voltage induced across the helical spring. 8. An apparatus as defined in claim 1, further comprising an analysis module to estimate a density of the fluid based an electromotive force (emf) voltage induced across the helical spring. 9. An apparatus as defined in claim 1, wherein the actuating current comprises at least one of a transient signal, a steady-state signal, or an alternating current signal. 10. An apparatus as defined in claim 1, wherein the actuating current is to pass through only a portion of the helical spring. 11. An apparatus as defined in claim 1, wherein the magnetic field encompasses only a first portion of the helical spring. 12. An apparatus as defined in claim 11, wherein the magnetic field encompasses a second portion of the helical spring, the first portion separated from the second portion. 13. An apparatus as defined in claim 12, further comprising a second magnet having a first polarity and disposed about the first portion of the helical spring, wherein the magnet has a second polarity opposite the first polarity and is disposed about the second portion of the helical spring. 14. An apparatus as defined in claim 1, wherein the magnet comprises Samarian-cobalt (SmCo). 15. An apparatus as defined in claim 1, further comprising a magnetic circuit to prevent the housing or a second magnetic field from interfering with the magnetic field. 16. An apparatus as defined in claim 1, further comprising a high relative magnetic permeable material to form a magnetic circuit within the housing. 17. An apparatus as defined in claim 1, wherein the housing comprises a cylindrical shape. 18. A method comprising: positioning a helical spring within a fluid;exposing the helical spring to a magnetic field, wherein the magnetic field radiates radially from an axis of the helical spring;passing a current through the helical spring to displace the helical spring within the fluid;measuring an electromotive force (emf) voltage induced across the helical spring by the displacement; andestimating a characterizing parameter of the fluid from the measured emf voltage. 19. A method as defined in claim 18, further comprising forming a magnetic field around at least a portion of the helical spring, wherein the displacement of the helical spring is responsive to the current and the magnetic field. 20. A method as defined in claim 18, wherein the current comprises at least one of a transient signal, a steady-state signal, or an alternating current. 21. A method as defined in claim 18, wherein the characterizing parameter of the fluid comprises at least one of a viscosity of the fluid or a density of the fluid. 22. A method as defined in claim 18, wherein the displacement of the helical spring comprises a resonant vibration. 23. An apparatus comprising: a helical spring held under tension in a fluid passageway;an actuating device to induce a displacement of the helical spring while a fluid is present in the fluid passageway, wherein the actuating device comprises a magnet to expose the helical spring to a magnetic field, the magnetic field radiating radially from an axis of the helical spring, and a wire to electrically conduct an actuating current through the helical spring; andan interpretation module to estimate a parameter of the fluid based the induced displacement of the helical spring. 24. An apparatus as defined in claim 23, wherein the interpretation module is to estimate a drag force based on the induced displacement, to define a fluid analysis model based on the estimated drag force, and to solve the fluid analysis model for the parameter of the fluid. 25. An apparatus as defined in claim 23, wherein the parameter of the fluid comprises at least one of a viscosity of the fluid or a density of the fluid.