GB2570323A

GB2570323A - Improved performance fluid level sensor

Info

Publication number: GB2570323A
Application number: GB1800919.1A
Authority: GB
Inventors: Paul Clarkson Melvin
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-01-19
Filing date: 2018-01-19
Publication date: 2019-07-24
Anticipated expiration: 2038-01-19
Also published as: GB2570323B; GB201800919D0

Abstract

A fluid level sensor is disclosed comprising an electrically conductive enclosure 4 and a central looped conducting wire 3 coated in electrical insulation. Fluid enters the open bottom of the conductive enclosure 4 and the level sensor measures the change in average permittivity caused by differing relative amounts of fluid and air inside the enclosure. The looped wire coated in electrical insulation creates an electric dipole which causes an area of zero electric field between the wires, as shown in fig. 3. Charged vapour droplets circulating in the void above the fluid level are attracted to the central electrode wire 3, but do not have an attracting force in the area between the wires. Charged vapour droplets in this area therefore fall down due to gravity, accumulating other vapour droplets as they travel downwards. The final effect is to clear the central electrode of any vapour droplets and maintain the sensor accuracy. The wire is preferably twisted. The sensor further comprises tensioner 5 to tension looped conducting wire 3; an electronic circuit board 2; electrical interface cable 6; electrical insulating material seal 1 and vent 8. Electronic circuit board 2 may be encapsulated in insulating material 7.

Description

Improved Performance Fluid Level Sensor

This invention relates to a device to measure the level of fluid inside a enclosure which is not affected by fluid vapour.

A common way to measure fluid is though the use of average permittivity, where the level sensing device measures the average permittivity of the fluid and air inside a conducting enclosure.

Commonly the construction of such a sensor uses a conducting tube to act as the enclosure with a central electrode running long the centre of the tube. As the fluid enters the bottom of the conducting tube the level of the fluid changes the average permittivity inside the conducting tube. The level sensing device measures the average permittivity to determine the level of the fluid. The conducting tube and centre electrode may be insulated for protection against the environment.

When using this method to measure the fluid inside a conducting enclosure vapour droplets from the fluid will circulate in the void above the fluid level. These vapour droplets will accumulate electrical charge from the conducting enclosure as this has the larger surface area. These charged vapour droplets will be attracted to the central electrode, since the central electrode will have the opposite charge to the charged vapour droplets and it is known opposite electrical charges attract. The charged vapour droplets will land on the central electrode and due to the force from the electrical charge on the vapour droplets and the opposite charge on the central electrode the vapour droplets will tend to maintain their position.

The charged vapour droplets accumulate around the central electrode and cause a measurement error.

This invention overcomes this measurement error due to the charged vapour droplets by using an electrical dipole for the central electrode which is construction using a conducting wire coated in electrical insulation which is looped and attached to the sensor electronics. The conducting wire coated in electrical insulation is then tensioned.

Using the electrical dipole for the central electrode modifies the electric field close to the central electrode as shown in Figure 3. The central area between the wires has zero electric field and so the charged vapour particles in this area do not have an attracting force to the central electrode. The charged vapour droplets in this central area are drawn down and fall due to gravity. As these vapour droplets travel down the vapour droplets accumulate other vapour droplets. The final effect is to clear the central electrode of any vapour droplets and maintain the sensor accuracy.

The conducting wire coated in electrical insulation may be twisted to improve stability and performance since the twist causes the falling vapour droplets to rotate around the central electrode and improve the vapour droplet clearing property of the central electrode.

The external conducting enclosure maybe coated in a insulating material to provide protection against the environment.

The electronic circuit board maybe encapsulated in an electrical insulating material to improve robustness.

The invention will now be described solely by way of example and with reference to the accompanying drawings is which:

Figure 1 shows a cross section through the Fluid Level Sensor.

Figure 2 shows how the conducting wire coated in insulation is terminated to the electronic circuit board.

In Figure 1 the Fluid Level sensor has a conducting enclosure 4. The conducting enclosure 4 maybe coated in a electrical insulating material. The top of the sensor has an electrical insulating material seal 1 through which a electrical cable 6 passes. Electrical signals pass through the electrical cable 6 from the electronic circuit board 2.

The conducting wire coated in electrical insulation 3 is looped and terminated to the electronic circuit board 2. The electronic circuit board 2 is attached to the conducting enclosure 4. The tensioner 5 tensions the conducting wire coated in electrical insulation 3 by being inserted through the loop created by looping the conducting wire coated in electrical insulation 3. The tensioner 5 also ensures the conducting enclosure 4 remains open at the bottom to allow fluid to enter inside the conducting enclosure 4. As fluid rises inside the conducting enclosure 4 air escapes through the vent hole 8.

The electronic circuit board 2 senses the change in the relative permittivity inside the conducting enclosure 4 due to the difference between the permittivity of air and the permittivity of the fluid. The fluid level information is transmitted via the electrical cable 6.

The electronic circuit board 2 maybe encapsulated in an insulating material 7 to protect it from the fluid rising in the conducting enclosure 4

In Figure 2 the looped conducting wire coated in electrical insulation 3 is terminated to the electronic circuit board 2. Using a looped conducting wire coated in electrical insulation creates a electric dipole which causes an area of zero electric field between the two wires. This prevents fluid vapour droplets build up and so the Fluid Sensor thus maintains accuracy.

Claims

1. A Fluid Level Sensor comprising:

a) an electrically conductive enclosure having an open top end and a open bottom end;

b) an electronic circuit board;

c) an electrical interface cable;

d) a looped conducting wire coated in electrical insulation; and

e) a tensioner, wherein said electronic circuit board is attached to the inside of the said electrically conductive enclosure top end, said looped conducting wire coated in electrical insulation is electrically attached to said electronic circuit board, said looped conducting wire coated in electrical insulation is attached to said tensioner, as fluid enters said electrically conductive enclosure bottom end the said electronic circuit board sends readings of the measured fluid level through said electrical interface cable.

2. A Fluid Level Sensor according to claim 1, wherein the said looped conducting wire coated in electrical insulation is twisted.

3. A Fluid Level Sensor according to claim 1, further comprising an electrically insulating material, wherein said electronic circuit board is encapsulated in said electrically insulating material.

4. A Fluid Level Sensor according to claim 1, further comprising an electrically insulating material, wherein said looped conducting wire coated in electrical insulation is twisted, said electronic circuit board is encapsulated in said electrically insulating material.

5. A Fluid Level Sensor according to any of the preceding claims, further comprising an electrical insulating coating, wherein said electrically conductive tube is coated in said electrical insulating coating.

5. A Fluid Level Sensor according to one of the claims 2 to 4, further comprising a vent hole in said electrically conductive enclosure, wherein the said vent hole is included to allow air to escape as fluid enters said electrically conductive enclosure bottom end.

6. A Fluid Level Sensor according to any of the preceding claims, further comprising an electrical insulating coating, wherein said electrically conductive enclosure is coated in said electrical insulating coating.

Amendments to the claims have been filed as follows

Claims

1. A Fluid Level Sensor comprising:

a) an electrically conductive tube having one end open and one end sealed and a vent hole;

b) an electronic circuit board;

c) an electrical interface cable;

d) a conducting wire which is coated in electrical insulation and folded in half; and

e) a tensioner, wherein the said vent hole is included to allow air to escape as fluid enters the said electrically conductive tube open end, said electronic circuit board is attached to the inside of the said electrically conductive tube and positioned at the sealed end of said electrically conductive tube, said conducting wire which is coated in electrical insulation and folded in half is positioned inside said electrically conductive tube, said conducting wire which is coated in electrical insulation and folded in half wire ends are electrically attached to said electronic circuit board, said conducting wire which is coated in electrical insulation and folded in half the folded end of which is tensioned by said tensioner inserted through the folded wire at the open end of the said electrically conductive tube, said electronic circuit board sends readings through said electrical interface cable of the measured change in average permittivity inside the said electrically conductive tube due to the fluid level held within said electrically conductive tube.

1— 2. A Fluid Level Sensor according to claim 1, wherein the said conducting wire which is coated in electrical insulation and folded in half is twisted.

4. A Fluid Level Sensor according to claim 1, further comprising an electrically insulating material, wherein said conducting wire which is coated in electrical insulation and folded in half is twisted, said electronic circuit board is encapsulated in said electrically insulating material.