Moisture sensor with an outer coating

Abstract

The present invention relates to a moisture sensor (100) for measuring the moisture of materials in the form of dry, liquid or gaseous particles or powders in at least one duct arranged at least partially along the axis of the sensor through which the material whose moisture is to be measured flows, the sensor consisting of at least one capacitor through which the material whose moisture is to be measured flows, wherein the aforementioned capacitor comprises rings made of dielectric material clamped between metal rings mounted coaxially with respect to said axis, both the rings made of dielectric material and the metal rings being closed by limiting flanges, characterized in that the aforementioned sensor comprises an outer coating (10) arranged outside the rings made of dielectric material and the metal rings, the outer coating having a thermal insulation layer (30) clamped between carbon fiber layers acting as electromagnetic interference shielding layers.

Description

Technical Field

[0001] This invention relates to moisture sensors for the industrial field, particularly sensors for measuring moisture in industrially processed products (such as materials in dry, liquid, or gaseous particle or powder form), wherein the moisture sensor has an outer coating. Background Technology

[0002] As is well known, there are now devices for measuring the moisture content in various substance samples, which are widely used in many industries, especially the food, chemical, and pharmaceutical industries.

[0003] Some known devices cannot actually measure moisture in the production process online; it can only be measured through sampling and subsequent measurements.

[0004] This method is cumbersome and time-consuming, and due to various factors that may lead to improper sampling, the measurement results are unreliable.

[0005] In addition, the sampling itself cannot be widely representative of the production process because laboratory systems can only extract a few grams of sample, and in some production processes, it is not possible to collect samples at specific target locations (such as silos or dryers in a nitrogen atmosphere).

[0006] Online moisture measurement systems also exist.

[0007] For example, document WO 2012 / 004621 describes an apparatus for measuring the moisture content of a material flowing in at least one conduit in the form of dry particles, liquid particles, gaseous particles, or powder, through which the material flows at least partially along an axis. The apparatus includes at least one capacitor through which the material to be measured flows. The capacitor further includes at least two metal rings and at least one dielectric element, the metal rings being coaxially mounted with the axis and close to the inner wall of the conduit through which the material to be measured flows, and the dielectric constant of the dielectric element changing substantially linearly with temperature.

[0008] When installed on industrial machines such as injection molding machines, extruders, and dryers, the equipment needs to be calibrated regularly to ensure the repeatability and accuracy of measurements.

[0009] In some industrial settings, calibration operations can only be performed under specific environmental temperature and humidity conditions, thus requiring a short production halt during calibration.

[0010] Another issue that needs attention is that when the measurement system is subjected to temperatures exceeding 50°C (mainly due to the thermal expansion and dielectric constant changes of the dielectric material used in the sensor), dimensional changes and dielectric constant changes will affect the accuracy of the measurement, and therefore measurement errors are unavoidable.

[0011] The total capacitance measurement of the sensor is a composite of the following: the capacitance of the sensor under no-load conditions (capacitor CX) + the dielectric constant of the material passing through the sensor (CM) + the dielectric constant induced by relative humidity (HRU). In other words, the total capacitance (Ctot) is obtained by the following formula: Ctot = CX + CM + HRU.

[0012] As the formula shows, the unloaded sensor value CX is essential for accurate measurement, especially for measurement repeatability. Capacitance drift caused by changes in dielectric capacitance is neither constant nor linear, as it depends on many factors, such as the thermal expansion of all materials constituting the sensor and the specific characteristics of certain devices (where mechanics can thermally and mechanically affect the sensor's structure). This leads to capacitance drift or frequent hysteresis, creating a more complex problem that is difficult to correct even using mathematical methods.

[0013] Due to its structure, the sensor is also susceptible to electromagnetic interference from interactions with other machines, which can further alter the signal value from the sensor. A metal shield eliminates this problem, but introduces another issue: it causes a further increase in the internal temperature of the system, leading to increased drift in the capacitance signal due to thermal expansion of the sensor components.

[0014] Another issue to be aware of is the heat generated by electronic components, which often exceeds 100°C. The sensor's PCB (electronic board) must be mounted as close as possible to the sensor's electrodes, primarily to avoid parasitic capacitance caused by contact impedance. The terminating capacitance must fall within a narrow window between 130fF (fl) and 170fF, and its temperature dependence is very weak, even negligible.

[0015] Therefore, one object of the present invention is to provide a system that can protect a moisture sensor from the effects of temperature changes.

[0016] Another object of the present invention is to provide a system that can protect a moisture sensor from electromagnetic interference.

[0017] Another object of the present invention is to achieve the above results in a practical and economical manner. Summary of the Invention

[0018] These and other objectives are achieved by a moisture sensor. This moisture sensor is used to measure the moisture content of a dry, liquid, or gaseous particle or powder material in at least one pipe, at least partially arranged along the axis of the sensor, through which the material to be measured flows. The sensor comprises at least one capacitor through which the material to be measured flows, wherein the aforementioned capacitor includes a ring made of dielectric material sandwiched between metal rings, the metal rings being coaxially mounted with respect to the axis between limiting flanges. The sensor is characterized by comprising an outer coating disposed outside the aforementioned dielectric material ring and metal rings, the outer coating having a heat-insulating layer sandwiched between carbon fiber layers serving as an electromagnetic interference shielding layer.

[0019] The advantages of this invention are numerous.

[0020] First, the structure of the sensor, especially the structure of its outer coating, can protect the moisture sensor from the effects of temperature changes.

[0021] Secondly, the structure of the sensor, especially the structure of its outer coating, can protect the moisture sensor from electromagnetic interference.

[0022] Further features of the invention can be derived from the dependent claims. Attached Figure Description

[0023] Further features and advantages of the invention will become clearer from the following description, which is given by way of example and not limitation with reference to the accompanying drawings shown in the table, wherein: Figure 1 A side view of the outer coating for a moisture sensor according to an embodiment of the present invention is shown; Figure 2 The outer coating for the moisture sensor is shown along... Figure 1 A view of section AA in the image; Figure 3 It shows Figure 2 Enlarged details of the mid-section; Figure 4 and Figure 6 A side view of a moisture sensor with an electronic board support according to an embodiment of the present invention is shown; Figure 5 It shows Figure 4 and Figure 6 Axonometric view of the sensor; Figure 7 It shows that it has Figures 4-6 The electronic board support shown and Figures 1-3 Axonometric view of a moisture sensor with an external coating of the type shown; and Figure 8It shows Figures 1-3 Axonometric view of the type of outer coating shown. Detailed Implementation

[0024] Now we will begin referencing Figure 1 The present invention will now be described. Figure 1 A side view of an outer coating for a moisture sensor according to an embodiment of the present invention is shown. The outer coating is generally indicated by reference numeral 10. The moisture sensor is as follows: Figure 4 , Figure 6 and Figure 7 As shown, it is generally indicated by reference numeral 100 in the attached figure.

[0025] Moisture sensors to which the outer coating of the present invention can be applied are known, which typically consist of a number of metal rings and a number of rings made of dielectric material, wherein each metal ring is sandwiched between two rings made of dielectric material, thereby forming a capacitor structure.

[0026] The metal ring and the ring made of dielectric material are assembled on the two annular limiting flanges 60 and 70 by assembly screws. Figures 4-7 (as shown) between.

[0027] The moisture sensor 100 of the present invention measures moisture online during the processing of materials flowing in the form of dry particles, liquid particles, gaseous particles, or powder.

[0028] This moisture sensor is suitable for placement in a pipe (not shown) where moisture can be measured online, i.e., the moisture sensor is arranged along an axis along which the material whose moisture is to be measured flows.

[0029] In particular, thanks to the aforementioned sensor structure, the capacitance of the capacitor is affected by the dielectric constant of the material between its plates. This dielectric constant varies depending on the measured moisture content of the material. This is because the dielectric constant of water is much higher than that of many solid materials or air, and through this phenomenon, the moisture content of the material passing through the sensor can be measured.

[0030] Figure 2 The outer coating 10 of the moisture sensor 100 according to the present invention is shown along... Figure 1 The view of section AA in the image.

[0031] Figure 3 It shows Figure 2 Enlarged detail B of section AA.

[0032] from Figure 3 The details show that the outer coating 10 is similar to a cylindrical shield, serving as both a Faraday cage and a heat shield.

[0033] The outer coating 10 has a heat insulation layer 30 sandwiched between carbon fiber layers 20 and 40, which serve as electromagnetic interference shielding layers.

[0034] The intermediate layer (or central layer) 30 is preferably made of glass fiber.

[0035] Specifically, the outer coating 10 thus provides three layers: a first outer carbon fiber layer 20, a second intermediate glass fiber layer 30, and a third inner carbon fiber layer 40.

[0036] This achieves a sandwich structure that enables two important effects: the carbon fiber layers 20 and 40 (which are conductive) are set to a negative potential (grounded) and act as a Faraday cage, thus becoming the best electromagnetic interference shielding layer.

[0037] The intermediate fiberglass layer 30 acts as a heat insulator, preventing heat generated by the material passing through the sensor from dissipating outwards and causing the electronic components of the moisture sensor 100 (especially its electronic board) to heat up. This differs from the metal shields commonly used in all applications, which instead conduct heat.

[0038] Preferably, the thickness of the intermediate layer 30, made of glass fiber, is greater than the thickness of the carbon fiber layers 20 and 40. The thickness of the intermediate layer 30 is preferably at least twice and less than seven times the thickness of the carbon fiber layers 20 and 40.

[0039] In a particularly preferred embodiment, the thickness of the heat insulation layer 30 is approximately between 0.40 mm and 0.60 mm, preferably equal to 0.50 mm, while the thickness of the carbon fiber layers 20 and 40 used as electromagnetic interference shielding layers is between 0.20 mm and 0.30 mm, preferably equal to 0.25 mm. Figure 4 and Figure 6 A side view of a moisture sensor 100 with an electronic board support 50 according to an embodiment of the present invention is shown. Figure 5 It shows Figure 4 and Figure 6 An isometric view of the sensor. Of course, the electronic board support 50 is optional, and a moisture sensor 100 with an outer coating 10 but without a support 50 also falls within the scope of this invention.

[0040] As previously described, the sensor 100 has metal rings, with a ring made of dielectric material sandwiched between the metal rings, and all these metal rings and the ring made of dielectric material are assembled between two annular limiting flanges 60 and 70 by assembly screws.

[0041] The bracket 50, made of thermal insulation material, for mounting the electronic board of the control sensor 100, is further connected to the annular limiting flanges 60 and 70.

[0042] Figure 7It shows Figures 4-6 The isometric view of the electronic board support shown in the figure has the following features: Figures 1-3 The type of outer coating shown is 10.

[0043] Figure 8 It shows Figures 1-3 The figure shows an isometric view of the outer coating 10 of the type shown. As can be seen from the figure, the outer coating 10 has a generally cylindrical structure and generally rectangular holes 12 for accommodating the electronic board support 50.

[0044] The cylindrical shape of the outer coating 10 has an opening at the end for accommodating the moisture sensor 100.

[0045] The outer coating 10 also has a hole 14 for inserting a screw 15 to secure the electronic board bracket 50 to the moisture sensor 100.

[0046] Obviously, those skilled in the art can make further modifications and variations to this invention. All modifications and variations made in accordance with the following claims to adapt to temporary and specific needs fall within the protection scope of this invention.

Claims

1. A moisture sensor (100) for measuring the moisture content of a dry, liquid, gaseous, or powdered material in at least one pipe, said at least one pipe being arranged at least partially along the axis of the sensor, the material containing the moisture to be measured flowing through the pipe, the moisture sensor (100) comprising at least one capacitor, the material containing the moisture to be measured flowing through the capacitor, wherein the capacitor includes a ring made of a dielectric material sandwiched between metal rings, the metal rings being coaxially mounted with respect to the axis between limiting flanges, characterized in that: The sensor (100) includes an outer coating (10) disposed outside the ring made of dielectric material and the metal ring, the outer coating having a heat insulation layer (30) sandwiched between carbon fiber layers (20, 40) serving as electromagnetic interference shielding layers.

2. The moisture sensor (100) according to claim 1, wherein the thickness of the heat insulation layer (30) is greater than the thickness of the carbon fiber layer (20, 40) used as an electromagnetic interference shielding layer.

3. The moisture sensor (100) according to claim 2, wherein the thickness of the heat insulation layer (30) is at least twice and less than seven times the thickness of the carbon fiber layer (20, 40) used as an electromagnetic interference shielding layer.

4. The moisture sensor (100) according to claims 2 and 3, wherein the thickness of the heat insulation layer (30) is approximately between 0.40 mm and 0.60 mm, preferably 0.50 mm, and the thickness of the carbon fiber layer (20, 40) used as an electromagnetic interference shielding layer is between 0.20 mm and 0.30 mm, preferably 0.25 mm.

5. The moisture sensor (100) according to any one of the preceding claims, wherein the heat insulation layer (30) is used to prevent the temperature of the electronic components of the sensor from rising due to the flow of material, and the carbon fiber layers (20, 40) act as a Faraday cage for shielding electromagnetic interference.

6. The moisture sensor (100) according to any one of the preceding claims, wherein the heat insulation layer (30) is made of glass fiber.

7. The moisture sensor (100) according to any one of the preceding claims, wherein the outer coating (10) has a cylindrical structure surrounding the sensor.

8. The moisture sensor (100) according to any one of the preceding claims, wherein the outer coating (10) has a rectangular hole (12) for receiving a bracket (50) made of a heat-insulating material for the electronic control board of the moisture sensor (100).

9. A moisture sensor (100) according to any one of the preceding claims, wherein the outer coating (10) includes a hole (14) for inserting a screw (15) to secure the bracket (50) of the electronic board to the moisture sensor.

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