Electronic housing with thermal fluid detection

Abstract

The process transmitter includes a transmitter housing and a liquid detector coupled to the transmitter housing. The liquid detector includes a temperature sensor configured to generate a signal indicative of the presence of liquid within the transmitter housing. The process transmitter also includes a controller coupled to the liquid detector, the controller configured to: receive the generated signal; determining the presence of a liquid within the transmitter housing based on the received signal; and generating an output indicative of the determined presence of the liquid within the transmitter housing.

Description

[0001] This application is a divisional application of the Chinese invention patent application with application date of March 5, 2019, application number 201910167045.0, and invention name “Electronic housing with thermal fluid detection”. Technical Field

[0002] The present application relates to a process transmitter. Background Art

[0003] Industrial process control systems are used to monitor and control industrial processes used to produce or transfer fluids, etc. In such systems, it is often important to measure "process variables" such as temperature, pressure, flow rate, etc. Process control transmitters are used to measure such process variables and transmit information related to the measured process variables back to a central location such as a central control room.

[0004] For example, one type of process variable transmitter is a pressure transmitter, which measures process fluid pressure and provides an output related to the measured pressure. Such an output can be pressure, flow rate, level of the process fluid, or other process variables that can be derived from the measured pressure.

[0005] In operation, process control transmitters may be installed in different environments for various processes. In one example, the process control transmitter may be field installable, so the process control transmitter may be subjected to high humidity, rain, flooding, etc. This may damage the electronic components of the process control transmitter. For example, improper installation of the process control transmitter may result in loose covers and / or leaky conduits and cable gland failures, which may introduce ambient moisture into the housing of the process control transmitter. The introduction of moisture often results in output errors and may even cause transmitter failure over time.

[0006] In order to detect the presence of moisture within the housing / terminal block of a process control transmitter, current attempts typically require the user to first remove the transmitter from the control loop and manually perform a multi-step diagnostic operation on the transmitter. However, this is typically a reactive indication of an error only after the transmitter output has undergone an output shift. In addition, other examples typically include using electrical conductivity (resistive or capacitive) to detect the presence of moisture. However, these methods are typically unreliable and sensitive to contamination, leakage current, and false alarms. For example, when contaminated, various sensors can become extremely sensitive to humidity, causing the sensor to falsely detect water when there is no water. Summary of the invention

[0007] The process transmitter includes a transmitter housing and a liquid detector coupled to the transmitter housing. The liquid detector includes a temperature sensor configured to generate a signal indicative of the presence of liquid within the transmitter housing. The process transmitter also includes a controller coupled to the liquid detector, the controller configured to: receive the generated signal; determine the presence of liquid within the transmitter housing based on the received signal; and generate an output indicative of the determined presence of liquid within the transmitter housing. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a diagrammatic perspective view of a process fluid pressure transmitter that may be used with embodiments of the present invention.

[0009] Figure 2 is a block diagram of a process fluid pressure transmitter in accordance with an embodiment of the present invention.

[0010] Figure 3 is a schematic diagram of a liquid detector according to an embodiment of the present invention.

[0011] Figure 4 is a schematic circuit diagram of a liquid detector coupled to a controller / processor according to an embodiment of the present invention.

[0012] FIG. 5A to FIG. 5B is a schematic circuit diagram of a liquid detector coupled to various components of a processor / controller according to an embodiment of the present invention.

[0013] Figure 6 is a stage diagram schematically showing the heating, cooling and measurement stages of a liquid detector according to an embodiment of the present invention.

[0014] Figure 7 is a diagram schematically showing a detector count difference value of a liquid detector according to an embodiment of the present invention.

[0015] FIG. 8A to FIG. 8B A method of detecting water in a transmitter housing according to an embodiment of the present invention. DETAILED DESCRIPTION

[0016] During operation of a process variable transmitter in a field application, it is necessary to detect the presence of moisture or other fluids within the housing of the process variable transmitter to ensure that an accurate output is provided while also ensuring that the process variable transmitter is not damaged.

[0017] According to various embodiments, a process variable transmitter is provided with a liquid detector that allows for the detection of moisture or other fluids within the housing of the process variable transmitter. The embodiments described herein generally provide a liquid detector that detects liquid within an electronic housing based on the thermal conductivity of the liquid rather than the electrical conductivity of the liquid. Thus, the detector is insensitive to conductive contamination. Additionally, this allows the liquid detector to be insensitive to false alarms caused by condensation of trace amounts of water droplets.

[0018] Although the present description is made with respect to a process fluid pressure transmitter, it is contemplated that the present invention may be used in a variety of other process devices having an electronics housing.

[0019] Figure 1 1 is a schematic perspective view of a process fluid pressure transmitter that is particularly useful with embodiments of the present invention. Pressure transmitter 100 includes process fluid connector 102, sensor body 106, electronics housing 108, display 112, and piping 110. In operation, pressure transmitter 100 may be coupled to a source of process fluid 104 via process fluid connector 102, wherein the received process fluid bears against a diaphragm in sensor body 106. When the process fluid is received, the diaphragm experiences a pressure drop that may be caused by a pressure sensor (e.g., a pressure sensor) disposed in sensor body 106. Figure 2 The pressure sensor has an electrical characteristic, such as capacitance or resistance, which is sensed by a measuring circuit (such as a sensor 126) in the electronic housing 108. Figure 2 The process fluid pressure may be measured by measurement circuitry 124 (shown) and converted to process fluid pressure by the controller using appropriate calculations. The process fluid pressure may be transmitted over a process communication loop via wires coupled through pipe 110 and / or displayed locally via display 112. Additionally, in other examples, the process fluid pressure may be transmitted wirelessly.

[0020] Figure 2 1 is a block diagram of a process fluid pressure transmitter according to an embodiment of the present invention. Pressure transmitter 100 schematically includes communication circuit 114, power circuit 118, measurement circuit 124, controller / processor 122, display 112, liquid detector 128, and pressure sensor 126 within sensor housing 106, and pressure sensor 126 is configured to couple with process fluid received via connector 102.

[0021] Before describing the operation of liquid detector 128, a brief description of the other components in transmitter 100 is first provided. Communication circuit 114 is disposed in electronics housing 108 and may be coupled to a process communication loop via conductor 116. By virtue of coupling to process communication loop 116, communication circuit 114 allows process pressure transmitter 100 to communicate according to an industry standard process communication protocol. Examples include addressable remote sensor highway Protocol, FOUNDATION™ Fieldbus protocol, etc. In some examples, communication circuit 114 also allows transmitter 100 to communicate wirelessly with other devices, such as according to IEC 62591 (WirelessHART). In addition, in some examples, transmitter 100 can receive all the power necessary for operation through its coupling to the process communication loop.

[0022] In one example, power module 118 is coupled to the process communication loop to provide appropriate operating power to all components of transmitter 100 , as shown by reference numeral 120 labeled “GO ALL.”

[0023] The measurement circuit 124 is coupled to one or more sensors 126, such as pressure sensors, to sense process variables. In one example, the measurement circuit 124 includes one or more analog-to-digital converters, linearization and / or amplification circuits, and provides one or more indications of sensed analog values ​​to the controller 122 in the form of digital signals.

[0024] Controller / processor 122 is coupled to communication circuit 114, measurement circuit 124, display 112, and detector 128 so that information received from measurement circuit 124 and / or detector 128 can be displayed and / or transmitted over a process communication loop or in accordance with a wireless communication protocol. In one example, the resulting display may include a measured process variable and / or an indication of whether moisture is present in the transmitter housing, which will be described later in detail. Figures 3 to 5B This is discussed. The controller / processor 122 may also include or be coupled to suitable memory that can store program data and process data. The memory may include volatile and / or non-volatile memory. In one example, the controller / processor 122 is a microprocessor with suitable memory that enables the controller / processor 122 to programmatically execute a series of process steps in order to perform its function as a measuring instrument.

[0025] Pressure sensor 126 measures the pressure of a process fluid sample received through process fluid connector 102. In one example, sensor 126 can be coupled to a diaphragm in sensor housing 106 that, in operation, directly contacts the process fluid received through connector 102. In this example, sensor 126 can be coupled to the diaphragm such that sensor 126 does not directly contact the received process fluid, but rather determines pressure based on deformation of the diaphragm caused by the received process fluid. However, in other examples where transmitter 100 is a different type of transmitter, sensor 126 can include a variety of sensors depending on the process variable desired to be measured.

[0026] During operation of transmitter 100, it may be necessary to detect the presence of moisture or fluid within the housing of transmitter 100. This may include sensor housing 106 and / or electronics housing 108. For example, transmitter 100 may be coupled to a field application, which may subject transmitter 100 to high humidity, rain, flooding, etc. This may, in turn, damage one or more electronic components of transmitter 100. To detect the presence of moisture or fluid within the housing of transmitter 100, controller / processor 122 is coupled to liquid detector 128, which detects moisture or other fluid based on changes in thermal mass and thermal conductivity.

[0027] Figure 3 is a schematic diagram of a liquid detector according to an embodiment of the present invention. The liquid detector 128 schematically includes a moisture or fluid detector 302 and an electrical connector 304, which couples the liquid detector 128 to the processor / controller 122 in operation. Additionally, for environmental protection, the liquid detector 128 can be coated with epoxy resin. In operation, the liquid detector 128 can be disposed in a transmitter housing and used to determine the presence of moisture or fluid within the transmitter housing. For example, the detector 302 includes a temperature sensor bound to a heating element, which allows the detection of moisture or fluid in the transmitter housing, which will be discussed later. However, in one example, the heating element and the temperature sensor may include a resistor and a diode. However, other types of heating elements and temperature sensors may also be used. In addition, it is clearly conceivable that the heater and the temperature sensor may be the same physical structure, such as a winding of a temperature-sensitive wire (e.g., platinum). In order to detect the presence of moisture or fluid within the transmitter housing, the liquid detector 128 is repeatedly heated and cooled by cycling the power to the heating element, as described below with reference to Figure 4 described.

[0028] Figure 41 is a schematic circuit diagram of a liquid detector coupled to a controller / processor according to an embodiment of the present invention. The liquid detector 128 schematically includes: a moisture or fluid detector 302, which includes a heating element 404 and a temperature sensor 402; and an electrical connector 304, which is coupled to the processor / controller 122.

[0029] Temperature sensor 402 and heating element 404 can adopt various forms and configurations according to moisture detection operation. Although one form of temperature sensor 402 and heating element 404 is now described as temperature sensor 402 is a diode and heating element 404 is a resistor, it is conceivable that various other temperature sensors and heating elements can also be used. However, in this example, diode 402 includes two types of semiconductor materials, p-type and n-type, which form a pn junction, and the pn junction allows current to flow in one direction while blocking current in the opposite direction. In one example, this allows diode 402 to operate in a forward bias mode and a reverse bias mode, allowing current to flow through diode 402 in the forward bias mode, and prohibiting current from flowing through diode 402 in the reverse bias mode. Diode 402 can be formed by a variety of different types of materials (e.g., silicon, gallium arsenide and germanium).

[0030] In operation, detector 302 is coupled to processor / controller 122 via electrical connector 304, which in one example includes copper wire. When detector 302 is coupled to processor / controller 122, processor / controller 122 may perform various functions that allow for the detection of moisture or fluid in the transmitter housing. For example, one operation for detecting the presence of moisture using controller / processor 122 and liquid detector 128 will be discussed.

[0031] In operation, the processor / controller 122 can provide a voltage potential for initially reverse biasing the diode 402. This forces all subsequent currents to pass through the resistor 404, thereby causing the resistor 404 and the diode 402 bound to the resistor 404 to heat up. When the diode 402 is heated, power can be removed from the liquid detector 128. Then, the processor / controller 122 can generate a current configured to flow through the heated diode 402 in a forward biased manner, in which case the voltage drop across the heated diode 402 is measured. The measured voltage drop indicates the current operating temperature of the liquid detector 128. For example, for the current generated to flow through the diode 402 in a forward biased manner, the current has to overcome the potential barrier at the pn junction. For silicon, the potential barrier is generally about 0.6 volts to 0.7 volts; for germanium, the potential barrier is generally about 0.3 volts to 0.35 volts. However, according to the temperature of the liquid detector 128, the potential barrier changes according to the Shockley diode equation. Thus, by determining the voltage drop across the heated diode 402, the operating temperature may be determined.

[0032] When the current operating temperature is determined, the diode 402 is allowed to cool for a predetermined amount of time. Subsequently, the processor / controller 122 generates another current configured to flow through the diode 402 in a forward biased manner. Then, the subsequent voltage drop across the diode 402 is determined. Based on the subsequent voltage drop, a new operating temperature is calculated. Using the two determined temperatures, the processor / controller 122 can determine a temperature difference to determine whether moisture or fluid is present within the transmitter housing. For example, depending on whether the liquid detector 128 is in air or in water (or another fluid), there is a measurable difference between the heated detector temperature and the cooled detector temperature. Therefore, based on the difference between the detector temperatures, the controller / processor 122 can detect the presence of moisture or fluid within the transmitter housing. Figure 7 This phenomenon is schematically illustrated in and will be discussed later.

[0033] FIG. 5A to FIG. 5B is a schematic circuit diagram of a liquid detector coupled to various components of a processor / controller according to an embodiment of the present invention. Figure 5A , the liquid detector 128 includes a diode 402, a resistor 404, and an electrical connector 304 configured to couple with various components of the processor / controller 122. During the heating phase of applying a voltage potential to reverse bias the diode 402, the processor / controller 122 may include switches 502 and 504 that modify the current path through the liquid detector 128. For example, Figure 5AAs schematically shown in FIG. 4 , during the heating phase, switches 502 and 504 may be in the positions shown to apply a voltage potential that reverse biases diode 402. In this example, the applied current may pass almost exclusively through resistor 404, thus causing resistor 404 and diode 402 to heat up.

[0034] Alternatively, Figure 5B As schematically shown in FIG. 5 , during the measurement and cooling phases in which the heated diode 402 is operated according to the forward bias, the positions of the switches 502 and 504 can be changed to allow the generated current to flow through the diode 402 and the analog-to-digital converter 506. Thus, the voltage drop across the diode 402 can be determined. However, despite Figure 5A and Figure 5B Example circuit diagrams for operating the liquid detector 128 during various heating, cooling, and measurement phases are shown, but other configurations are contemplated herein.

[0035] Figure 6 Schematically shows the heating, cooling and measurement stages of a liquid detector according to an embodiment of the present invention. Figure 6 6, graph 600 includes a plurality of phases generally indicated by lines 602, 604, and 606. For example, line 602 generally refers to a period of time when a heater (e.g., resistor 404) begins generating heat at time T0 (generally indicated by line 616) and is turned off at time T1 (generally indicated by line 618). During this period of time between T0 and T1, resistor 404 generates heat, and the heat causes the temperature of the temperature sensor (e.g., diode 402) to increase, as schematically indicated by line 604.

[0036] For example, at time T0, corresponding to the time when resistor 404 begins to generate heat, the temperature of the temperature sensor (e.g., diode 402) increases, as generally indicated by lines 608 and 610. In one example, line 608 corresponds to the temperature of diode 402 in the absence of moisture or liquid within the transmitter housing. Alternatively, line 610 corresponds to the temperature of diode 402 in an example in which moisture or fluid is present within the transmitter housing. As schematically shown along line 604, the temperature of diode 402 is greater in the case where liquid detector 128 is operating in a relatively dry environment, as shown by line 608, compared to line 610. At time T1, corresponding to the time when resistor 404 stops generating heat, the temperature of diode 402 generally decreases, as schematically shown.

[0037] Line 606 shows various times at which the temperature of diode 402 is measured. For example, a first measurement is obtained at time T1 (generally indicated by line 612), corresponding to the time when resistor 404 stops generating heat. After a predetermined period of time (e.g., the period between T1 and T2), a second measurement is obtained at T2 (generally indicated by line 614). Based on the temperature difference of diode 402 between T1 and T2, the presence of moisture or fluid within the transmitter housing of liquid detector 128 can be determined.

[0038] For example, Figure 6 , the temperature of the liquid detector 128 varies depending on the environment of the liquid detector 128. For example, the temperature of the diode 402 in dry conditions (generally indicated by line 608) is greater than the temperature of the diode 402 in wet conditions (generally indicated by line 610). Therefore, based on the temperature difference of the diode 402 between T1 and T2, the presence of moisture or fluid within the transmitter housing can be determined.

[0039] Figure 7 Schematically illustrates the detector count difference of the liquid detector according to the embodiment of the present invention. Figure 7 As schematically shown in , the count obtained from the liquid detector 128 varies based on different environmental factors. For example, line 702 represents the detector count obtained when the liquid detector 128 is relatively cool. Alternatively, line 704 represents the detector count obtained when the liquid detector 128 is operated at an elevated temperature. At point 706, the liquid detector 128 operates in a relatively dry environment, and at point 708, the liquid detector 128 is immersed in water. Subsequently, at point 712, the liquid detector 128 is removed from the water. As schematically shown at point 706, typically, the liquid detector 128 operating in a dry environment has a count difference of 300 when the liquid detector 128 cools (as shown in line 702) and when the liquid detector 128 heats up (as shown in line 704). Alternatively, at point 710, the liquid detector 128 is immersed in water and exhibits a count difference of 100. Thus, liquid detector 128 may indicate the presence of moisture within the transmitter housing based on the respective count differences obtained when liquid detector 128 is operated in dry or humid environments.

[0040] FIG. 8A to FIG. 8B800 is a flow chart of a method for detecting water in a transmitter housing according to an embodiment of the present invention. It should be understood that method 800 can be used for a variety of different transmitters to detect the presence of moisture or fluid in a transmitter housing. However, in this example, processing begins at block 802, where the processor / controller 122 generates a voltage potential across the liquid detector 128. In one example, the generated voltage potential can bias a diode (e.g., diode 402) in a reverse manner to almost exclusively allow current to flow through a heater (e.g., resistor 404), as shown in block 804. However, it is conceivable that various other components can also be used, as shown in block 806.

[0041] When a voltage potential is generated across the liquid detector 128, processing proceeds to block 808 where the processor / controller 122 generates a current for the liquid detector 128. In one example, the generated current flows almost exclusively through the heater to generate heat, as shown in block 810. However, it is contemplated that in other examples the current may also flow through additional components, as shown in block 812. In one example, because the heater is in proximity to the diode, the heat generated from the heater is applied to the diode, causing the operating temperature of the diode to increase.

[0042] After the predetermined amount of time, the process proceeds to block 814, where the processor / controller 122 removes power from the liquid detector 128. In one example, by removing power from the liquid detector 128, the heating element stops generating heat. The process then proceeds to block 816, where the processor / controller 122 generates a current for the liquid detector 128 in a forward biased manner to allow the generated current to flow through the diode. This operation is indicated by block 818. However, in other examples, the current may also flow through additional components, as shown in block 820.

[0043] When a current configured to travel along the diode is generated in a forward biased manner, the processor / controller 122 determines a voltage drop across the liquid detector 128, as shown in block 822. In one example, the operation includes determining the voltage drop across the diode. Based on the determined voltage drop, the processor / controller 122 determines an initial operating temperature of the diode, as shown in block 834. However, various other characteristics and operating parameters of the liquid detector 128 may also be determined, as shown in block 826.

[0044] When the initial operating temperature of the liquid detector 128 is determined, the processor / controller 122 waits a predetermined amount of time for the liquid detector 128 to cool, as shown in block 828. The predetermined amount of time can span any desired amount of time and can include a few seconds, a few minutes, etc. When the liquid detector 128 is allowed to cool, the process transfers to block 830, where the processor / controller 122 generates an additional current for the liquid detector 128. In one example, the additional current can also pass through the diode in a forward biased manner. The processor / controller 122 then determines the subsequent voltage drop, as shown in block 832. In one example, the subsequent voltage drop across the diode can be determined, as shown in block 836, thereby allowing the processor / controller 122 to determine the new operating temperature of the liquid detector 128, as shown in block 840. However, other characteristics of the liquid detector 128 can also be determined, as shown in block 838.

[0045] The process then passes to block 842 where the processor / controller 122 determines the difference between the determined detector temperatures. In one example, the processor / controller 122 may also first determine the voltage drop difference across the liquid detector 128, as shown in block 844. However, various other information may also be determined, as shown in block 846.

[0046] The processor / controller 122 then determines whether moisture or fluid is present based on the determined difference, as shown at block 848. For example, the determined voltage drop or temperature difference for the liquid detector 128 will change based on the presence of moisture or fluid. The voltage drop or temperature difference in the presence of moisture or fluid will be relatively small compared to the voltage drop or temperature difference in the absence of fluid. Figure 6 and Figure 7 This phenomenon is shown in .

[0047] If moisture or fluid is present, the process transfers to block 850, where the processor / controller 122 notifies the operator that moisture has been detected. In one example, such notification may include generating a display (as shown in block 852), or generating various other signals (as shown in block 854). However, if moisture or fluid is not detected, the process then ends.

[0048] Although the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes in form and detail may be made without departing from the spirit and scope of the present invention. For example, it is readily apparent that all necessary circuitry, heating components, and sensing components may be provided on a single silicon die. Such a die / chip may then provide a simple indication (i.e., logic level output or communication) based on the presence of water or liquid within the transmitter housing.

Claims

1. A process transmitter comprising: a transmitter housing having a pipe coupling; A liquid detector is arranged in the transmitter housing, and the liquid detector comprises: a temperature sensor configured to generate a signal indicative of the presence of liquid within the transmitter housing; communications circuitry disposed within the transmitter housing and configured to communicate in accordance with an industry standard process communications protocol; and a controller disposed within the transmitter housing and coupled to the communication circuit and the liquid detector, the controller being configured to: receive the generated signal; determine the presence of liquid within the transmitter housing based on the received signal; and generate an output indicative of the determined presence of liquid within the transmitter housing, Wherein, the liquid detector further comprises: a heating element coupled to the temperature sensor and configured to receive current from the controller and generate heat for the temperature sensor, Wherein, the heating element and the temperature sensor have the same physical structure, wherein the heating element comprises a resistor, and the temperature sensor comprises a diode connected in parallel with the resistor in the electronic circuit of the liquid detector, and The diode generates the signal corresponding to the voltage drop across the diode at different times.

2. The process transmitter of claim 1, wherein: When the controller receives the signal from the diode, the controller determines an operating temperature of the diode based on the voltage drops across the diode at the different times.

3. The process transmitter of claim 2, wherein: The controller determines the presence of liquid based on a difference in operating temperatures of the diodes.

4. The process transmitter of claim 1, wherein: The signal includes a first signal corresponding to a first voltage drop of the diode at a first time and a second signal corresponding to a second voltage drop of the diode at a second time.

5. The process transmitter of claim 4, wherein: The first time includes a time when the diode operates at an elevated operating temperature after receiving generated heat from the heating element, and the second time includes a subsequent time when power is not supplied to the heating element.

6. The process transmitter of claim 1, wherein: The controller generates the output for a user interface device, the user interface device being configured to display the determined presence of liquid within the transmitter housing upon receipt of the output.

7. A process transmitter comprising: a transmitter housing having a pipe coupling; A liquid detector is arranged in the transmitter housing, and the liquid detector comprises: an electronic circuit including a heating element configured to generate heat and a temperature sensor electrically coupled to the heating element, the temperature sensor configured to receive the generated heat and generate a signal indicative of the presence of liquid within the transmitter housing; communications circuitry disposed within the transmitter housing and configured to communicate in accordance with an industry standard process communications protocol; and a controller coupled to the communication circuit and the liquid detector, the controller being configured to receive the signal and determine the presence of liquid within the transmitter housing based on the received signal, wherein the temperature sensor comprises a diode, and the heating element comprises a resistor connected in parallel with the diode in the electronic circuit, Wherein, the heating element and the temperature sensor have the same physical structure, and The generated signal corresponds to the voltage drop across the diode at different times.

8. The process transmitter of claim 7, when the controller receives the generated signal, the controller determines the operating temperature of the diode at different times based on the voltage drop across the diode.

9. The process transmitter of claim 8, wherein: The controller determines the presence of liquid within the transmitter housing based on a temperature difference of the liquid detector.

10. The process transmitter of claim 9, wherein: When the presence of liquid within the transmitter housing is determined, the controller is configured to generate an output for a user interface device.

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