APPARATUS FOR IN SITU LEVEL AND FLOW MEASUREMENT

Abstract

An apparatus for measuring at least one of the level and the velocity of a media in a channel, the apparatus including a remote measuring device which comprises: a sensing unit having at least one sensing assembly arranged to measure at least one of the level and the velocity of the media, a two-wire interface arranged to receive power from an external power source and permit data transfer between the sensing assembly and an external control unit over the two-wire interface, an energy store for storing energy transmitted to the measurement device over the two-wire interface, a controller, and characterised in that the remote measuring device further comprises: an indicator means for providing in-situ feedback to a user on the status of the measuring device, and a switching means which is operable in response to signals from the controller to selectively connect each of the sensing unit and the indicator means to the energy store.

Claims

1. Apparatus for measuring at least one of the level and the velocity of a media in a channel, the apparatus including a remote measuring device which comprises: a sensing unit having at least one sensing assembly arranged to measure at least one of the level and the velocity of the media, a two-wire interface arranged to receive power from an external power source and permit data transfer between the sensing assembly and an external control unit over the two-wire interface, an energy store for storing energy transmitted to the measurement device over the two-wire interface, a controller, and characterised in that the remote measuring device further comprises: an indicator for providing in-situ feedback to a user on the status of the measuring device, and one or more switches operable in response to signals from the controller to selectively connect each of the sensing unit and the indicator to the energy store.

2. Apparatus according to claim 1 in which the one or more switches comprises a first switch that is connected in series between the energy store and the sensing unit and a second switch that is connected in series between the energy store and the indicator.

3. Apparatus according to claim 1 in which the one or more switches are configured such that one or all of the switches are normally open in the absence of a respective control signal from the controller such that with the controller disconnected from the energy store the sensing unit and the indicator are disconnected from the energy store.

4. Apparatus according to claim 1 which further includes a timer circuit which draws power from the energy store and which in use may be activated by the controller prior to the controller putting itself into a sleep mode, the timer circuit awakening the controller after a predetermined or dynamically determined period of time has elapsed.

5. Apparatus according to claim 4 in which the timer circuit includes a third switch which selectively connects the controller to the energy store configured such that when the controller is in the sleep mode the third switch is open to isolate the controller from the energy store.

6. Apparatus according to claim 1 in which the two-wire interface is arranged to function with the well-known 4-20 mA current loop standard.

7. Apparatus according to claim 1 in which the feedback provided by the indicator is in a form that can be interpreted by an installer without the requirement of an additional device.

8. Apparatus according to claim 1 in which the indicator includes one or more of: a visual indicator in the form of a light signal on the enclosure of the device; an audio indicator in the form of sound emitted by the device; and a graphical user interface in particular an electronic paper display, such that information is conveyed via characters and symbols; and a mechanical vibrator that induces vibration on the enclosure.

9. Apparatus according to claim 1 in which the indicator is controlled by the controller so as to operate in an installation mode at a first instant and in a measurement mode at a second instant.

10. Apparatus according to claim 9 in which the controller is configured to cause the indicator to switch into the installation mode in response to a command signal received across the two wire interface or to a command signal received by a wireless receiver of the apparatus having been transmitted over a wireless communication link.

11. Apparatus according to claim 1 which further includes an external control unit which is connected to the measurement device through the two wire interface and in use may be sited at a location remote from the measurement device.

12. A method of operation of the apparatus of claim 1, in which the controller monitors and replenishes the energy store from the two-wire interface by disabling power to the sensor unit and the indicator.

13. The method of claim 12 further comprising disabling power to the controller and transferring control to a timed trigger circuitry to maximise power saving, the method returning power to the controller after the timed trigger circuit has determined an elapsed time.

14. The method of claim 12 comprising during sensor installation in the installation mode using the indicator as a user feedback tool for optimisation of the quality of the installation.

15. The method of claim 12 comprising processing measurement parameters such as received signal strength from the sensor unit versus distance to the media measured to assist the user in determining if the installation is optimal, followed by a session of indicator activation to convey the information.

16. The method of claim 12 comprising setting the loop current to maximum during operation in the installation mode and disabling signalling on the loop.

17. The method of claim 12 comprising during operation in a measurement mode setting the loop current to be proportional to the measurement value, whilst the indicator provides updates on device status and application condition.

Description

[0078] FIG. 1 schematically illustrates a channel including a device for measuring the flow of media in the channel;

[0079] FIG. 2 schematically illustrates a first embodiment of an apparatus according to a first aspect of the invention;

[0080] FIG. 3 is shows in more detail the functional parts of the remote measurement unit of the apparatus of FIG. 2;

[0081] FIG. 4 shows in more detail the functional parts of the external control unit of the apparatus of FIG. 2;

[0082] FIG. 5 shows the current applied to the loop during a charging mode;

[0083] FIG. 6 shows the current applied to the loop during a measurement mode;

[0084] FIG. 7 shows the current applied to the loop during an installation mode; and

[0085] FIG. 8 shows the current applied to the loop during an alert mode.

[0086] FIG. 1 shows a schematic illustration of a channel 1 carrying a flowing media 2, such as water. A remote measuring device 3 is positioned in the channel 1, above the water surface 4, to measure in this embodiment the flow rate of the water 3. The remote measuring device 3 includes a sensing assembly which in this example has two sensor devices. The first sensor assembly 5 is a level measurement device, and the second sensor assembly 6 is a velocity measurement device. Both level and velocity measurement assemblies may be combined to form a single device, or the flow measurement device may measure only level or only flow.

[0087] FIG. 2 shows the inclusion of the remote measuring device 3 in a complete measurement apparatus. The remote measuring device 3 is connected by a two-wire field loop 7 to an external control unit 8 which is in turn connected to a loop power supply 9. The two wires of the loop 7 carry power and signals to and from the remote measuring device 3 allowing the external control unit 8 to be located at a more convenient central location. In this example the two-wire loop is 7 configured in accordance with the IEC standard for fieldbus configuration IEC 61784/61158 set by the International Electrotechnical Commission. The loop power supply 9 provides a constant voltage, for example 24 volts, with the external controller and the remote measuring device setting the current in the loop 7. In use, power for the remote measuring device 3 is supplied across the loop 7 and any measurements made by the remote measuring device 3 are communicated across the loop 7 to the external control unit 8 using analogue current amplitude modulation.

[0088] FIG. 4 shows the main components of the external control unit 8. It comprises a controller 8a, a memory 8b which stores instructions, a user interface 8c through which a user can operate the external control unit 8, the controller 8a including a microprocessor for computational calculations, data communication means 8d to receive instruction and transmit data, and a power source 8e.

[0089] The user interface 8c also allows for output of the measurements taken by the measuring device 3 to the user. Optionally, information on device status may also be provided through the user interface 8c. In addition to or instead of the user interface, the external control unit 8 may comprise a wireless communications interface that allows output of the measurement information, and optionally device status, by wireless communications means.

[0090] Various wireless communications technologies may be used. For example, the wireless communications interface may use short range communications technologies such as WiFi, BTLE, RFID, BlueTooth, Digital Enhanced Cordless Telecommunications (DECT) or ZigBee. Alternatively, longer range communications technologies such as 3G, 4G or 5G signals and other cellular signals may be used.

[0091] In the case of short range communications technologies, the power of any transmitter in the external control unit 8 may be controlled to modify the range of the communications. This may provide an additional security feature, ensuring that only users within a defined geographic area can access the signals. For example, where the remote measuring device 3 and external unit 8 are provided in a pumping station, the power of the transmitter may be set so that only users within the pumping station can access the signal.

[0092] Further encryption and other security measures may be used.

[0093] The use of short and/or long-range wireless communications allows the user interface to be presented to a user through a separate device, such as a tablet, mobile phone, computer or the like. Users may also provide input through any such device, in a similar manner to how they would provide input through the user interface 8c.

[0094] The user interface 8c may also be presented to a remote user by connection of the external control unit to an external network such as the internet.

[0095] FIG. 3 shows the remote measuring device 3 in more detail. Each block in FIG. 3 represents a key functional part of the device, with a solid line between blocks representing a path along which the part can draw power or supply power to other functional parts. A dashed line represents a path along which control signals or measurement data can be passed between blocks either unidirectionally or bidirectionally. The skilled person will appreciate that a common conductor could be used to carry both power and for signaling or measurements. All the parts shown may be located within a common housing (not shown) to protect them from the environment.

[0096] The device 3 comprises an energy store 10 which is connected to the two wires of the field loop 7 and thereby back to the external control unit 8. The energy store 10 will charge up when the current flowing from the external control unit 8 to the energy store 10 exceeds the total instantaneous power consumption of the functional parts of the remote measuring device 2. When no current is supplied, or at any other time when the power consumed by the remote device 3 exceeds that which can be drawn at that time from the loop 7, the energy in the energy store 10 will deplete. The purpose of the energy store 10 is to enable more instantaneous power to be drawn by the remote device 3, in particular the power-hungry sensor apparatus, than is available over the field loop 7.

[0097] The remote measuring device 3 also includes one or both of the sensor assemblies 5, 6 shown in FIG. 1. This is indicated in FIG. 3 as a radar sensor assembly 11 in this example that measures the level of the fluid.

[0098] In addition to the sensor assembly 11 the device 3 includes an indicator means 12. This comprises in this example a single multi-color light emitting diode and a driver. The color, intensity of light emitted by the indicator means 12 can be modulated to provide status or installation information as will be explained hereinafter.

[0099] The radar sensor assembly 11 and the indicator means 12 are each selectively connected to the energy store 10 by respective switches. A first switch 13 when closed supplies power to the indicator driver of the indicator means 12. A second switch 14 when closed provides power to the radar sensor assembly 11.

[0100] The heart of the remote device is a controller 15. This may comprise a microcontroller, a remote memory and a set of instructions stored in the remote memory that may be executed by the controller. The controller 15 is connected to the energy store 10 through a third switch 16 when the switch is closed. The controller comprises a microprocessor which when drawing power from the energy store 10 executes program instructions stored in an area of memory 17.

[0101] The controller performs several functions: [0102] to manage the energy in the energy store by controlling switches that selectively connect the controller, the sensor apparatus and the indicator means to the energy store (charging mode); [0103] to receive measurement values from the sensor apparatus and set a loop current that is a function of the measurement value thereby to communicate back to the external controller (a measurement mode); and [0104] to drive the indicator means that provides status information (indicator mode) and assists a user in the installation of the device (installation mode).

[0105] Each of these functions is described in detail below.

[0106] Energy Store Management (Charging Mode)

[0107] The energy store 10 is permanently connected to the loop 7 and in a charging mode is disconnected from the sensor apparatus 11 and the indicator means 12 by the controller 15 opening the switches 14 and 13. The controller 15 enters this mode when it determines that the energy in the energy store 10 has dropped below a predefined threshold. It may also enter this mode in response to a defined current being detected on the loop 7, allowing the external control unit 8 to force entry to this mode. The mode may also be entered as part of a cycle through the other modes, for instance this mode may be entered on exiting the measurement mode or on exiting the indicator mode of installation mode.

[0108] The controller 15 may maintain the charging mode until the energy stored in the energy store 10 exceeds a predetermined upper threshold, for example an 80 percent charge of the energy store 10.

[0109] In the charging mode the controller 15 does not communicate with the indicator means 12 or the radar sensor assembly 11. The controller 15 may remain connected to the energy store 10 when in this mode. The external control unit 8 applies a maximum current to the loop 7 when in this mode as shown in FIG. 5.

[0110] Measurement Mode

[0111] In this mode the controller 15 closes the switch 14 to connect the radar sensor assembly 11 to the energy store 10. When this happens the radar sensor assembly 11 will continuously or intermittently transmit a signal to the controller 15 indicative of a value of the measurement that is made, for example a digital signal encoding the level of the media or encoding the flow rate. The controller 15 receives this signal and sets an appropriate current at the output terminal of the loop 7, the current set being in the range 4 mA to 20 mA and proportional to the value of the measurement. This is shown in FIG. 6. The external control unit detects and converts this current to a voltage signal, for instance by measuring the voltage dropped across a fixed resistance in series with the loop wire returning from the remote measurement device 3.

[0112] During the measurement mode the indicator means 12 is isolated from the energy store by opening the switch 13. This ensures that the indicator means 12 does not draw energy from the energy store 10 during the measurement mode.

[0113] Indicator Mode

[0114] Entry to this mode is achieved by the controller 15 closing the switch 13 to connect the indicator means 12 to the energy store 10 and opening the switch 14 to isolate the radar sensor assembly 11 from the energy store 10 if that switch is not already open. The controller 15 sends control signals to the driver of the indicator means causing the LED to be modulated to encode status information that can be viewed by a user, such as the health of the energy store 10, state of charge, fault codes if a fault has been detected by the controller and so on. No measurements are made in this mode, and energy may be drawn from the energy store 10 and from any current set on the loop by the external control unit 8.

[0115] Installation Mode

[0116] In this mode, the switches 13 and 14 are set by the controller 15 so that both the radar sensor assembly 11 and the indicator means are connected to the energy store 10 at the same time. In this mode, the controller 15 takes readings of the inclination of the measurement device 3 from a tilt sensor 17 built into the remote measuring device 3 and from radar sensor assembly 11 to determine the quality of the measurement signal, e.g., the signal strength. The controller 15 then commands the indicator means 12 to output information by modulating the LED that assists a user in setting up the measurement device correctly. This may comprise, for example, a pass or fail signal with a pass being indicated when the measuring device is correctly installed and a fail when it is not. The color of the LED may be set to red for a fail and green for a pass, or some other encoding strategy may be used.

[0117] To conserve the energy in the energy store the external control unit 8 may at this time set the loop current to a maximum value, for example in excess of 20 mA, and the signaling on the loop is disabled. Any measurement information obtained in that mode may be conveyed using the indicator means. This is shown in FIG. 7.

[0118] It will be apparent from the above description that the external control unit 8 behaves as a master, and controls the operation of the remote measurement unit 3, as a slave. In particular, the external control unit 8 may control when the remote measurement unit 3 enters each of the modes of operation. The operation of the external control unit 8, and hence the remote measurement unit 3 as a whole is managed by the external control unit 8.

[0119] Switching into installation mode may be carried out by user input via digital modulation on the loop 7 or over a wireless communication link. Alternatively, the remote measurement unit may be switched into installation mode by other forms of user input such as the motioning of the unit in a pre-determined pattern which is detected by the tilt sensor, then automatically returning to measurement mode after a configurable duration of inactivity.

[0120] During installation of the measurement device 3, the indicator LED is used as a user feedback tool for optimization. The controller 15 alternates between taking measurement and providing feedback to the user, replenishing the energy store 10 in between. Measurement parameters such as received signal strength versus distance may be utilized to determine if the installation is optimal, followed by a session of indicator activation to convey the information. Other criteria based on angle of installation, or a weighted combination of signal strength and tilt angle may be used.

[0121] Alert Mode

[0122] An optional alert mode may also be selected by the controller. This mode is entered whenever the value measured by the radar sensor assembly enters an alert region defined as a range of values in which the measured level or velocity warrants further attention by the user or the control system. The alert region may be pre-determined or adaptive. The alert region may be scaled to correspond with higher current in the loop to maximize available power whilst operating in alert conditions. For example, for a device measuring level which can vary over a range of 0 to 3 meters, the 4 to 20 mA available will be scaled accordingly, i.e. 0 meter=>4 mA, and 3 meters=>20 mA. This is fine if 2.5 to 3 meters is the alert region, as the device will be indicating close to 20 mA and so plenty of current on the loop to use. However, in applications where 0 to 0.5 m is the alert region, then the loop will only have around 4 mA, which is very restrictive. To get around this, one can reverse the scaling so 0 to 3 meters is proportional from 20 mA to 4 mA instead, i.e. 0 meter=>20 mA, and 3 meter=>4 mA. The ensures power is maximized when in the alert region in each situation.

[0123] If the velocity or level is deemed to be far or rapidly moving away from the alert region, the controller may reduce frequency of measurement. The controller may also cut off power to itself and transfer control to a very low power timer circuitry that will restart the controller at pre-set intervals. This mechanism enables excess capacity in the power store to be filled up. The controller monitors the velocity or level, and as application condition approaches the alert region, the frequency of measurement and status indication may be increased with the higher signaling current on the loop and excess power storage.

[0124] Sleep Mode

[0125] A further optional mode that may be selected by the controller 15 is a sleep mode. In this mode the controller 15 initiates a low power timed trigger 18 and immediately after, or coincident with this, opens the switch 16 to disconnect power to the controller and opens the switches 13 and 14. The energy store in this mode is only connected to the low power timed trigger 18. The trigger counts until a predefined count value corresponding to a predefined elapsed time, or to a count value that may be set dynamically by the controller on initiating the trigger. Once the trigger count value is reached, the switch 16 is opened to reconnect power to the controller 15. This awakens the controller from the sleep mode.

[0126] The controller 15 may be provided and configured to operate the various systems or functions of the apparatus or parts thereof. The controller 15 (which may comprise a micro-controller) may be a suitable computer control for example, including a computing device that may comprise one or more processor(s) or microprocessors, PLC controllers or any other suitable system, configured to execute computer-executable instructions, such as instructions composing operation of one or more components of the apparatus. A computer typically includes a variety of computer readable media and can be any available media that can be accessed by computer. The system memory may include computer storage media in the form of volatile and/or nonvolatile memory such as read only memory (ROM) and/or random access memory (RAM). By way of example, and not limitation, there may be provided an operating system, application programs, other program modules, and program data. A user or operator is enabled to enter commands and information into the computer, such as through a user interface 8c. In this example, the controller 15 may include a suitable interface to allow setting and selection of operation of the apparatus and/or other associated components or systems. The controller may thus operate the remote sensing device 3, the external control unit 8 and/or other equipment or components as described, which may be performed by an unskilled operator. The controller 15 may include the use of sensors to monitor all aspects of operation of the apparatus, such as level measurement device, a velocity measurement device, or any other suitable sensor for monitoring operating functions of the apparatus.

[0127] While specific examples of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details are contemplated in the invention. These examples are thus meant to be illustrative only and not limiting as to the scope of the invention as set forth in the appended claims and any and all equivalents thereof.