Utility meter including temperature sensor detection algorithm

Abstract

A utility meter for measuring thermal energy delivered to a consumption point by a fluid supplied via a supply flow and a return flow, the utility meter comprising: a flow meter unit for measuring a supply flow rate or a return flow rate of the fluid; a pair of temperature sensing probes for measuring the temperature of the supply flow and the return flow, each temperature sensing probe comprising a resistance temperature device; and a calculator device configured to execute a measurement algorithm for determining an amount of thermal energy delivered to the consumption point over a period of time based on the flow rate received from the flow meter unit and the temperature received from the temperature sensing probes, respectively; wherein the calculator device is configured to detect the type of resistance temperature devices included in the temperature sensing probes and adapt the measurement algorithm according to the type of the resistance temperature device.

Description

Technical Field

[0001] The present invention relates to a utility meter for measuring thermal energy (such as heating or cooling) that is configured to autonomously detect the type of temperature sensing probe connected to the meter. Background Art

[0002] Utility meters are used to measure the flow and consumption of fluids from utilities such as heating, cooling or water. Utility meters, such as heat meters for heating or cooling, measure flow and calculate consumption over a period of time. When measuring heat or cold delivered to a point of consumption, both flow and temperature must be measured to determine consumption. Flow can be measured using various technologies such as mechanical flow meters and ultrasonic flow meters. Temperature can also be measured using various technologies such as thermocouples, thermistors, or resistance temperature devices (RTDs).

[0003] Temperature sensing probes that utilize resistance temperature devices are commonly used due to their accuracy and long-term stability. When using a probe that includes a resistance temperature device, temperature changes are detected by measuring changes in the resistance of the RTD. The resistance of the RTD changes with temperature in a known manner, and by continuously monitoring the resistance, the temperature change can be detected. A common material for a resistance temperature device is platinum, but other metals can also be used.

[0004] Resistive temperature devices are classified by the material they are made of and the reference resistance of the RTD in ohms (Ω) at 0°C. A common material is a platinum (Pt) device, which has a reference resistance of 100 or 500 ohms at 0°C. Such devices are designated Pt-100 and Pt-500, respectively.

[0005] Traditionally, utility meters are configured during manufacturing to use a sensing probe that includes a specific type of RTD, such as Pt-100 or Pt-500. Since the measurement algorithm varies by sensor type, the configuration is done during manufacturing. When a utility meter has been configured to use a probe with a specific type of RTD, only probes using that type of RTD can be connected to the utility meter during installation.

[0006] However, this creates variances, and creating variances during manufacturing should be deferred as far downstream in the value chain as possible. On the other hand, configuring utility meters during installation can increase the risk of installation errors, leading to erroneous consumption measurements.

[0007] Therefore, it would be advantageous to be able to use a utility meter that includes a temperature sensing probe that includes different types of resistance temperature devices.

[0008] Purpose of the Invention

[0009] It is an object of the present invention to provide an alternative to the prior art. In particular, it is an object of the present invention to provide a utility meter that allows the connection of temperature sensing probes comprising different types of resistance temperature devices. Summary of the invention

[0010] In a first aspect of the present invention, the above-mentioned objects and several other objects are intended to be achieved by providing a utility meter for measuring thermal energy delivered to a consumption point by a fluid supplied via a supply flow and a return flow, the utility meter comprising: a flow meter unit for measuring the supply flow rate or the return flow rate of the fluid; a pair of temperature sensing probes for measuring the temperature of the supply flow and the return flow, each temperature sensing probe comprising a resistive temperature device; and a calculator device configured to execute a measurement algorithm for determining the amount of thermal energy delivered to the consumption point over a period of time based on the flow rate received from the flow meter unit and the temperature received from the temperature sensing probes, respectively; wherein the calculator device is configured to detect the type of resistive temperature device included in the temperature sensing probes and adapt the measurement algorithm according to the type of the resistive temperature device. The type of the resistive temperature device included in the temperature sensing probe is detected using a sensor detection algorithm, the algorithm comprising the following steps:

[0011] - attempting to measure the temperature using a measurement algorithm adapted for a first type of temperature sensing probe, such as a temperature sensing probe comprising a Pt-100 type resistance temperature device,

[0012] - attempting to measure the temperature using a measurement algorithm suitable for a second type of temperature sensing probe, such as a temperature sensing probe comprising a Pt-500 type resistance temperature device, and

[0013] -Determine which temperature measurements are valid.

[0014] Based on knowledge of the validity (ie, correctness) of the temperature measurements made during the sensor detection algorithm, the computer device of the utility meter selects a measurement algorithm that matches the temperature sensing probe. The selected measurement algorithm is then subsequently used by the utility meter in daily operation.

[0015] An advantage of the sensor detection algorithm is that different types of temperature sensing probes can be connected to the utility meter or the calculator device, and the calculator device can detect the effective temperature difference independent of the type of resistance temperature device used in the temperature sensing probe connected to the calculator device.

[0016] Typically, the calculator device of the utility meter is set to a default measurement algorithm at the factory, and the algorithm corresponds to the RTD of the temperature sensing probe. Advantageously, the sensor detection algorithm can be started when a quality check is performed in the factory or when the utility meter is installed or when a maintenance technician installs a new probe. When started, the sensor detection algorithm of the utility meter initially assumes that a specific temperature probe is connected, and usually assumes the default settings or the last settings. The resistance range (i.e., the resistance that varies with temperature) of the probe is known to the meter. The measured resistance value is then compared with the data value within the known range, and if the measured resistance value is outside the range, the initial assumption is abandoned and a new assumption is made. This time it is assumed that another type of temperature sensing probe is connected and another measurement algorithm is used. A new measurement is performed, and if the measured resistance value is within the ohm range for this type of sensor, the type of temperature probe can be determined. The technical effect of this sensor detection algorithm is that the calculator device of the utility meter automatically performs only one or a few measurements to achieve effective verification of the connected temperature sensing probe in a short time. The algorithm is simple and does not require time or data storage to establish the complete characteristics of the probe to complete the verification.

[0017] Advantageously, after taking the sensor detection measurement, the configuration of the utility meter is permanently changed to another measurement algorithm only if the measurements performed during the sensor detection algorithm provide completely reliable data. Sometimes, even if the sensor in reality matches the measurement algorithm, floating voltages in the sensing probes can lead to erroneous measurements. Therefore, the detection algorithm is repeated several times before automatically deciding to change the measurement algorithm.

[0018] If a measurement made on a temperature sensing probe using a first signal injection type during a sensor detection algorithm results in a sensor determination that is different from another determination of the same temperature sensing probe using said first signal injection type, the configuration will not be changed to another measurement algorithm. This means that if contradictory measurements occur, the original or actual configuration file will be maintained.

[0019] It is particularly advantageous that the resistance ranges of the RTDs of the two temperature sensing probes do not overlap. When designing a utility meter and selecting the type of temperature sensing probe, care should be taken that the two sensing probes do not give a signal output at the same temperature, for example this can be achieved with a first probe covering the range of 100 to 180 ohms and a second probe covering 500 to 880 ohms. This non-overlap makes detection of the temperature sensing probes easier.

[0020] The terms "type of temperature sensing probe," "type of resistance temperature device," "type of sensing probe," and "type of sensor probe" may be used interchangeably to refer to different types of temperature sensing probes using different types of resistance temperature devices.

[0021] This and other aspects of the invention will become apparent from the following description with reference to the embodiments described. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The utility meter according to the present invention will now be described in more detail with reference to the accompanying drawings. These drawings illustrate one way of implementing the invention and should not be construed as limiting other possible embodiments falling within the scope of the appended claims.

[0023] Figure 1 A schematic diagram showing a utility meter for measuring thermal energy,

[0024] Figure 2a A circuit diagram showing a circuit for measuring temperature using a resistance temperature device,

[0025] Figure 2b A circuit diagram showing another circuit for measuring temperature using a resistance temperature device, and

[0026] Figure 3 A diagram demonstrating a sensor detection algorithm is shown. DETAILED DESCRIPTION

[0027] Figure 1 A schematic diagram of a utility meter 1 for measuring thermal energy delivered to a consumption point by a fluid supplied via a supply stream 20 and a return stream 21 is shown. The utility meter comprises a calculator device 10 receiving flow information from a flow meter unit 13 and temperature information from a pair of temperature sensing probes 11,12.

[0028] In the illustrated embodiment, the flow meter unit is installed in the return flow to measure the return flow rate of the fluid. In another embodiment, the flow meter unit can be installed in the supply flow to measure the supply flow rate. The temperature sensing probe is installed to measure the temperature of the supply flow and the return flow respectively.

[0029] In the illustrated embodiment, the calculator device 10, the flow unit 13 and the temperature sensing probe are shown as separate units connected by cables. However, as is known in the art, two or more of these devices may be integrated into one common device.

[0030] The flow meter unit may comprise an ultrasonic flow meter which uses transit time flow measurements to determine the flow rate of the return flow. The operating principle of known transit time flow meters is based on the transmission of ultrasonic signals to a transducer upstream and downstream in the flowing fluid between. Based on the transit time difference between the oppositely propagating signals, the flow rate is determined. However, the flow meter unit may also comprise a flow meter using other known technologies for measuring fluid flow, such as a mechanical flow meter or a magnetic induction flow meter.

[0031] The temperature sensing probe is a pair of matched Pt-S00 or Pt-100 type probes. However, the temperature sensing probe may also include other specifications of resistance temperature devices that use metal resistors other than platinum and have different reference resistances. For example, the resistance temperature device may have a reference resistance of 50 to 1000 ohms at 0°C.

[0032] The computer device comprises a temperature measuring circuit 101 to which the wires of the temperature sensing probe are connected, such as Figure 2a and Figure 2b As shown. In addition, the computer device is configured to execute a measurement algorithm for determining the amount of thermal energy delivered to the consumption point over a period of time based on the flow rate received from the flow meter unit and the temperature received from the temperature sensing probe, respectively. The measurement algorithm depends on the type of temperature sensing probe used and is configured to measure inlet and outlet temperatures in the range of 0.00°C to 195.00°C.

[0033] During each temperature measurement, the calculator device Figure 2a and Figure 2b The schematic electrical diagram shown in Figure 1 performs signal injection and sends a measurement current through each of the two temperature sensing probes. In one embodiment, when the Pt-S00 sensing probe is connected to the computer device, the measurement current is about 0.5 mA, and when the Pt-100 probe is connected, the measurement current is about 2.5 mA. The measurement current is sent through the temperature sensor only during the brief duration of the temperature measurement, thereby reducing the effective power accumulated in the sensor element and its effect on the self-heating of the temperature sensor.

[0034] See also Figure 2a , the temperature sensing probe connected to the computer device is a 4-wire sensing probe. Two power lines 111 are connected to the constant current generator 101 and are used to power a resistance temperature device 113 (RTD), and two sensing lines 112 are used to measure the voltage drop across the RTD. Amplifier 114 amplifies the voltage difference across the RTD 113.

[0035] exist Figure 2b In another embodiment shown, only two wires 111 are connected to the RTD 113. In this embodiment, the same wires are therefore used to provide the supply current and to measure the voltage drop across the RTD.

[0036] The above use of a constant current generator should be considered as an exemplary embodiment only. Other measurement circuits such as circuits including a voltage source, a voltage divider, or a Wheatstone bridge may also be used to measure the change in RTD resistance. In some embodiments, a 3-wire temperature sensing probe may also be used as contemplated by the skilled person.

[0037] The computer device is further configured to use a sensor detection algorithm to detect the type of temperature sensing probe connected to the computer device (i.e., what type of resistance temperature device is included in the sensing probe). Based on the detected type of temperature sensing probe, the measurement algorithm is adapted to use the correct measurement current and correctly associate the resistance change of the RTD with the temperature change.

[0038] refer to Figure 3 , describes a sensor detection algorithm that implements a two-step process for detecting the type of temperature sensing probe. In the first step, the sensor detection algorithm first attempts to measure the temperature assuming that a first type of temperature sensing probe is connected to the computer device. In one embodiment, a Pt-500 type sensing probe is first used, however other types of sensing probes may also be used for the first measurement attempt. After the first attempt, the sensor detection algorithm attempts to measure the temperature assuming that a second type of sensing probe (such as a Pt-100 sensing probe) is connected to the computer device.

[0039] After these two measurement sequences, the measurement results are analyzed and the sensor detection algorithm determines whether the results are valid. The validity of the measurement results can be determined in a variety of ways known to the skilled person. In one embodiment, the measured voltage drop is input to an analog-to-digital converter (ADC) to determine whether the voltage indicates that the temperature sensing probe is of the type assumed.

[0040] In one embodiment, the sensor detection algorithm is configured to determine whether a Pt-100 or a Pt-500 temperature sensing probe is connected to the computer device. However, the sensor detection algorithm may also be configured to determine whether other types of sensing probes are connected to the computer device, such as whether a Pt-500 and a Pt-1000 temperature sensing probe are connected, or a Pt-100 and a Pt-1000, or a Pt-100, a Pt-500, and a Pt-1000. Pt-100, Pt-500, and Pt-1000 should only be considered as examples, and temperature sensing probes including resistive temperature devices having other reference resistors may also be used.

[0041] If the measured voltage indicates that the resistance of the RTD is within the range of 100-180 ohms, the sensor detection algorithm can consider the measurement result of the Pt-100 sensing probe to be valid. Similarly, if the measured value indicates that the resistance of the RTD is within the range of 500-880 ohms, the measurement result of the Pt-500 sensing probe is considered to be valid. Those skilled in the art will readily recognize that wider or narrower ranges may also be applied.

[0042] If measurements of all temperature sensing probes of the first type or all temperature sensing probes of the second type (Pt-100 or Pt-500 in the exemplary embodiment) are deemed valid and measurements of the other type are deemed invalid, the algorithm preliminarily determines that a temperature sensing probe producing a valid result is connected to the computer device.

[0043] The first step of the sensor detection algorithm may be repeated multiple times, such as 2-4 times, and the algorithm may set an integer i to indicate the number of iterations performed.

[0044] After the first step, the sensor detection algorithm proceeds to the second step. In the second step, the algorithm determines whether all preliminary determinations indicate that the same sensor probe type is connected to the computer device. If this is the case, the computer device determines that the corresponding sensor probe type is connected and configures the computer accordingly. If not all preliminary determinations indicate that the same sensor probe type is connected to the computer device, the current configuration of the computer device can be maintained or not configured based on the sensor detection algorithm.

[0045] Table 1 details the logical sequence and measurement steps performed during the sensor detection algorithm. Three different scenarios A, B and C are shown. In all scenarios, the type of the two temperature sensing probes Sensor 1 and Sensor 2 connected to the calculator device is initially unknown to the calculator device of the utility meter. By default, the calculator device is configured to measure Pt-100 probes and the detection algorithm will determine in the next steps whether this is correct or whether it should switch to another measurement algorithm. In the first measurement step, it injects the current C-Pt-100, which in the case of a Pt-100 connected will produce a result within the operating range of Pt-100. In the table, the first measurement is made for sensor 1 under scenario A and the ohmic value so detected is within the operating range of Pt-100. The flag True is set. The next sensor 2 is measured and the flag True is set. The control device now changes the measurement algorithm to the Pt-500 algorithm and in the second measurement injects a signal injection type C-Pt-500 into sensor 1. The detected value falls outside the Pt-500 range and the flag False is set. The same result is obtained for sensor 2. The first measurement sequence for both sensors is now complete, but an iteration is performed in the second measurement sequence with the third and fourth measurements. The temperature measurement value of the Pt-100 is considered valid and the Pt-100 is identified as the actual temperature probe connected to the computer device. The original measurement algorithm is maintained, i.e., no swapping.

[0046] Table 1

[0047]

[0048] In scenario B, the control again assumes that a Pt-100 is connected to it. But in the first and third measurements, the results fall outside the range of Pt-100. Because all the results from the first to the fourth measurement do not contradict each other, the temperature measurements are considered valid and a final determination of a Pt-S00 sensor is made. The control switches the measurement algorithm from Pt-100 to Pt-500 and maintains this setting for future operations. In scenario C, the first measurement sequence for the first and second measurements indicates that the sensor type is Pt-100. But the second measurement sequence (i.e. iteration) gives an uncertain result in the fourth measurement of sensor 2, because this result contradicts the result False in the second measurement of sensor 2. In this case, the sensor detection algorithm decides not to change the measurement algorithm and therefore maintains the Pt-100 algorithm.

[0049] The present invention can be implemented by hardware, software, firmware or any combination of these. The present invention or some of its features can also be implemented as software running on one or more data processors and / or digital signal processors. The various elements of an embodiment of the present invention can be implemented physically, functionally and logically in any suitable manner, such as in a single unit, in multiple units or as a part for a separate functional unit. The present invention can be implemented in a single unit, or physically and functionally distributed between different units and processors.

[0050] Although the present invention has been described in conjunction with specific embodiments, it should not be interpreted as being limited in any way to the examples given. The scope of the present invention should be interpreted in accordance with the appended claims. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. In addition, references such as "a" or "an" should not be interpreted as excluding multiple. The figure marks used in the claims for the elements indicated in the figures should not be interpreted as limiting the scope of the present invention. In addition, the individual features mentioned in different claims can be advantageously combined, and the mention of these features in different claims does not exclude that the combination of features is not possible and advantageous.

Claims

1. A utility meter (1) for measuring thermal energy delivered to a consumption point by a fluid supplied via a supply flow (20) and a return flow (21), the utility meter comprising: - a flow meter unit (13) for measuring a supply flow rate or a return flow rate of the fluid; - a pair of temperature sensing probes (11, 12) for measuring the temperature of the supply flow and the return flow, each temperature sensing probe comprising a resistive temperature device; as well as - a computer device (10) configured to execute a measurement algorithm for determining the amount of thermal energy delivered to the consumption point over a period of time based on the flow rate received from the flow meter unit and the temperature received from the temperature sensing probes, respectively; Characterized in that the calculator device (10) is configured to detect the type of the resistance temperature device (113) included in the temperature sensing probes (11, 12) and to adapt the measurement algorithm according to the type of the resistance temperature device, and the type of the resistance temperature device (113) included in the temperature sensing probes is detected using a sensor detection algorithm, the sensor detection algorithm comprising the following steps: - attempting to measure the temperature using a measurement algorithm adapted for a first type of temperature sensing probe, such as a temperature sensing probe comprising a Pt-100 type resistance temperature device, - attempting to measure the temperature using a measurement algorithm suitable for a second type of temperature sensing probe, such as a temperature sensing probe comprising a Pt-500 type resistance temperature device, and - determine which temperature measurements are valid, - if the measurements of all temperature sensing probes of the first type or all temperature sensing probes of the second type are considered valid and the measurements of the other type are considered invalid, The sensor detection algorithm then determines that a temperature sensing probe that produces a valid result is connected to the computing device (10).

2. The utility meter (1) according to claim 1, wherein: The resistance temperature device (113) is of the platinum type having a reference resistance of 50 to 1000 ohms at 0°C.

3. The utility meter (1) according to claim 1 or 2, wherein: The calculator device (10) is configured to detect whether the resistance temperature device included in each temperature sensing probe connected to the calculator device is of the Pt-100 type or the Pt-500 type.

4. The utility meter (1) according to claim 3, wherein: The sensor detection algorithm includes performing a plurality of iterations of attempting to measure temperature using measurement algorithms appropriate for the first type and the second type of temperature sensing probes, respectively, before the utility meter is configured to use either the first type or the second type of temperature sensing probe.

5. The utility meter (1) according to claim 4, wherein: If a measurement made on a temperature sensing probe (11, 12) during the sensor detection algorithm using a first signal injection type results in a sensor determination that is different from another determination of the same temperature sensing probe using the first signal injection type, the configuration is not changed to another measurement algorithm.

6. The utility meter (1) according to claim 1 or 2, wherein: The ohmic ranges of the resistive temperature devices (113) in the first type and the second type of temperature sensing probes (11, 12) are different and do not overlap.

7. The utility meter (1) according to claim 2, wherein: The resistance temperature device (113) is a Pt-100, Pt-500 or Pt-1000 resistance temperature device.

8. The utility meter (1) according to claim 4, wherein: The temperature sensing probe of the first type or the temperature sensing probe of the second type is of the Pt-500 or Pt-100 type.

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