Liquid condition detection sensor

Abstract

This liquid state detecting sensor is provided with: an electrode unit (10) including a pair of electrodes which are arranged in the flow path of a liquid, and which are provided facing one another; a voltage value acquisition time setting unit (30) for setting a voltage value acquisition time, which is the length of time during which an inter-electrode voltage value of the pair of electrodes of the electrode unit (10) is to be acquired; a voltage value acquiring unit (40) for acquiring the inter-electrode voltage value during the voltage value acquisition time; and an electrical conductivity calculating unit (60) for calculating the electrical conductivity of the liquid on the basis of the inter-electrode voltage value after a predetermined time has elapsed from the start of the voltage value acquisition time, among the inter-electrode voltage value acquired by the voltage value acquiring unit (40).

Description

[Technical Field]

[0001] The present invention relates to a liquid-condition detection sensor. [Background technology]

[0002] Devices for detecting the condition of oil, which is circulated and supplied to rotating and sliding parts to prevent wear and ensure smooth operation of these parts, are known. In this type of device, two electrodes are installed parallel to each other in the oil flow path, and an AC voltage is applied between the two electrodes to measure the inter-electrode voltage value. The permittivity and conductivity of the oil are then calculated based on the obtained inter-electrode voltage value. The condition of the oil is then detected based on the calculated permittivity and conductivity (see, for example, JP2009-2693A). Summary of the Invention

[0003] However, in a device such as that described in JP2009-2693A, the interelectrode voltage value becomes unstable immediately after applying an AC voltage between the two electrodes, and there is a risk that the accuracy of the interelectrode voltage value during the interelectrode voltage value acquisition period will deteriorate. A similar phenomenon may occur when the interelectrode voltage value is obtained by applying a DC voltage between the two electrodes.

[0004] An object of the present invention is to provide a liquid-condition detection sensor that can accurately detect the state of a liquid by obtaining highly accurate conductivity.

[0005] According to one aspect of the present invention, a liquid condition detection sensor for detecting the condition of a liquid comprises: an electrode unit arranged in a flow path of the liquid and having a pair of electrodes arranged opposite each other; a voltage value acquisition time setting unit that sets a voltage value acquisition time, which is the length of time for acquiring an inter-electrode voltage value of the pair of electrodes of the electrode unit; a voltage value acquisition unit that acquires the inter-electrode voltage value during the voltage value acquisition time; and a conductivity calculation unit that calculates the conductivity of the liquid based on the inter-electrode voltage value acquired by the voltage value acquisition unit after a predetermined time has elapsed since the start of the voltage value acquisition time. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram showing the electrical configuration of the liquid-condition detection sensor according to the first embodiment. [Figure 2] FIG. 2 is a diagram showing a processing flow of the liquid-condition detection sensor according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing the relationship between the voltage value acquisition time, the inter-electrode voltage value, and the A / D converted waveform of the inter-electrode voltage value in the liquid-condition detection sensor according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing the electrical configuration of the liquid-condition detection sensor according to the second embodiment. [Figure 5] FIG. 5 is a diagram showing the processing flow of the liquid-condition detection sensor according to the second embodiment. [Figure 6] FIG. 6 is a diagram showing the electrical configuration of the liquid-condition detection sensor according to the third embodiment. [Figure 7] FIG. 7 is a diagram showing the processing flow of the liquid-condition detection sensor according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] First Embodiment The liquid-condition detection sensor 1 according to the first embodiment will be described below with reference to FIGS.

[0008] <Electrical configuration of liquid state detection sensor 1> 1, the liquid-condition detection sensor 1 according to this embodiment detects the condition of a liquid as a fluid flowing through a flow path, and includes an electrode unit 10, a DC voltage application unit 20 that applies a DC voltage to the electrode unit 10, a voltage value acquisition time setting unit 30 that sets a voltage value acquisition time, which is the length of time for acquiring the inter-electrode voltage value of the electrode unit 10, a voltage value acquisition unit 40 that acquires the inter-electrode voltage value during the voltage value acquisition time, a voltage value calculation unit 50 that calculates a voltage value based on the inter-electrode voltage value acquired by the voltage value acquisition unit 40, and a conductivity calculation unit 60 that calculates the conductivity of the liquid based on the voltage value calculated by the voltage value calculation unit 50. The voltage value acquisition time setting unit 30, the voltage value acquisition unit 40, the voltage value calculation unit 50, and the conductivity calculation unit 60 are all functions of a CPU 100.

[0009] The electrode unit 10 has, for example, a pair of electrodes arranged opposite each other and is installed in a flow path through which a liquid flows. The pair of electrodes of the electrode unit 10 are concentric cylindrical electrodes consisting of an inner electrode and an outer electrode with a gap d between them. Note that the pair of electrodes of the electrode unit 10 is not limited to a concentric cylindrical type, and may be, for example, a parallel plate type or a comb type.

[0010] DC voltage application unit 20 has a voltage source (not shown) that supplies a DC voltage, and a connection unit that connects the output of the voltage source to one electrode and the other electrode of electrode unit 10 in response to a control signal from CPU 100. In order to cancel out ionization of the electrode surface of electrode unit 10, DC voltage application unit 20 preferably applies a positive voltage and a negative voltage alternately to one electrode and the other electrode of electrode unit 10.

[0011] The voltage value acquisition time setting unit 30 sets a voltage value acquisition time, which is the length of time required to acquire an inter-electrode voltage value between a pair of electrodes of the electrode unit 10. Here, the inter-electrode voltage value is the potential difference between one electrode and the other electrode of the electrode unit 10. The voltage value acquisition time is the time from when the voltage value acquisition unit 40 starts acquiring the inter-electrode voltage value to when it finishes acquiring the inter-electrode voltage value, and is also the length of time from when the DC voltage application unit 20 starts applying a voltage between the electrodes of the electrode unit 10 to when it finishes applying the voltage. An initial value for the voltage value acquisition time is set in advance. However, for example, if the voltage value acquisition time is set longer, the number of inter-electrode voltage values acquired by the voltage value acquisition unit 40 increases, as described below, and the accuracy of the inter-electrode voltage value calculated by the voltage value calculation unit 50 improves. However, in this case, the time required for the conductivity calculation unit 60 to calculate the conductivity tends to be longer. On the other hand, if the voltage value acquisition time is set shorter, the accuracy of the inter-electrode voltage value calculated by the voltage value calculation unit 50 decreases, but the time required for the conductivity calculation unit 60 to calculate the conductivity tends to be shorter.

[0012] The length of the voltage value acquisition time to be set here will vary depending on the purpose of calculating the conductivity, the system requirements, etc. Therefore, for example, the liquid-condition detection sensor 1 may be provided with a touch panel, allowing the user to set the voltage value acquisition time by touching it. Alternatively, the liquid-condition detection sensor 1 may be connected to a network, and the voltage value acquisition time may be set from a management terminal or the like. Similarly, when the conductivity calculation unit 60 calculates the conductivity at predetermined intervals, it is also possible to set the interval for calculating the conductivity; in other words, the interval for performing a series of operations by the voltage value acquisition unit 40 to acquire multiple inter-electrode voltage values, as will be described later.

[0013] As shown in Fig. 3, the voltage value acquisition unit 40 acquires the inter-electrode voltage value during the voltage value acquisition time at predetermined time intervals. The voltage value acquisition unit 40 has, for example, an A / D converter (not shown). For example, the voltage value acquisition unit 40 acquires the inter-electrode voltage value of the electrode unit 10 at predetermined intervals in response to a control signal from the CPU 100. The inter-electrode voltage value is a continuously obtained analog voltage value. The voltage value acquisition unit 40 converts the acquired inter-electrode voltage value into a digital signal using the A / D converter and outputs the digital signal to the voltage value calculation unit 50 in the CPU 100.

[0014] The voltage value calculation unit 50 calculates the voltage value during the voltage value acquisition time based on a plurality of interelectrode voltage values acquired by the voltage value acquisition unit 40 after a predetermined time has elapsed since the start of the voltage value acquisition time (the start of acquisition of interelectrode voltage values and the start of application of DC voltage by the DC voltage application unit 20). The voltage value calculated by the voltage value calculation unit 50 is, for example, the average value (simple average) of the plurality of interelectrode voltage values. The voltage value calculation unit 50 outputs the calculated voltage value to the conductivity calculation unit 60. Here, the "predetermined time" refers to the time from the start of acquisition of interelectrode voltage values during the voltage value acquisition time until the interelectrode voltage value stabilizes, and is also the time from the start of application of DC voltage by the DC voltage application unit 20 until the interelectrode voltage value stabilizes. For example, the "predetermined time" is 150 ms.

[0015] The conductivity calculation unit 60 calculates the conductivity of the liquid based on the voltage value output from the voltage value calculation unit 50. Specifically, the conductivity calculation unit 60 calculates the resistance component between one electrode and the other electrode of the electrode unit 10 based on the voltage value output from the voltage value calculation unit 50, and calculates the conductivity (σ) of the liquid from the calculated resistance component. This calculates the conductivity of the liquid flowing through the flow path. Alternatively, the voltage value acquisition unit 40 may continuously acquire the inter-electrode voltage value of the electrode unit 10 as a digital voltage value, and the conductivity calculation unit 60 may acquire the inter-electrode voltage value acquired by the voltage value acquisition unit 40 at predetermined intervals in response to a control signal from the CPU 100. The conductivity calculation unit 60 may then calculate the conductivity of the liquid based on the average (simple average) of the acquired inter-electrode voltage values after a predetermined time has elapsed since the start of the voltage value acquisition period. In other words, the voltage value calculation unit 50 is not an essential component of the liquid condition detection sensor 1.

[0016] <Processing of liquid state detection sensor 1> The processing of the liquid-condition detection sensor 1 according to this embodiment will be described with reference to FIGS.

[0017] As shown in FIG. 2, first, the CPU 100 activates the DC voltage application unit 20 to apply a DC voltage to one electrode and the other electrode of the electrode unit 10 (step S101).

[0018] Next, CPU 100 activates voltage value acquisition unit 40. Voltage value acquisition unit 40 acquires an inter-electrode voltage value, which is the potential difference between one electrode and the other electrode of electrode unit 10, at predetermined intervals in response to a control signal from CPU 100. The inter-electrode voltage value is a continuously obtained analog voltage value. Then, the acquired inter-electrode voltage value is converted into a digital signal by an A / D converter and output to CPU 100 (step S102).

[0019] The CPU 100 stores the inter-electrode voltage value output from the voltage value acquisition unit 40 in a storage unit (not shown) (step S103).

[0020] Then, CPU 100 determines whether or not the voltage value acquisition time has elapsed since voltage value acquisition unit 40 started to acquire the inter-electrode voltage value (step S104). At this time, if CPU 100 determines that the voltage value acquisition time has not elapsed ("NO" in step S104), the process returns to step S102.

[0021] On the other hand, when CPU 100 determines that the voltage value acquisition time has elapsed since voltage value acquisition unit 40 started to acquire the inter-electrode voltage value ("YES" in step S104), it stops the operation of DC voltage application unit 20 and starts voltage value calculation unit 50 (step S105). Then, CPU 100 reads out the inter-electrode voltage value stored in the storage unit and outputs it to voltage value calculation unit 50.

[0022] The voltage value calculation unit 50 derives the voltage value by calculating the average value of multiple inter-electrode voltage values output from the storage unit, for example, from the start of the voltage value acquisition time (the start of acquisition of inter-electrode voltage values and the start of application of DC voltage by the DC voltage application unit 20) after a predetermined time has elapsed. The voltage value calculation unit 50 outputs the derived voltage value to the conductivity calculation unit 60.

[0023] The conductivity calculation section 60 calculates the conductivity of the liquid based on the voltage value output from the voltage value calculation section 50 (step S106), and the process ends.

[0024] <Actions and Effects> In the liquid condition detection sensor 1 of this embodiment, the voltage value acquisition unit 40 acquires inter-electrode voltage values during a voltage value acquisition time at predetermined intervals. The voltage value calculation unit 50 calculates a voltage value from multiple inter-electrode voltage values acquired by the voltage value acquisition unit 40 after a predetermined time has elapsed since the start of the voltage value acquisition time, and outputs the calculated voltage value to the conductivity calculation unit 60. The conductivity calculation unit 60 calculates the conductivity of the liquid based on the voltage values output from the voltage value calculation unit 50. That is, the conductivity calculation unit 60 calculates the conductivity of the liquid based on multiple inter-electrode voltage values acquired by the voltage value acquisition unit 40 after a predetermined time has elapsed since the start of the voltage value acquisition time. Therefore, the conductivity calculation unit 60 calculates the conductivity of the liquid based on at least the inter-electrode voltage values acquired by the voltage value acquisition unit 40, excluding those immediately after the start of the voltage value acquisition time (immediately after application of AC voltage to the electrode unit 10), when the inter-electrode voltage value is most unstable. As a result, the liquid-condition detection sensor 1 can prevent deterioration in the accuracy of the inter-electrode voltage value and obtain highly accurate conductivity, thereby enabling accurate detection of the state of the liquid.

[0025] Furthermore, in the liquid-condition detection sensor 1 of this embodiment, the predetermined time is the time from the start of the voltage value acquisition period until the inter-electrode voltage value stabilizes. In other words, because the conductivity calculation unit 60 calculates the conductivity of the liquid based on the stable inter-electrode voltage value, the liquid-condition detection sensor 1 can suppress deterioration in the accuracy of the inter-electrode voltage value and obtain highly accurate conductivity, thereby accurately detecting the state of the liquid.

[0026] Furthermore, the conductivity calculation unit 60 of the liquid condition detection sensor 1 in this embodiment calculates the conductivity of the liquid based on the average value of the inter-electrode voltage value after a predetermined time has elapsed since the start of the voltage value acquisition period. In other words, the conductivity calculation unit 60 calculates the conductivity of the liquid based on the average value (voltage value) of the inter-electrode voltage values acquired by the voltage value acquisition unit 40, excluding at least the inter-electrode voltage value immediately after the start of the voltage value acquisition period, when the inter-electrode voltage value is most unstable. Therefore, by suppressing deterioration in the accuracy of the inter-electrode voltage value and obtaining a highly accurate conductivity, the state of the liquid can be accurately detected.

[0027] Experiments have shown that there is a difference of approximately 10 mV in inter-electrode voltage between when the liquid-condition detection sensor 1 of this embodiment is processed and when it is not. This difference in inter-electrode voltage corresponds to approximately 380 pS / m in conductivity. If the target accuracy for the liquid-condition detection sensor's conductivity is set to ±30 pS / m or less, the accuracy achieved when the liquid-condition detection sensor 1 is not processed will deviate significantly from this target accuracy, and the impact will be significant.

[0028] Second Embodiment A liquid-condition detection sensor 1A according to the second embodiment will be described using Figures 4 and 5. In the first embodiment, the "predetermined time" was defined as "the time from the start of the voltage value acquisition period until the inter-electrode voltage value stabilizes," and was a predetermined time. In this embodiment, an example will be described in which the "predetermined time" is determined appropriately based on the inter-electrode voltage obtained from the voltage value acquisition unit 40.

[0029] <Electrical configuration of liquid condition detection sensor 1A> 4, the liquid-condition detection sensor 1A in this embodiment includes an electrode section 10, a DC voltage application section 20, a voltage value acquisition time setting section 30, a voltage value acquisition section 40, a voltage value calculation section 50A, a conductivity calculation section 60, and a predetermined time determination section 70. Note that components with the same reference numerals as those in the first embodiment have the same functions, and therefore detailed descriptions thereof will be omitted.

[0030] The voltage value calculation unit 50A calculates a voltage value based on a plurality of inter-electrode voltage values acquired by the voltage value acquisition unit 40 after a predetermined time has elapsed as determined by the predetermined time determination unit 70 as described below, and outputs the calculated voltage value to the conductivity calculation unit 60.

[0031] The predetermined time determination unit 70 determines the predetermined time, which is the time from the start of the voltage value acquisition period until the inter-electrode voltage value becomes stable, based on the inter-electrode voltage value acquired by the voltage value acquisition unit 40. The specific determination method will be described later.

[0032] <Predetermined Time Determination Process of Liquid-State Detection Sensor 1A> The predetermined time determination process of the liquid-condition detection sensor 1A in this embodiment will be described with reference to FIG.

[0033] The predetermined time determination unit 70 stores the inter-electrode voltage values acquired by the voltage value acquisition unit 40 in a storage unit (not shown) in the order of input (step S201).

[0034] The predetermined time determination unit 70 calculates a difference value, which is the difference between the inter-electrode voltage values stored in the memory unit for the Nth time and the (N+1)th time (the initial value of N is 1), and stores the difference value in the storage unit (step S202).

[0035] The predetermined time determination unit 70 then determines whether the stored difference value is within a predetermined range (step S203). Here, the "predetermined range" refers to the range of attenuation when the inter-electrode voltage value follows an expected attenuation behavior, as shown in FIG. 3, for example. That is, when the difference value is larger than the predetermined range, the input inter-electrode voltage value is zero data. That is, when the difference value of the inter-electrode voltage value acquired by the voltage value acquisition unit 40 is larger than the predetermined range, it is determined that the inter-electrode voltage value acquired by the voltage value acquisition unit 40 is not stable, and that the predetermined time, which is the time from the start of the voltage value acquisition time until the inter-electrode voltage value stabilizes, has not elapsed. When the predetermined time determination unit 70 determines that the stored difference value is not within the predetermined range ("NO" in step S203), it performs a process of incrementing N to N+1 (step S204) and transitions the process to step S202.

[0036] On the other hand, if the predetermined time determination unit 70 determines that the calculated difference value is within a predetermined range ("YES" in step S203), the voltage value calculation unit 50A determines that the predetermined time, which is the time from the start of the voltage value acquisition time until the interelectrode voltage value stabilizes, has elapsed. Then, the voltage value calculation unit 50A calculates the average value of the interelectrode voltage values input after the predetermined time, that is, the interelectrode voltage values stored in the storage unit after the interelectrode voltage value used to calculate the difference value, and outputs the calculated average value as the voltage value to the conductivity calculation unit 60 (step S205).

[0037] The conductivity calculation section 60 calculates the conductivity of the liquid based on the voltage value output from the voltage value calculation section 50A, and then ends the process.

[0038] <Actions and Effects> In this embodiment, the predetermined time determination unit 70 appropriately determines the "predetermined time" based on the inter-electrode voltage value obtained from the voltage value acquisition unit 40. Specifically, the predetermined time determination unit 70 determines whether the inter-electrode voltage obtained from the voltage value acquisition unit 40 is stable, and determines whether the "predetermined time" has elapsed. Therefore, the time required to calculate the conductivity can be shortened while maintaining the accuracy of the conductivity calculation in the conductivity calculation unit 60, and the state of the liquid can be accurately detected in a short time.

[0039] It should be noted that the number of inter-electrode voltage values used by voltage value calculation unit 50A to calculate the voltage values may be reduced depending on the predetermined time determined by predetermined time determination unit 70. In such a case, CPU 100A may actively change the voltage value acquisition time.

[0040] Third Embodiment A liquid-condition detection sensor 1B according to a third embodiment will be described with reference to FIGS. 6 and 7. In the voltage value acquisition unit 40 of the first embodiment, for example, due to the influence of external disturbance noise or the like, the acquired inter-electrode voltage value may occasionally become an abnormal value even after a predetermined time has elapsed. Even if such an abnormal value is included and an average value is calculated together with other inter-electrode voltage values, the error from the true value is large, making it impossible to obtain a highly accurate conductivity. Therefore, in this embodiment, an abnormally high inter-electrode voltage value is detected and removed to obtain a highly accurate conductivity.

[0041] <Electrical configuration of liquid condition detection sensor 1B> 6, the liquid-condition detection sensor 1B according to this embodiment includes an electrode section 10, a DC voltage application section 20, a voltage value acquisition time setting section 30, a voltage value acquisition section 40, a voltage value calculation section 50B, a conductivity calculation section 60, and an abnormal voltage value detection section 80. Note that components with the same reference numerals as those in the first or second embodiment have the same functions, and therefore detailed descriptions thereof will be omitted.

[0042] The voltage value calculation unit 50B calculates a voltage value from the inter-electrode voltage values acquired by the voltage value acquisition unit 40 after a predetermined time has elapsed since the start of the voltage value acquisition time and after abnormal voltage values detected by the abnormal voltage value detection unit 80 as described below have been removed. The voltage value calculation unit 50B outputs the calculated voltage value to the conductivity calculation unit 60.

[0043] The abnormal voltage value detection unit 80 detects interelectrode voltage values that exceed a predetermined threshold voltage value among the interelectrode voltage values acquired by the voltage value acquisition unit 40, and outputs the interelectrode voltage values excluding the detected interelectrode voltage value to the voltage value calculation unit 50B. Note that a specific detection method will be described later.

[0044] The abnormal voltage value detection unit 80 may detect, from among the interelectrode voltage values acquired by the voltage value acquisition unit 40, those that indicate interelectrode voltage values that exceed a predetermined threshold voltage value, and output the detection result to the voltage value calculation unit 50B. Then, the voltage value calculation unit 50B may calculate an average value (voltage value) of the interelectrode voltage values excluding the interelectrode voltage values that are abnormal, from the detection result output from the abnormal voltage value detection unit 80 and the interelectrode voltage values input from the voltage value acquisition unit 40, and output the average value (voltage value) to the conductivity calculation unit 60.

[0045] <Abnormal voltage detection process of liquid state detection sensor 1B> The abnormal voltage value detection process of the liquid condition detection sensor 1B according to this embodiment will be described with reference to FIG.

[0046] The abnormal voltage value detection unit 80 receives the inter-electrode voltage value acquired by the voltage value acquisition unit 40 (step S301).

[0047] The abnormal voltage value detection unit 80 compares the inter-electrode voltage value output from the voltage value acquisition unit 40 with a threshold value (step S302).

[0048] If the abnormal voltage value detection unit 80 determines that the inter-electrode voltage value output from the voltage value acquisition unit 40 is smaller than the threshold value ("NO" in step S302), it stores the inter-electrode voltage value in a storage unit (step S303). On the other hand, if the abnormal voltage value detection unit 80 determines that the inter-electrode voltage value input from the voltage value acquisition unit 40 is larger than the threshold value ("YES" in step S302), it does not store the inter-electrode voltage value in a storage unit and transitions the process to step S304.

[0049] The abnormal voltage value detection unit 80 determines whether or not the determination in step S302 has been made for all inter-electrode voltage values output from the voltage value acquisition unit 40 during the voltage value acquisition time (step S304). If the abnormal voltage value detection unit 80 determines that the determination in step S302 has not been made for all inter-electrode voltage values during the voltage value acquisition time ("NO" in step S304), the process returns to step S301.

[0050] On the other hand, if the abnormal voltage value detection unit 80 determines that it has made the judgment in step S302 for all inter-electrode voltage values during the voltage value acquisition time ("YES" in step S304), it outputs the inter-electrode voltage values stored in the memory unit to the voltage value calculation unit 50B (step S305), and terminates the processing.

[0051] For example, when the abnormal voltage value detection unit 80 determines that the interelectrode voltage value output from the voltage value acquisition unit 40 is greater than a threshold value, the abnormal voltage value detection unit 80 may add a flag to the interelectrode voltage value and store the value in the storage unit. Then, the voltage value calculation unit 50B may calculate the voltage value based on the interelectrode voltage values stored in the storage unit, excluding the interelectrode voltage value to which the flag has been added.

[0052] <Actions and Effects> In this embodiment, abnormal voltage value detection unit 80 detects, from among the inter-electrode voltage values acquired by voltage value acquisition unit 40, any inter-electrode voltage value that exceeds a predetermined threshold voltage value, and outputs the inter-electrode voltage values excluding the detected inter-electrode voltage value to voltage value calculation unit 50B. Voltage value calculation unit 50B then calculates a voltage value based on multiple inter-electrode voltage values output from abnormal voltage value detection unit 80 that are obtained after a predetermined time has elapsed from the start of the voltage value acquisition period, and outputs the calculated voltage value to conductivity calculation unit 60. This improves the accuracy of the inter-electrode voltage value used to calculate the conductivity in conductivity calculation unit 60, and therefore liquid condition detection sensor 1B is able to suppress deterioration in the accuracy of the inter-electrode voltage value and obtain a highly accurate conductivity, thereby accurately detecting the state of the liquid.

[0053] Note that, since the abnormal voltage value detection unit 80 detects interelectrode voltage values exceeding a predetermined threshold voltage value from among the interelectrode voltage values acquired by the voltage value acquisition unit 40 and excludes the detected interelectrode voltage values, the number of interelectrode voltage values used in the calculation by the voltage value calculation unit 50B may be reduced. In such a case, the CPU 100B may actively change the voltage value acquisition time.

[0054] <Variation 1> In the voltage value calculation units 50, 50A, and 50B in the first to third embodiments, the voltage value to be output to the conductivity calculation unit 60 is calculated by calculating a simple average of multiple inter-electrode voltage values acquired by the voltage value acquisition unit 40 after a predetermined time has elapsed since the start of the voltage value acquisition period. However, if there is no influence from external disturbances, the curve representing the inter-electrode voltage decays over time and then stabilizes. In other words, the longer the time elapsed after the application of a DC voltage to the electrode unit 10, the closer the inter-electrode voltage value at that time is to the true value. Therefore, the inter-electrode voltage value to be output to the conductivity calculation unit 60 may be calculated by using the inter-electrode voltage value acquired just before the end of the voltage value acquisition period as a reference, calculating a weight based on the difference between the inter-electrode voltage value and the reference value, and then calculating a weighted average of multiple inter-electrode voltage values after the predetermined time has elapsed. Calculating the inter-electrode voltage value in this manner improves the accuracy of the inter-electrode voltage value used to calculate the conductivity in the conductivity calculation unit 60. This highly accurate conductivity allows the liquid condition detection sensors 1, 1A, and 1B to accurately detect the liquid condition. It is preferable to provide a function for detecting interelectrode voltage values that deviate from the curve showing the interelectrode voltage due to disturbances or the like, and to perform processing such as excluding the detected interelectrode voltage values.

[0055] <Variation 2> In the voltage value calculation units 50, 50A, and 50B in the first to third embodiments, the voltage value to be output to the conductivity calculation unit 60 is calculated from a plurality of inter-electrode voltage values acquired by the voltage value acquisition unit 40 within an arbitrary voltage value acquisition time, the inter-electrode voltage values being obtained after a predetermined time has elapsed since the start of the voltage value acquisition time. However, for example, the voltage value to be output to the conductivity calculation unit 60 may be calculated after performing an averaging process using the voltage values to be output to the conductivity calculation unit 60 calculated within an arbitrary voltage value acquisition time and the voltage values to be output to the conductivity calculation unit 60 calculated within a voltage value acquisition time prior to the arbitrary voltage value acquisition time. By calculating the voltage value in this manner, the accuracy of the inter-electrode voltage value used to calculate the conductivity in the conductivity calculation unit 60 can be improved, and highly accurate conductivity can be obtained, thereby accurately detecting the state of the liquid.

[0056] The configuration, operation, and effects of the embodiment of the present invention configured as above will be described below.

[0057] The liquid condition detection sensors 1, 1A, 1B that detect the state of a liquid comprise an electrode unit 10 that is arranged in a liquid flow path and has a pair of electrodes arranged opposite each other, a voltage value acquisition time setting unit 30 that sets a voltage value acquisition time, which is the length of time for acquiring the inter-electrode voltage value of the pair of electrodes of the electrode unit 10, a voltage value acquisition unit 40 that acquires the inter-electrode voltage value during the voltage value acquisition time, and a conductivity calculation unit 60 that calculates the conductivity of the liquid based on the inter-electrode voltage value acquired by the voltage value acquisition unit 40 after a predetermined time has elapsed since the start of the voltage value acquisition time.

[0058] In this configuration, the voltage value acquisition unit 40 acquires the inter-electrode voltage value of the pair of electrodes of the electrode unit 10 during the voltage value acquisition time. The conductivity calculation unit 60 calculates the conductivity of the liquid based on the inter-electrode voltage value acquired by the voltage value acquisition unit 40, which is the inter-electrode voltage value acquired after a predetermined time has elapsed since the start of the voltage value acquisition time (start of acquisition of the inter-electrode voltage value). In other words, the conductivity calculation unit 60 calculates the conductivity of the liquid based on the inter-electrode voltage value acquired by the voltage value acquisition unit 40, which is the inter-electrode voltage value acquired after a predetermined time has elapsed since the application of voltage (DC voltage and AC voltage) to the electrode unit 10. Therefore, the conductivity calculation unit 60 calculates the conductivity of the liquid based on at least the inter-electrode voltage values acquired by the voltage value acquisition unit 40, excluding the inter-electrode voltage value immediately after the start of the voltage value acquisition time (immediately after the application of voltage to the electrode unit 10), when the inter-electrode voltage value is most unstable. As a result, the liquid-condition detection sensors 1, 1A, and 1B can prevent deterioration in the accuracy of the inter-electrode voltage value and obtain highly accurate conductivity, thereby enabling accurate detection of the liquid condition.

[0059] In the liquid-condition detection sensors 1, 1A, and 1B, the predetermined time is the time from the start of the voltage value acquisition period until the inter-electrode voltage value stabilizes.

[0060] In this configuration, the conductivity calculation unit 60 calculates the conductivity of the liquid based on a stable inter-electrode voltage value. As a result, the liquid condition detection sensors 1, 1A, and 1B can accurately detect the state of the liquid by suppressing deterioration in the accuracy of the inter-electrode voltage value and obtaining highly accurate conductivity.

[0061] In the liquid-condition detection sensors 1, 1A, and 1B, the conductivity calculation section 60 calculates the conductivity of the liquid based on the average value of the inter-electrode voltage value after a predetermined time has elapsed during the voltage value acquisition time.

[0062] In this configuration, the conductivity calculation unit 60 calculates the conductivity of the liquid based on the average value of the inter-electrode voltage values acquired by the voltage value acquisition unit 40, excluding at least the inter-electrode voltage value immediately after the start of the voltage value acquisition period, when the inter-electrode voltage value is most unstable. In other words, since the conductivity of the liquid is calculated based on the average value of a sufficient number of inter-electrode voltage values acquired after the inter-electrode voltage value has stabilized, it is possible to calculate a conductivity that is closer to the true value in a short period of time. Therefore, the liquid condition detection sensors 1, 1A, and 1B can accurately detect the state of the liquid by suppressing deterioration in the accuracy of the inter-electrode voltage value and obtaining a highly accurate conductivity.

[0063] Although an embodiment of the present invention has been described above, the above embodiment merely shows one application example of the present invention, and is not intended to limit the technical scope of the present invention to the specific configuration of the above embodiment.

[0064] This application claims priority based on Patent Application No. 2020-218839 filed with the Japan Patent Office on December 28, 2020, and Patent Application No. 2021-029516 filed with the Japan Patent Office on February 26, 2021, the entire contents of which are incorporated herein by reference.

Claims

1. A liquid condition detection sensor for detecting the condition of a liquid, an electrode unit disposed in the liquid flow path and having a pair of electrodes facing each other; a voltage value acquisition time setting unit that sets a voltage value acquisition time, which is a length of time for acquiring an inter-electrode voltage value between the pair of electrodes of the electrode unit; a voltage value acquisition unit that acquires the inter-electrode voltage value during the voltage value acquisition time; a conductivity calculation unit that calculates the conductivity of the liquid based on the inter-electrode voltage value acquired by the voltage value acquisition unit after a predetermined time has elapsed since the start of the voltage value acquisition period; A liquid state detection sensor comprising:

2. 2. The liquid condition detection sensor according to claim 1, The predetermined time is the time from the start of the voltage value acquisition period until the inter-electrode voltage value stabilizes.

3. 2. The liquid condition detection sensor according to claim 1, The liquid state detection sensor is configured such that the conductivity calculation unit calculates the conductivity of the liquid based on an average value of the inter-electrode voltage value after the predetermined time has elapsed during the voltage value acquisition time.

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