Processing device and abnormality determination method

Abstract

The purpose of the present invention is to provide a processing device that makes it possible to prevent carry-over due to liquid shortage during ultrasonic cleaning. For this purpose, a processing device according to the present invention is provided with: a probe that suctions and / or discharges liquid; a storage tank that stores the liquid for cleaning the probe; an ultrasonic vibrator that is disposed at least partially inside the storage tank and that emits ultrasonic waves; a current measurement unit that measures a current flowing through the ultrasonic vibrator; and a control unit that causes the probe to suction the liquid to clean the probe when the tip of the probe is in a positional relationship of being placed inside the storage tank and being placed below the lower end of the ultrasonic vibrator, and that determines whether or not the probe is in an abnormal state on the basis of the current measured by the current measurement unit when the tip of the probe is in said positional relationship.

Description

Processing device and abnormality determination method

[0001] The present invention relates to a processing device and an abnormality determination method.

[0002] In automated analyzers, the same nozzle is repeatedly used to dispense samples, so the nozzle tip must be cleaned before aspirating another sample. If the nozzle tip is not cleaned properly, the previous sample will be carried over into the next sample, reducing analytical accuracy. However, high-throughput automated analyzers perform dispensing at high speeds, so there is not enough time to clean the nozzle. Therefore, a cleaning mechanism using ultrasound has been proposed to clean the nozzle more effectively.

[0003] For example, Patent Document 1 discloses a nozzle cleaning mechanism that includes an ultrasonic vibrator that is partially immersed in a liquid such as a cleaning liquid stored in a liquid storage tank and that applies ultrasonic waves to the liquid, and a current measuring unit that measures the current flowing through the ultrasonic vibrator (paragraph 0026). Patent Document 1 also discloses a technology that, when a current greater than a predetermined threshold is detected, determines that the ultrasonic vibrator is immersed in the liquid and that the liquid storage tank has been filled with the liquid up to a reference range (paragraphs 0035-0036).

[0004] JP 2018-48892 A

[0005] According to Patent Document 1, the liquid volume is determined by measuring the current before ultrasonic cleaning begins, i.e., before the dispensing nozzle is moved to the cleaning position. However, after the dispensing nozzle is lowered and immersed in the liquid, and ultrasonic cleaning begins, no current-based determination is made. When the dispensing nozzle aspirates liquid during ultrasonic cleaning, the liquid level drops. As a result, if the liquid level falls below the tip of the dispensing nozzle during ultrasonic cleaning, the dispensing nozzle will suck the liquid dry, and if the liquid level falls below the bottom end of the ultrasonic vibrator, the ultrasonic vibrator will heat up dry. Dry sucking of the dispensing nozzle can cause poor cleaning, and dry heating of the ultrasonic vibrator can cause ultrasonic vibrator failure or subsequent cleaning failure, ultimately leading to carryover of samples or reagents.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide a processing apparatus that can prevent carryover due to a lack of liquid during ultrasonic cleaning.

[0007] In order to achieve the above-mentioned object, the processing device of the present invention comprises a probe that aspirates and / or ejects liquid, a storage tank that stores the liquid for cleaning the probe, an ultrasonic vibrator at least a portion of which is disposed inside the storage tank and emits ultrasonic waves, a current measuring unit that measures the current flowing through the ultrasonic vibrator, and a control unit that, when the tip of the probe is inside the storage tank and is positioned lower than the lower end of the ultrasonic vibrator, causes the probe to aspirate the liquid to clean the probe, and determines whether or not an abnormal state exists based on the current measured by the current measuring unit when the tip is in the positional relationship.

[0008] According to the present invention, it is possible to provide a processing apparatus that can prevent carryover due to a lack of liquid during ultrasonic cleaning.

[0009] 1 is a diagram showing a schematic diagram of the overall configuration of an automatic analyzer; an external perspective view of a cleaning mechanism; a cross-sectional view of the cleaning mechanism showing functions related to ultrasonic cleaning and abnormality determination; a flowchart showing the cleaning process of a sample probe by the cleaning mechanism; a diagram showing an example of when the amount of detergent supplied is sufficient (normal) and when it is insufficient (abnormal) when a first abnormality is determined; a diagram showing an example (Example and Comparative Example) of when the amount of detergent supplied is sufficient when a second abnormality is determined; a diagram showing an example (Example and Comparative Example) of when the amount of detergent supplied is clearly insufficient when a second abnormality is determined; a diagram showing an example (Example and Comparative Example) of when the amount of detergent supplied is insufficient when a second abnormality is determined.

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] One method for analyzing specific components contained in samples such as blood and urine uses LC-MS (Liquid Chromatography-Mass Spectrometry), which connects liquid chromatography (LC) and a mass spectrometer (MS) online. Therefore, in this embodiment, an automatic analyzer that combines LC-MS as an analytical mechanism with a sample pretreatment function will be described as an example. However, the analytical mechanism may also be an automatic analyzer that combines a separation means such as capillary electrophoresis with a detector such as an absorptiometer.

[0012] 1 is a diagram showing a schematic diagram of the overall configuration of an automatic analyzer 100. The automatic analyzer 100 includes a preprocessing unit 101 that purifies samples, a separation unit 103 that performs LC separation of components in the purified sample, an analysis unit 102 that analyzes the LC-separated components, a control unit 110 that controls the operation of the entire apparatus, an input unit 111 through which a user inputs information to the apparatus, an output unit 112 that outputs information to the user, and a storage unit 109 such as a storage medium that stores various information related to the control of the automatic analyzer 100.

[0013] The control unit 110 , the input unit 111 , the output unit 112 and the storage unit 109 constitute a control device that controls the overall operation of the automatic analyzer 100 .

[0014] 1, the input unit 111 and the output unit 112 are shown as separate units, but the input unit 111 and the output unit 112 may be integrated into one unit, for example, like a touch panel monitor. The output unit 112 may also have a function of outputting sound, such as a speaker, in addition to a display unit such as a monitor.

[0015] The pretreatment unit 101 comprises a transport mechanism 114 that transports a sample container 107 containing a sample to be analyzed to a sample dispensing position, a reaction disk 120 that can maintain the solution in the reaction container 116 at a constant temperature by mounting the reaction container 116 in multiple openings 119, a reagent disk 122 that holds multiple reagent containers 108 containing reagents, and a reagent dispensing mechanism 123 that dispenses reagent from the reagent container 108 into the reaction container 116 on the reaction disk 120.

[0016] The pretreatment unit 101 also includes a sample dispensing mechanism 113 that dispenses a sample from a sample container 107 transported to the sample dispensing position into a reaction container 116 accommodated in an opening 119 of the reaction disk 120, a cleaning mechanism 105 that cleans the nozzle (probe) of the sample dispensing mechanism 113 after dispensing, and a waste liquid tank 106 that discards the liquid sucked by the sample dispensing mechanism 113 to clean the nozzle. Note that the arrangement of the cleaning mechanism 105 and the waste liquid tank 106 is not limited to that shown in Figure 1 as long as they are located in positions accessible to the sample dispensing mechanism 113. For example, the cleaning mechanism 105 and the waste liquid tank 106 may be located closer to each other.

[0017] Furthermore, the pre-treatment unit 101 is equipped with a container mounting rack 117 on which unused reaction containers 116 are mounted, and a transport mechanism 118 for transporting used reaction containers 116 from an opening 119 of the reaction disk 120 to a disposal unit (not shown), and for transporting unused reaction containers 116 from the container mounting rack 117 to the opening 119 of the reaction disk 120.

[0018] The pretreatment unit 101 also includes a magnetic separation mechanism 124 that separates magnetic beads in the solution contained in the reaction vessel 116 using the magnetic force of a magnet, a transport mechanism 125 that transports the reaction vessel 116 between the reaction disk 120 and the magnetic separation mechanism 124, and an evaporation and concentration mechanism 131 that evaporates and concentrates the components to be analyzed in the solution in the reaction vessel 116.

[0019] Furthermore, the pretreatment unit 101 includes a transport mechanism 132 that transports the reaction vessel 116 between the reaction disk 120 and the evaporation and concentration mechanism 131, and a purified liquid dispensing mechanism 133 that dispenses the solution in the reaction vessel 116 after evaporation and concentration to the separation unit 103 that separates the components in the sample.

[0020] The magnetic separation mechanism 124 is provided on a rotation track 126 of the reagent dispensing mechanism 123. The reagent dispensing mechanism 123 can dispense a reagent into a reaction vessel 116 supported by the magnetic separation mechanism 124, and can aspirate a solution in the reaction vessel 116.

[0021] The reaction disk 120 functions as an incubator that keeps the temperature of the reaction vessel 116 placed in the opening 119 constant, and incubates the reaction vessel 116 placed in the opening 119 for a certain period of time.

[0022] The waste liquid tank 104 is a tank that stores waste liquid discharged from the waste liquid tank 106 of the pretreatment unit 101 through a flow path (not shown).

[0023] The separation unit 103 is, for example, a liquid chromatograph, and includes a column or the like for separating components in the reaction solution dispensed by the purified liquid dispensing mechanism 133. The separation unit 103 separates the components in the reaction solution dispensed from the reaction vessel 116 by the purified liquid dispensing mechanism 133, and sequentially introduces the separated components into the analysis unit 102.

[0024] The analysis unit 102 is, for example, a mass spectrometer, and includes an electron multiplier or the like for the function of ionizing and mass analyzing the components introduced from the separation unit 103. The analysis unit 102 ionizes the components introduced from the separation unit 103, detects the amount of ions (i.e., the amount of components), and outputs the detection result to the control unit 110.

[0025] The control unit 110 controls the operation of each mechanism, such as the sample dispensing mechanism 113 and the cleaning mechanism 105. The control unit 110 also calculates the concentration values ​​of components in the sample using the detection results (ion amounts) from the analysis unit 102 and a previously obtained calibration curve, stores the results as analysis results in the memory unit 109, and displays the analysis results on the output unit 112.

[0026] The memory unit 109 is composed of a storage for storing analysis results and the like, and a memory for storing programs used by the control unit 110 to control the operation of each mechanism and perform calculations such as concentration calculations and abnormality determination. The memory stores, for example, a cleaning control unit and an abnormality determination unit as functions executed by the control unit 110. The cleaning control unit controls the probe to suck liquid and ultrasonically clean the probe when the tip of the probe of the sample dispensing mechanism 113 is located inside a storage tank (described later) and below the lower end of an ultrasonic vibrator (described later). The abnormality determination unit determines whether or not an abnormal state exists based on the current measured by a current measurement unit (described later) when the tip is in the aforementioned positional relationship.

[0027] The program may be provided by being pre-installed in a ROM or the like, or by being recorded in an installable or executable file format on a computer-readable recording medium such as a CD-ROM and provided or distributed. Furthermore, the program may be stored on a computer connected to a network such as the Internet and provided or distributed by being downloaded via the network.

[0028] Here, when the sample probe of the sample dispensing mechanism 113 finishes dispensing a sample from one sample container 107, it accesses the cleaning mechanism 105 before dispensing the next sample. In the cleaning mechanism 105, the sample probe aspirates liquid in a storage tank (described later) while an ultrasonic vibrator (described later) generates ultrasonic waves, thereby cleaning the sample probe. Thereafter, the sample probe accesses the waste liquid tank 106 and discharges the liquid aspirated from the storage tank.

[0029] FIG. 2A is an external perspective view of the cleaning mechanism, and FIG. 2B is a cross-sectional view of the cleaning mechanism, showing functions related to ultrasonic cleaning and abnormality determination.

[0030] The cleaning mechanism includes a storage tank 201 that stores detergent used to clean the sample probe 113a, and a detergent supply unit 203 that supplies the detergent via a flow path 202 provided on the bottom surface of the storage tank 201. Here, an example will be described in which the sample probe 113a is cleaned using detergent, but the sample probe 113a may also be cleaned using other liquids such as pure water.

[0031] The storage tank 201 has a container shape with an opening at the top. The detergent supply unit 203 supplies the storage tank 201 with detergent in an amount exceeding the capacity of the storage tank 201, and the excess detergent overflows from the top opening and is discharged to the outside, thereby maintaining a sufficient liquid level 500. The detergent in the storage tank 201 is connected to a ground 400. Methods for connecting the detergent to the ground 400 include, for example, constructing the storage tank 201 from a conductor and connecting it to the ground 400, immersing an electrode connected to the ground 400 in the detergent, or connecting a position (conductor portion) of the flow path 202 or the detergent supply unit 203 that comes into contact with the detergent to the ground 400. The detergent supply unit 203 is composed of a pump or the like that sucks the detergent from a detergent tank (not shown) and delivers it to the flow path 202.

[0032] The cleaning mechanism further includes an ultrasonic vibrator 301, at least a portion of which is disposed inside the storage tank 201 and which emits ultrasonic waves, a vibrator driving unit 302 which drives the ultrasonic vibrator 301 by transmitting a drive signal, a voltage application unit 303 which applies a voltage between the ultrasonic vibrator 301 and the detergent, and a current measurement unit 304 which measures the current flowing from the voltage application unit 303 to the ultrasonic vibrator 301. The control unit 110 controls the ultrasonic vibrator 301 by transmitting a control signal to the vibrator driving unit 302 based on the measurement result of the current measurement unit 304, and also controls the operation of the detergent supply unit 203.

[0033] The ultrasonic vibrator 301 has a portion composed of an element such as a piezoelectric element, and when this portion is driven at high speed by a drive signal from the vibrator driver 302, the tip portion is ultrasonically vibrated to apply ultrasonic waves to the detergent. The tip portion of the ultrasonic vibrator 301 also has a hole that penetrates vertically, and during cleaning, the sample probe 113a is inserted into this hole. The voltage application unit 303 applies a predetermined reference voltage between the conductor that constitutes the tip portion of the ultrasonic vibrator 301 and the ground 400 via the current measurement unit 304. When the reference voltage is applied, the current measurement unit 304 measures the current flowing through the ultrasonic vibrator 301 and the detergent from the voltage application unit 303 and transmits the measurement result to the control unit 110.

[0034] FIG. 3 is a flowchart showing the cleaning process of the sample probe by the cleaning mechanism.

[0035] After dispensing of the previous sample is completed, before cleaning the sample probe 113a, the voltage application unit 303 first applies a voltage between the ultrasonic vibrator 301 and the detergent (step S301), and the current measurement unit 304 measures the current flowing through the ultrasonic vibrator 301 and the detergent at this time (step S302).

[0036] Next, as a first abnormality determination, the control unit 110 determines whether or not detergent is being normally supplied into the storage tank 201 based on the current measured by the current measurement unit 304 (step S303).

[0037] 4 shows examples of when the detergent supply amount is sufficient (normal) and when it is insufficient (abnormal) when the first abnormality is detected. When the first abnormality is detected, the sample probe 113a is not in the storage tank 201 but is at the reference height (origin position). When the detergent supply is normal, at least the lower end of the ultrasonic vibrator 301 is immersed in the detergent, so a certain amount of current flows from the ultrasonic vibrator 301 to the ground 400 via the detergent. On the other hand, when the detergent supply is abnormal, the lower end of the ultrasonic vibrator 301 is not immersed in the detergent, so almost no current flows from the ultrasonic vibrator 301 to the ground 400. Therefore, by setting a threshold value between a certain current value and a current value that is as close to zero as possible, it is possible to determine whether or not there is an abnormality in the detergent supply depending on whether the measurement value of the current measurement unit 304 is equal to or greater than the threshold. Possible causes of abnormal detergent supply include, for example, leakage or clogging in the flow path 202 that supplies detergent to the reservoir 201, and malfunction of the syringe or solenoid valve that constitutes the detergent supply unit 203. The threshold value is set before shipping the automatic analyzer (for example, at the design stage).

[0038] If an abnormality is determined in step S303, the control unit 110 causes the output unit 112 to output a message indicating an abnormality in the detergent supply, warns the user, and cancels the analysis that has already been requested (step S304). In this way, if an abnormality is determined in the first abnormality determination, it is clear that there will be a shortage of detergent in the subsequent wash. Therefore, it is possible to take measures such as issuing a warning at an early stage before the sample probe 113a is lowered and the wash begins. Furthermore, so-called "dry boiling," in which ultrasonic waves are emitted from the ultrasonic vibrator 301 when it is not immersed in the liquid surface, can be prevented, thereby reducing the risk of failure of the ultrasonic vibrator 301.

[0039] On the other hand, if the result of step S303 is normal, the control unit 110 controls the transducer driver 302 to cause the ultrasonic transducer 301 to start oscillating ultrasonic waves (step S305). Furthermore, the control unit 110 lowers the sample probe 113a into the reservoir 201, and after the tip of the sample probe 113a penetrates the hole at the tip of the ultrasonic transducer 301, stops the sample probe 113a at a predetermined position below the bottom end of the ultrasonic transducer 301 (step S306). At this time, the control unit 110 controls the amount of descent of the sample probe 113a by rotating the motor included in the sample dispensing mechanism 113 at a predetermined number of pulses. Thereafter, the current measurement unit 304 starts measuring the current flowing through the ultrasonic transducer 301 and the detergent (step S307).

[0040] Next, the control unit 110 controls the sample dispensing mechanism 113 to cause the sample probe 113a to aspirate the detergent and perform ultrasonic cleaning of the sample probe 113a (step S308). After the ultrasonic cleaning is completed, the control unit 110 stops the ultrasonic oscillator 301 from emitting ultrasonic waves and also stops the current measurement by the current measurement unit 304 (step S309).

[0041] Next, as a second abnormality determination, the control unit 110 determines whether detergent was normally supplied into the storage tank 201 based on the current measured by the current measurement unit 304 during ultrasonic cleaning (step S310).

[0042] 5 shows examples (Example and Comparative Example) in which the amount of detergent supplied is sufficient when a second abnormality is detected. The Example shows a case in which the tip of the sample probe 113a is located at a position (first position) below the bottom end of the ultrasonic vibrator 301, while the Comparative Example shows a case in which the tip of the sample probe 113a is located at a position (second position) above the bottom end of the ultrasonic vibrator 301. The liquid level in each example in FIG. 5 indicates the liquid level of the detergent at the end of ultrasonic cleaning (at the end of detergent suction) (the same applies to FIGS. 6 and 7 described below).

[0043] In both the example and the comparative example, at least the lower end of the ultrasonic vibrator 301 is immersed in the detergent, so a certain amount of current flows from the ultrasonic vibrator 301 to the ground 400 via the detergent, and the current value exceeds the threshold. Therefore, in both the example and the comparative example, it is correctly determined that the detergent supply is normal. Note that in Figure 5, the second abnormality determination is made based on current values ​​measured at multiple (four) timings during the ultrasonic cleaning, but the number of current values ​​used for the determination is not limited as long as it includes at least the current value at the end of the ultrasonic cleaning (the same applies to Figures 6 and 7 described below).

[0044] 6 shows an example (Example and Comparative Example) in which the amount of detergent supplied is clearly insufficient when the second abnormality is detected. As in FIG. 5, in the Example, the sample probe 113a is in the first position, and in the Comparative Example, the sample probe 113a is in the second position.

[0045] In both the example and the comparative example, the lower end of the ultrasonic vibrator 301 is not immersed in the detergent, so almost no current flows from the ultrasonic vibrator 301 to the earth 400, and the current value does not exceed the threshold. Therefore, in both the example and the comparative example, it is correctly determined that the amount of detergent supplied is abnormal.

[0046] 7 shows an example (Example and Comparative Example) of a case where the amount of detergent supplied is insufficient when the second abnormality is detected. As in FIG. 5, in the Example, the sample probe 113a is in the first position, and in the Comparative Example, the sample probe 113a is in the second position.

[0047] In this embodiment, the lower end of the ultrasonic vibrator 301 is not immersed in the detergent, so the current value measured by the current measuring unit 304 does not exceed the threshold, and it is determined that the amount of detergent supplied is abnormal. In fact, the tip of the sample probe 113a is not immersed in the detergent either, and it is not possible to suck in the detergent, so it can be said that the determination that the amount of detergent supplied is abnormal is correct.

[0048] On the other hand, in the comparative example, the lower end of the ultrasonic vibrator 301 is immersed in the detergent, so the current value measured by the current measuring unit 304 exceeds the threshold value, and it is determined that the amount of detergent supplied is normal. However, in reality, the tip of the sample probe 113a is not immersed in the detergent, and it is not possible to suck in the detergent, so it can be said that the determination that the amount of detergent supplied is normal is incorrect.

[0049] That is, as in the embodiment, by performing the second abnormality determination when the tip of the sample probe 113a is located inside the reservoir 201 and below the lower end of the ultrasonic vibrator 301, an accurate abnormality determination of the detergent supply amount is possible. Furthermore, even if the detergent supply amount is sufficient when the first abnormality determination is performed, the second abnormality determination can also detect an insufficient detergent supply amount due to a drop in the liquid level caused by the suction of detergent during ultrasonic cleaning. Therefore, it is possible to detect the presence or absence of so-called "empty suction," in which the sample probe 113a performs a suction operation without being immersed in the liquid level, and to avoid dispensing the next sample when the sample probe 113a is insufficiently cleaned due to empty suction. As a result, even in a sample dispensing mechanism 113 that does not have a liquid level detection means such as a pressure sensor or a capacitance sensor, sample carryover due to improper cleaning of the sample probe 113a can be prevented.

[0050] If an abnormality is determined in step S310, the process proceeds to step S304, where the control unit 110 causes the output unit 112 to output a message indicating that the detergent supply is abnormal, warns the user, and cancels the analysis that has already been requested. If an abnormality is determined in the second abnormality determination, the output unit 112 may distinguish this from an abnormality determined in the first abnormality determination and output, for example, a message indicating that the amount of detergent supplied during ultrasonic cleaning (during detergent suction) has become insufficient.

[0051] On the other hand, if it is determined to be normal in step S310, the control unit 110 ends the cleaning process of the sample probe 113a by the cleaning mechanism.

[0052] The present invention is not limited to the above-described embodiment, but includes various modifications. For example, although the above-described embodiment describes the case where a sample probe is ultrasonically cleaned, the same technique can also be applied to the case where a reagent probe is ultrasonically cleaned.

[0053] 100...automatic analyzer, 101...pretreatment unit, 102...analysis unit, 103...separation unit, 104...waste tank, 105...cleaning mechanism, 106...waste tank, 107...sample container, 108...reagent container, 109...memory unit, 110...control unit, 111...input unit, 112...output unit, 113...sample dispensing mechanism, 113a...sample probe, 114...transport mechanism, 116...reaction container, 117...container mounting rack, 118...transport mechanism, 119... Opening, 120... reaction disk, 122... reagent disk, 123... reagent dispensing mechanism, 124... magnetic separation mechanism, 125... transport mechanism, 126... rotational orbit, 131... evaporation concentration mechanism, 132... transport mechanism, 133... purified liquid dispensing mechanism, 201... storage tank, 202... flow path, 203... detergent supply unit, 301... ultrasonic vibrator, 302... vibrator driving unit, 303... voltage application unit, 304... current measurement unit, 400... earth, 500... liquid level

Claims

1. A processing device comprising: a probe that sucks and / or ejects liquid; a storage tank that stores the liquid for cleaning the probe; an ultrasonic vibrator that is at least partially disposed inside the storage tank and emits ultrasonic waves; a current measurement unit that measures the current flowing through the ultrasonic vibrator; and a control unit that, when the tip of the probe is inside the storage tank and is positioned lower than the bottom end of the ultrasonic vibrator, causes the probe to suck in the liquid to clean the probe, and determines whether or not an abnormal state exists based on the current measured by the current measurement unit when the probe is in the positional relationship.

2. The processing apparatus according to claim 1, wherein the abnormal state is a state in which the liquid level in the storage tank is lower than the bottom end of the ultrasonic vibrator.

3. The processing device according to claim 2, further comprising an output unit that warns a user when it is determined that the abnormal state has occurred as a result of the suction of the liquid by the probe.

4. The processing device according to claim 3, wherein the control unit cancels an analysis that has already been requested when it determines that the abnormal state has occurred.

5. The processing device according to claim 2, wherein the control unit determines whether the abnormal state exists even before the probe is cleaned and when the tip of the probe is not inside the storage unit.

6. The processing device according to claim 1, further comprising a liquid supply unit that supplies the liquid to the storage tank through a flow path, and wherein the control unit controls the liquid supply unit so that the liquid level in the storage tank after the probe has sucked the liquid is above the lower end of the ultrasonic vibrator.

7. A method for determining abnormalities in a processing device comprising a probe that sucks and / or discharges liquid, a storage tank that stores the liquid for cleaning the probe, an ultrasonic vibrator that is at least partially disposed inside the storage tank and emits ultrasonic waves, a current measurement unit that measures the current flowing through the ultrasonic vibrator, and a control unit that controls the probe, the ultrasonic vibrator, and the current measurement unit, the method comprising the steps of: the control unit making the probe suck the liquid to clean the probe when the tip of the probe is inside the storage tank and is lower than the bottom end of the ultrasonic vibrator; and the control unit determining whether or not an abnormal state exists based on the current measured by the current measurement unit when the tip is in the above positional relationship.

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