Autoanalyzer

Abstract

To improve convenience of liquid surface detection with a probe using a heater.SOLUTION: An autoanalyzer according to an embodiment comprises a probe, a heater, and a liquid surface detection circuit. The heater heats liquid inside the probe. The liquid surface detection circuit is electrically connected to the probe, and detects the contact between the probe and a liquid surface. The liquid surface detection circuit includes a capacitance adjustment circuit that adjusts the capacitance of a capacitor connected to a circuit used for liquid surface detection on the basis of temperature related to heating of the liquid.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The embodiments disclosed in this specification and the drawings relate to an automatic analyzer.

Background Art

[0002] Conventionally, in an automatic analyzer, a liquid level detection circuit for detecting the contact between a probe and a liquid level is known. This liquid level detection circuit detects the liquid level using a differentially input signal. For example, one connection point of the differential input of the liquid level detection circuit is connected to the probe, and the other connection point is open. The liquid level detection is performed by detecting changes in the amplitude and phase of the signal accompanying changes in impedance when the probe contacts the liquid level.

[0003] This liquid level detection circuit may be provided with an automatic phase shift circuit that keeps the phase difference of the differentially input signal constant when the probe and the liquid level are not in contact. This automatic phase shift circuit can set the output in a state where the probe and the liquid level are not in contact to zero.

[0004] Furthermore, the above-described liquid level detection circuit may be provided with a capacitance adjustment circuit that can adjust the balance with the capacitance related to the accessories of the probe. The above accessories are, for example, a piasa needle for making a hole in a stopper and a heater for warming the liquid in the probe. When these accessories are used, since the capacitance is large, it may not be possible to adjust it only with the above-described automatic phase shift circuit. Therefore, this capacitance adjustment circuit can adjust the capacitances of one connection point and the other connection point of the liquid level detection circuit so as to cancel the above capacitance based on the differentially input signal.

[0005] However, since the aforementioned capacitance adjustment circuit adjusts the capacitance of the connection point based on the differentially input signal, there may be cases where adjustment cannot be performed in advance. For example, the capacitance generated with respect to the heater used with the probe changes depending on the temperature of the heater. Therefore, in the aforementioned capacitance adjustment circuit, since the adjustment is completed after the heater reaches a predetermined temperature, adjustment continues until the heater reaches the predetermined temperature, and the convenience of liquid level detection using the probe with the heater may decrease.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to improve the convenience of liquid level detection using a probe with a heater. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problems. The problems corresponding to the respective effects of each configuration shown in the embodiments described later can also be regarded as other problems.

Means for Solving the Problems

[0008] The automatic analyzer according to the embodiment includes a probe, a heater, and a liquid level detection circuit. The heater heats the liquid in the probe. The liquid level detection circuit is electrically connected to the probe and detects the contact between the probe and the liquid level. The liquid level detection circuit includes a capacitance adjustment circuit that adjusts the capacitance of a capacitor connected to the circuit used for liquid level detection based on the temperature related to the heating of the liquid.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the automatic analyzer will be described in detail with reference to the drawings.

[0011] (First Embodiment) FIG. 1 is a block diagram illustrating the functional configuration of the automatic analyzer 1 according to the first embodiment. The automatic analyzer 1 includes an analysis mechanism 2, an analysis circuit 3, a drive mechanism 4, an input interface 5, an output interface 6, a communication interface 7, a memory circuit 8, and a control circuit 9. The automatic analyzer 1 measures the components in a sample by measuring a mixed solution of a sample to be measured and a reagent.

[0012] The analysis mechanism 2 mixes a sample such as a standard sample or a test sample (which is also called a specimen) with a reagent used for each test item set for this sample. The analysis mechanism 2 measures the mixed solution of the sample and the reagent, and generates standard data and test data represented by, for example, absorbance. Further, the analysis mechanism 2 has a liquid level detection circuit 21. Note that detailed descriptions of the analysis mechanism 2 and the liquid level detection circuit 21 will be given later.

[0013] The analysis circuit 3 is a processor that generates calibration data, analysis data, etc. by analyzing the standard data and the test data generated by the analysis mechanism 2. The analysis circuit 3 reads an analysis program from the memory circuit 8 and generates calibration data, analysis data, etc. according to the read analysis program. For example, the analysis circuit 3 generates calibration data indicating the relationship between the standard data and a standard value preset for the standard sample. Further, the analysis circuit 3 generates analysis data represented as a concentration value and an enzyme activity value based on the test data and the calibration data of the test item corresponding to this test data. The analysis circuit 3 outputs the generated calibration data, analysis data, etc. to the control circuit 9.

[0014] The drive mechanism 4 drives the analysis mechanism 2 according to the control of the control circuit 9. The drive mechanism 4 is realized by, for example, a gear, a stepping motor, a belt conveyor, and a lead screw.

[0015] The input interface 5 receives, for example, test orders and settings such as analysis parameters for each test item related to the samples requested for measurement from an operator or via the in-hospital network NW. The analysis parameters include, for example, the reagents set for each test item and information on the set temperature for preheating (preheating) the reagents. The input interface 5 is realized, for example, by a mouse, a keyboard, and a touch pad where instructions are input by touching the operation surface. The input interface 5 is connected to the control circuit 9, converts the operation instructions input from the operator into electrical signals, and outputs the electrical signals to the control circuit 9.

[0016] Note that in this specification, the input interface 5 is not limited to only those equipped with physical operation components such as a mouse, a keyboard, and a touch pad. For example, as the input interface 5, a processing circuit may be included that receives an electrical signal corresponding to an operation instruction input from an external input device provided separately from the automatic analyzer 1 and outputs this electrical signal to the control circuit 9.

[0017] The output interface 6 is connected to the control circuit 9 and outputs the signal supplied from the control circuit 9. The output interface 6 is realized, for example, by a display device, a printing device, and an audio output device. The display device includes, for example, a CRT display, a liquid crystal display, an organic EL display, an LED display, and a plasma display. Also, as the display device, a processing circuit may be included that converts data representing the display target into a display signal and outputs the display signal to an external display device or the like. The printing device includes, for example, a printer. Also, as the printing device, an output circuit may be included that outputs data representing the printing target to an external printing device or the like. The audio output device includes, for example, a speaker. Also, as the audio output device, an output circuit may be included that outputs an audio signal to an external audio device.

[0018] The communication interface 7 is connected to, for example, the in-hospital network NW. The communication interface 7 performs data communication with a hospital information system (HIS) via the in-hospital network NW. Note that the communication interface 7 may perform data communication with the HIS via an examination department system (LIS: Laboratory Information System) connected to the in-hospital network NW.

[0019] The memory circuit 8 includes a recording medium readable by a processor, such as a magnetic recording medium, an optical recording medium, or a semiconductor memory. Note that the memory circuit 8 does not necessarily have to be realized by a single storage device. For example, the memory circuit 8 may be realized by a plurality of storage devices.

[0020] Also, the memory circuit 8 stores an analysis program executed by the analysis circuit 3 and a control program for realizing the functions provided in the control circuit 9. The memory circuit 8 stores an examination order input by an operator or an examination order received via the in-hospital network NW by the communication interface 7. Further, the memory circuit 8 stores a table associating a set temperature for a reagent with a capacitance value for a heater.

[0021] The control circuit 9 is a processor that functions as the center of the automatic analyzer 1. The control circuit 9 outputs, for example, a control signal for driving each part of the analysis mechanism 2 to the drive mechanism 4. The control circuit 9 realizes the functions corresponding to the executed control program by executing the control program stored in the memory circuit 8. Note that the control circuit 9 may include a storage area for storing at least a part of the data stored in the memory circuit 8. The functions of the control circuit 9 in the first embodiment will be described later.

[0022] The functional configuration of the automatic analyzer 1 has been described above. Next, the configuration of the analysis mechanism 2 will be described with reference to FIG. 2.

[0023] FIG. 2 is a schematic diagram illustrating the configuration of the analysis mechanism 2 in FIG. 1. The analysis mechanism 2 includes a reaction disk 201, a thermostat 202, a rack sampler 203, a first reagent reservoir 204, and a second reagent reservoir 205. The analysis mechanism 2 also includes a sample dispensing arm 206, a sample dispensing probe 207, a first reagent dispensing arm 208, a first reagent dispensing probe 209, a second reagent dispensing arm 210, a second reagent dispensing probe 211, an electrode unit 212, a photometry unit 213, a cleaning unit 214, and a stirring unit 215. Note that the liquid level detection circuit 21 is not shown in FIG. 2. Also, the automatic analyzer 1 is provided with a top cover (not shown) that covers the entire analysis mechanism 2.

[0024] First, the reaction disk 201, the thermostat 202, the rack sampler 203, the first reagent reservoir 204, and the second reagent reservoir 205 will be described below.

[0025] The reaction disk 201 holds a plurality of reaction vessels 2011 arranged in a ring. The reaction disk 201 conveys the plurality of reaction vessels 2011 along a predetermined path. Specifically, the reaction disk 201 is rotated and stopped alternately at a predetermined time interval (hereinafter referred to as one cycle), for example, 4.5 seconds or 9.0 seconds, by the drive mechanism 4. The reaction vessel 2011 is formed of, for example, glass, polypropylene (PP), or acrylic.

[0026] The thermostat 202 stores a heat medium (for example, water) maintained at a predetermined temperature (usually 37°C). The thermostat 202 immerses the reaction vessel 2011 in the stored heat medium to heat the liquid (mixed solution) contained in the reaction vessel 2011 and maintain it at a constant temperature.

[0027] The rack sampler 203 movably supports a sample rack 2031. The sample rack 2031 can hold a plurality of sample containers 2032 that accommodate samples for which measurements have been requested. In FIG. 2, a sample rack 2031 that can hold five sample containers 2032 in parallel is illustrated.

[0028] The rack sampler 203 is provided with a transport area for transporting the sample rack 2031 from the loading position where the sample rack 2031 is loaded to the recovery position where the sample rack 2031 after the measurement is completed. In the transport area, a plurality of sample racks 2031 aligned adjacent to each other in the short side direction of the sample rack 2031 are moved in the direction D1 (the long side direction of the transport area) by the drive mechanism 4.

[0029] In addition, the rack sampler 203 is provided with a retraction area for retracting the sample rack 2031 from the transport area in order to move the sample container 2032 held by the sample rack 2031 to a predetermined sample suction position. The sample suction position is provided, for example, at a position where the rotation orbit of the sample dispensing probe 207 intersects with the movement orbit of the opening of the sample container 2032 supported by the rack sampler 203 and held by the sample rack 2031. In the retraction area, the transported sample rack 2031 is moved in the direction D2 (the short side direction of the transport area) by the drive mechanism 4.

[0030] In addition, the rack sampler 203 is provided with a return area for returning the sample rack 2031 holding the sample container 2032 from which the sample has been sucked to the transport area. In the return area, the sample rack 2031 is moved in the direction D3 (the direction opposite to the direction D2) by the drive mechanism 4.

[0031] The first reagent reservoir 204 refrigerates a plurality of reagent containers 100 that contain a first reagent that reacts with a predetermined component contained in the standard sample and the test sample. Although not shown in FIG. 2, during the operation of the automatic analyzer 1, the first reagent reservoir 204 is covered with a detachable reagent cover. Inside the first reagent reservoir 204, a reagent rack is rotatably provided. The reagent rack holds a plurality of reagent containers 100 arranged in an annular shape. The reagent rack is rotated by the drive mechanism 4.

[0032] At a predetermined position on the first reagent reservoir 204, a first reagent suction position is set. The first reagent suction position is provided, for example, at a position where the rotation orbit of the first reagent dispensing probe 209 described later intersects with the movement orbit of the openings of the reagent containers 100 arranged in an annular shape on the reagent rack.

[0033] The second reagent reservoir 205 stores and keeps cold a plurality of reagent containers 100 containing a second reagent that pairs with the first reagent in a two-reagent system. Although not shown in FIG. 2, during the operation of the automatic analyzer 1, the second reagent reservoir 205 is covered with a detachable reagent cover. A reagent rack is rotatably provided in the second reagent reservoir 205. The reagent rack arranges and holds a plurality of reagent containers 100 in an annular shape. Incidentally, the second reagent kept cold in the second reagent reservoir 205 may be a reagent having the same component and the same concentration as the first reagent kept cold in the first reagent reservoir 204.

[0034] At a predetermined position on the second reagent reservoir 205, a second reagent suction position is set. The second reagent suction position is provided, for example, at a position where the rotation orbit of the second reagent dispensing probe 211 described later intersects with the movement orbit of the openings of the reagent containers 100 arranged in an annular shape on the reagent rack.

[0035] Next, the sample dispensing arm 206, the sample dispensing probe 207, the first reagent dispensing arm 208, the first reagent dispensing probe 209, the second reagent dispensing arm 210, the second reagent dispensing probe 211, the electrode unit 212, the photometry unit 213, the cleaning unit 214, and the stirring unit 215 will be described.

[0036] The sample dispensing arm 206 is provided between the reaction disk 201 and the rack sampler 203. The sample dispensing arm 206 is provided by the drive mechanism 4 so as to be vertically movable up and down and horizontally rotatable. The sample dispensing arm 206 holds the sample dispensing probe 207 at one end.

[0037] The sample dispensing probe 207 rotates along an arc-shaped rotation orbit as the sample dispensing arm 206 rotates. The openings of the sample containers held in the sample rack 2031 on the rack sampler 203 are positioned on this rotation orbit.

[0038] Also, on the rotation orbit of the sample dispensing probe 207, a sample discharge position for discharging the sample aspirated by the sample dispensing probe 207 into the reaction vessel 2011 is provided. The sample discharge position corresponds to the intersection of the rotation orbit of the sample dispensing probe 207 and the movement orbit of the reaction vessel 2011 held on the reaction disk 201.

[0039] Also, the sample dispensing probe 207 is driven by the drive mechanism 4 and moves vertically above the opening of the sample container held in the sample rack 2031 on the rack sampler 203 or at the sample discharge position.

[0040] Also, the sample dispensing probe 207 aspirates the sample from the sample container located directly below according to the control of the control circuit 9. Also, the sample dispensing probe 207 discharges the aspirated sample into the reaction vessel 2011 located directly below the sample discharge position according to the control of the control circuit 9. The sample dispensing probe 207 performs a series of dispensing operations of aspiration and discharge, for example, once per cycle.

[0041] The first reagent dispensing arm 208 is provided, for example, between the reaction disk 201 and the first reagent reservoir 204. The first reagent dispensing arm 208 is provided by the drive mechanism 4 so as to be vertically movable up and down and horizontally rotatable. The first reagent dispensing arm 208 holds the first reagent dispensing probe 209 at one end.

[0042] The first reagent dispensing probe 209 rotates along an arcuate rotation orbit as the first reagent dispensing arm 208 rotates. A first reagent suction position is provided on this rotation orbit. Also, a first reagent discharge position for discharging the reagent sucked by the first reagent dispensing probe 209 into the reaction vessel 2011 is set on the rotation orbit of the first reagent dispensing probe 209. The first reagent discharge position corresponds to the intersection of the rotation orbit of the first reagent dispensing probe 209 and the movement orbit of the reaction vessel 2011 held on the reaction disk 201.

[0043] The first reagent dispensing probe 209 is driven by a drive mechanism 4 and moves vertically at the first reagent suction position or the first reagent discharge position on the rotation orbit. Also, the first reagent dispensing probe 209 sucks the first reagent from a reagent container positioned directly below the first reagent suction position in accordance with the control of the control circuit 9. Further, the first reagent dispensing probe 209 discharges the sucked first reagent into the reaction vessel 2011 positioned directly below the first reagent discharge position in accordance with the control of the control circuit 9.

[0044] Note that the first reagent dispensing probe 209 in the first embodiment includes a probe heater for heating the first reagent and the like. Hereinafter, the first reagent dispensing probe and the heater will be described with reference to FIG. 3.

[0045] FIG. 3 is a schematic diagram illustrating the first reagent dispensing probe 209 and the heater 2090 in the first embodiment. The heater 2090 includes a heating element 2091 and a heater shield 2092. FIG. 3(a) shows the first reagent dispensing probe 209 housed in the heater shield 2092 around which the heating element 2091 is wound, and FIG. 3(b) shows a cross section thereof. Note that the first reagent dispensing probe 209 and the heater shield 2092 are not electrically connected.

[0046] The heating element 2091 has a structure in which a metal such as a nickel-chromium alloy wire (nichrome wire) is formed into a spiral shape. The heater shield 2092 is, for example, a conductive member formed of a vertically long cylindrical tube. The heating element 2091 is used in a state of being wound around the heater shield 2092.

[0047] Also, the heater shield 2092 allows the first reagent dispensing probe 209 to penetrate. The first reagent held by the first reagent dispensing probe 209 is heated by the heat generated by the heating element 2091 being conducted to the heater shield 2092 and the heat of the heater shield 2092 being radiated to the first reagent dispensing probe 209. In other words, the heater 2090 heats the liquid in the first reagent dispensing probe 209.

[0048] The second reagent dispensing arm 210 is provided, for example, between the reaction disk 201 and the second reagent reservoir 205. The second reagent dispensing arm 210 is provided by the drive mechanism 4 so as to be vertically movable up and down and horizontally rotatable. The second reagent dispensing arm 210 holds a second reagent dispensing probe 211 at one end.

[0049] The second reagent dispensing probe 211 rotates along an arc-shaped rotation orbit as the second reagent dispensing arm 210 rotates. A second reagent suction position is provided on this rotation orbit. Also, on the rotation orbit of the second reagent dispensing probe 211, a second reagent discharge position for discharging the reagent sucked by the second reagent dispensing probe 211 into the reaction vessel 2011 is set. The second reagent discharge position corresponds to the intersection of the rotation orbit of the second reagent dispensing probe 211 and the movement orbit of the reaction vessel 2011 held on the reaction disk 201.

[0050] The second reagent dispensing probe 211 is driven by the drive mechanism 4 and moves vertically at the second reagent suction position or the second reagent discharge position on the rotation trajectory. Further, the second reagent dispensing probe 211 sucks the second reagent from the reagent container located directly below the second reagent suction position in accordance with the control of the control circuit 9. Further, the second reagent dispensing probe 211 discharges the sucked second reagent into the reaction vessel 2011 located directly below the second reagent discharge position in accordance with the control of the control circuit 9.

[0051] The configuration of the analysis mechanism 2 has been described above. Next, the configuration of the liquid level detection circuit 21 included in the analysis mechanism 2 will be described with reference to FIG. 4.

[0052] FIG. 4 is a block diagram illustrating the configuration of the liquid level detection circuit 21 in the first embodiment. The liquid level detection circuit 21 includes an oscillation circuit 310, a bridge circuit 320, a differential amplifier circuit 330, a synchronous detection circuit 340, an integration circuit 350, an amplifier circuit 360, a comparison circuit 370, an automatic phase shift circuit 380, and a capacitance adjustment circuit 390. Note that the capacitance adjustment circuit 390 may not be included in the liquid level detection circuit 21.

[0053] The liquid level detection circuit 21 is electrically connected to the first reagent dispensing probe 209. The liquid level detection circuit 21 detects the contact between the first reagent dispensing probe 209 and the liquid level, and outputs the detected information (detection information) to the control circuit 9. The detection information includes, for example, information at the moment of contact with the liquid level and information while in contact with the liquid level.

[0054] Further, the liquid level detection circuit 21 receives a zero adjustment signal that serves as a trigger for adjusting the liquid level detection circuit 21 from the control circuit 9. When the zero adjustment signal is input, the liquid level detection circuit 21 has a function of automatically adjusting variations so that the output in a state where the first reagent dispensing probe 209 is not in contact with the liquid level becomes zero. The variations here include, for example, those caused by errors in the capacitance of the fixed capacitor C0 included in the bridge circuit 320 and those caused by changes in the parasitic capacitance accompanying the movement of the first reagent dispensing probe 209.

[0055] Furthermore, the liquid level detection circuit 21 receives capacitance adjustment information from the control circuit 9 for adjusting the capacitance of the capacitor in the capacitance adjustment circuit 390. The liquid level detection circuit 21 automatically adjusts the capacitance deviation caused by the heater 2090 used together with the first reagent dispensing probe 209 and the capacitance change caused by the temperature change of the heater 2090 according to the capacitance adjustment information. The capacitance deviation is generated by connecting the heater shield 2092 to the liquid level detection circuit 21. Specifically, the capacitance change is caused by the temperature change of the heater shield 2092 around which the heating element 2091 is wound.

[0056] Hereinafter, each circuit included in the liquid level detection circuit 21 will be specifically described.

[0057] The oscillation circuit 310 generates an oscillation signal of a predetermined frequency. The oscillation circuit 310 outputs the oscillation signal to the bridge circuit 320 and the automatic phase shift circuit 380.

[0058] The bridge circuit 320 inputs the oscillation signal from the oscillation circuit 310. The bridge circuit 320 is electrically connected to the first reagent dispensing probe 209, the heater shield 2092, and the capacitance adjustment circuit 390, respectively. The bridge circuit 320 outputs the voltage of the potential difference between two connection points in the circuit to the differential amplification circuit 330. The specific configuration of the bridge circuit 320 will be described later.

[0059] The differential amplification circuit 330 inputs the voltage signal of the potential difference between two connection points in the circuit from the bridge circuit 320. The differential amplification circuit 330 outputs the differential amplification signal generated by differentially amplifying the input voltage signal to the synchronous detection circuit 340.

[0060] The synchronous detection circuit 340 receives the differential amplification signal from the differential amplification circuit 330 and the reference signal from the automatic phase shift circuit 380. The synchronous detection circuit 340 operates to selectively extract only the differential amplification signal having the same frequency component as the reference signal. Specifically, the synchronous detection circuit 340 outputs a synchronous detection signal generated by performing full-wave rectification on both waves according to the polarity of the reference signal synchronized with the differential amplification signal to the integration circuit 350.

[0061] For example, when the first reagent dispensing probe 209 is not in contact with the liquid surface, since the phase difference between the differential amplification signal and the reference signal is set to 90 degrees, the synchronous detection signal output by the synchronous detection circuit 340 indicates zero. Also, even when there is some variation in the differential amplification signal due to the movement of the first reagent dispensing probe 209 or the like, the phase of the reference signal is adjusted by the automatic phase shift circuit 380, so the synchronous detection signal output by the synchronous detection circuit 340 indicates zero.

[0062] The integration circuit 350 receives the synchronous detection signal from the synchronous detection circuit 340. The integration circuit 350 blocks the frequency components of the synchronous detection signal above a predetermined frequency and outputs a low-pass signal generated by passing the other frequency components to the amplification circuit 360.

[0063] The amplification circuit 360 receives the low-pass signal from the integration circuit 350. The amplification circuit 360 outputs the output signal generated by amplifying the low-pass signal to the comparison circuit 370 and the automatic phase shift circuit 380.

[0064] The comparison circuit 370 receives the output signal from the amplification circuit 360. The comparison circuit 370 generates detection information by comparing the output signal with a preset detection level (threshold value). For example, the information at the moment of contact with the liquid level included in the detection information is obtained by inputting the output signal (the first signal) into a differentiating circuit (not shown) and inputting the output signal (the second signal) from the differentiating circuit into a comparator (not shown). Also, for example, the information while in contact with the liquid level included in the detection information is obtained by inputting the output signal (the first signal) into a comparator (not shown). The comparison circuit 370 outputs the detection information to the control circuit 9.

[0065] The automatic phase shift circuit 380 receives the oscillation signal from the oscillation circuit 310, the output signal from the amplification circuit 360, and the zero adjustment signal from the control circuit 9. The automatic phase shift circuit 380 generates a reference signal based on the oscillation signal and the input signal upon receiving the zero adjustment signal. The automatic phase shift circuit 380 outputs the reference signal to the synchronous detection circuit 340. Hereinafter, the specific configuration of the automatic phase shift circuit 380 will be described with reference to FIG. 5.

[0066] FIG. 5 is a block diagram illustrating the configuration of the automatic phase shift circuit 380 in FIG. 4. The automatic phase shift circuit 380 includes a sample and hold circuit 381 and a reference signal generation circuit 382.

[0067] When the zero adjustment signal is input, the sample and hold circuit 381 amplifies the output signal by an error amplification circuit (not shown) and holds the generated amplified signal. The sample and hold circuit 381 outputs the held amplified signal to the reference signal generation circuit 382.

[0068] When the amplified signal is input from the sample and hold circuit 381, the reference signal generation circuit 382 generates a reference signal based on the oscillation signal and the amplified signal. At this time, the phase difference between the reference signal and the oscillation signal is 90 degrees. Specifically, the reference signal generation circuit 382 includes a phase delay circuit 3821, a multiplication circuit 3822, a phase advance circuit 3823, and an addition circuit 3824.

[0069] The phase delay circuit 3821 generates a phase delay signal by imparting a predetermined phase delay to the oscillation signal. The phase delay circuit 3821 outputs the phase delay signal to the multiplication circuit 3822.

[0070] The multiplication circuit 3822 generates a multiplication signal by multiplying the amplified signal and the phase delay signal. The multiplication circuit 3822 outputs the multiplication signal to the addition circuit 3824.

[0071] The phase advance circuit 3823 generates a phase advance signal by imparting a predetermined phase advance to the oscillation signal. The phase advance circuit 3823 outputs the phase advance signal to the addition circuit 3824.

[0072] The addition circuit 3824 receives the multiplication signal from the multiplication circuit 3822 and the phase advance signal from the phase advance circuit 3823. The addition circuit 3824 generates a reference signal by adding the multiplication signal and the phase advance signal. The addition circuit 3824 outputs the reference signal to the synchronous detection circuit 340.

[0073] As described above, the liquid level detection circuit 21 can absorb to some extent the variations in the output when the first reagent dispensing probe 209 is not in contact with the liquid level by means of the automatic phase shift circuit 380. For example, even if the capacitance of the fixed capacitor C0 mounted on the bridge circuit 320 deviates from a predetermined value (for example, 3.3 pF), the liquid level detection circuit 21 can absorb changes up to ±4 pF. Also, for example, the liquid level detection circuit 21 can similarly absorb the change in the parasitic capacitance associated with the movement of the first reagent dispensing probe 209.

[0074] In other words, the liquid level detection circuit 21 can detect the changes in the amplitude and phase of the signal associated with the impedance conversion when the probe comes into contact with the liquid level, and can adjust the voltage value based on the above signal to a predetermined value when the probe and the liquid level are not in contact. The predetermined value is, for example, 0.4 V.

[0075] Next, before explaining the capacitance adjustment circuit 390, each function of the control circuit 9 in the first embodiment will be described. After the description of each function of the control circuit 9, the capacitance adjustment circuit 390 will be described.

[0076] The control circuit 9 shown in FIG. 1 realizes functions corresponding to the control program by executing the control program stored in the memory circuit 8. For example, the control circuit 9 realizes a system control function 91 and a capacitance determination function 92 by executing the control program.

[0077] In the first embodiment, a case where the system control function 91 and the capacitance determination function 92 are realized by a single processor will be described, but it is not limited thereto. For example, a control circuit may be configured by combining a plurality of independent processors, and each processor may execute a control program to realize the system control function 91 and the capacitance determination function 92. This also applies to other embodiments and the like.

[0078] By the system control function 91, the control circuit 9 controls the respective parts in the automatic analyzer 1 in an overall manner based on, for example, an inspection order input from the input interface 5. Specifically, the control circuit 9 controls the reagent racks of the first reagent storage 204, the reagent racks of the second reagent storage 205, the rotation operation of the reaction disk 201, the rotation operation and dispensing operation of the sample dispensing probe, the rotation operation and dispensing operation of the first reagent dispensing probe, and the rotation operation and dispensing operation of the second reagent dispensing probe.

[0079] Further, by the system control function 91, the control circuit 9 receives the set temperature regarding the first reagent. Further, the control circuit 9 controls the temperature of the heater 2090 used together with the first reagent dispensing probe 209. In other words, the control circuit 9 controls the temperature of the heater 2090 according to the set temperature regarding the first reagent.

[0080] The capacity determination function 92 causes the control circuit 9 to determine the value of the capacitance of the capacitor adjusted by the capacitance adjustment circuit 390. Specifically, the control circuit 9 sets the temperature of the heater 2090 so as to be the set temperature for the first reagent, and determines the value of the capacitance related to the heater 2090 at the set temperature. The value of the capacitance related to the heater 2090 is the same as the value of the capacitance of the capacitor adjusted by the capacitance adjustment circuit 390. For example, a table associating the set temperature for the first reagent with the value of the capacitance is used for the determination of the capacitance. The control circuit 9 outputs capacitance adjustment information related to the determined value of the capacitance to the capacitance adjustment circuit 390.

[0081] Note that the control circuit 9 may determine the value of the capacitance related to the heater 2090 in a state where the heater 2090 is not being heated, by the capacity determination function 92. A state where the heater 2090 is not operating is assumed, for example, when performing maintenance operations such as position adjustment of the first reagent dispensing probe 209. During maintenance operations, if it is not necessary to warm the first reagent, it is not always necessary to operate the heater 2090. Also, during maintenance operations, the top cover may be opened and the user may perform work, and if the heater 2090 were operating, there would also be a risk of burns. When performing such maintenance operations, when it is necessary to perform liquid level detection by the first reagent dispensing probe 209, the value of the capacitance related to the heater 2090 in a state where the heater 2090 is not being heated is required.

[0082] In other words, the control circuit 9 determines the value of the capacitance related to the heater according to the temperature, by the capacity determination function 92. Specifically, the control circuit 9 determines the value of the capacitance related to the heater using a table associating the temperature with the value of the capacitance related to the heater. Also, the control circuit 9 determines the value of the capacitance related to the heater in a state where the heater is not operating, by the capacity determination function 92.

[0083] The capacitance adjustment circuit 390 is electrically connected to the bridge circuit 320. The capacitance adjustment circuit 390 inputs capacitance adjustment information from the control circuit 9. The capacitance adjustment circuit 390 changes the capacitor connected to the bridge circuit 320 according to the capacitance adjustment information. The capacitance adjustment information relates to the value of the capacitance regarding the heater 2090, and this capacitance value relates to the set temperature regarding the first reagent. In other words, the capacitance adjustment circuit 390 adjusts the capacitance of the capacitor regarding the circuit used for liquid level detection based on the temperature related to the heating of the liquid. Hereinafter, the specific configuration of the capacitance adjustment circuit 390 and the specific configuration of the bridge circuit 320 will be described with reference to FIG. 6.

[0084] FIG. 6 is a diagram illustrating the connection between the bridge circuit 320 of FIG. 4, the capacitance adjustment circuit 390, the heater shield 2092, and the first reagent dispensing probe 209. The bridge circuit 320 includes four resistors R1 to R4 and a fixed capacitor C0. The four resistors R1 to R4 each have the same resistance value. The fixed capacitor C0 has a capacitance that balances with the stationary state of the first reagent dispensing probe 209. The stationary state is a state where the first reagent dispensing probe 209 is stationary and not in contact with the liquid surface. For example, when the heater shield 2092 is not connected to the bridge circuit 320, the bridge circuit 320 cancels out the capacitance generated regarding the stationary first reagent dispensing probe 209 with the fixed capacitor C0, thereby keeping the input to the differential amplifier circuit 330 balanced. At this time, the capacitance of the fixed capacitor C0 is, for example, 3.3 pF.

[0085] Hereinafter, the connection relationship between the bridge circuit 320, the first reagent dispensing probe 209, and the capacitance adjustment circuit 390 will be described in detail. Also, the case where the heater shield 2092 is connected to the bridge circuit 320 will be considered. For convenience of explanation, the point where elements are connected, etc. is called a connection point. Also, the bridge circuit 320 has four connection points P1 to P4.

[0086] One end of the oscillation circuit 310, one end of the resistor R1, and one end of the resistor R4 are connected to the connection point P1. The other end of the oscillation circuit 310 is grounded. The other end of the resistor R1 is connected to the connection point P2. The other end of the resistor R4 is connected to the connection point P4.

[0087] One end of the other end of the resistor R1, one end of the resistor R2, one end of the fixed capacitor C0, and the heater shield 2092 are connected to the connection point P2. The other end of the resistor R2 and the end of the fixed capacitor C0 are connected to the connection point P3. That is, the resistor R2 and the fixed capacitor C0 are connected in parallel. Also, the connection point P2 is connected to the first input of the differential amplifier circuit 330.

[0088] One end of the other end of the resistor R2, the other end of the fixed capacitor C0, and the other end of the resistor R3 are connected to the connection point P3 and grounded.

[0089] One end of the resistor R3, the other end of the resistor R4, the first reagent dispensing probe 209, and the capacitance adjustment circuit 390 are connected to the connection point P4. Also, the connection point P4 is connected to the second input of the differential amplifier circuit 330.

[0090] For example, in the stationary state of the first reagent dispensing probe 209, when the input to the differential amplifier circuit 330 is kept balanced by the capacitance adjustment circuit 390, when the first reagent dispensing probe 209 comes into contact with the liquid surface, the capacitance on the connection point P4 side to which the first reagent dispensing probe 209 is connected becomes larger than the capacitance on the connection point P2 side. As a result, the balance between the first input and the second input to the differential amplifier circuit 330 is disrupted, and the liquid level detection circuit 21 can detect the contact between the first reagent dispensing probe 209 and the liquid surface.

[0091] The bridge circuit 320 configured as described above can detect the presence or absence of contact between the first reagent dispensing probe 209 and the liquid surface based on the voltage of the potential difference between the connection point P2 and the connection point P4. Hereinafter, the liquid level detection when the capacitance is balanced will be described with reference to FIG. 7.

[0092] FIG. 7 is a graph for explaining liquid level detection when the capacitance balance is achieved. In FIG. 7, a graph 710 and a graph 720 are shown, where the horizontal axis represents time and the vertical axis represents voltage. The graph 710 is the change of the first signal in the comparison circuit 370. The graph 720 is the change of the second signal in the comparison circuit 370.

[0093] In FIG. 7, since the capacitance balance is achieved, the voltages of the graph 710 and the graph 720 increase from the time t0 when the probe actually contacts the liquid surface. To prevent false detection, the time when the probe contacts the liquid surface is, for example, the time when the second signal, which is the graph 720, exceeds the voltage threshold Vth. However, in the example of FIG. 7, since the time when the second signal, which is the graph 720, exceeds the voltage threshold Vth is immediately after the time t0, the time when the probe contacts the liquid surface can be regarded as the time t0.

[0094] Next, consider the influence of the heater shield 2092. If the capacitance adjustment circuit 390 is not connected to the connection point P4, since the heater shield 2092 is connected to the connection point P2, the input to the differential amplifier circuit 330 may not be kept balanced even in the stationary state of the first reagent dispensing probe 209. This is due to the fact that the capacitance generated with respect to the heater shield 2092 is as large as about 60 pF, and the capacitance on the connection point P2 side becomes larger than the capacitance on the connection point P4 side. Hereinafter, the liquid level detection when the capacitance balance is not achieved will be described with reference to FIG. 8.

[0095] FIG. 8 is a graph for explaining liquid level detection when the capacitance balance is not achieved. In FIG. 8, a graph 810 and a graph 820 are shown, where the horizontal axis represents time and the vertical axis represents voltage. The graph 810 is the change of the first signal in the comparison circuit 370. The graph 720 is the change of the second signal in the comparison circuit 370.

[0096] In FIG. 8, since the capacitance balance is not achieved, in graphs 810 and 820, the voltage increases after decreasing from the time t0 when the probe actually contacts the liquid surface. Similar to the example of FIG. 7, the time when the probe contacts the liquid surface is the point in time when the second signal, which is graph 820, exceeds the voltage threshold Vth. Therefore, in the example of FIG. 8, the timing of liquid surface detection is delayed by the period Δt during which the voltage value is decreasing. Further, due to the delay in the timing of liquid surface detection, the penetration time (penetration amount) of the probe into the liquid surface increases. This is undesirable because it causes variations in the inspection conditions.

[0097] From the above, when the heater shield 2092 is connected to the connection point P2, by connecting the capacitance adjustment circuit 390 to the connection point P4 and setting the appropriate capacitance on the connection point P4 side, the input imbalance to the differential amplifier circuit 330 can be eliminated. Hereinafter, the specific configuration of the capacitance adjustment circuit 390 will be described.

[0098] The capacitance adjustment circuit 390 includes a switch control circuit 391, a plurality of switches SWp1 to SWpM, and a plurality of capacitors Cp1 to CpM. Note that M is a design value and can be any number.

[0099] The switch control circuit 391 inputs capacitance adjustment information from the control circuit 9. The switch control circuit 391 generates a control signal for controlling each of the plurality of switches SWp1 to SWpM based on the capacitance adjustment information. The switch control circuit 391 outputs the control signal to each of the plurality of switches SWp1 to SWpM.

[0100] One end of each of the plurality of switches SWp1 to SWpM is connected to the connection point P4 of the bridge circuit 320, and the other end of each is connected to one end of each of the plurality of capacitors Cp1 to CpM. The plurality of switches SWp1 to SWpM each receive a control signal from the switch control circuit 391. Then, the plurality of switches SWp1 to SWpM each switch between the on state and the off state according to the control signal.

[0101] For the plurality of capacitors Cp1 to CpM, one end of each is connected to the other end of each of the plurality of switches SWp1 to SWpM, and the other end of each is grounded. The plurality of capacitors Cp1 to CpM may each have a different capacitance, or at least two of them may have the same capacitance.

[0102] In other words, the capacitance adjustment circuit 390 adjusts the capacitance by switching each of the plurality of capacitors connected to the circuit used for liquid level detection. Further, when the circuit used for liquid level detection is a bridge circuit, the capacitance adjustment circuit 390 adjusts the capacitance by switching each of the plurality of capacitors connected to the bridge circuit.

[0103] The configuration of the liquid level detection circuit 21 included in the analysis mechanism 2 has been described above. Next, the operation of the automatic analyzer according to the first embodiment will be described with reference to the flowchart of FIG. 9.

[0104] FIG. 9 is a flowchart illustrating the operation of the automatic analyzer according to the first embodiment. The flowchart of FIG. 9 is started, for example, when the user executes a control program.

[0105] (Step ST110) When the control program is executed, the control circuit 9 receives, by the system control function 91, the set temperature for the first reagent.

[0106] (Step ST120) After receiving the set temperature, the control circuit 9 determines, by the capacitance determination function 92, the value of the probe capacitance according to the set temperature. Specifically, the control circuit 9 determines the value of the probe capacitance corresponding to the set temperature using a table associating the set temperature with the capacitance value. The control circuit 9 outputs capacitance adjustment information regarding the determined capacitance value to the capacitance adjustment circuit 390. Hereinafter, the table associating the set temperature for the first reagent with the capacitance value will be described with reference to FIG. 10.

[0107] Figure 10 is a table 1000 associating the set temperature and the capacitance value for the first reagent in the first embodiment. In table 1000, the capacitance values are associated with the case where the heating temperature (set temperature) of the first reagent (R1) is set in 2°C increments from 46°C to 70°C. For example, when the R1 set temperature is "50°C", the capacitance "61.6 pF" is associated, and when the R1 set temperature is "64°C", the capacitance "62.5 pF" is associated.

[0108] (Step ST130) After the capacitance value is determined, the switch control circuit 391 controls the switches of the capacitance adjustment circuit based on the capacitance value. Specifically, the switch control circuit 391 switches a plurality of switches of the capacitance adjustment circuit 390 based on the capacitance adjustment information. By switching the plurality of switches by the switch control circuit 391, the connection state of the plurality of capacitors connected to the bridge circuit 320 is switched, and the capacitance adjustment circuit 390 can adjust the number of capacitors connected to the bridge circuit 320. Note that the number of capacitors connected to the bridge circuit 320 corresponds to the total capacitance.

[0109] As described above, the automatic analyzer according to the first embodiment includes a probe, a heater for heating the liquid in the probe, and a liquid level detection circuit that is electrically connected to the probe and detects the contact between the probe and the liquid level. The liquid level detection circuit includes a capacitance adjustment circuit that adjusts the capacitance of the capacitors of the circuit used for liquid level detection based on the temperature related to the heating of the liquid.

[0110] Therefore, since the automatic analyzer according to the first embodiment can adjust the capacitance of the capacitors of the circuit used for liquid level detection regardless of the temperature of the heater, the convenience of liquid level detection by the probe using the heater can be improved. In addition, since this automatic analyzer can design the capacitance adjustment circuit according to the performance of the heater, it can also cope with variations in capacitance due to the secular deterioration of the heater.

[0111] (Modification of the First Embodiment) In the automatic analyzer according to the first embodiment, the heater shield 2092 is connected to the connection point P2 of the bridge circuit 320 shown in FIG. 6, but it is not limited to this. In the automatic analyzer according to the modification of the first embodiment, the heater shield 2092 may be connected to the connection point P3 of the bridge circuit 320. When the heater shield 2092 is connected to the connection point P3, since the capacitance on the connection point P4 side becomes larger than the capacitance on the connection point P2 side, the capacitance adjustment circuit 390 is connected to the connection point P2. By connecting in this way, the automatic analyzer according to the modification of the first embodiment can eliminate the input imbalance to the differential amplifier circuit 330 using the same method as the automatic analyzer according to the first embodiment.

[0112] (Second Embodiment) The description of the liquid level detection when using a heater for the first reagent dispensing probe in the automatic analyzer according to the first embodiment is not limited to this. In the automatic analyzer according to the second embodiment, a heater may be used for the second reagent dispensing probe. The liquid level detection when using a heater for the second reagent dispensing probe may use the same method as the first embodiment that described the case when using a heater for the first reagent dispensing probe. Hereinafter, a table associating the set temperature and the capacitance value for the second reagent will be described with reference to FIG. 11.

[0113] FIG. 11 is a table 1100 associating the set temperature and the capacitance value for the second reagent in the second embodiment. In the table 1100, the capacitance values are associated with the case where the heating temperature (set temperature) of the second reagent (R2) is set at 2°C intervals from 50°C to 72°C. For example, when the R1 set temperature is "50°C", the capacitance "40.2 pF" is associated, and when the R1 set temperature is "64°C", the capacitance "41.3 pF" is associated.

[0114] When comparing Table 1000 in FIG. 10 with Table 1100 in FIG. 11, the capacitance value set for the first reagent is larger than the capacitance value set for the second reagent. This is related to the difference in the amount of reagent aspirated by the reagent probe. Typically, the usage amount of the first reagent is larger than that of the second reagent. For this reason, by increasing the number of turns of the heater winding for the first reagent dispensing probe compared to the number of turns of the heater winding for the second reagent dispensing probe, the size of the heater shield increases, and as a result, the capacitance value set for the first reagent becomes larger than the capacitance value set for the second reagent.

[0115] Note that the tables in FIGS. 10 and 11 may adjust the capacitance value in accordance with the replacement of the reagent dispensing probe. This is because there are individual differences in the capacitance generated for the reagent dispensing probe.

[0116] As described above, the automatic analyzer according to the second embodiment can also adjust the capacitance of the capacitor in the circuit used for liquid level detection with respect to the second reagent dispensing probe 211 using a heater.

[0117] Therefore, the automatic analyzer according to the second embodiment can improve the convenience of liquid level detection by the probe using a heater, similar to the automatic analyzer according to the first embodiment.

[0118] (Third Embodiment) The automatic analyzer according to each of the above embodiments connects a capacitance adjustment circuit either to the side where the fixed capacitor is connected or to the side where the probe is connected. On the other hand, the automatic analyzer according to the third embodiment will be described in terms of connecting capacitance adjustment circuits to both of them.

[0119] FIG. 12 is a diagram illustrating the connection between the bridge circuit 320A and the capacitance adjustment circuit 390A in the third embodiment. Note that in FIG. 12, the illustration of the probe and the heater (heater shield) used together with the probe is omitted.

[0120] The bridge circuit 320A has a configuration substantially the same as that of the bridge circuit 320 in FIG. 6. Specifically, the bridge circuit 320A includes four resistors R1A to R4A and a fixed capacitor C0A. The four resistors R1A to R4A each have the same resistance value. The fixed capacitor C0A has a capacitance that balances with the static state of a reagent dispensing probe (not shown). The static state is a state where the reagent dispensing probe is stationary and not in contact with the liquid surface.

[0121] Hereinafter, the connection relationship between the bridge circuit 320A and the capacitance adjustment circuit 390A will be described in detail. For convenience of explanation, a point where elements are connected is called a connection point. Also, the bridge circuit 320A has four connection points P1A to P4A. Note that since the connection relationship between the four resistors R1A to R4A and the fixed capacitor C0A is the same as the connection relationship between the four resistors R1 to R4 and the fixed capacitor C0 in FIG. 6, the description thereof is omitted.

[0122] The capacitance adjustment circuit 390A includes a switch control circuit 391A, a plurality of switches SWs1 to SWsN, a plurality of capacitors Cs1 to CsN, a plurality of switches SWp1 to SWpM, and a plurality of capacitors Cp1 to CpM. Note that both N and M are design values and may be any numbers.

[0123] The switch control circuit 391A inputs capacitance adjustment information from the control circuit 9. The switch control circuit 391 generates a control signal for controlling at least one of the plurality of switches SWs1 to SWsN and the plurality of switches SWp1 to SWpM based on the capacitance adjustment information. The switch control circuit 391A outputs the control signal to at least one of the plurality of switches SWs1 to SWsN and the plurality of switches SWp1 to SWpM.

[0124] One end of each of the plurality of switches SWs1 to SWsN is connected to the connection point P2A, and the other end of each is connected to one end of each of the plurality of capacitors Cs1 to CsN.

[0125] For the plurality of capacitors Cs1 to CsN, one end of each is connected to the other end of each of the plurality of switches SWs1 to SWsN, and the other end of each is grounded. The plurality of capacitors Cs1 to CsN may have different capacitances respectively, or at least two of them may have the same capacitance.

[0126] For the plurality of switches SWp1 to SWpM, one end of each is connected to the connection point P4A, and the other end of each is connected to one end of each of the plurality of capacitors Cp1 to CpM. Since the plurality of capacitors Cp1 to CpM are the same as those in the first embodiment, the description thereof is omitted.

[0127] According to the above configuration, when connecting the heater shield to the bridge circuit 320A, the automatic analysis device according to the third embodiment can make the two outputs of the bridge circuit 320A balanced regardless of whether it is connected to the connection point P2A or the connection point P4A. In addition, the automatic analysis device according to the third embodiment can perform control with higher accuracy than each of the above-described embodiments by combining and controlling the plurality of switches SWs1 to SWsN and the plurality of switches SWp1 to SWpM.

[0128] (Other embodiments) In the automatic analysis device according to the first to third embodiments, a fixed capacitor is mounted on the bridge circuit to balance with the probe, but it is not limited thereto. The automatic analysis device according to these embodiments may balance with the probe by a capacitance adjustment circuit without mounting a fixed capacitor.

[0129] According to at least one of the embodiments described above, the convenience of liquid level detection by a probe using a heater can be improved.

[0130] Although several embodiments have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations of embodiments can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, as well as in the invention described in the claims and the equivalent scope thereof.

Explanation of Reference Numerals

[0131] 1 Automatic analyzer 2 Analysis mechanism 3 Analysis circuit 4 Driving mechanism 5 Input interface 6 Output interface 7 Communication interface 8 Memory circuit 9 Control circuit 91 System control function 92 Capacity determination function 100 Reagent container 201 Reaction disk 2011 Reaction vessel 202 Thermostatic bath 203 Rack sampler 2031 Sample rack 2032 Sample container 204 First reagent storage 205 Second reagent storage 206 Sample dispensing arm 207 Sample dispensing probe 208 First reagent dispensing arm 209 First reagent dispensing probe 2090 Heater 2091 Heating element 2092 Heater shield 210 Second reagent dispensing arm 211 Second reagent dispensing probe 212 Electrode unit 213 Photometry unit 214 Cleaning unit 215 Stirring unit 21 Liquid level detection circuit 310 Oscillation circuit 320, 320A Bridge circuit 330 Differential amplifier circuit 340 Synchronous detection circuit 350 Integrating circuit 360 Amplifier circuit 370 Comparison circuit 380 Automatic phase-shifting circuit 381 Sample-and-hold circuit 382 Reference signal generation circuit 3821 Phase delay circuit 3822 Multiplication circuit 3823 Phase advance circuit 3824 Addition circuit 390, 390A Capacitance adjustment circuit 391, 391A Switch control circuit 710, 720, 810, 820 Graph 1000, 1100 Table

Claims

1. A probe, a heater for heating the liquid in the probe, a liquid level detection circuit that is electrically connected to the probe and detects contact between the probe and the liquid level, and comprising, The liquid level detection circuit includes a capacitance adjustment circuit that adjusts the capacitance of a capacitor in the circuit used for liquid level detection based on the temperature related to the heating of the liquid. An automatic analyzer.

2. A control circuit for determining a capacitance value related to the heater according to the temperature, further comprising, The capacitance adjustment circuit adjusts the capacitance of the capacitor based on the capacitance value related to the heater. The automatic analyzer according to claim 1.

3. The control circuit determines the capacitance value related to the heater using a table associating the temperature with the capacitance value related to the heater. The automatic analyzer according to claim 2.

4. The control circuit determines the capacitance value related to the heater in a state where the heater is not being heated. The automatic analyzer according to claim 2.

5. The capacitance adjustment circuit adjusts the capacitance of the capacitor by switching each of a plurality of capacitors connected to the circuit used for liquid level detection. The automatic analyzer according to claim 1.

6. The circuit used for liquid level detection is a bridge circuit. The capacitance adjustment circuit adjusts the capacitance by switching each of the plurality of capacitors connected to the bridge circuit. The automatic analyzer according to claim 5.

7. The capacitance adjustment circuit includes a plurality of switches, the plurality of capacitors, and a switch control circuit. The plurality of switches are electrically connected between each of the plurality of capacitors and the circuit used for liquid level detection. The switch control circuit controls the on / off of the plurality of switches based on the capacitance value related to the heater. The automatic analyzer according to claim 5.

8. The capacitance adjustment circuit adjusts the capacitance of the capacitor to adjust the capacitance deviation caused by the conductive member provided in the heater. The automatic analyzer according to claim 1.

9. The conductive member is electrically connected to the circuit used for liquid level detection. The automatic analyzer according to claim 8.

10. The liquid level detection circuit detects changes in the amplitude and phase of a signal accompanying a change in impedance when the probe comes into contact with the liquid level, and adjusts a voltage value based on the signal to a predetermined value when the probe and the liquid level are not in contact. The automatic analyzer according to claim 1.

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