JP5200126B2 - Liquid level contact detection method and apparatus - Google Patents

Description

  The present invention relates to a liquid level contact detection method and apparatus, and in particular, is applied to sample liquid level detection, liquid level contact detection, etc. in an analytical instrument or the like that involves a process of dispensing a sample with one or more probes. And a method and apparatus suitable for doing this.

  Conventionally, for example, it is known to detect a sample liquid level using a change in capacitance, and there are various methods and apparatuses. Here, for example, in the case of using a sample container and a dispensing probe, basically, the liquid level can be detected by a change in capacitance between the probe and the electrode near the container. It is possible to detect the sample liquid level in the container by a change in capacitance between the probe made of the conductive material and an electrode installed in the vicinity of the container.

Japanese Patent Laid-Open No. 4-290941 JP-A-8-114604

  Therefore, according to the following considerations by the present inventors, the following can be pointed out.

  (A) When the sample liquid level in the container is to be detected by a change in capacitance, this can be done using a comparison circuit that determines that the sample liquid level has been detected. By the way, in the conventional example so far, many proposals have been made to detect the liquid level by changing the capacitance, but the threshold value in the comparison circuit for determining the liquid level detection depends on a predetermined condition. For example, there is no mention of using values set according to conditions such as the shape of the sample container, the liquidity of the sample, and the simultaneous operation of a plurality of probes. In the field of automatic analyzers, various sample cups are usually used according to various samples with different dispensing volume ranges. Since there are various sample cups, the type is input to the device, and the cup Japanese Patent Laid-Open No. 4-290941 (Document 1) discloses that the sample mechanism is lowered by a predetermined amount corresponding to the type, but this is not limited (originally, various threshold values in the comparison circuit as described above are used. It is not intended to detect a liquid level using a threshold value for each condition by setting a plurality according to the conditions).

  (B) However, when the sample liquid level in the container is detected by a change in the capacitance between the probe made of the conductive material and the electrode placed in the vicinity of the container, the electrostatic charge may be generated depending on various conditions as exemplified above. As a result of the different volumes, the stable detection of the liquid level is affected when the conditions are different, and therefore it is difficult to achieve a stable sample collection, and therefore in the case of applications where the sample is dispensed with a probe. This also contributes to hindering accurate dispensing of the sample.

(D) This will be further described with reference to the drawings. FIGS. 6 and 7 to 10 are consideration views also referred to in the examples of the present invention described later. FIG. 6 shows the shape of the sample container and the sample. FIG. 7 to FIG. 10 illustrate cases where the capacitance varies depending on conditions such as the number of probe operations, respectively. In the figure, 101 is a probe (conductive probe), 106 is a sample container, 107 is a rack, 108 is a conductive cradle that also serves as an electrode near the container, and 109 is an oscillation voltage source (oscillation) connected to the electrode. Circuit). In the left part of FIG. 6, the relationship of the liquid dielectric constant ε in each container 106 as shown in FIG.
ε1> ε2 = ε2 (Equation 1)
In general, the capacitance C is
C = ε · (s / d) (Equation 2)
(Ε: dielectric constant, s: electrode area, d: distance between electrodes)
Therefore, as shown in the equivalent diagram on the right side of FIG. 6, there are cases where the capacitance values C1, C2, and C3 are different due to different conditions.
That is, in C1 and C2, the capacitance C1 has a larger capacitance (capacitance value C1) than the equations 1 and 2 in terms of the dielectric constant (ε1 is larger than ε2). On the other hand, in C2 and C3, the capacitance C2 has a larger capacitance (capacitance value C2) than Equations 1 and 2 in terms of the distance from the bottom to the electrode, the container cross-sectional area, and the liquid volume.
Thus, the capacitance varies depending on the conditions.

(E) Further, as shown in FIG. 7 and the following figures, for example, a plurality of independently suspended probes 101 are provided, and a capacitance between the probe made of a conductive material and an electrode (a cradle 108) installed in the vicinity of the container 106. When the sample liquid level in the container is detected due to a change (for example, the shape of the target sample container, the type of the sample (including the liquid property of the sample (dielectric constant of the liquid), etc.) Depending on the conditions, the capacitance may be different, even if the other conditions are the same.) The capacitance may be different, and a case depending on this may occur.
That is, as shown in the equivalent diagrams of the left part and the right part of FIG. 7, when a plurality of probes (four in the illustrated example) move up and down at the same time (in the direction of the arrow in the figure), a capacitor is formed between the probes. (Capacitance is taken as shown in the equivalent diagram on the right), and the capacitance is smaller than when the probe is used alone (for example, the case shown in FIG. 8). Therefore, the capacitance change is small.
On the other hand, if one probe (for example, only the second probe from the left) operates as shown in FIG. 8, unlike the equivalent diagram in the right part of FIG. 7, no capacitor is formed between the probes. (Capacitance is not taken between probes as shown in the equivalent diagram of FIG. 8), and the capacitance is larger than when there are multiple probes (case in FIG. 7). Therefore, the capacitance change is large.
On the other hand, as shown in the equivalent diagram of FIG. 9, this probe (second probe from the left) is the liquid in the other container (in each container corresponding to each of the first and third adjacent probes from the left). Of the liquid) also forms a capacitor.
As shown in the equivalent diagram of FIG. 10, this probe (the second probe from the left lowered by itself) is the other probe (the first, third, and fourth probes from the left). When it reaches the surface (falls), the capacitor that has constituted the other container disappears (the capacitor is taken by another probe).

  (F) Thus, according to the above-mentioned consideration by the present inventor, when the sample liquid level in the container is detected by a change in capacitance between the probe made of the conductive material and the electrode placed in the vicinity of the container. As shown in FIG. 6, the capacitance varies depending on conditions such as the shape of the sample container, the liquidity of the sample (dielectric constant of the liquid), and the number of probe operations (influence of interference of adjacent probes) as shown in FIGS. Therefore, it has become clear that it is difficult to set the threshold value of the comparison circuit to one for the processing result of the change amount.

  (G) Therefore, it is desirable that the liquid level can be detected stably even when the above conditions are different. It is also desirable that the electrostatic capacity such as the sample container, the type of sample, the number of probe operations, etc. It is possible to achieve this regardless of one or more conditions that may affect the volume, and regardless of the combination of these conditions, to enable stable sampling and therefore also to It is to make it possible to dispense accurately.

(H) As already mentioned, the technology for detecting the liquid level by changing the capacitance between the probe (conductive material probe) and the electrode near the container is already known, and many proposals have been made so far. However, if one step further considers here, the proposal about determining that the probe was attached to the sample liquid by the capacitance change has not yet been found.
Here, Japanese Patent Laid-Open No. 8-114604 (Document 2) determines whether a probe has been kept in contact with a sample solution for a predetermined time after the start of aspiration. Because it is a book, a liquid level detection signal is generated due to a change in capacitance when the liquid level is detected, and it is also possible to confirm whether the probe is in contact with the sample liquid level by monitoring the signal. It was made.

However, considering liquid level contact detection in the case of a large number of (multiple) conductive material probes, as already mentioned, there are independent suspended conductive probes that can move up and down individually. When there are two or more probes that require a liquid level detection function, such as detecting the liquid level of the sample in the container by changing the capacitance between the electrode and the electrode installed in the vicinity of the container, each probe is used as a physical phenomenon. Since the liquid level detection signals interfere with each other, it has become clear that the conventional circuit system cannot detect stable liquid level and liquid level contact. Here, if it is not possible to detect that the probe is in contact with the liquid surface, there is a possibility that a problem such as insufficient suction amount may occur. That is, it cannot be confirmed whether or not a predetermined amount of sample has been collected.
Due to interference of liquid level detection signals between multiple probes, if it is not possible to properly determine that the probe was on the sample liquid level due to changes in capacitance (contacted with the liquid), In order to guarantee the suction operation and to realize stable sampling, it becomes a factor that hinders these, and also affects the reliability of the obtained data.

  (N) Therefore, it is desirable that even when there are a plurality of probes having a liquid level detection function that uses a change in capacitance, it is possible to cope with not only the detection of the liquid level but also whether the probe is in contact with the liquid. It is also possible to make an appropriate determination, and it is also desirable that interference of the liquid level detection signal between multiple probes is a physical phenomenon that cannot be avoided. It is possible to detect contact with the liquid level and prevent disadvantages such as insufficient suction volume, and therefore, the liquid level in a dispenser having a large number of conductive material probes. A method and apparatus suitable as a method and apparatus for contact detection can be realized.

  The present invention is based on the above considerations and also based on the considerations described later, and is intended to improve from these points.

  The present invention provides the following liquid level contact detection method and apparatus. In other words, it has a plurality of independent suspended probes made of conductive materials, detects the sample liquid level in the container by the change in capacitance between the probe and the electrode installed near the container, stops the descent of the probe, and connects to the probe The liquid level contact detection method is characterized in that when the probe is lifted after the sample is sucked into the probe by the dispenser, the rising start timing of each probe is changed when detecting the separation from the liquid level. (Claim 1).

  Also, equipped with a plurality of independent suspended probes of conductive material, the sample liquid level in the container is detected by the capacitance change between the probe and the electrode installed in the vicinity of the container, and the probe descends and connected to the probe The liquid level is configured to change the rising start timing of each probe when detecting the separation of the liquid level when the probe is lifted after the sample is sucked into the probe by the dispenser. It is a contact detection device (claim 2).

  In the present invention, when the sample liquid level in the container is detected by a change in capacitance, a plurality of various threshold values in the comparison circuit that determines that the sample liquid level has been detected are set according to the condition, and the threshold value for each condition is set. It is possible to provide a method and an apparatus that can realize liquid level detection that detects the liquid level by using the liquid level and that can stably detect the liquid level even under different conditions. According to the liquid level detection according to the present invention, it does not depend on one or more conditions that may affect the capacitance, such as the sample container, the type of sample, and the number of probe operations, and also depends on the combination of these conditions. Instead, this can be achieved.

  In a preferred embodiment, even if the amount of signal change differs depending on the combination of conditions such as the sample container, the type of sample, and the number of probe operations, the probe is set at the liquid level by setting the threshold voltage according to the corresponding condition in advance. It is possible to minimize the variation in the response time from detection to detection, and thus the liquid level can be detected stably, so that the sample can be accurately dispensed. Here, after the probe detects the sample liquid level and its driving means decelerates to a stop, for example, the amount of penetration from the sample liquid level at the tip of the probe depends on the conditions of the target sample container, the type of sample, and the number of probe operations. Regardless of the combination, the variation is suppressed to the minimum, so that stable sampling can always be realized.

  In the present invention, it is possible to realize suitable liquid level contact detection when there are a plurality of probes that use capacitance change. For example, in the case of a single probe, there is no interference, so when the distance from the liquid level is exceeded. Although it is possible to detect that the probe has been immersed in the liquid by amplifying the signal amount of the capacitance change and making it larger than a certain threshold voltage, a plurality of probes may change the capacitance depending on, for example, the sample container and the liquid amount. The amount of attenuation due to interference may be greater than the amount of signal, and the liquid that embodies this is based on the idea that each probe can be moved away from the liquid in order to avoid this. A surface contact detection method and apparatus can be provided. According to the liquid level contact detection according to the present invention, it is possible to handle only the change in capacitance when each probe unit whose rise start timing has been changed is separated from the liquid. In addition, it is possible to appropriately detect that the liquid is in contact with the liquid level and to prevent disadvantages such as insufficient suction.

  In this case, according to the preferred embodiment, the probe not only detects the liquid level, but also guarantees the aspiration operation by the probe by determining whether the sample is still in contact with the liquid after sampling by the dispenser. Therefore, it is possible to immediately know that the suction amount is insufficient, and it is possible to always realize stable sampling.

FIG. 2 is a diagram for explaining an embodiment of the present invention, and is an overall schematic configuration diagram showing a specific example for carrying out a method and an apparatus according to the present invention. The partial configuration diagram of FIG. 1 shows an equivalent circuit of a part related to a probe, a container, a sample, and the like, and also shows an example of contents of a receiving circuit part. It is a figure which illustrates the signal processing system by the equivalent circuit which comprises capacity | capacitance, and the receiving circuit connected to it. It is a figure which shows an example of the content of the comparison circuit part which can be applied, and an example of the component concerning threshold value setting. It is a figure which shows an example of the output of the differentiation circuit obtained when a probe touches a liquid level in relation to a threshold value (level variable). Similarly, it is a figure which shows the other example of the output of a differentiation circuit in relation to a threshold value (level variable). It is a consideration figure with which it uses for background description. Similarly, it is a consideration drawing. Similarly, it is a consideration drawing. Similarly, it is a consideration drawing. Similarly, it is a consideration drawing. 1 is a partial configuration diagram of FIG. 1 based on another aspect, showing an equivalent circuit of a portion related to a probe, a container, a sample, and the like, and showing another configuration example of contents of a receiving circuit portion. In this case, the sample in the container is a diagram illustrating a signal processing system of an equivalent circuit in which a capacitance constitutes a capacitance and a receiving circuit connected thereto. It is a figure which shows an example of the output of the differentiation circuit obtained when a probe leaves | separates from a sample liquid level. It is a figure which shows the inversion output of the same output. It is a figure of the comparative example in case there exists attenuation shown in contrast with FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIGS. 1 to 14 are diagrams for explaining embodiments of the present invention. Among these, FIG. 1 is an overall schematic configuration diagram showing a specific example for carrying out the method and apparatus according to the present invention. FIG. 2 is a partial configuration diagram of FIG. 1 and shows an equivalent circuit of a part related to a probe, a container, a sample and the like, and an example of contents of a receiving circuit part. FIG. 3 is a diagram illustrating a signal processing system including an equivalent circuit in which a sample in the capacitor constitutes an electrostatic capacity and a receiving circuit connected to the equivalent circuit, and FIG. 3 illustrates an example of contents of a comparison circuit portion that can be applied and a configuration relating to threshold setting. FIG. 4 shows an example of the output of the differentiating circuit obtained when the probe touches the liquid level in relation to a threshold (variable level). FIG. 5 shows the differentiating circuit. Another example of the output is shown in relation to a threshold value (variable level). Further, as will be described later, FIG. 11 is a partial configuration diagram of FIG. 1 based on another aspect, showing an equivalent circuit of a portion related to a probe, a container, a sample, and the like, and other contents of the receiving circuit portion. FIG. 12 is a diagram illustrating a configuration example, and illustrates a signal processing system of an equivalent circuit in which a sample in a container forms a capacitance and a receiving circuit connected to the sample when detecting contact of a liquid. FIG. FIG. 13 shows an example of the output of the differentiating circuit obtained when is separated from the sample liquid surface, and FIG. 13 shows the inverted output of the same output.

  In FIG. 1 showing a specific example for carrying out the method of the present invention, in this example, the probe 1, the pipe 2, the dispenser 3, the shield wire 4, the receiving circuit 5, the container 6 (sample container), the rack 7, It has a container cradle 8 and an oscillation circuit 9, and these elements can be provided as shown in the figure.

  Here, the probe is conductive and can be configured as a plurality (four in the illustrated example) of independent suspension probes. The conductive probe 1 is movable up and down with respect to the sample container 6 for storing the sample and the container cradle 8 (arrows in FIGS. 1 and 2), and connected to the dispenser 3 by the pipe 2 and to each of the probes. The connection line may be covered with the shield line 4 and connected to the reception circuit 5. The configuration of the receiving circuit and the like will be further described later.

  The probe 1 is mounted on a driving means (not shown) that can move up and down with respect to the cradle 8 and constitutes an independent suspension probe. Here, the material is such that the liquid level of the sample liquid and the liquid contact can be detected. It is possible to employ a configuration in which the sample liquid is sucked and discharged by the pressure of the pipe 2 generated by driving the dispenser 3 after the liquid level is detected. The dispenser 3 can employ a configuration in which a pulse motor (not shown) for operating the required suction amount is mounted. Here, according to the above, it is assumed that a configuration in which a predetermined sample is sucked into the probe with a quantitative dispenser connected to each independent suspension probe, and a configuration in which each independent suspension probe is raised after the suction is realized. It shall be.

  The shield wire 4 is used so as not to be affected by noise between the probe 1 and the receiver (reception circuit), and the reception substrate (reception circuit) processes the signal from the probe 1 and performs digital conversion as described later. Made.

  As the sample container 6, a test tube placed on the rack 7, a microplate arranged in a grid, or the like can be used. The cradle 8 is made of a conductive material so as to constitute one end of the electrode. For example, an oscillating circuit 9 that outputs a sine wave voltage having a constant amplitude and frequency (angular frequency ω) is connected to the cradle 8. Receive. Thus, here, the conductive cradle is a cradle for the sample container 6 and the sample liquid level in the container is changed by a change in capacitance between the probe 1 made of the conductive material and the electrode disposed in the vicinity of the container. When detecting, it also functions as an electrode installed in the vicinity of the container.

  In this example, the detection of the sample liquid level in the container 6 is detected by a change in capacitance. In this case, the sample liquid level is detected by the comparison circuit that determines that the sample liquid level has been detected. The threshold value is set according to conditions such as the shape of the sample container, the liquid property of the sample, and the simultaneous operation of a plurality of probes, and the liquid level is detected using the threshold value for each of the set conditions.

  FIG. 2 shows an equivalent circuit in which a sample in a sample container forms a capacitance and a signal processing process in a receiving circuit connected to the sample when detecting the liquid level. FIG. 3 shows a specific example of the contents of the comparison circuit part that can be applied and a specific example of a component part related to threshold setting. Here, for example, the signal processing system amplifies the output of the IV (current-voltage) conversion circuit 10 that converts the current flowing through the probe into a voltage corresponding to the capacitance C of the equivalent circuit portion, for example. An amplifier circuit 11, a differentiating circuit 12 for differentiating the output of the circuit, and a circuit using the output of the differentiating circuit (see, for example, FIG. 4) in the subsequent stage of the provided differentiating circuit, A comparison circuit 14 having a threshold value may be provided, and further, an MPU 15 (host MPU) as shown in FIG. 3 may be provided.

  The host MPU 15 (interface), in addition to the control function described later, stores data relating to a threshold voltage (for example, see FIGS. 4 and 5) that should be applied by the comparison circuit 14 in accordance with various conditions in advance. Read data (threshold voltage information) read from a system (for example, a personal computer (personal computer) 16 and a storage device 17 as shown in FIG. 3) that can be used in accordance with conditions is read out by the comparison circuit 14. As shown in FIG. 3, the comparison circuit includes a threshold setting circuit 18 for a threshold voltage obtained through the MPU 15 and the non-inversion circuit. The output from the amplifier circuit 13 and the output of the threshold setting circuit 18 (DA converter output) are input to each input. It is possible to adopt a configuration having a comparator COM for sending their comparison result to the host MPU15 Te. Based on the comparison result obtained by the comparison circuit 14, the host MPU performs probe lowering, raising operation, etc. (deceleration stop, raising start operation control by the above-described driving means (not shown) when each independent suspension probe 1 moves up and down. For example, this also relates to the driving of the dispenser 3 at the time of sample dispensing as described above (including control for the pulse motor that operates the required suction amount as mentioned above). It can be configured as a control means that also has a function of controlling the entire apparatus of this embodiment when controlling the controlled object, such as control, and the liquid level detection circuit includes the comparison circuit 14 as described above. can do. As shown in the figure, the personal computer 16 including a display can be used for various displays (input / output displays) for an operator (user of this apparatus), warnings, and the like.

  Here, when collecting a sample from the sample container 6 by dispensing, an operator or a user, for example, previously stores a plurality of threshold voltage information for each combination of conditions such as each sample container, the type of sample, and the number of probe operations. The data can be input to the storage device 17 in advance. The type of the sample container 6 is recognized in advance in the storage device 17 or is detected by means such as detection by a sensor during the operation of the device, and the descending operation in which the probe 1 is stopped by liquid level detection. It is good to have completed by just before the start of. Moreover, the setting of the sample type and the number of probe operations can be input to the storage device 17 by the operator, for example, before the operation of the apparatus is started. The device (actually a program for operating the device) reads the combination of the relevant conditions from the storage device 17 immediately before starting the descent operation in which the probe is stopped by the liquid level detection, and detects the liquid level based on that. A threshold voltage is set in the comparison circuit 14 in the circuit.

  According to this, even if the amount of signal change varies depending on the combination of conditions such as the sample container, the type of sample, and the number of probe operations, the probe is set on the liquid surface by setting the threshold voltage according to the corresponding condition in advance. Variation in response time from arrival to detection can be minimized. Therefore, since the liquid level can be detected stably, the sample can be accurately dispensed.

  Hereinafter, the liquid level detection method using the apparatus having the above-described configuration will be described with reference to FIG.

Under the control of the host MPU 15, the probe 1 is lowered toward the sample in the sample container 6 by driving means that can move up and down with respect to the cradle 8. When the tip of the probe 1 comes into contact with the sample liquid surface, the impedance (1 / ωC) of the equivalent circuit section decreases as the capacitance C between the probe 1 and the cradle 8 increases (where ω is the oscillation circuit 9). Can be constant at the angular frequency).

  Here, since the current flowing through the probe 1 and the output voltages of the IV conversion circuit 10 and the amplifier circuit 11 rise, the differentiation circuit 12 outputs only the AC component as shown in FIG. FIG. 4 shows an example of the output of the differentiating circuit obtained when the probe 1 touches the liquid level, and the timing at which the liquid level is detected and the timing at which the liquid level is detected based on the output differential waveform shown in FIG. FIG. 5 also shows another example of the output of the differentiating circuit (an example in which the output waveform of the differential waveform is different from the case of FIG. 4). In the same manner, it is shown in relation to the threshold voltage (variable level)).

  Thus, the differentiation circuit 12 outputs only the AC component as described above, and the AC component is digitally converted by the comparison circuit 14 by comparison with the threshold voltage. This result is sent to the host MPU 15 to determine whether the tip of the probe 1 has detected the liquid level. When the MPU 15 determines that the probe 1 has detected the liquid level, the MPU 15 decelerates and stops the driving means, and the descending operation of the probe 1 ends.

  Here, as mentioned above, the threshold voltage of the comparison circuit 14 is determined in advance by a combination of conditions such as the sample container, the type of sample, and the number of probe operations, and the value is stored in the storage device 17 in advance. As mentioned earlier, the personal computer 16 reads the threshold voltage corresponding to the combination of the conditions from the storage device 17 until the probe 1 moves down toward the sample container 6, and compares it with the comparison circuit. 14 to the threshold value setting circuit 18. Thus, the comparator COM compares the output of the differentiating circuit 12 with the threshold voltage set by the threshold setting circuit 18.

  By adopting such a method, even if the output waveform of the differential waveform by the differentiating circuit 12 differs depending on the combination of the corresponding conditions, the variation in the response up to the threshold voltage is minimized as shown in FIGS. Therefore, the comparison circuit 14 can determine stable liquid level detection and send the digital conversion result to the host MPU 15. In addition, even when there are a plurality of probes 1, it is possible to reduce the influence of interference between adjacent probes and realize stable liquid level detection.

  By enabling the threshold voltage of the comparison circuit 14 to be changed corresponding to the combination of the target sample container, the type of sample, and the number of probe operations, the comparison circuit 14 determines stable liquid level detection, and the probe 1 The apparatus and method of this embodiment according to the present invention, which can suppress the variation in the amount of penetration from the surface of the sample liquid at the tip, is a sample liquid in an analytical instrument or the like that involves a process of dispensing a sample with a probe. It is suitable to be applied to surface detection and implement this, and can provide a good solution from the viewpoint described in the considerations (a) to (g) at the beginning of the specification, even when the conditions are different Can be detected stably, regardless of one or more conditions that may affect the capacitance C, such as the sample container, the type of sample, and the number of probe operations, and the combination of these conditions. This And could be practically, are possible stable sampling, it is possible to accurately dispense the sample.

  If the present invention is not adopted, when the sample liquid level in the sample container is detected by the change in capacitance between the probe made of the conductive material and the electrode installed in the vicinity of the container, as shown in FIG. Since the capacitance varies depending on the shape, liquid property of the sample (dielectric constant of the liquid), and the number of probe operations (influence of interference of adjacent probes) as shown in FIGS. If the comparison circuit has a single threshold value for the result, the response is insufficient, and it is difficult to stably detect the liquid level when the above conditions are different. According to the surface detection method and apparatus, the probe 1 detects the sample liquid level and the driving means decelerates to a stop after the probe 1 detects the sample liquid level. Sample container, sample type, number of probe operations Regardless of the combination of matter, so it is even suppress the variation to a minimum, always it is possible to realize a stable sample taken.

  The following example shows that the embodiment according to the above embodiment detects the sample liquid level in the container by changing the capacitance, and sets the threshold value in the comparison circuit for determining that the sample liquid level is detected in various conditions. In the following example of liquid level contact detection, the probe not only detects the liquid level, but it is an example of detecting the liquid level using a threshold value for each condition. By determining whether the sample is still in contact with the sample after sampling by the dispenser, it is possible to assure the suction operation by the probe and immediately know that the suction amount is insufficient, and always realize stable sampling. Aiming at this, the sample liquid level in the container is detected by the capacitance change between the probe and the electrode installed in the vicinity of the container having independent suspended probes of conductive materials, and the descent of the probe is stopped. With a dispenser connected to the probe After aspiration to the probe fees, when raising the probe, contact to detect that leaving the liquid surface, is that trying to change the rise start timing of each probe.

  Here, even in the present example involving the process of shifting the timing at which each probe is separated from the liquid as described above, the basic configuration and method may be the same as those according to the above-described embodiment, and the liquid level contact detection according to the present invention. An overall schematic configuration diagram showing a specific example for carrying out the method and apparatus is also the same as in FIG. 1 and, as will be apparent from the following description, a part of the signal processing system in the receiving circuit, other The same configuration can be adopted for the constituent parts, and these are the same as those already described, and therefore a detailed description thereof will not be repeated. The part will be described.

  FIG. 11 shows an equivalent circuit in which the sample in the sample container constitutes the capacitance C and the signal processing process in the receiving circuit 5 connected thereto when the liquid contact is detected. Here, also in this embodiment, the signal processing system by the receiving circuit 5 in the overall schematic configuration shown in FIG. 1 is the same as the case of FIG. An amplifying circuit 11 and a differentiating circuit 12 for differentiating the output of the circuit.

  On the other hand, in the case of the present embodiment, as shown in FIG. 11, unlike the case of FIG. 2, an inversion circuit 23 is provided in the subsequent stage of the differentiation circuit 12, and a comparison having a threshold value in the subsequent stage. The circuit 14 is provided and the MPU 15 (host MPU) can be provided as in the above embodiment.

  Here, based on the comparison result obtained by the comparison circuit 14, the host MPU 15 lowers the probe by a driving means (not shown) when the plurality of independent suspension probes 1 in FIG. It also has a function to control the entire apparatus, such as control relating to operation (including control of operation) and control relating to driving of the dispenser 3 (including control over a pulse motor that operates the required suction amount). As already described, in this embodiment, in order to incorporate finer details regarding the probe elevation control, the sample liquid level in the container 6 is detected by the capacitance change, and the lowering operation of the probe is stopped. After the suction operation with the probe, when the probe is to be raised, the rise start timing of each probe is detected when detecting the separation from the liquid level. Changing As a control function of performing control for driving means also causes consideration.

  This is based on the following viewpoint. That is, regarding the detection that the probe was in contact with the liquid surface, as described above, in the case of one probe, since there is no interference, the signal amount of the capacitance change when leaving the liquid surface is amplified, It was possible to detect that the probe was attached to the liquid by making it larger than a certain threshold voltage. However, as shown in the example of FIG. 1, in the case of detecting the separation from the liquid level with a plurality of (here, four) probes 1, for example, the sample container (6) to be applied, the amount of liquid in the container, Since the amount of attenuation due to interference may be larger than the signal amount of capacitance change depending on the sample container and liquid volume (see, for example, FIG. 15 showing an example of attenuation due to interference), Based on this, based on this, in the present embodiment, in order to avoid this, the timing at which each probe 1 is separated from the liquid is shifted. As a result, only the change in capacitance when each probe 1 is separated from the liquid can be handled, so the signal amount is amplified and detected to be higher than a certain threshold voltage to detect that the probe 1 is attached to the liquid. To do.

  According to this, even in the case of FIG. 1 having an apparatus configuration including a plurality of probes 1, the voltage generated by the capacitance change when each probe 1 leaves the sample exceeds the threshold voltage, so that each probe becomes a sample. It can be ensured that the probe 1 is properly in contact with the sample liquid until the liquid level is detected, the sample aspirating operation is completed, and immediately before the ascending operation is performed. By detecting whether the probe 1 is in contact with the sample liquid, it is possible to prevent the suction amount from being insufficient, and this can improve the data reliability. If it is determined that the contact has continued, the apparatus recognizes that the probe 1 has completed a predetermined amount of suction, and continues the subsequent operation. If it is determined that the contact has not been continued, the apparatus determines that there is an abnormality, notifies the operator of the abnormality, and stops the suction operation for the same container. The operation is resumed for the next container. Such processing can also be configured to be executed under the control of the host MPU 15, for example.

  Hereinafter, regarding the liquid level contact detection method by the apparatus having the above-described configuration, FIG. 12 showing an example of the output of the differentiation circuit 12 obtained when the probe leaves the sample liquid level, FIG. 13 showing the inverted output of the same output, In addition, the comparison will be described with reference to FIG. 14 of the comparative example in the case where there is attenuation. First, a case where the probe operates with one probe will be described. Next, a case where the probe operates with two or more probes will be described.

  First, when a single probe moves up and down, as described in the above embodiment, the downward movement of the probe 1 toward the sample container 6 is stopped by detecting the liquid level, and the dispenser After the suction operation by 3, it rises by the driving means. On the other hand, when the probe 1 moves away from the sample liquid level in the container 6, in this case, the capacitance C between the probe 1 and the cradle 8 is decreased, contrary to the liquid level detection described in the above embodiment. As a result, the impedance (1 / jωC) of the equivalent circuit portion increases.

  Therefore, since the current flowing through the probe 1 and the output voltages of the IV conversion circuit 10 and the amplifier circuit 11 decrease, the differentiation circuit 12 outputs only the AC component as shown in FIG. 12 at a timing away from the liquid surface. Here, in this example, the AC component is inverted by the inversion circuit 13 as shown in the waveform of FIG. In this way, the input to the subsequent comparison circuit 14 can be treated as having the same polarity as that in FIG.

  Thus, the AC component is inverted and output by the inversion circuit 13 as shown in FIG. 13, and the comparison circuit 14 performs digital conversion by comparison with the threshold voltage. This result is sent to the host MPU to determine whether the probe 1 is in contact with the liquid level.

  Next, a case where the probe moves up and down with two or more will be described. Each probe can be connected to a circuit similar to that shown in FIG. 11, for example. Now, if the same sample is used and the liquid volume is the same, if two or more probes 1 are separated from the liquid surface at the same time, the output of the inverting circuit 13 is attenuated by the influence of interference as shown in FIG. 14 of the comparative example. To do. However, when avoiding the influence of interference as aimed at in this example, each probe 1 is stopped by the liquid level detection function, and one probe 1 is provided at the time of ascending after the suction operation by the dispenser 3. The timing rises in order by shifting the timing. Thus, even when four probes 1 are provided, when detecting that each probe 1 leaves the liquid surface in the corresponding container 6 when the probe 1 is lifted after the suction operation by each probe 1, The detection can be performed by changing the rising start timing.

  By performing such an operation, the signal from each probe 1 is not attenuated as shown in FIG. 13 (therefore, the disadvantage as in the case of Comparative Example 14 can be avoided, and one probe described above is used. As a result, the comparison circuit 14 can determine the stable detection of the liquid level contact and send the digital conversion result to the host MPU 15. If it is determined that the contact has been continued, the apparatus recognizes that the corresponding probe 1 has completed the predetermined amount of suction, and can continue the subsequent operation. If it is determined that the contact has not been continued, the apparatus is abnormal. Judgment is made, the operator is notified of the abnormality, and the suction operation for the same container is stopped, while the operation can be resumed for the next container.

  By detecting whether or not the probe is in contact with the sample liquid, it is possible to prevent a shortage of the suction amount, and for this reason, the apparatus and method of the present embodiment, which can improve the reliability of the data, are provided with a plurality of probes. It is suitable to be applied to the liquid level contact detection in an analytical instrument or the like with a process that performs a note, and is good from the viewpoint described in the consideration items (h) to (n) at the beginning of the specification. It is possible to provide solutions, even when there are multiple probes with liquid level detection function that uses capacitance change, not only detect the liquid level but also determine whether it was in contact with the liquid properly It is possible to stably detect that the probe is in contact with the liquid surface even after the suction operation, and to prevent disadvantages such as insufficient suction amount.

  In the case where there are two or more probes that do not require the liquid level detection function, the liquid level detection signal interferes between the probes as a physical phenomenon. When contact cannot be detected and it cannot be detected that the probe is in contact with the liquid surface, there is a possibility that a problem such as insufficient suction amount may occur, and it will not be possible to confirm whether a predetermined amount of sample has been collected. According to the above liquid level contact detection method and apparatus according to the above, the probe not only detects the liquid level, but also determines whether the probe is still in contact with the liquid even after the sample is collected by the dispenser. Therefore, it is possible to immediately know that the suction amount is insufficient, and it is possible to always realize stable sampling.

In addition, this invention is not limited to the above embodiment.
For example, in the above:
(I) When the sample liquid level in the container is detected by a change in capacitance, the threshold value in the comparison circuit that determines that the sample liquid level has been detected is set to the shape of the sample container, the liquidity of the sample, the multiple probe A liquid level detection characterized by detecting a liquid level using a threshold value for each condition by setting a plurality according to conditions such as simultaneous operation,
(Ii) Provided with a plurality of independent suspension probes, the sample liquid level in the container is detected by a change in capacitance between the conductive material probe and the electrode installed in the vicinity of the container, and the descending operation of the probe is stopped. After detecting the liquid level, the liquid level contact detection is characterized by changing the rising start timing of each probe in detecting the separation of the liquid level when each probe is lifted. These (i) and (ii) can be carried out independently, or can be carried out in combination with each other. When combined, it becomes more effective.

  The contents described above can also be regarded as the following invention.

[Additional Item 1] In the method of detecting the sample liquid level in the container based on the capacitance change, a plurality of threshold values in the comparison circuit for determining that the sample liquid level is detected are set according to various conditions, and the threshold value for each condition is set. A liquid level detection method and an apparatus having the above-described configuration, wherein the liquid level is detected using a liquid crystal.

[Additional Item 2] The method and apparatus according to Additional Item 1, wherein the various conditions are the shape of the sample container, the liquidity of the sample, the simultaneous operation of a plurality of probes, and the like.

[Additional Item 3] Provided with a plurality of independent suspension probes, the sample liquid level in the container is detected by the change in capacitance between the conductive material probe and the electrode installed in the vicinity of the container, and the lowering of the probe is stopped. It is characterized by changing the rising start timing of each probe when detecting the separation from the liquid level when ascending each probe after sucking a predetermined sample into the probe with a quantitative dispensing machine connected to the probe A liquid level contact detection method and an apparatus having the above-described configuration.

[Additional Item 4]
In Additional Item 3, when detecting the sample liquid level in the container and stopping the descent of the probe, the liquid level detection method or the liquid level detection device according to Additional Item 1 or 2 is used. A liquid level contact detection method characterized by:

1 Probe (conductive probe)
2 Piping 3 Dispenser 4 Shielded wire 5 Receiving circuit 6 Container (sample container)
7 racks 8 container cradle (conductive cradle)
DESCRIPTION OF SYMBOLS 9 Oscillation circuit 10 IV conversion circuit 11 Amplification circuit 12 Differentiation circuit 13 Non-inverting amplification circuit 14 Comparison circuit 15 MPU (host MPU)
16 PC (personal computer)
17 Storage Device 18 Threshold Setting Circuit 23 Inverting Circuit COM Comparator

Claims (2)

Dispensing connected to the probe with independent suspended probes of multiple conductive materials, detecting the sample liquid level in the container by the capacitance change between the probe and the electrode installed in the vicinity of the container, and stopping the descent of the probe A liquid surface contact detection method, wherein when the probe is lifted after the sample is sucked into the probe by a container, the rising start timing of each probe is changed when detecting the separation of the liquid surface. Dispensing connected to the probe with independent suspended probes of multiple conductive materials, detecting the sample liquid level in the container by the capacitance change between the probe and the electrode installed in the vicinity of the container, and stopping the descent of the probe Liquid level contact detection, which is configured to change the rising start timing of each probe when detecting the separation of the liquid level when the probe is lifted after the sample is sucked into the probe apparatus.

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