JPH10206432A - Analyzer with liquid surface detecting function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce erroneous detection of a liquid level even when the moisture of atmospheric air is low in the detecting of the liquid level of a liquid using a pipetting probe. SOLUTION: A liquid level detection circuit 8 is printed on a substrate in a pattern. The liquid level detection circuit 8 has a pair of discharge elements 11a and 11b and a detection circuit 16 for changes in the electrostatic capacitance. One discharge element 11a is electrically grounded and the other discharge element 11b is connected to a pipetting probe 6 and a detection circuit 16 for changes in the electrostatic capacitance. The pipetting probe 6 lowers to a container housing a liquid desired to detect a liquid level and when an extraneous noise signal like static electricity charged on the surface of the container is fetched through the pipetting probe 6, it is discharged to the ground through the pair of discharge elements 11a and 11b thereby inhibiting the transmission of noise signals to the detection circuit 16 for changes in the electrostatic capacitance. An inductance 12 mounted between the other discharge element 11b and the detection circuit 16 for changes in the electrostatic capacitance promotes the discharging of the noise signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analyzer, and more particularly, to an analyzer having a function of detecting a liquid level as a sample or a reagent is dispensed.

[0002]

2. Description of the Related Art When analyzing an analysis item to be examined on a biological sample such as blood or urine by an automatic analyzer, a movable pipetting probe is used to transfer a liquid from a sample cup or a reagent bottle to a reaction vessel. -Is used. The deeper the penetration into the liquid to be dispensed, the more
As the amount of liquid adhering to the outer wall of the valve increases, contamination increases. In order to minimize the depth of penetration of the pipetting probe into the liquid, for example, US Pat.
0,468 and U.S. Pat. No. 4,818,49.
A pipetting mechanism as described in US Pat.

In the pipetting mechanism described in US Pat. No. 4,970,468 and US Pat. No. 4,818,492, the pipetting probe serves as an electrode for liquid level detection. As described above, the pipetting probe is connected to a detection circuit for detecting a change in capacitance. Then, the pipetting probe is lowered with respect to the sample container or the reagent container, and when the probe comes into contact with the liquid surface, the lowering operation of the probe is stopped, and then the probe is moved into the probe. Liquid is inhaled.

[0004]

According to the inventor's experience, the pipetting probe itself is used as an electrode for liquid level detection, especially when the humidity of the atmosphere is low.
It often appeared that an incorrect liquid level detection signal was obtained. The cause of such an erroneous detection of the liquid level was predicted to be that the sample container or the reagent container was made of a non-conductive material such as plastic or glass.

SUMMARY OF THE INVENTION An object of the present invention is to provide a structure capable of reducing erroneous detection of a liquid level when detecting the liquid level of the liquid using a pipetting probe even if the humidity of the atmosphere is low. .

[0006]

SUMMARY OF THE INVENTION The present invention comprises an apparatus for discharging liquid from one container to another using a pipetting probe, wherein the pipetting probe has one side. Acts as an electrode for detecting the level of the liquid in the container, and the contents in the other container are applied to an analyzer that is measured by the measuring means. In the present invention, the holding means for holding one of the containers is electrically grounded, and a change in the capacitance between the pipetting probe and the holding means is detected by a detection circuit. One of the pair of discharge elements arranged to face each other is connected between the pipetting probe and the detection circuit, and the other discharge element is electrically grounded.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a reaction disk 109 is placed on a water bath (constant temperature water bath) maintained at a constant temperature.
Are rotatably arranged. A large number of reaction vessels 106 are held in a circular shape on a reaction disk 109 and are intermittently transferred at predetermined intervals. A sample pipetting probe 105 attached to a movable arm dispenses a liquid sample from a sample cup 101 installed on a sample disk 102 to a reaction vessel 106. On the other hand, a reagent pipetting probe 11 attached to a movable arm
No. 0 dispenses a reagent solution from the reagent bottle 112 installed on the reagent disk 125 to the reaction vessel 106.

[0008] Sample pipetting probe 105
Performs a suction operation and a discharge operation of the liquid sample in association with the operation of the sample syringe pump 107. The reagent pipetting probe 110 performs a suction operation and a discharge operation of the reagent liquid in accordance with the operation of the reagent syringe pump 111. Both pipetting probes 105 and 110 are made of a chemical-resistant metal and also serve as electrodes for liquid level detection. Each of the probes 105 and 110 is electrically connected to an electric detection circuit provided correspondingly. The sample disk 102 and the reagent disk 125 are each rotated so as to position a desired container at the liquid suction position.

An analysis item to be analyzed for each sample is input from an input device such as a keyboard 121.
The operation of each unit in the analyzer is performed by the computer 10
3 is controlled.

The sample pipetting probe 105 descends into the sample cup 101 transferred to the sample suction position by the sample disk 102, and the probe 1
When the tip of the nozzle 05 comes in contact with the liquid surface of the sample, the lowering operation is stopped. When the reaction vessel 106 containing the sample is moved to the reagent addition position, a reagent solution corresponding to the relevant analysis item is added by the reagent pipetting probe 110. Prior to the addition of such a reagent, a predetermined amount of the reagent is drawn into the probe 110 from the corresponding reagent bottle 112. With the dispensing of these samples and reagents, the liquid level of the sample in the sample cup 101 and the reagent bottle 112
The liquid level of the reagents inside is detected, and the lowering operation of each probe is controlled accordingly.

In the reaction vessel 106 to which the sample and the reagent have been added, the mixture is stirred at the position of the stirrer 113.
When the reaction vessel 106 is transferred, it crosses the light beam emitted from the light source 114. Then, the absorbance of the reaction solution at this time is measured by a photometer 115 as a measuring means. The absorbance signal passes through the A / D converter 116,
The user enters the computer 103 via the interface 104, and the concentration of the analysis item is calculated. The analysis result is sent to the printer 117 or the CRT via the interface 104.
118 on the screen and a memory
It is stored on the disk 122. The reaction container 106 for which the photometry has been completed is washed at the position of the washing mechanism 119. The washing pump 120 supplies washing water to the reaction vessel and discharges waste liquid from the reaction vessel.

The pipetting mechanism 20 in FIG.
The common configuration of the sample pipetting mechanism and the reagent pipetting mechanism is shown together for convenience of explanation.

In FIG. 2, a container transfer holder 4 such as a sample disk or a reagent disk holds a container 3 containing a liquid 5 such as a sample or a reagent. In this holder, a conductive member, for example, a metal is disposed in a region surrounding the side surface of the outer wall of the container 3, and the conductive member is electrically grounded. That is, the holder-4 functions as one of the electrodes of the liquid level detection unit. A pipetting probe 6 for a sample or a reagent is mounted on a movable arm 2 which can be raised and lowered and which can be pivoted in a horizontal direction. The movable arm 2 is operated by a drive unit 1 controlled by a computer 103. When the pipetting probe 6 descends and comes into contact with the liquid surface of the liquid 5, the descending of the probe 6 is stopped, and a predetermined volume of liquid is sucked into the probe 6.

Next, the phenomenon that external noise is detected is shown in FIG.
This will be described with reference to FIG. Containers 3 such as sample cup 101 and reagent bottle 112 are made of a non-conductive material such as glass or plastic. The pipetting probe 6 as a liquid level detecting electrode is made of a conductive material such as a metal. Since the surface electric resistance of the container 3 is high, static electricity is likely to be charged on the surface of the container particularly when the humidity in the atmosphere is low. Charging is greater in plastic containers than in glass containers. The pipetting probe 6 descends toward the container 3 charged with static electricity, and when the probe 6 approaches the container 3, the charged charge is transferred to the probe 3.
Is discharged toward the node 6.

Such a discharge phenomenon occurs before the tip of the pipetting probe 6 comes into contact with the liquid surface of the liquid 5.
This discharge signal is detected by a capacitance change detection circuit electrically connected to the probe 6. FIG. 5 shows such a state. In FIG. 5, the horizontal axis indicates the time at which the pipetting probe 6 descends, and corresponds to the descending distance of the probe 6. The vertical axis in FIG. 5 indicates the magnitude of the signal level, where A is a level that is not detected and B is a level that is detected. The magnitude of the extraneous noise signal based on such a discharge can reach several kV. Therefore,
When such a discharge occurs, the tip of the pipetting probe 6 has not reached the liquid level,
It will be incorrectly determined that the liquid level has been reached.

Each of the electric circuits in the liquid level detecting unit shown in FIG. 4 is printed on the substrate in a pattern, but is not limited to such an embodiment. However, it is desirable that the liquid level detection circuit 8 including the pair of discharge elements 11a and 11b and the capacitance change detection circuit 16 has a pattern printed thereon. The AC signal output from the AC transmission circuit 7 is input to the liquid level detection circuit 8 so that a change in the capacitance value detected through the probe 6 can be detected. A proper sine wave is used as the AC signal, but a square wave or a triangular wave may be used instead. The circuit for detecting the change in capacitance includes a known electric circuit such as a bridge circuit as shown in, for example, US Pat. No. 4,818,492.

The liquid level detection circuit 8 amplifies the detected change in the capacitance while maintaining the AC state, and the amplified signal is input to the rectifier circuit 9. The rectifying circuit 9 converts the input AC signal into a DC signal, and the DC signal is
Input to 0. The comparison circuit 10 compares the change of the input capacitance signal with the value before the change, and compares the probe 6 with the container 3.
A detection signal 15 is obtained which indicates whether or not the liquid inside has contact with the liquid level, that is, whether or not the liquid level has been detected. The reason why the comparison circuit 10 operates with a DC signal is that the circuit is simplified.

The pattern of a pair of discharge elements 11a and 11b formed of a conductive material on a printed circuit board is equal to 0.1.
They face each other with a gap of about 1 mm. Each discharge element has a pointed end on the opposite side which is sharp so that static electricity can be concentrated and discharged easily. One discharge element 11a of the pair of discharge elements is electrically grounded. The other discharge element 11b is electrically connected to the pipetting probe 6 and also to the capacitance change detection circuit 16.

As a result, an external noise signal due to static charge or the like detected through the probe 6 is discharged to the ground through the pair of discharge elements 11a and 11b, and is sent to the capacitance change detection circuit section 16. Is suppressed. Further, an inductance 12 is provided between the discharge element 11b of the pair of discharge elements and the capacitance change detection circuit 16.
Has been implemented. The inductance 12 exhibits a high impedance characteristic with respect to a high frequency. Accordingly, the discharge of the noise signal to the ground is promoted, and the transmission of the noise signal to the capacitance change detection circuit 16 is further suppressed. Therefore, erroneous detection of an external noise signal as a liquid level detection signal is greatly reduced.

The output signal of the capacitance change detection circuit 16 passes through the operational amplifier 13. The amplification factor of the operational amplifier 13 depends on the minimum detection capacity of the device, but is generally several tens to several hundreds. The output AC signal of the operational amplifier 13 is supplied to a rectifier 9
DC.

In the conventional DC conversion method, it is general to convert AC into DC by integrating by using a capacitor discharge. However, according to such a method, static electricity noise and other extraneous noises are generated. Since it also integrates sudden signals,
The liquid level may be erroneously detected.

On the other hand, in the example of the DC conversion method shown in FIG. 4, since the positive and negative outputs of the operational amplifier 13 are clamped by the Zener diode 14, sudden signals such as static electricity and other external noises, that is, , Unnecessary signals are not transmitted to the rectifier circuit and are not integrated. With the configuration as shown in FIG. 4, when the amount of static electricity discharged from the surface of the container 3 is the same as in the example of FIG. 5, the external noise signal obtained by the capacitance change detection circuit 16 is as shown in FIG. As in the example of No. 6, the width becomes small. Since such signals are not integrated,
It is not included in the detection signal output from the comparison circuit 10. Therefore, a change in capacitance caused when the pipetting probe 6 comes into contact with the liquid surface is properly detected. In the example of FIG. 5 to which the present invention is not applied, the signal width of the external noise is several tens of milliseconds.
In the above example, the width of the external noise signal is millisecond (ms)
Reduced to:

[0023]

According to the present invention, a pipetting pro-
When detecting the liquid level of a liquid using a probe, a configuration is provided that can reduce erroneous detection of the liquid level even when the humidity of the atmosphere is low.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the overall configuration of an automatic analyzer to which the present invention is applied.

FIG. 2 is a diagram for explaining an operation of a pipetting mechanism when detecting a liquid level.

FIG. 3 is a diagram for explaining the influence of extraneous noise accompanying liquid level detection.

FIG. 4 is a diagram for explaining an electrical system in a liquid level detection unit applied to the analyzer of FIG. 1;

FIG. 5 is a diagram illustrating an example of an external noise signal when the present invention is not applied.

FIG. 6 is a diagram illustrating an example in which external noise having the same magnitude as in FIG. 5 is reduced by applying the present invention;

[Explanation of symbols]

3: container, 6: pipetting probe, 7: AC oscillation circuit, 8: liquid level detection circuit, 9: rectification circuit, 10: comparison circuit, 11a, 11b: discharge element, 12: inductance, 16: static Detection circuit for capacitance change.

Claims (5)

[Claims] An apparatus for dispensing a liquid from one container to another using a pipetting probe is provided.
The pipetting probe functions as an electrode for detecting the liquid level of the liquid in the one container, and the contents in the other container are connected to the one container in an analyzer which is measured by measuring means. Holding means, a detection circuit for detecting a change in capacitance between the pipetting probe and the holding means, a pair of discharge elements arranged so as to face each other, and the pipetting. Professional
Means for electrically connecting the switching means to the capacitance change detection circuit via one of the pair of discharge elements, and the other of the holding means and the other of the pair of discharge elements. An analyzer having a liquid level detecting function, wherein each of the discharge elements is electrically grounded. 2. The analyzer according to claim 1, wherein said pair of discharge elements and said capacitance change detection circuit are formed by a printing pattern. . 3. The analyzer with a liquid level detecting function according to claim 2, wherein said pair of discharge elements have a pointed shape at their leading ends facing each other. 4. The liquid level detecting function according to claim 1, wherein said electric connection means has an inductance between said one discharge element and said capacitance change detecting circuit. Analyzer. 5. An analyzer with a liquid level detecting function according to claim 1, wherein said holding means includes a container transfer means for positioning said one container at a liquid suction position.