JP2797100B2 - Liquid level detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to clinical chemistry in which a reagent is added to a liquid sample such as serum and reacted, the absorbance is automatically measured, and the concentration is calculated and displayed based on the absorbance. And a liquid level detecting device applied to an automatic analyzer in the field of biochemistry.

(Prior Art) Conventionally, as this type of detection device, for example, a reciprocating drive in a vertical direction at a constant speed from above with respect to a storage container containing a liquid to be detected and a liquid level sensor are also provided. An operation control means for calculating the liquid amount in the storage container based on a signal change of the liquid level sensor and displaying the result when the dispensing probe and the dispensing probe come into contact with the evaporation prevention lid and the liquid level. (Japanese Patent Application Laid-Open No. 62-1944)
No. 64) Also, from a liquid level detector comprising two nozzles for detecting the liquid level of the reagent liquid in the reagent liquid storage section, and a reagent remaining amount display device for displaying the remaining amount of the reagent liquid by the output of the detector. (Japanese Patent Application Laid-Open No. 57-82769), a liquid level detecting device utilizing dielectric capacitance (Japanese Patent Application Laid-Open No. 62-218818), and a dielectric material which contacts a tray cup using dielectric capacitance. (Japanese Patent Application Laid-Open No. 62-289769) is disclosed.

(Problems to be Solved by the Invention) However, in the liquid level detection device using two nozzles, it is necessary to reduce the interval between the two nozzles or increase the volume of a reaction tube into which the nozzles are inserted. If the width is too narrow, a liquid junction due to washing water etc. will occur, making it impossible to detect the liquid level correctly, and at the time of measuring serum, the electrode will be corroded due to the electrolysis phenomenon. Liquids and non-conductive liquids cannot be detected, and have drawbacks such as an increase in cross contamination for immersing unnecessary sub-probes in the sample for aspirating the sample.

Also, Japanese Patent Application Laid-Open No. Sho 62-1994464 discloses air and an evaporation prevention lid,
It is merely a liquid amount detection device that calculates the liquid amount of the container using air and the dielectric constant of the liquid in the container.
No. 18 includes, as detecting means, a change in impedance caused by the presence or absence of contact of the liquid surface to be detected of the sampling probe constituting the liquid level sensor, and measures the stray capacitance between the liquid level sensor unit and the test liquid surface. Although it has a bridge circuit as a part of the components, this device does not have an effective virtual ground because the tray of the automatic analyzer is made of plastic,
The signal obtained from the bridge circuit is too small to accurately detect the liquid level. Further, JP-A-62-289769 discloses that a virtual ground is formed by forming a dielectric in contact with the cup of the tray, but a conductor must be used, and in the case of a synthetic resin tray, etc. There are drawbacks such as difficulty in detection.

In order to solve the above-mentioned problems, the present invention constitutes a new detection method for liquid level detection and its circuit, and unifies the nozzle part of the dispensing probe also as a liquid level detection sensor. It is an object of the present invention to provide a liquid level detecting device which is capable of solving the above problems and improving detection performance and reliability.

(Means for Solving the Problems) The present invention relates to a dispensing probe which is disposed above a liquid container and moves up and down to suck the liquid, comprising a nozzle portion of the dispensing probe itself and the air in the container. A liquid level detection sensor that detects the capacitance of the liquid, a detection signal setting circuit that outputs a digital waveform detection signal based on the detection, a basic clock setting circuit that outputs a basic clock signal, and the detection signal It has an arithmetic processing circuit that inputs it via a filter, compares it with the basic clock signal, and outputs it as a digitized liquid level detection signal.This highly accurate detection and excellent signal processing significantly improve the liquid level detection performance and reliability. Has improved.

(Operation) The present invention has the above-described configuration, and the liquid level detection sensor and the detection signal setting circuit formed by the nozzle portion itself of the dispensing probe are provided with the air in the container and the capacitance of the liquid level. Is directly detected, and a change in capacitance based on the detected signal is reliably and accurately output as a detection signal of a digital waveform.The arithmetic processing circuit inputs the detection signal via a filter and outputs the detection signal from the basic clock setting circuit. It is output as a liquid level detection signal which is digitized and compared with the basic clock signal, and directly detects the capacitance of the air and the liquid level as described above, detects it as a digital waveform, and counts the digitized signal which is compared with the basic clock signal. Is highly unaffected by ambient conditions and the like, and provides high-precision detection and excellent signal processing, effectively improving the liquid level detection performance and reliability.

In addition, the above-mentioned liquid level detection sensor is also used as the dispensing probe itself including the nozzle portion, and is integrated into one, so that cross contamination is minimized, and the tip end portion of the nozzle portion itself is the liquid of the liquid to be detected. Since the liquid level is detected when it comes in contact with the surface, the lowering of the dispensing probe is controlled by a detection signal based on the detection signal, and the immersion depth of the tip of the nozzle (3a) below the liquid surface is easily set. , The accuracy and reliability of the amount of liquid suctioned by the nozzle portion can be obtained.

Embodiment An embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, for example, a container (1) containing a liquid (a) to be detected such as a sample placed on a turntable (2) of an automatic chemical analyzer is placed upward. A dispensing probe (3) that is arranged and moved up and down is provided, and the dispensing probe (3) descends into the storage container (1), is immersed in the liquid (a), and dispenses a certain amount of the liquid. It has a nozzle (3a) for dispensing after being sucked, raised, swirled, and discharged into another container (not shown), and the upper part of the nozzle (3a) is controlled by appropriate means. Pump (not shown)
A suction pipe (3b) for suction and discharge control is connected integrally to the nozzle, and the nozzle (3a) and the working pipe (3b) are made of conductive material and the liquid level detection sensors (3a, b) It is composed.

The dispensing probe (3) is supported by a vertical moving member (4), and the vertical moving member (4) is guided by a vertical guide shaft (5) so as to be vertically movable and controlled by appropriate means. A drive rod (6) controlled up and down by a pulse motor (7) is attached, and the dispensing probe is driven up and down at a constant speed by the pulse motor (7) via the drive rod (6) and the up and down moving member (4). Probe drive mechanism (4,
5,6,7) are provided. Dispensing probe (3)
A rod-shaped heater (8) is built therein.

Further, as shown in FIG. 1, a liquid level detection sensor (3a, b) composed of a nozzle portion (3a) of a dispensing probe (3) and an operating tube portion (3b) is connected via a signal line (3c). The liquid level detection circuit (10) is connected to the liquid level detection sensor (3a, b) via a signal line (3c). The detection signal transmission circuit is connected to the liquid level detection circuit (10). (11), a filter (12) connected to the detection signal oscillation circuit (11), a basic clock oscillation circuit (1
3) a liquid level setting circuit (14), a filter (12), a basic clock transmission circuit (13), and an arithmetic processing circuit (15) connected to the liquid level setting circuit (14). 1
A display device (16) is connected to 5).

The detection signal transmission circuit (11) includes a liquid level detection sensor (3
a, b) via a signal line (3c), and when the liquid level detection sensor (3a, b) descends, the tip of the nozzle (3a) causes the air (b) in the storage container (1) to be discharged. The capacitance is directly grasped as a potential by the capacitance and the capacitance of the liquid (a) when the tip comes into contact with the liquid (a), and is shown in FIG. The detection signal (11a) grasped as a waveform based on such capacitance is output, and the filter (1
After clearing through 2), input to the arithmetic processing circuit (15). The difference between the capacitances of the air (b) and the liquid (a) is large, and the waveform of the detection signal (11a) is appropriately obtained.
The wavelength (l) of the detection signal (11a) changes in proportion to the height of the liquid level in the container (1).

The basic clock transmission circuit (13) outputs a basic clock signal (13a) as shown in FIG.
5), the signal is compared with the detection signal (11a), the wavelength (l) is calculated as the number of clocks (n), and is used as a digital signal. The liquid level setting circuit (14) Various data of air (b) and liquid (a) in the storage container (1) are input in advance, and a data signal (14a) for liquid level determination
(Set value) is input to the arithmetic processing circuit (15).

The arithmetic processing circuit (15) includes a detection signal detection circuit (11)
The detection signal (11a) output from the filter (12) and cleared by the filter (12) is input and compared with the basic clock signal (13a) input from the basic clock transmission circuit (13).
The wavelength (1) of 1a) is counted and converted into the number of clocks (n) of the basic clock (13a) to be converted into a digital signal,
The count clock number (n) changes according to the height within the volume of the liquid (a) and is compared with the data signal (14a) input from the liquid level setting circuit (14). Only when the number of counting clocks (n) is equal to or greater than a predetermined value with respect to the set value, the tip of the nozzle portion (3a) of the dispensing probe (3) is brought into contact with the liquid surface of the liquid (a) in the container (1). Judging that it has arrived, it outputs the liquid level detection signal (15a) and displays it on the display (16). The counting clock number (n) is equal to the detection signal (11
by counting an integer multiple wavelengths of a) the (nl), the processing n _o + alpha number of alpha values shown in Figure 2 is increased, it is possible to improve the detection accuracy.

Further, the liquid level detection signal (15a) is input as a control signal of a pulse motor (7) for vertically moving the dispensing probe (3), and the pulse motor (7) receives the liquid level detection signal (15a). The dispensing probe (3) is controlled based on the input of (1), descends by a predetermined length and stops, and the tip of the nozzle (3a) is immersed for a predetermined length below the liquid level of the liquid level (a). The dispensing probe (3) is raised when a predetermined amount of the liquid (a) is sucked into the nozzle section (3a) while ensuring the amount of water absorption of the liquid (a) by the section (3a).

In the automatic analyzer as described above, the amount of the liquid (a) contained in the container (1), that is, the height of the liquid level is not constant, and the nozzle of the dispensing probe (3) is contained in the container. It is unclear whether the tip of the nozzle has reached below the liquid level simply by descending the part (3a).
Even when the liquid level is below the liquid level, the liquid level is lowered by the suction of the liquid by the nozzle portion, and the liquid level cannot be suctioned midway, causing a variation in the suction amount. Therefore, the liquid level detection of the liquid is extremely important. As described above, the dispensing probe (3) itself is also used as a liquid level detection sensor (3a, b), and both the air (b) and the liquid (a) in the storage container (1) are statically detected by the liquid level detection sensor. The capacitance is used as a detection signal (11a), and the detection signal (11a) is obtained as a reliable and accurate waveform signal based on a large capacitance difference between air and liquid. It is not necessary to grasp the small electric conductivity of the liquid and the storage container, etc., and even if a small amount of air or liquid in the relatively small storage container (1) used in the analyzer, it is determined based on the capacitance. The detection signal (11a)
Can be properly grasped, and excellent detection signals and reliability can be obtained. The detection signal (11a) is converted into a digital signal by the liquid level detection circuit (10), and the data signal (14a) (set value) by the liquid level setting circuit (14) is used to correct the noise and the like. The liquid level detection performance and reliability are further improved.

The dispensing nozzle (3) is provided with a rod-shaped heater (8), and noise generated from the rod-shaped heater (8) directly affects the detection of the liquid level detection sensors (3a, b). When the dispensing probe (3) is lowered, the rod-shaped heater (8) is automatically and inoperatively controlled by turning on / off the wiring by a suitable control means (not shown).

(Effect of the Invention) The present invention is configured as described above, and the nozzle portion itself of the dispensing probe that is disposed above the liquid container and moves up and down to suck the liquid is placed inside the container. A detection signal setting circuit that outputs a digital waveform detection signal based on the detection of the liquid level detection sensor, and a basic clock setting circuit that outputs a basic clock signal And an arithmetic processing circuit for inputting the detection signal through a filter, comparing with a basic clock signal, and outputting as a liquid level detection signal which is counted and digitized, by the liquid level detection sensor and the detection signal setting circuit, The capacitance of air and liquid in the container is directly detected, and a reliable and accurate digital waveform detection signal is obtained by a change in capacitance due to the presence or absence of the liquid level.
The arithmetic processing circuit compares the detection signal with the basic clock signal from the basic clock setting circuit to obtain a digitized liquid level detection signal, and obtains the above-described highly accurate detection and excellent signal processing to detect the liquid level. Performance and reliability have been significantly improved. Therefore, the vertical movement control performance of the dispensing probe,
Dispensing performance is effectively enhanced.

Further, since the contact with the liquid surface is detected by the tip end of the nozzle portion of the dispensing probe, the dispensing probe is controlled to descend from the time of the contact based on the detection signal, and the tip of the nozzle portion The immersion depth below the liquid level of the part is controlled appropriately, and the amount of liquid suctioned by the nozzle part, accuracy,
Reliability is obtained, and excellent dispensing performance is obtained by the dispensing probe.

[Brief description of the drawings]

FIG. 1 is a diagram showing the mechanism of an apparatus according to an embodiment of the present invention, and FIG. 2 is a waveform comparison diagram between a detection signal of a liquid level detection circuit in FIG. 1: Storage container, 3: Dispensing probe, 3a: Nozzle, 3a, b: Liquid level detection sensor, 10: Liquid level detection circuit

Claims (1)

(57) [Claims] 1. A dispensing probe which is disposed above a liquid container and moves up and down to suck the liquid, comprising a nozzle portion of the dispensing probe itself and detecting the capacitance of air and liquid in the container. A liquid level detection sensor, a detection signal setting circuit that outputs a digital waveform detection signal based on the detection, a basic clock setting circuit that outputs a basic clock signal, and a basic clock that inputs the detection signal via a filter. A liquid level detection device comprising: an arithmetic processing circuit that outputs a count level digitized liquid level detection signal as compared with a signal.