JP3204772B2 - Liquid level detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detecting device incorporated in, for example, an automatic biochemical analyzer for detecting the liquid level of a test solution in a test solution container or a reagent in a reagent container.

[0002]

2. Description of the Related Art For example, an automatic biochemical analyzer includes a test solution container containing a test solution such as serum, a reagent container containing a reagent mixed with the test solution, and the like.
In this type of analyzer, when a test solution or reagent is collected, if a probe for collection is carelessly inserted into the solution, the probe adheres to the probe when the test solution or reagent is next collected. It is necessary to stop the probe before the probe penetrates deeply into the liquid, because the residual liquid may be mixed and adversely affect the analysis accuracy.

[0003] Techniques for detecting the liquid level are disclosed, for example, in Japanese Patent Application No. 3-77976 and Japanese Patent Application No. 3-1 by the present applicant.
No. 34294, or Japanese Utility Model Application Laid-Open No. 54-19790.
It is shown in Japanese Patent Publication No.

In the automatic liquid sampler disclosed in Japanese Utility Model Laid-Open Publication No. 54-19790, the liquid level is detected by utilizing the conductivity of the test solution. That is, a pair of liquid level detecting needles (electrodes) interlocked with the sample collecting probe are inserted into the sample container, and the detecting needle descends toward the liquid level of the sample together with the sample probe. . Since a voltage is applied between the two detection needles, the two detection needles are electrically connected to each other via the test solution when they come into contact with the liquid surface. Then, the liquid level is detected based on the conduction.

[0005] In addition, a probe is made of a conductive material such as stainless steel, and the probe is also used as a detecting needle. In this case, there is an advantage that one of the pair of detection needles can be omitted.

[0006] Further, there is an electrostatic capacity type liquid level detecting device in which a single detecting needle is used or a conductive probe is used. In a capacitance type liquid level detecting device, a detecting needle is used as a part of an oscillation circuit. Then, since the capacitance changes when the detection needle reaches the liquid level, the liquid level is detected based on the change in the oscillation frequency.

[0007]

By the way, in the above-mentioned conventional liquid level detecting devices provided with a detecting needle, the detecting needle is energized through the liquid or the detecting needle is thin. Since it is sharply processed, handling is troublesome. Also, when there are a plurality of detection needles, it is necessary to position the detection needles with respect to the container quite accurately in order to insert these detection needles into the container without fail.

Further, in the case of the capacitance type, when the amount of liquid in the container is very small, the change in the capacitance is extremely small, so that it is difficult to stably detect the change in the oscillation frequency. An object of the present invention is to provide a liquid level detecting device which can simplify the configuration and can detect the liquid level with high accuracy regardless of the liquid amount.

[0009]

In order to achieve the above object, the present invention provides a conductive member insertable into a liquid contained in a predetermined container, and an electric signal to the conductive member. Signal providing means, a resistor connected to a line between the conductive member and the signal providing means, a comparing means for comparing signals on lines on both sides of the resistor, and an input of the comparing means. Rectifying means connected to the line on the output side or the output side, taking out signals in the lines on both sides sandwiching the resistor when the conductive member comes into contact with the liquid, based on a change in the rectified waveform of both signals. The liquid level of the liquid in the container is detected. By doing so, the present invention makes it possible to simplify the configuration of the liquid level detecting device and to detect the liquid level with high accuracy regardless of the liquid amount.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 and FIG. 2 show a first embodiment of the present invention, in which reference numeral 1 denotes a liquid level detecting device. The liquid level detection device 1 is provided with an oscillator 2 as a signal supply means, and a liquid level detection needle (hereinafter, referred to as a detection needle) 3 as a rod is connected to the oscillator 2.

The detection needle 3 is made of a conductive material.
The electric signal output from the oscillator 2 is sent to the detection needle 3. Here, the detection needle 3 is schematically shown by an arrow in FIG. The detection needle 3 is moved up and down by mechanical means (not shown) and inserted into the container 4. Since various mechanisms generally known as mechanical means for raising and lowering the detection needle 3 can be used, the description thereof is omitted here.

A high resistance 5 is interposed between the detection needle 3 and the oscillator 2 in series. The portion between the high resistance 5 and the oscillator 2 is connected to the positive input side of the differential amplifier 6, and the portion between the high resistance 5 and the detection needle 3 is connected to the negative input side of the differential amplifier 6. It is connected. The output side of the differential amplifier 6 is connected to the negative input side of the comparator 7, and a rectifier 8 and a smoothing capacitor 9 are connected between the differential amplifier 6 and the comparator 7. The reference value is input to the positive input side of the comparator 7. Next, the operation of the liquid level detecting device 1 will be described.

First, a signal having a predetermined waveform (for example, a sine waveform) is output from the oscillator 2, and the signal is sent to the detection needle 3 through the high resistance 5. The detection needle 3 is inserted into a container 4 together with a probe (not shown).
A predetermined analysis liquid (for example, a test solution or a reagent) 10 is stored. This liquid 10 has a certain degree of conductivity.

Before the detection needle 3 reaches the liquid level 11, FIG.
As shown on the left side in the middle, the waveform of the signal A at the preceding stage of the high resistance 5 and the waveform of the signal B at the subsequent stage thereof are substantially the same. Therefore, the output C from the differential amplifier 6 is at a substantially zero level.

When the detection needle 3 reaches the liquid level 11, conduction between the detection needle 3 and the liquid 10 becomes possible, and the oscillator 2
Output escapes from the detection needle 3 to the liquid 10. Since the high resistance 5 exists at the front stage of the detection needle 3, as shown on the right side of FIG. The amplitude of B decreases according to the change in the capacitance between the detection needle 3 and the liquid 10. As a result, the output C of the differential amplifier 6 becomes a sine waveform having an amplitude corresponding to the difference between the two signals A and B, ignoring the effects of the rectifier 8 and the capacitor 9. Here, the resistance value of the high resistance 5 is
The setting is such that a sufficient difference is generated between the signals A and B when the detection needle 3 comes into contact with the liquid surface 11.

The output C of the differential amplifier 8 is rectified and smoothed and input to the comparator 7, where the level is compared. Then, the comparison result is the liquid level detection signal D
Is output from the comparator 7. Comparator 7
Is used for cutting out an output C having an insufficient difference between the signals A and B as noise, and cutting an output range below a certain value that can be determined as noise. The output range to be cut is set in advance according to the performance of the machine and the like.

That is, in the liquid level detecting device 1 as described above, the high resistance 5 is connected between the detection needle 3 and the oscillator 2, and the difference between the signal A at the preceding stage and the signal B at the subsequent stage of the high resistance 5 is different. The liquid level 11 is detected based on. For this reason, even if the amount of the liquid 10 in the container 4 is very small, the change in the capacitance is large,
The liquid level 11 can be detected without being affected by the amount of the liquid 10. Therefore, the liquid level can be detected with high accuracy regardless of the liquid amount.

Further, in the liquid level detecting device 1 of the present embodiment, the liquid level can be detected by using only one detecting needle 3. Therefore, the number of the detection needles 3 can be reduced and the number of rods inserted into the container 4 can be reduced as compared with the conventional detection device that requires two detection needles. And it becomes easy to insert the detection needle 3 into the container 4, and it becomes easy to position the detection needle. Also, the handling of the detection needle becomes easy.

Although the high resistance 5 is connected to the detecting needle 3 in the present embodiment, the present invention is not limited to this. For example, a probe for supplying a liquid or a probe for collecting a liquid is used. The probe may be connected to the oscillator 2 via the high resistance 5 by using a conductive material. In this case, since the liquid level can be detected without using the detection needle 3, the detection needle 3 can be omitted. And the number of rods inserted into the container 4 is further reduced (only the probe),
Insertion and positioning of the rod are facilitated.

The type of the liquid 10 in this embodiment is not particularly limited as long as it is a liquid having conductivity. The liquid level detecting device 1 of the present embodiment can be applied to the case where the liquid 10 is, for example, a reagent or the case of a test solution. In addition, the liquid level detection device 1
The present invention can be applied to a case where the liquid 10 is supplied to the container 4 or a case where the liquid 10 is collected from the container 4.
If an earth electrode is connected to the liquid 10 in the container 4, the liquid level 11 can be detected more reliably.

Further, in the present embodiment, the rectifier 8 and the smoothing capacitor 9 are connected between the differential amplifier 6 and the comparator 7, but these are connected, for example, at the subsequent stage of the comparator 7. Is also good. Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 2 shows a second embodiment of the present invention.
Reference numeral 21 in the drawing is a liquid level detecting device. In the liquid level detecting device 21, a rectifier is provided between a stage preceding the high resistance 5 and the positive input side of the differential amplifier 6 and between a stage following the high resistance 5 and the negative input side of the differential amplifier 6, respectively. 22, 22 'and smoothing capacitors 23, 23' are connected. And
The rectified and smoothed signals A and B are input to the differential amplifier 6, and the output C of the differential amplifier 6 is sent to the negative input side of the comparator 7.

A signal is taken out from both sides of the high resistance 5, and this signal is rectified and smoothed before being input to the differential amplifier 6. Therefore, when the detection needle 3 comes into contact with the liquid 10, a difference in DC voltage is output from the differential amplifier 6, as shown in FIG. Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those in the above-described embodiments are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 5 shows a third embodiment of the present invention.
Reference numeral 31 in the drawing denotes a liquid level detecting device. In the liquid level detecting device 31, a level adjuster 3 as a level adjuster is provided between a stage preceding the high resistance 5 and the positive input side of the differential amplifier 6.
2 is connected, and a driven shield 33 is connected between the subsequent stage of the high resistance 5 and the negative input side of the differential amplifier 6. Further, the differential amplifier 6 returns to the negative input side.

Even before the sensing needle 3 reaches the liquid level 11, the voltage at the subsequent stage of the high resistance 5 may be lower than the voltage at the previous stage due to the influence of stray capacitance and the like. In this case, when both signals A and B are differentially amplified as they are, the liquid level detection signal D is output from the comparator 7 regardless of whether the detection needle 3 is in contact with the liquid level 11. Therefore, if the level adjuster 32 is inserted as in the present embodiment and the voltage at the previous stage of the high resistance 7 is reduced in advance, the liquid level detection signal D is output before the detection needle 3 reaches the liquid level 11. Can be prevented.

As means for preventing the influence of external noise on the detecting needle 3, for example, as shown by a white circle in FIG. 5, a shield wire 34 is used for the base 3a of the detecting needle 3. However, when the shield line 34 is used, the signal level is reduced by the capacitance of the shield line 34, so that the output difference due to the high resistance 5 is particularly likely to be affected. Therefore, if an appropriate driven shield 33 is interposed between the preceding stage of the high resistance 5 and the differential amplifier 6 as in the present embodiment, a decrease in signal level can be prevented. Next, a fourth embodiment of the present invention will be described with reference to FIG. The same parts as those in the above-described embodiments are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 6 shows a fourth embodiment of the present invention.
Reference numeral 41 in the figure denotes a liquid level detection device. In the liquid level detecting device 41, the rectifiers 22 and 22 'are provided between the level adjuster 32 and the positive input side of the differential amplifier 6, and between the driven shield 33 and the negative input of the differential amplifier 6. And the smoothing capacitors 23 and 23 'are connected. Then, the outputs of the level adjuster 32 and the driven shield 33 are rectified and smoothed before being input to the differential amplifier 6.

The resistors 35, 35 'arranged in parallel with the smoothing capacitors 23, 23' are connected to
When the liquid is returned above the liquid surface 11 for reuse or when the probe is brought into a non-contact state with the liquid again with the suction of the liquid, the output C generated in the differential amplifier 6 is reset to zero. It is for returning to the level. Therefore, according to this embodiment, the liquid level can be repeatedly detected for a plurality of liquids. In this case, by adding a means for washing or replacing the detection needle 3 between each detection, it is possible to effectively apply liquids having various properties.

The present invention is not limited to the above embodiments, but can be variously modified without departing from the scope of the invention. For example, even if a capacitor is used instead of the high resistance 5, the same operation and effect as described above can be realized. Further, for the same reason as used in the fourth embodiment,
Needless to say, the resistor 35 (and / or 35 ') is provided in the same manner as in the first to third embodiments according to the number of capacitors and the like.

As described above, the present invention provides a conductive member which can be inserted into a liquid contained in a predetermined container, signal providing means for providing an electric signal to the conductive member, and the conductive member. A resistor connected via a line between the signal providing unit and the signal providing unit, a comparing unit for comparing signals on both lines sandwiching the resistor, and a rectifier connected to a line on an input side or an output side of the comparing unit. Means for taking out signals on both sides of the resistor when the conductive member comes into contact with the liquid, and detecting the liquid level of the liquid in the container based on a change in the waveform after rectification of both signals. Is to do. Therefore, the present invention has an effect that the configuration of the liquid level detecting device can be simplified and the liquid level can be detected with high accuracy regardless of the liquid amount.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing signal processing according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

FIG. 4 is a graph showing an input signal to a differential amplifier according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a third embodiment of the present invention.

FIG. 6 is a circuit diagram showing a fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Liquid level detection device, 2 ... Oscillator (signal supply means), 3 ...
Detection needle (rod), 5: High resistance (resistance), 10: Liquid, 3
2 ... Level adjuster (level adjusting means), 33 ... Driven shield.

Claims (2)

(57) [Claims] A conductive member that can be inserted into a liquid contained in a predetermined container; a signal providing unit that provides an electrical signal to the conductive member; and a conductive member and the signal providing unit. A resistor connected via a line between them, and a comparing means for comparing signals on lines on both sides of the resistor,
Rectifying means connected to the input side or output side line of the comparison means, and when the conductive member comes into contact with a liquid, takes out signals on both sides of the resistor, and obtains a rectified waveform of both signals. A liquid level detecting device for detecting a liquid level of the liquid in the container based on a change in the liquid level. 2. A circuit according to claim 1, wherein a level adjusting means for correcting an influence of stray capacitance or the like is interposed on a line between a former stage of said resistor and said rectifying means. The liquid level detection device according to any one of the above.