JP2006214912A - Out-of-liquid sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve operability and reliability of sensitivity adjustment of an air sensor for sensing out-of-liquid in liquid feed piping. <P>SOLUTION: The output of the air sensor 1 is converted into a digitally converted value after it is input to a sensor output conversion part 2 to be properly amplified. The digitally converted value is stored to a sensor output storage part 3 at a constant sampling interval to be displayed on a sensor output display part 5. A worker inputs a threshold by referring the display of the sensor output display part 5 in a threshold input storage part 6. A comparison calculation part 4 compares the sensor output from the sensor output storage part 3 with the threshold from the threshold input storage part 6 to output a determination result concerning the out-of-liquid to a counter 7. The counter 7 counts the number of times determined continuously as the out-of-liquid. A counting setting value that is a reference for the number of times of a continuous out-of-liquid is input to a count setting value input storage part 9. A count comparison part 8 compares the number of times of the continuous out-of-liquid of the counter 7 with a count setting value of the count setting value input storage part 9 to output the out-of-liquid determination result. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid shortage detection device for detecting liquid shortage in a liquid feed channel.

  In a liquid sample automatic analyzer, transferring a liquid sample or solvent using a liquid supply pipe is one of the basic functions of the apparatus. In particular, in order to automate liquid chromatographic analysis, the sample and solvent are stably supplied from the storage tank containing a limited amount of sample and solvent to the separation column via the liquid feed pipe without air mixing. There is a need to. As a method of transferring the liquid from the liquid storage tank to the liquid feeding pipe, it is usually performed to immerse one end of the liquid feeding pipe to the bottom of the liquid storage tank and suck the liquid with a suction liquid feeding pump. In this case, it is necessary to detect the state of running out of liquid in which liquid feeding is interrupted during suction feeding. For this purpose, it is common to install an air sensor that detects that gas has been mixed in the liquid supply pipe.

  As an apparatus that is attached in the middle of the liquid supply pipe and detects liquid shortage, there is a liquid shortage sensor described in Patent Document 1, for example. This liquid shortage sensor is installed by inserting a light-transmitting dedicated flow cell equipped with a photosensor in the middle of a liquid supply pipe. This device enables long-term, stable detection of liquid breakage with a constant detection sensitivity, regardless of the type and pipe diameter of the liquid supply pipe, if a dedicated flow cell can be installed in the middle of the liquid supply pipe with an appropriate joint. .

Japanese Patent Laid-Open No. 2003-248812

  The “problem to be solved by the invention” in Patent Document 1 is mainly a type that is attached to the outside of the tube of the liquid supply piping and detects the presence or absence of the liquid in the tube. The problem that the air sensor must be selected or the sensitivity adjusted according to the type of the sensor is described. However, as disclosed in Patent Document 1, a special flow cell that is installed by being interrupted in the middle of the liquid supply pipe requires an elaborate manufacturing technique, tends to be expensive, and has a problem of versatility.

  In addition, the determination of running out of liquid is performed by, for example, inputting the output voltage of the air sensor and the threshold value from the voltage generating means to the comparator, and increasing or decreasing the threshold value as one method of sensitivity adjustment. . Actually, the sensitivity is often adjusted by manually adjusting the volume of the threshold value in an analog manner.For example, in liquid chromatographic analysis, adjusting the threshold value each time the analysis conditions such as the type of eluent are frequently changed is troublesome. This is a cumbersome operation and has a problem that the reliability of the determination of running out of liquid is lowered.

  Accordingly, an object of the present invention is to improve the operability of adjusting the sensitivity of a sensor for detecting the out of liquid in the liquid supply pipe and the reliability of determining the out of liquid. If this purpose can be achieved, an air sensor of the type attached to the outside of the liquid supply pipe can be widely used. Further, even in the case of a liquid shortage sensor of a type using a dedicated flow cell as described in Patent Document 1, it is necessary to adjust the sensitivity as in the case of flowing various liquids having different liquidity through a thin channel. Will provide useful technology.

  The inventor of the present invention paid attention to digitizing the output signal of the air sensor, and converting the threshold value into a numerical value and inputting it to the comparison calculation means. Completed the device. That is, the first of the present invention is a liquid shortage detection device for detecting liquid shortage in the liquid feed pipe, an air sensor for detecting the presence of gas at a specific part in the liquid feed pipe, and the air sensor A sensor output conversion unit that appropriately amplifies the output and outputs a digital conversion value; a sensor output storage unit that receives the digital conversion value and stores the digital conversion value at a constant sampling interval; and outputs the sensor output; A sensor output display unit for displaying the threshold value, a threshold value input storage unit for receiving and storing a threshold value for determining that the liquid has run out, a sensor output from the sensor output storage unit, and a threshold value from the threshold input storage unit. The liquid shortage detection device comprising: a comparison operation unit that compares and outputs a determination result relating to liquid shortage.

  The sensor output display section may display the instantaneous value of the digitally converted sensor output or the average value of a plurality of sampling times, or may display a graph with elapsed time as the horizontal axis and sensor output as the vertical axis. Good.

  In the threshold value input storage unit, an operator can input an arbitrary threshold value within a predetermined range using an input device such as a keyboard or a touch panel. The threshold value to be input is determined as follows, for example. First, the sensor output W when the liquid feeding pipe is filled with the liquid is confirmed from the sensor output display unit in advance. Next, the sensor output A when the gas is filled in the liquid feeding pipe is confirmed from the sensor output display unit. The worker can determine the optimum threshold value for the situation within the range having these sensor outputs at both ends, and can input the threshold value to the threshold value input storage unit. In the situation where air should never be mixed even if it is a small bubble depending on the purpose of liquid feeding, the threshold value is set to a value close to the sensor output W, and conversely, even if a little bubble is mixed In a situation where it is desired to use up the liquid without waste, it is preferable to set the threshold value to a value close to the sensor output A.

Rather than relying on the operator to input the threshold value, it may be desired that the device automatically determine the threshold value to increase the objectivity of the liquid shortage detection device and reduce the burden on the operator. . The second aspect of the present invention responds to such a request. That is, the second aspect of the present invention is a liquid shortage detecting device for detecting liquid shortage in the liquid feed pipe, an air sensor for detecting the presence of gas at a specific part in the liquid feed pipe, and the air sensor A sensor output conversion unit that appropriately amplifies the output and outputs a digital conversion value, a sensor output storage unit that receives the digital conversion value and stores it at a constant sampling interval, and outputs a sensor output; and The sensor output W when the liquid feeding pipe is filled with the liquid and the sensor output A when the liquid feeding pipe is filled with the gas are received,
Threshold = F (A−W) + W; (0.1 <F <0.9) (Equation 1)
A threshold value automatic setting unit that calculates the threshold value using a threshold value, a threshold value input storage unit that receives and stores a threshold value for determining that the liquid has run out from the threshold value automatic setting unit, and a sensor output from the sensor output storage unit And a comparison operation unit that compares the threshold value from the threshold value input storage unit and outputs a determination result relating to liquid shortage. In Equation 1, the range of values that the coefficient F can take is 0.1 to 0.9. However, it is generally preferable to set the value around 0.5 unless there is a special request.

  The air sensor that detects the presence of gas at a specific part in the liquid supply pipe continuously monitors the specific part in the liquid supply pipe itself. The output of the air sensor is converted into a digital conversion value through the sensor output conversion unit, and then stored in the sensor output storage unit at a constant sampling interval. What is necessary is just to determine the sampling interval suitably with the flow velocity of liquid feeding. For example, in liquid chromatography, a sampling interval of about 100 ms is selected. Each sensor output digitized and sampled is an instantaneous value of a specific portion in the liquid feeding pipe. Therefore, there is a possibility that the first sampling data happens to detect small bubbles mixed in the flowing liquid. However, if the subsequent second sampling data and further the third sampling data detect gas, the introduction of such an algorithm that determines that the liquid has run out significantly increases the reliability of the liquid running detection. Useful for. That is, the liquid shortage detection device according to the present invention receives, in addition to the above-described components, the determination result of the comparison calculation unit, and how many times the determination result is the determination of liquid shortage, that is, A counter that counts the number of times of continuous liquid run, a count set value input storage unit that receives and stores a count set value serving as a reference for determining whether the liquid runs out when the liquid runs out continuously, and the counter Reliability is increased by providing a count comparison unit that compares the number of continuous liquid runouts from the above and the count set value from the count set value input storage unit and outputs a determination result related to liquid runout.

  The specific part in the liquid feeding pipe in the present invention is a part to which the liquid shortage detection device is attached, and the position in the liquid feeding pipe is not limited. Moreover, there is no limitation also about the air sensor which detects that gas exists in the specific site | part in liquid feeding piping, An electric conductivity sensor, an electrostatic capacitance sensor, etc. can be illustrated including a photo sensor. However, when a transmissive photosensor is used as an air sensor, a specific part in the liquid feeding pipe needs to be light transmissive. In short, any air sensor suitable for the liquid supply pipe used is suitable. Furthermore, even if it is a type which inserts a dedicated flow cell as disclosed in Patent Document 1 by interrupting the pipe, it is of course possible.

  However, the liquid breakage detection apparatus according to the present invention is most effective when applied to a liquid breakage detection apparatus of the type that is attached to the outside of the tube of the liquid supply piping and detects the presence or absence of liquid in the tube. That is, it is most preferable to use a transmissive photosensor suitable for being attached to the outside of the light transmissive tube portion of the liquid feeding pipe. The effectiveness of the present invention is exhibited in a situation where the degree of wetness of the liquid flowing inside varies depending on the material and the pipe diameter of the liquid feeding pipe and the malfunction and misjudgment of the sensor is likely to occur.

  In the first aspect of the invention, since the operator inputs the threshold value after referring to the output signal of the liquid shortage sensor displayed in digital form, the material and the pipe diameter of the liquid supply pipe change, Even in situations where malfunctions and misjudgments are likely to occur, the sensitivity of the sensor can be adjusted easily and accurately each time. In the second aspect of the invention, since the apparatus automatically determines the threshold value, the objectivity of the liquid shortage detection apparatus can be improved and the burden on the operator can be further reduced.

  Therefore, in the present invention, it is possible to easily set the threshold value according to the analysis conditions, and to provide a highly reliable determination of running out of liquid. Also, if the air sensor is a transmissive photosensor, it can be attached outside the light-transmitting pipe part of the liquid supply pipe, and the presence or absence of liquid can be detected, and mounting is easy without cutting the liquid supply pipe. It is possible to easily determine the optimum mounting position by sliding on the pipe.

  For further understanding of the present invention, embodiments will be described with reference to the drawings.

  FIG. 3 shows a typical embodiment of a liquid feeding pipe to which the liquid breakage detecting device of the present invention is applied and an air sensor for detecting the presence of gas at a specific part in the liquid feeding pipe. Refractive index when a transmissive photosensor configured by combining a light emitting diode 21 and a phototransistor 22 is attached to the outside of a Teflon (registered trademark) tube 20 (showing a cross section), and the liquid in the tube is replaced with gas. The intensity of transmitted light caused by the difference is converted into a voltage output and measured. 23 is a power supply voltage of the phototransistor circuit, and 24 is a load resistance.

  FIG. 4 is an explanatory view schematically showing a change in sensor output when shifting from a state in which liquid is present in the liquid feeding pipe to a state in which gas is present due to running out of liquid. This figure shows that it is necessary to select and set a threshold value as a criterion for determination from a certain range in order to detect liquid shortage.

  FIG. 1 illustrates the configuration and information flow of a liquid shortage detection apparatus according to the first aspect of the present invention. The output of the air sensor 1 is input to the sensor output conversion unit 2 and appropriately amplified, and then converted into a digital conversion value. The digital conversion values are stored at a constant sampling interval in the sensor output storage unit 3 and displayed on the sensor output display unit 5. An operator can input an arbitrary threshold within a predetermined range to the threshold input storage unit 6 using an input device such as a keyboard or a touch panel. The threshold value to be input is determined as follows, for example. First, the sensor output W when the liquid feeding pipe is filled with the liquid is confirmed from the sensor output display unit 5 in advance. Next, the sensor output A when the gas is filled in the liquid feeding pipe is also confirmed from the sensor output display unit 5. The worker determines the optimum threshold value for the situation within a range where these sensor outputs are both ends, and inputs the threshold value to the threshold value input storage unit 6. In the figure, a dotted arrow pointing from the sensor output display unit 5 to the threshold value input storage unit 6 indicates that the operator inputs a threshold value to the threshold value input storage unit 6 with reference to the display on the sensor output display unit 5. The comparison calculation unit 4 compares the sensor output from the sensor output storage unit 3 with the threshold value from the threshold value input storage unit 6, and outputs a determination result relating to liquid shortage to the counter 7. The counter 7 counts the number of times that it has been determined that the liquid has run out continuously. On the other hand, the count set value input storage unit 9 receives and stores a count set value serving as a reference for determining how many times the liquid runs out continuously. Next, the count comparison unit 8 compares the number of continuous liquid runs out from the counter 7 with the count set value from the count set value input storage unit 9 and outputs a determination result relating to liquid runout. The output destination is output to the liquid running out display unit 10 in this figure, but the output destination of the determination result is not necessarily limited to the liquid running out display unit. For example, measures such as installing a flow path switching valve equipped with a control means downstream of the liquid shortage detection unit and discharging the mixed gas from the flow path by setting the output destination of the determination result as the control means. It is also possible to take.

FIG. 2 illustrates the configuration and information flow of the liquid shortage detection device according to the second aspect of the present invention. The output of the air sensor 1 is input to the sensor output conversion unit 2 and appropriately amplified, and then converted into a digital conversion value. This digital conversion value is stored in the sensor output storage unit 3 at a constant sampling interval and sent to the threshold automatic setting unit 11. The threshold automatic setting unit 11 receives, from the sensor output storage unit 3, for example, a sensor output W when the liquid feeding pipe is filled with liquid and a sensor output A when the liquid feeding pipe is filled with gas. And
Threshold = F (A−W) + W; (0.1 <F <0.9) (Equation 1)
Is used to automatically calculate the threshold value. The threshold value input storage unit 6 receives and stores an input of the threshold value calculated by the threshold value automatic setting unit 11. From this stage onward, the same comparison operation as shown in FIG. 1 and the number of continuous liquid discharges are checked, and the determination of liquid shortage is displayed.

It is a figure which illustrates the structure of the liquid shortage detection apparatus which concerns on the 1st of this invention, and the flow of information. It is a figure which illustrates the structure of the liquid shortage detection apparatus which concerns on the 2nd of this invention, and the flow of information. Composition and operating principle of liquid breakage detection unit using tube-shaped liquid feed pipe to which liquid breakage detection device of the present invention is applied and a transmissive photosensor attached to the outside of the liquid feed pipe to detect liquid breakage FIG. It is explanatory drawing which represented typically the change of the sensor output when it transfers to the state in which gas exists by liquid shortage from the state in which liquid exists in liquid feeding piping.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor 2 Sensor output conversion part 3 Sensor output memory | storage part 4 Comparison calculating part 5 Sensor output display part 6 Threshold input memory | storage part 7 Counter 8 Count comparison part 9 Count setting value input memory | storage part 10 Liquid outage display part 11 Threshold value automatic setting part 20 Teflon (registered trademark) tube 21 Light emitting diode 22 Phototransistor 23 Power supply voltage 24 Load resistance

Claims (4)

A liquid shortage detection device for detecting liquid shortage in a liquid delivery pipe,
An air sensor for detecting the presence of gas at a specific site in the liquid feeding pipe;
A sensor output conversion unit that appropriately amplifies the output of the air sensor and outputs a digital conversion value;
Receiving the digital conversion value, storing it at a constant sampling interval, and outputting a sensor output; a sensor output storage unit;
A sensor output display unit for displaying the sensor output on a screen;
A threshold value input storage unit for receiving and storing a threshold value for determining that the liquid has run out;
A comparison operation unit that compares a sensor output from the sensor output storage unit with a threshold value from the threshold value input storage unit and outputs a determination result relating to liquid shortage;
The out-of-liquid detection device comprising: A liquid shortage detection device for detecting liquid shortage in a liquid delivery pipe,
An air sensor for detecting the presence of gas at a specific site in the liquid feeding pipe;
A sensor output conversion unit that appropriately amplifies the output of the air sensor and outputs a digital conversion value;
Receiving the digital conversion value, storing it at a constant sampling interval, and outputting a sensor output; a sensor output storage unit;
From this sensor output storage unit, the sensor output W when the liquid feeding pipe is filled with the liquid and the sensor output A when the liquid feeding pipe is filled with the gas are received,
Threshold = F (A−W) + W; (0.1 <F <0.9) (Equation 1)
A threshold automatic setting unit that calculates the threshold using
A threshold value input storage unit that receives and stores an input of a threshold value for determining that the liquid has run out from the threshold value automatic setting unit;
A comparison operation unit that compares a sensor output from the sensor output storage unit with a threshold value from the threshold value input storage unit and outputs a determination result relating to liquid shortage;
The out-of-liquid detection device comprising: 3. The liquid shortage detection device according to claim 1 or 2, further comprising receiving the determination result of the comparison operation unit, and how many times the determination result is the determination of liquid shortage, that is, the number of continuous liquid shortages. A counter to count,
A count setting value input storage unit that receives and stores a count setting value serving as a reference for determining whether or not the liquid runs out when the liquid runs out continuously,
A count comparison unit that compares the count of continuous liquid runs from the counter with a count setting value from the count setting value input storage unit and outputs a determination result relating to liquid running;
The out-of-liquid detection device comprising: The liquid breakage detection device according to any one of claims 1 to 3, wherein the air sensor is a transmission type photosensor suitable for being attached to the outside of a light transmission tube portion of a liquid supply pipe.

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