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US 6,604,418 B2Granted
Liquid-level detection method and device thereof
AssigneeARKRAY, Inc.
InventorToshikazu Iwao
Life of this patent
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AssigneeARKRAY, Inc.
InventorToshikazu Iwao
Estimating the term…
An ALC circuit is turned on (S1), a nozzle is shifted to a sampling position (S2), and after the ALC circuit has been turned off (S3), the nozzle is allowed to start discharging air from its tip (S4). While the nozzle is being lowered, the inner pressure of the nozzle is monitored (S5, S6), and upon detection of an increase in the pressure, the discharging process of air and the nozzle lowering process are stopped (S7), while the monitoring of the magnitude of the pressure is continued (S8). When the magnitude of the pressure is being maintained within a permissible range of the change for a predetermined time, it is judged that the tip of the nozzle has come into contact with the true liquid level, and after a suction operation of a sample (S9), the nozzle is raised (S10). When the magnitude of the pressure has dropped below the permissible range of the change within the predetermined time, it is judged that the tip of the nozzle has not come into contact with the true liquid level, the nozzle is again lowered (S11).
A liquid-level detection device comprising:
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
No references of this kind are recorded.
Devices for transferring samples or any liquids to, in, or from, the analysis apparatus, e.g. suction devices, injection devices: characterised by…
Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm: by…
Characterised by arrangements for controlling the aspiration or dispense of liquids: fluid level sensing
Investigating or analysing materials by determining their chemical or physical properties
Term ended 18 Apr 2021 (estimated)
1. Field of the Invention
The present invention relates to a method and device for detecting a liquid level, and more specifically, concerns a liquid-level detection method and device, in which a nozzle is lowered toward a liquid level while a gas is being suctioned or discharged from a tip of the nozzle through a pipe by a pump so that, when the inner pressure of the pipe changes, it is judged that the tip of the nozzle has come into contact with the liquid level.
Such liquid-level detection method and device are applied to a biochemical automatic analyzer for measuring a sample such as blood or urine.
FIG. 1 is a schematic drawing that shows the construction of an extraction device in accordance with one embodiment of the present invention.
FIG. 2 is a block diagram that shows a control system of the embodiment.
FIG. 3 is a circuit diagram that shows one example of a pressure sensor and a signal processing part.
With respect to the liquid level detection method of the present invention, in the detection step, it is preferable to make a judgment as to the change in the inner pressure based upon comparison between the differential signal of the inner pressure and a threshold value, and in the judging step, it is preferable to make a judgment based upon the pressure signal itself from the inner pressure. As a result, it is possible to quickly detect the clogging of the tip of the nozzle, and also to accurately monitor the variations in the inner pressure.
In the liquid-level detection device of the present invention, the control part is preferably provided with an ALC (Auto Level Control) circuit that sets the output of the pressure sensor at the time when the nozzle is open to atmosphere to a center of the input range of an AD (analog-to-digital) converter of the control part.
In the case of a device which carries out sample injection in fine amount, for example, approximately 10 micro-liters, the inner diameter of a nozzle and a pipe, such as a tube, between the nozzle and the pump is very small, and the change in the inner pressure of the pipe that takes place when the tip of the nozzle comes into contact with the liquid level is also small; therefore, the output of the pressure sensor needs to be amplified with a great gain. However, when the amplification is made with a great gain, problems arise in which the dynamic range is exceeded or it is not possible to maintain a constant value, caused by changes in offsets in the pressure sensor and the amplifier due to temperature changes, or influences of deviations due to aged deterioration. Therefore, the ALC circuit is used to set the output of the pressure sensor when the nozzle is open to atmosphere, to a center of the input range of an AD converter, and immediately before the start of the liquid level detection, the ALC circuit is turned off so that an output in accordance with the inner pressure of the pipe can be monitored by using a proper range.