JP2014176600A - Droplet detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow detection of free flow occurring in a drip tube even if the brightness around the drip tube changes.SOLUTION: A signal processing part 10 of a droplet detecting device 1 includes: a first filter 13 which performs a process of acquiring a central value from the signal in a specific period which is outputted from an upper side first light receiving element 3 and upper side second light receiving element 4; a second filter 14 which performs a process of acquiring a central value from the signal in a specific period which is outputted from the upper side first light receiving element 3 and a lower side light receiving element 5; and a determination part 15 which, when a voltage difference between the signal obtained through processing with the first filter 13 and the signal obtained through the second filter 14 comes to be a specified value or higher, determines that a free flow is occurring in a drip tube 101.

Description

  The present invention relates to a droplet detection device that detects, for example, a free flow state of a droplet in an infusion tube of an infusion set, for example.

  Conventionally, when infusion treatment is performed using a natural drop-type infusion set, it is important to manage the flow rate of the chemical solution.Therefore, the number of droplets dropped per unit time in the infusion tube is detected to control the flow rate of the chemical solution. Information is displayed or displayed when an abnormality occurs (for example, see Patent Documents 1 and 2).

  In Patent Documents 1 and 2, droplets in a drip tube are detected using a sensor composed of a light emitting element and a light receiving element. That is, the light emitting element and the light receiving element are arranged so that the drip tube is sandwiched from the outside, and the light irradiated from the light emitting element toward the inside in the radial direction of the drip tube is received by the light receiving element, and light is emitted when the droplet falls. It is determined that the liquid droplet has fallen because the light from the element is blocked.

  Since the fluctuation of the signal voltage output from the light receiving element when the drop of the droplet is detected is small, as disclosed in Patent Document 2, the output signal of the light receiving element is amplified by an amplifier.

JP 2009-240428 A JP 2012-125450 A

  By the way, at the time of normal infusion treatment, the drug solution is dropped as a droplet in the drip tube as described above, but for some reason, the drug solution flows down like a continuous thread in the drip tube. So-called free flow may occur. When free flow occurs, the dose of the drug solution increases more than specified, so it is desirable to detect and notify quickly.

  However, in a state where the drug solution flows down in the drip tube so as to pull the thread, the signal voltage output from the light receiving element hardly changes with time, and becomes a signal with a substantially constant voltage. Although it is conceivable to compare the signal voltage at the time of this free flow with some reference voltage and determine whether it is free flow based on the difference, it is a problem how to determine Become. That is, if the brightness around the drip tube becomes bright due to, for example, the influence of sunlight or the passage of time (morning, noon, night), the signal voltage of the light receiving element increases, and conversely, it decreases when it becomes dark. Thus, even if the signal voltage that rises and falls regardless of the detection of the droplet is compared with a certain reference, it cannot be accurately determined whether or not it is a free flow, and setting the reference voltage itself is not possible. Have difficulty.

  The present invention has been made in view of such a point, and an object of the present invention is to detect a free flow that occurs in the infusion tube even if the brightness around the infusion tube changes. There is to do.

  In order to achieve the above object, in the present invention, signals obtained by light receiving elements separated vertically are obtained by a light receiving element provided in a place affected by external light in the same way as those light receiving elements receive. It was set as the structure which compares a signal.

The first invention is
In a droplet detection device that detects a droplet falling in a drip tube,
A light projecting element for irradiating the drip tube with light;
A first light receiving element, a second light receiving element and a third light receiving element that receive light emitted from the light projecting element;
A signal processing unit that processes signals output from the first light receiving element, the second light receiving element, and the third light receiving element;
The first light receiving element and the second light receiving element are arranged apart from each other in a vertical direction where there is a change in the intensity of light received from the light projecting element due to a drop of a droplet,
The third light receiving element is disposed in a place that is affected by external light in the same manner as the installation place of the first light receiving element, and in which the intensity of light received from the light projecting element does not change due to a drop of a droplet. And
The signal processing unit includes a first differential amplifier to which signals output from the first light receiving element and the third light receiving element are input, and a median value from signals in a specific period output from the first differential amplifier. Obtained by a first filter that performs a process for obtaining a median value from signals in a specific period output from the first light receiving element and the second light receiving element, and a process by the first filter. And a determination unit that determines that a free flow is occurring in the infusion tube when the difference between the calculated median value and the median value obtained by the processing by the second filter is equal to or greater than a predetermined value. It is characterized by this.

  As shown in FIG. 12, when the sampling period is Δt, the specific period is the number of samples (2; S1, S2) in the signal during the dropping, the number of samplings during the period when the dropping is not performed (3 Pieces; S3, S4, S5) means the time required to become less than or equal to.

  According to this configuration, for example, when the first light receiving element is arranged above the second light receiving element, when the liquid droplet falls in the drip tube, the light emitted from the light projecting element is blocked by the liquid droplet Is detected by the second light receiving element after the first light receiving element is detected, and this is repeated, so that a continuous signal is output. The output signal is collected for the specific period and processed by the second filter to obtain the median value of the signal.

  When the droplet falls in the drip tube, the first light receiving element detects that the light irradiated from the light projecting element is blocked by the droplet, and the output signal of the first light receiving element changes. Since it is not detected by the three light receiving elements, the output signal of the third light receiving element does not change. In the first differential amplifier, as described later, the difference between the signal voltage of the first light receiving element and the signal voltage of the third light receiving element is obtained. This signal is then processed by the first filter to obtain a median value. Here, the first filter described above is a means that can repeat the exclusion of the maximum value and the minimum value from the sampled values of the odd number of times in the so-called continuous sampling of the signal and obtain the median value. However, the present invention is not particularly limited, and the median value may be obtained by excluding the maximum value and the minimum value in a hardware configuration, or the median value may be obtained in software.

  Further, it is assumed that the median value of the signals acquired as described above is obtained by the values collected during the specific period as described above. The signal output from the first filter is a signal for determining whether or not free flow is occurring.

  Then, the determination unit has a free flow in the drip tube when the difference between the median value obtained by the processing by the first filter and the median value obtained by the processing by the second filter becomes a predetermined value or more. Is determined.

  At this time, for example, assuming that the brightness around the infusion tube changes, the first and third light receiving elements are equally affected by external light, so the brightness around the infusion tube changes. Even so, the signal voltages of the first and third light receiving elements only rise and fall in the same way, and the relative difference between the signal voltage output from the first filter and the median value obtained by the processing by the second filter Will be maintained.

According to a second invention, in the first invention,
The signal processing unit includes a second differential amplifier to which signals output from the first light receiving element and the second light receiving element are input, and the second filter is output from the second differential amplifier. In addition, a process for obtaining a median value from a signal in a specific period is performed.

  According to this configuration, when noise is included in the signals of the first light receiving element and the second light receiving element, the signal including the noise is input to the second differential amplifier. At this time, since the first light receiving element and the second light receiving element are attached to the same drip tube and are not so far apart, almost the same noise enters the first light receiving element and the second light receiving element. Therefore, since the noise of the second light receiving element is subtracted from the noise of the first light receiving element in the second differential amplifier, the influence of the noise can be suppressed.

  According to the first invention, the signal used for the determination of the free flow obtained by the first light receiving element and the third light receiving element, and the signal obtained by the first light receiving element and the second light receiving element separated in the vertical direction of the drip tube Can be determined that a free flow is occurring in the infusion tube when the difference between them becomes equal to or greater than a predetermined value. Thereby, even if the brightness around the infusion tube changes, it is possible to detect free flow that occurs in the infusion tube.

  According to the second invention, it is possible to accurately detect a droplet while suppressing the influence of noise.

It is a figure explaining the use condition of the droplet detection apparatus concerning an embodiment. It is a block diagram of a droplet detection apparatus. It is a side view which shows the attachment state to the drip tube of a light projection element and a light receiving element. It is the IV-IV sectional view taken on the line of FIG. It is a figure which shows the signal waveform output from a 2nd differential amplifier. It is a side view which shows the state which a droplet falls, (a) is a state in which a droplet is above an upper 1st light receiving element, (b) is a state in which a droplet is the same height as an upper 1st light receiving element (C) shows a state where the droplet is between the upper first light receiving element and the lower light receiving element, and (d) shows a state where the droplet is at the same height as the lower light receiving element. It is a figure which shows an actual dripping signal. It is a figure which shows the waveform after filtering a drop signal. It is a figure which shows the signal waveform output from a 1st differential amplifier. It is a figure which shows the signal after a filter process, and a free flow reference signal. FIG. 6 is a view corresponding to FIG. 5 showing a state where a free flow has occurred. It is a figure explaining a specific period.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

  FIG. 1 is a diagram for explaining a use state of a droplet detection device 1 according to an embodiment of the present invention. The droplet detection device 1 is attached to an infusion tube 101 included in the infusion set 100, and detects the state of the droplet falling in the infusion tube 101. In addition to the drip tube 101, the infusion set 100 includes a drug solution container 102 containing a drug solution, an upstream tube 103 extending from the drug solution container 102 to the drip tube 101, and a downstream tube 105 extending from the drip tube 101 to the puncture needle 104. And. In the middle of the downstream tube 105, an infusion pump 106 is provided, and the infusion pump 106 administers the medicinal solution to the patient at a predetermined flow rate.

  The drip tube 101 is conventionally well-known, and is composed of a translucent member (for example, a colorless and transparent member). That is, a droplet grows in the upper part of the drip tube 101, and when the grown droplet reaches a predetermined size as shown in FIG. Administered to patients. The lower part of the drip tube 101 is a chemical solution storage unit 101a, and the upper side of the chemical solution storage unit 101a is a droplet passage place through which a droplet passes.

  As shown in FIGS. 2 and 3, the droplet detection device 1 includes a light projecting element 2, an upper first light receiving element (corresponding to the first light receiving element of the present invention) 3, and an upper second light receiving element (the present invention). 4), a lower light-receiving element (corresponding to the second light-receiving element of the present invention) 5, and a control device 6, which are infused via a signal line 108 shown in FIG. Connected to the pump 106. The light projecting element 2 can be composed of a light emitting element such as an LED. The light projecting element 2 irradiates light from the outside of the drip tube 101 to the inside of the drip tube 101 with respect to the droplet passage location of the drip tube 101. It is comprised so that it may irradiate. The light emitted from the light projecting element 2 covers a predetermined range from the upper side to the lower side of the droplet passage location of the drip tube 101.

  The light projecting element 2 may be composed of a single LED, or may be composed of a plurality of LEDs, for example. In the case of a single LED, it is preferable to widen the light emission range and ensure a wide droplet detectable range. By widening the detectable range of the droplet, for example, when the drip tube 101 is tilted due to some influence, even if the droplet falls vertically in the tilted drip tube 101, it can be detected effectively. Is possible.

  On the other hand, when comprised by several LED, the irradiation range as the light projection element 2 whole is made to cover with the number of LED. This makes it possible to detect a wide range with high accuracy. The light emitted from the light projecting element 2 may be visible light or infrared light. In this embodiment, the light projecting element 2 is composed of three LEDs, and these LEDs are arranged in the horizontal direction.

  The upper first light receiving element 3, the upper second light receiving element 4, and the lower light receiving element 5 are well-known elements configured such that the higher the intensity of received light, the higher the voltage of the output signal. The upper first light receiving element 3 is disposed at a position facing the light projecting element 2 on the upper side of the droplet passage location of the drip tube 101, and the droplet passage location of the drip tube 101 irradiated from the light projecting device 2. The light which permeate | transmitted is received.

  The upper second light receiving element 4 is a place that is affected by external light in the same manner as the place where the upper first light receiving element 3 is installed, and changes in the intensity of light received from the light projecting element 2 even when a liquid droplet falls. It is located where there is no. The place where the brightness is equivalent to the place where the upper first light receiving element 3 is installed is the light intensity where the upper first light receiving element 3 is installed and the place where the upper second light receiving element 4 is installed. Of course, the light intensity includes exactly the same part, but even if it is slightly different, there is a slight difference that is within the range of the light detection error of the upper first light receiving element 3 and the upper second light receiving element 4. Is also included. That is, the installation place of the upper second light receiving element 4 is a place where the brightness of the external light is substantially the same as the installation place of the upper first light receiving element 3.

  In addition, even if a droplet falls, there is no change in the intensity of light received from the light projecting element 2. Even if a droplet falls, the light receiving intensity of the upper second light receiving element 4 does not change at all. Of course, even a slight change includes a minute change that falls within the range of the light detection error of the upper second light receiving element 4. That is, the installation location of the upper second light receiving element 4 is a place where there is substantially no change in the intensity of light received from the light projecting element 2 even when a droplet drops.

  In this embodiment, as shown in FIG. 4, the upper first light receiving element 3 is disposed so as to sandwich the drip tube 101 together with the light projecting element 2, while the upper second light receiving element 4 is infused from the light projecting element 2 to the drip. It arrange | positions away from the outer surface of the drip pipe | tube 101 so that the light irradiated toward the outer side of the pipe | tube 101 may be received.

  The upper first light receiving element 3 and the upper second light receiving element 4 may be disposed at substantially the same height or at different heights.

  The lower light receiving element 5 is separated from the lower side of the droplet passage place of the drip tube 101, that is, downward from the upper first light receiving element 3, and separated from the light projecting element 2 in the circumferential direction of the drip tube 101, for example. It is disposed at a position facing the light projecting element 2, and receives light emitted from the light projecting element 2 and transmitted through the droplet passage location of the drip tube 101. That is, the lower light receiving element 5 and the upper first light receiving element 3 are arranged apart from each other in the vertical direction where the intensity of the light received from the light projecting element 2 is changed due to the drop of the liquid droplet.

  The control device 6 is configured to receive signals output from the upper first light receiving element 3, the upper second light receiving element 4, and the lower light receiving element 5. That is, as shown in FIG. 2, the control device 6 includes a signal processing unit 10 that processes signals output from the upper first light receiving element 3, the upper second light receiving element 4, and the lower light receiving element 5. The signal processing unit 10 includes a first differential amplifier 11, a second differential amplifier 12, a first filter 13, a second filter 14, and a determination unit 15.

  As shown in FIG. 3, signals output from the upper first light receiving element 3 and the upper second light receiving element 4 are input to the first differential amplifier 11. The first differential amplifier 11 subtracts the signal of the upper first light receiving element 3 from the signal of the upper second light receiving element 4 and amplifies it with a constant amplification factor. The first differential amplifier 11 may be configured to subtract the signal of the upper second light receiving element 4 from the signal of the upper first light receiving element 3.

  Further, the second differential amplifier 12 receives signals output from the upper first light receiving element 3 and the lower light receiving element 5. The second differential amplifier 12 subtracts the signal of the lower light receiving element 5 from the signal of the upper first light receiving element 3 and amplifies the signal with a constant amplification factor.

  The first filter 13 performs processing for obtaining a median value from a signal in a specific period output from the first differential amplifier 11, and details thereof will be described later. Similarly to the above, the second filter 14 performs processing for obtaining a median value from a signal in a specific period output from the second differential amplifier 12, and details thereof will be described later.

  When the droplet A (shown in FIGS. 4 and 6) falls in the drip tube 101, the droplet A passes between the light projecting element 2 and the upper first light receiving element 3, and then the light projecting element 2 and It passes between the lower light receiving element 5. As shown in FIG. 6A, before the droplet A passes between the light projecting element 2 and the upper first light receiving element 3 in the drip tube 101, a signal output from the second differential amplifier 12 is received. 5, the value obtained by subtracting the signal of the lower light-receiving element 5 from the signal of the upper first light-receiving element 3 is amplified by a predetermined amplification factor, as indicated by an area a in FIG.

  While the droplet A passes through the drip tube 101, first, the droplet A passes between the light projecting element 2 and the upper first light receiving element 3 as shown in FIG. At this moment, the light from the light projecting element 2 is blocked, and the signal voltage output from the upper first light receiving element 3 instantaneously decreases. Thereby, as shown by the arrow b in FIG. 5, the signal output from the 2nd differential amplifier 12 falls. Next, when the droplet A falls between the upper first light receiving element 5 and the lower light receiving element 5 as shown in FIG. 6C, the droplet A does not block the light of the light projecting element 2. Therefore, the signal output from the second differential amplifier 12 is the same as the region a in FIG. 5 (indicated by an arrow c in FIG. 5).

  Thereafter, as shown in FIG. 6 (d), the droplet A passes between the light projecting element 2 and the lower light receiving element 5. At this moment, the light from the light projecting element 2 is blocked, and the signal voltage output from the lower light receiving element 5 instantaneously decreases. As a result, the signal output from the second differential amplifier 12 rises as indicated by an arrow d in FIG. Accordingly, the signal voltage output from the second differential amplifier 12, that is, the signal voltage output from the upper first light receiving element 3 and the lower light receiving element 5, fluctuates up and down each time the droplet is repeatedly dropped. , It becomes a continuous signal.

  The signal processing unit 10 is configured to determine that a droplet has fallen when the signal voltage output from the second differential amplifier 12 exceeds a predetermined drop detection range. The drop determination range is generally a range narrower than the fluctuation of the signal voltage output from the second differential amplifier 12 when a drop of the drop occurs, and wider than a small signal voltage that fluctuates due to noise or the like. This is a range indicated by the upper broken line and the lower broken line in FIG.

  The control device 6 is configured to notify the outside when the signal processing unit 10 determines that a droplet has dropped. For example, when a light emitting body such as an LED or a device that emits sound is connected to the control device 6 and the signal processing unit 10 determines that a droplet has dropped, the light emitting body emits light or generates sound. I will let you.

  FIG. 7 is a diagram showing an actual waveform of the signal voltage output from the second differential amplifier 12, and the signal voltage output from the second differential amplifier 12 is a signal indicating the presence or absence of dropping. Therefore, it will be called a drip signal. As shown schematically in an enlarged view in FIG. 5, the drop-drop signal is composed of repetition of a signal before passing the droplet and a signal during passage of the droplet. It becomes a flat shape only with the signal before passing.

  The second filter 14 can be configured using a well-known signal processing filter. In this embodiment, the signal during droplet passage is removed from the droplet signal, and before the droplet passes (see FIG. 5). The process of making the signal voltage in the areas a and e) continuous is performed. As a result, the drop signal after filtering does not have a clear peak as indicated by symbols b and d in FIG. 5, and becomes a signal that is nearly flat as shown in FIG.

  When the droplet A falls in the drip tube 101, the droplet A passes between the light projecting element 2 and the upper first light receiving element 3, while the light projecting element 2 and the second upper light receiving element 3 pass. It does not pass between the light receiving element 4. Therefore, at the moment when the droplet A passes through the light projecting element 2 and the upper first light receiving element 3, light from the light projecting element 2 is blocked and the signal voltage output from the upper first light receiving element 3 is instantaneous. However, the signal voltage output from the upper second light receiving element 4 does not change.

  The signal output from the first differential amplifier 11 has a waveform that is enlarged and schematically shown in FIG. The first filter 13 can be configured by using a well-known signal processing filter. In this embodiment, the signal passing through the droplet (region protruding downward) in the signal waveform shown in FIG. 9 is used. Removal is performed, and the signal voltage before passing through the droplet (flat region) is made continuous. This eliminates a clear peak in the filtered signal. The signal output from the first filter 13 (that is, the free flow signal) has a nearly flat shape except for the change when free flow occurs, as shown only in the median value in FIG.

  The determination unit 15 of the signal processing unit 10 includes a signal (free flow signal) obtained by the processing by the first filter 13 and a signal (droplet signal after the filter processing) obtained by the processing by the second filter 14. Based on the voltage difference, it is configured to determine whether or not free flow is occurring in the infusion tube 101. As shown in FIG. 10, the waveform of the drop signal after the filter processing obtained by the processing by the second filter 14 also has a nearly flat shape. The signal obtained by the processing by the first filter 13 is a free flow signal that can confirm the presence or absence of free flow. As shown in FIG. 10, in the state of dropping, the signal voltage value obtained by processing by the second filter 14 (that is, the dropping signal after filtering) and the first filter 13 are obtained. When the measured signal voltage value (free flow signal) is compared, the difference is small, but when free flow occurs, the voltage difference between the two (filtered drop signal and free flow signal) is significant. It becomes.

  The reason why the voltage difference between the filtered drop signal and the free flow signal becomes significant when free flow occurs can be explained by the following mechanism. That is, when the liquid is dropping normally, the main signal voltage that is output from the upper first light-receiving element 3 and the lower light-receiving element 5 when light is not blocked by the liquid droplets is main. That is, the voltage value of the drop signal after the filter processing is that at the time of non-blocking. On the other hand, since the upper second light receiving element 4 that is not affected by the drop also has a signal voltage due to light reception when the liquid droplet is not blocked, the signal voltage output from the upper first light receiving element 3 and the upper second light receiving element 4 The difference between the free flow signal voltage value obtained by differentially amplifying the signal voltage output from the element 4 and obtaining its median value and the drop signal voltage value after the filter processing is small.

  However, when free flow occurs, the chemical solution flows down like pulling a thread. Therefore, the upper first light receiving element 3 and the lower light receiving element 5 both have a main signal voltage due to light reception when shut off. Since the upper second light receiving element 4 has a signal voltage due to non-blocking light reception, the difference between the signal voltages output from the upper first light receiving element 3 and the upper second light receiving element 4 becomes large. Accordingly, when the free flow occurs, the voltage value of the free flow signal is significantly different from the voltage value of the drop signal (after filtering) with little difference between the signal voltage at the time of the drop and the free flow. .

  The voltage difference between the free flow signal and the filtered drop signal is continuously detected, and if the voltage difference is less than a predetermined value, it is determined that the droplet is falling normally, while the voltage difference is a predetermined value. When it becomes above, it determines with the free flow having occurred. The predetermined voltage difference is a value larger than the noise level so that when the filtered drop signal changes due to noise or the like, it is not erroneously determined as free flow.

  Further, the control device 6 can be configured to output a signal to the infusion pump 106 when a droplet is detected or when a free flow is detected. For example, the infusion pump 106 that has obtained a signal from the control device 6 determines whether or not the number of drops per unit time falls within the normal range and issues an alarm when the normal range is exceeded. It can be configured to issue an alarm when a free flow occurs.

  Next, how to use the droplet detection device 1 configured as described above will be described. First, the light projecting element 2, the upper first light receiving element 3, the upper second light receiving element 4 and the lower light receiving element 5 of the droplet detecting apparatus 1 are attached to the drip tube 101 as shown in FIGS.

  When a droplet falls in the drip tube 101, signals output from the upper first light receiving element 3 and the lower light receiving element 5 change, and these signals are input to the second differential amplifier 12. In the second differential amplifier 12, the signal of the lower light receiving element 5 is subtracted from the signal of the upper first light receiving element 3. At this time, the signals of the upper first light receiving element 3 and the lower light receiving element 5 may contain noise, but the upper first light receiving element 3 and the lower light receiving element 5 are attached to the same drip tube 101. Since both are not so far away, almost the same noise enters the upper first light receiving element 3 and the lower light receiving element 5. Therefore, in the second differential amplifier 12, the noise of the lower light receiving element 5 is subtracted from the noise of the upper first light receiving element 3, so that it is hardly noticeable. Since the signal obtained in this way is amplified at a constant amplification factor, it becomes possible to suppress the influence of noise and to clearly grasp the drop of the droplet as shown in FIG. A drop signal can be obtained.

  Also, the second filter 14 of the signal processing unit 10 processes the signal output from the second differential amplifier 12 to obtain a filtered drop signal shown in FIG. On the other hand, the first filter 13 processes a signal output from the first differential amplifier 11 to obtain a free flow signal.

  As shown in FIG. 11, a free flow may occur in which the chemical solution continuously pulls the thread in the drip tube 101. When the free flow occurs, the upper first light receiving element 3 and the lower light receiving element 5 detect the chemical solution continuously and continuously, so the voltage of the free flow signal is free as shown in FIG. Starting from the occurrence of the flow, the voltage is different from that in a state where the droplet is falling normally. The determination unit 15 compares the drop signal after filtering and the voltage of the free flow signal, and determines that a free flow has occurred if the difference is equal to or greater than a predetermined value. At this time, for example, assuming that the brightness around the infusion tube 101 changes, the upper first light receiving element 3, the upper second light receiving element 4, and the lower light receiving element 5 are provided in the same infusion tube 101. Even if the brightness around the drip tube 101 changes, the signal voltage of the upper first light receiving element 3, the upper second light receiving element 4, and the lower light receiving element 5 is the same as long as dripping continues. It only moves up and down, and the relative difference between the voltage of the free flow signal and the voltage of the drop signal after filtering is maintained.

  As described above, according to the droplet detection device 1 according to this embodiment, the upper first light receiving element 3 and the upper second light receiving element 4 obtain signals having specific waveforms, respectively, When the median value is obtained by filtering the signals output from the light receiving element 3 and the lower light receiving element 5, and the difference between the voltage of the free flow signal and the voltage of the dropped signal after the filtering process becomes a predetermined value or more It can be determined that free flow is occurring in the drip tube 101. Thereby, even if the brightness around the infusion tube 101 changes, it is possible to detect a free flow that occurs in the infusion tube 101.

  Further, the upper first light receiving element 3 and the lower light receiving element 5 are arranged apart from each other in the vertical direction, and signals output from the upper first light receiving element 3 and the lower light receiving element 5 are input to the second differential amplifier 12. Since it did in this way, the influence of noise can be suppressed and a droplet can be detected correctly.

  In addition, although the said embodiment demonstrated the case where the light projection element 2 was one, not only this but two or more light projection elements 2 may be provided.

  The first filter 13 and the second filter 14 can be configured by hardware or can be configured by software.

  In addition, the upper first light receiving element 3, the upper second light receiving element 4, and the lower light receiving element 5 may be formed of a single light receiving element or a plurality of light receiving elements.

  The above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  As described above, the droplet detection device according to the present invention can be used, for example, when performing infusion therapy.

DESCRIPTION OF SYMBOLS 1 Droplet detection apparatus 2 Light projection element 3 Upper side 1st light receiving element 4 Upper side 2nd light receiving element 5 Lower side light receiving element 6 Control apparatus 10 Signal processing part 11 1st differential amplifier 12 2nd differential amplifier 13 1st filter 14 Second filter 15 determination unit 101 drip tube

Claims (2)

In a droplet detection device that detects a droplet falling in a drip tube,
A light projecting element for irradiating the drip tube with light;
A first light receiving element, a second light receiving element and a third light receiving element that receive light emitted from the light projecting element;
A signal processing unit that processes signals output from the first light receiving element, the second light receiving element, and the third light receiving element;
The first light receiving element and the second light receiving element are arranged apart from each other in a vertical direction where there is a change in the intensity of light received from the light projecting element due to a drop of a droplet,
The third light receiving element is disposed in a place that is affected by external light in the same manner as the installation place of the first light receiving element, and in which the intensity of light received from the light projecting element does not change due to a drop of a droplet. And
The signal processing unit includes a first differential amplifier to which signals output from the first light receiving element and the third light receiving element are input, and a median value from signals in a specific period output from the first differential amplifier. Obtained by a first filter that performs a process for obtaining a median value from signals in a specific period output from the first light receiving element and the second light receiving element, and a process by the first filter. And a determination unit that determines that a free flow is occurring in the infusion tube when the difference between the calculated median value and the median value obtained by the processing by the second filter is equal to or greater than a predetermined value. A droplet detection apparatus characterized by the above. The droplet detection device according to claim 1,
The signal processing unit includes a second differential amplifier to which signals output from the first light receiving element and the second light receiving element are input, and the second filter is output from the second differential amplifier. A droplet detection apparatus that performs a process for obtaining a median from a signal in a specific period.

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