JPH0458565B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultraviolet measuring device that measures the difference between the flow rate of dialysis fluid flowing out from a dialyzer and the flow rate of dialysate flowing into the dialyzer as an ultraviolet amount.

<Prior art> As shown in Fig. 1, the dialysis machine has a liquid supply line 1.
Dialysate is supplied to the dialyzer 12 through the dialyzer 1 , and the dialysate effluent from the dialyzer 12 is discharged through the drain line 13 . The patient's blood is supplied to the dialyzer 12 through a blood line 14, and the blood from which waste products have been removed by dialysis in the dialyzer 12 is passed through the blood line 1.
5 and returned to the patient.

In the conventional ultraviolet amount measuring device, a flowmeter 1 is installed in the liquid supply line 11 and the liquid drainage line 13, respectively.
6 and 17 are provided, the flow rate F _i of the dialysate flowing into the dialyzer 12 is measured by the flowmeter 16, the measured value V _i is obtained, and the flow rate F _p of the dialysate effluent discharged from the dialyzer 12 is obtained.
was measured with a flowmeter 17 to obtain a measured value V _p , and V _p -V _i was determined as an ultra-high excess amount.

However, this conventional ultraviolet amount measuring device has the following problems. That is, flowmeters generally have measurement errors, and if the flow rate is F and the flow rate sensor output signal of the flowmeter is E, then the formula E=KF+E _p holds true. Here, K is the flow rate-sensor output signal conversion coefficient, and E _p is the zero error, that is, the sensor output signal when the flow rate F is zero. Also, if the flowmeter output value is V, then between V and E, V=μE+ε
holds true. Here, μ is the sensor output signal-flowmeter output value conversion coefficient, and ε is the zero error, that is, the flowmeter output value output when the sensor output signal is zero. Normally, this flowmeter output value V is used as the final output in most cases, and in the conventional ultra-overflow measuring device shown in FIG. 1, the output value V ₁ of the flowmeter 16 is V ₁ = μ ₁ E ₁ + ε ₁ = μ ₁ (K ₁ Fi + E _p1 ) + ε ₁ Also, the output value V ₂ of the flowmeter 17 can be expressed as V ₂ = μ ₂ E ₂ + ε ₂ = μ ₂ (K ₂ Fo + E _p2 ) + ε ₂ . Therefore, the ultraviolet amount is V ₂ −V ₁ =μ ₂ E ₂ +ε ₂ −(μ ₁ E ₁ +ε ₁ ) = μ ₂ (K ₂ F _p +E _O2 ) +ε ₂ −μ ₁ (K ₁ Fi+E _p1 )− ε ₁ =(μ ₂ K ₂ F _p −μ ₁ K ₁ Fi) +(μ ₂ E _p2 −μ ₁ E _p1 )+(ε ₂ −ε ₁ )...(1). If both the flowmeters 16 and 17 have no errors, V ₁ =F _i , V ₂ =F _p , therefore μK _i =1, E _p1 =ε ₁ =0, μ ₂ K ₂ = 1, E _p1 = ε ₂ =
0, V ₂ −V ₁ =F _p −F _i , which is equal to the true value. However, reality always contains errors. If the sensor output signal-flow rate meter output value conversion coefficient and the flow rate-sensor output signal conversion coefficient are μ _p and K _p in the case of zero error, μ ₁ = μ _p +Δμ ₁ , μ ₂ = μ _p +Δμ ₂
，
It can be written as K ₁ =K _p +ΔK ₁ , K ₂ =K _p +ΔK ₂ . Using this, equation (1) becomes equation (2).

V ₂ −V ₁ = (μ _p + Δμ ₂ ) (K _p + ΔK ₂ ) F _p − (μ _p + Δμ ₁ ) (K _p + ΔK ₁ ) F _i +C _p = μ _p +K _p (F _p −F _i )+μ _p (ΔK ₂ F _p −ΔK ₁ F _i ) +K _p (Δμ ₂ F _p −Δμ ₁ F _i )+(Δμ ₂ ΔK ₂ F _p −Δμ ₁ ΔK ₁ F _i )+C _p ……(2) Here, μ _p ·K _p =1, and the true value of the ultraviolet excess is only the first term, and the other terms are errors. This error is ΔK ₁ , ΔK ₂ , Δμ ₁ , Δμ ₂ , E _p1 , E _p2 ,
It is determined by the values of ε ₁ and ε ₂ , but this varies depending on the flowmeter. For example, if the flow rate introduced into the dialyzer 12 (hereinafter referred to as inlet flow rate) is 500 ml/min, the flow meter 16
Assuming that the error is +1%, the flow rate flowing out from the dialyzer 12 (hereinafter referred to as outlet flow rate) is 505 ml/min, and the error of the flowmeter 17 is -1% (the error of a normal flowmeter is ±1%) ), the output value of the flowmeter 16 is 505ml/min, and the output value of the flowmeter 16 is 505ml/min.
The output value of 7 is 499.5ml/min. Therefore, while the actual ultraviolet amount is 5 ml/min, the measured value is -50.5 ml/min, which is a totally unbelievable value. Typically, ultra-overdose measurements are made by ±
There is no practical problem if the error range is around 10%, but
Inlet flow rate 500ml/min, outlet flow rate 505ml/min
In this case, in order for the measurement error of the ultraviolet amount to be within ±10%, (505−500)×±0.1/2=0.25ml/
A flowmeter with a resolution of min or more is required.
This means that when measuring a flow rate of about 500 ml/min, the error is less than ±0.25/500, that is, less than ±0.05%, which is a high degree of accuracy, and such a highly accurate flow meter is unrealistic.

In other words, in the conventional technology in which two flowmeters 16 and 17 are used and the difference in their output values is simply measured as the ultra-limit amount, the above-mentioned ΔK ₁ , ΔK ₂ , Δμ ₁ ,
Errors due to Δμ ₂ , E _p1 , E _p2 , ε ₁ , and ε ₂ occur, making it impossible to accurately measure the ultraviolet amount. For this purpose, the applicant first applied
We attempted to solve this problem by proposing the device shown in the issue. In other words, in the calibration mode, the same flow rate of liquid is flowed through the two flow meters only once, and the flow rate sensor output signals (E _c1 , E _c2 ) of the two flow meters at that time and the first flow rate measured in advance are calculated. Characteristic values of the meter (sensor output signal - flow meter output value conversion coefficient (μ ₁ ), zero error ε ₁ )
From this, the characteristic values (μ ₂ , ε ₂ ) of the second flowmeter were determined and calibrated. However, this device is designed to have the same zero error (ε ₁ , ε ₂ ) for the two flowmeters used, and in that sense is based on the premise that flowmeters with similar characteristics are combined. The problem was that the degree of freedom in doing so was extremely limited.

<Summary of the Invention> The purpose of the present invention is to provide an apparatus for determining the ultra-high excess amount from the difference between the flow rate of outflow dialysis fluid and the flow rate of inflow dialysate, without using a particularly high-precision flowmeter.
Moreover, it is intended to be possible to accurately measure the extreme excess amount without requiring a combination of flowmeters with similar characteristics.

According to this invention, separate flowmeters are used to measure the flow rate of inflow dialysate and outflow dialysate waste, and there is a measurement mode in which dialysis is performed using a dialyzer and measurement of ultra-excess amount; The mode switching means is configured to switch between a calibration mode in which the other flowmeter is calibrated based on the characteristics of the flowmeter. When switched to the calibration mode, a predetermined flow rate of liquid is passed through the flowmeter that measures inflow dialysate and a flowmeter that measures outflow dialysate, and then a liquid at a flow rate different from the above flow rate is passed through the flowmeter. Using the output signal of each flowmeter in each case and the characteristic value of one flowmeter,
The characteristics of one flowmeter are used as a reference to calibrate the other flowmeter.

<Example> FIG. 2 shows an example of the ultraviolet amount measuring device according to the present invention, and parts corresponding to those in FIG. 1 are given the same reference numerals. In this invention, the control section 2
A mode for measuring the ultraviolet amount by the control of step 1;
It is possible to switch to a calibration mode in which either one of the two flowmeters 16 or 17 is calibrated.
In its calibration mode, flowmeters 16 and 17 have two
The liquid is made to flow at different flow rates in different times, but with the same flow rate in each time. Therefore, in this embodiment, an operating valve 22 is installed in the liquid supply line 11 between the flow meter 16 and the dialyzer 12.
However, an operating valve 23 is provided in the drain line 13 between the dialyzer 12 and the flow meter 17, and a side passage 18 is provided between the fluid supply line 11 and the drain line 13, which includes an operating valve 23. Operation valve 25 and valve 2 in parallel with 24
6 are provided respectively.

In the measurement mode, the dialysate in the liquid supply line 11 flows between the flow rate sensor 16a of the flow meter 16 and the operation valve 22.
The fluid flows through the dialyzer 12, the operating valve 23, and the flow sensor 17a of the flow meter 17, and is discharged from the drain line 13. On the other hand, in the calibration mode, first the operating valves 22, 2
3 and 25 are closed and the dialysate flows through the flow sensor 1
6a-operation valve 24-flow rate sensor 17a.
When the calibration at this stage is completed, the operation valve 2
4 is closed, the operating valve 25 is opened, and the dialysate flows through the flow rate sensor 16a - the operating valve 25 - the valve 26 - the flow rate sensor 17a.

The output signal of the flow rate sensor 16a is E ₁ and the flow rate is F.
Then, according to the above, E ₁ =K ₁ F+E _p1 (3).

Furthermore, if the output signal of the flow rate sensor 16a is E ₁ and the flow rate is F, then E ₁ =K ₁ F+E _p1 . . .
(3).

Furthermore, since the output signal of the flow rate sensor 16a is usually a very small signal, it is necessary to convert this output signal _E1 into a flowmeter output value _V1 corresponding to the flow rate.
This conversion is performed by setting F in equation (3) to V ₁ and using the equation solved for V ₁ . This conversion is performed by the signal processing circuit 16b of the flowmeter 16, but since an inherent error occurs in the conversion in the signal processing circuit 16b, generally,
The relationship is V ₁ = μ ₁ E ₁ + ε ₁ (4).

On the other hand, the flow rate sensor 17a also has a unique flow rate-sensor output signal conversion formula, which is E ₂ =
It can be expressed as K ₂ F + E _p2 ...(5).

Similarly to the flowmeter 16, the formula for converting the output signal E ₂ of the flow sensor 17a into the flowmeter output value V ₂ in the signal processing circuit 17b is V ₂ =μ ₂ E ₂ +ε ₂ .
It is expressed as (6).

A case will be described below in which the flowmeter 17 is calibrated in the calibration mode based on the characteristics of the flowmeter 16.

The characteristic values μ ₁ and ε ₁ of the flowmeter 16, which serve as a reference, are determined from a regression line in a regression analysis of the sensor output signal E ₁ and the output value V ₁ performed in advance, and are known.

Each of the two types of flow rate in calibration mode
F _c , F _c ′ The output signals of the flow rate sensors 16a and 17a when the flow rate F _c is V _c1 and E _c2 , the flow rate F _c ′
The output signals when the flow rate is F _c are respectively V _c1 and V _c2 , and the output values of the flow systems 16 and 17 are V _c1 and V _c2 when the flow rate is F _c ′, respectively. _c1 ' and V _c2 ', and the output value conversion coefficient for μ of the flowmeter 17 is μ _c2 . In the calibration mode, the same flow rates F _c and F _c ' flow, so in each case, V _c2 = V _c1 , V _c2 ′=V _c1 ′, that is, from equations (4) and (6), μ _c2 E _c2 +ε ₂ = μ ₁ E _c1 +ε ₁・μ
_c2
It must be E _c2 ′+ε ₂ =μ ₁ E _c1 ′+ε ₁ . Therefore, from these two equations, μ _c2 = μ ₁ E _c1 −E _c1 ′/E _c2 −E _c2 ′ ……(7) ε ₂ = ε ₁ + μ ₁ E _c2 E _c1 ′−E _c1 E _c2 ′/ E _c2 −E _c2 ′……(8). Therefore, the calculation unit 27 directly takes in E _c1 , E _c2 , E _c1 ′, and E _c2 ′ under the control of the control unit 21 .
Using these values and the known output value conversion coefficients μ ₁ and ε ₁ for the flowmeter 16, the output value conversion coefficients μ _c2 and ε ₂ for the flowmeter 17 are determined from equations (7) and (8).

Then, the conversion formula from the sensor output signals E ₁ and E ₂ in the signal processing circuits 16b and 17b to the flowmeter output values V ₁ and V ₂ in the measurement mode is V ₁ = μ ₁ E ₁ +
ε ₁ ...For (4), V ₂ =μ _c2 E ₂ +ε ₂ =μ ₁ E _c1 −E _c1 ′／E _c2 −E _c2 ′・E ₂ +ε ₁ +μ ₁ E _c2 E _c1 ′−E _c1 Calibrate as E _c2 ′/E _c2 −E _c2 ′……(9).

For example, μ ₁ = 95, ε ₁ = 5.15, F _c = 500 ml/min,
When F _c ′ = 400ml/min, E _c1 = 5.37, E _c1 ′ = 4.32,
To illustrate the case of E _c2 = 5.02 and E _c2 ′ = 4.02, (3),
From equations (7) and (8), μ _c2 = 95×5.37−4.32/5.02−4.02=99.75 ε ₂ =−5.15+95 ×5.02×4.32−5.37×4.02/5.02−4.02=4.255, and in measurement mode , the conversion formula from the sensor output signal to the flowmeter output value in the signal processing circuits 16b and 17b is V ₁ =95×E ₁ −5.15, and V ₂
It is calibrated as =99.75×E ₂ +4.255.

As described above, in the calibration mode, the characteristics (μ ₂ , ε ₂ ) of the flowmeter 17 are calibrated based on the characteristics (μ ₁ , E _c1 , E _c1 ', ε ₁ ) of the flow meter 16. After this, the measurement mode is entered, and the measurement error in the measurement mode will be described below.

The flow rate of dialysate flowing through the flow rate sensor 16a in the measurement mode is F ₁ , the flow rate of dialysis waste flowing through the flow rate sensor 17a is F _p , and the output signals of the flow rate sensors 16 a and 17a at that time are E ₁ and E _p , respectively. If the output values are V _i and V _p , respectively, (3) and (5)
From the equations, E _i = K ₁ F _i + E _p1 , E _p = K ₂ F _p + E _p2 , and the conversion equations to the flowmeter output values in the signal processing circuits 16b and 17b are obtained from (4) and (9), respectively. _i = μ ₁ E _i +ε ₁ ...(10), V _p = μ _c2 E _p +ε ₂ ...(11). Therefore, the measured value U _pb of the ultraviolet excess amount is given by the following equation.

U _pb = V _p −V _i = μ _c2 (K ₂ F _p + E _p2 ) + ε ₂ − μ ₁ (K ₁
F _i + E _p1 ) + ε ₁ = μ _c2 K ₂ F _p − μ ₁ K ₁ F _i ( μ _c2 E _p2 − _{μ 1} E _p1 ) + ε
₂
−ε ₁ ……(12) By the way, as mentioned in the previous calibration mode, μ _c2 E _c2
+ε ₂ = μ ₁ E _c1 +ε ₁ , so from equations (3) and (5) μ _c2 (K ₂ F _c
+E _p2 )+ε ₂ = μ ₁ (K ₁ F _c +E _p1 )+ε ₁ Therefore μ _c2 E
_p2
−μ ₁ E _p1 = μ ₁ K ₁ F _c +ε ₁ −μ _c2 K ₂ F _c −ε ₂ , and by substituting this into (12), U _pb = μ _c2 K ₂ F _p −μ ₁ K ₁ F _i +μ ₁ K ₁ F _c +ε ₁ −μ _c2 K ₂ F _c
−ε ₂ +ε ₂ −ε ₁ =μ _c2 K ₂ F _p −μ ₁ K ₁ F _i −(μ _c2 K ₂ F _c −μ
₁
K ₁ F _c )...(13). In addition, in the calibration mode, E _c2 = K ₂ F _c + E _p2 , E _c2 ′=K ₂ F _c ′ + E _p2 and
From E _c1 =K ₁ F _c +E _p1 , E _c1 ′=K ₁ F _c ′+E _p1 respectively
K ₂ = E _c2 −E _c2 ′/F _c −F _c ′……(14) and K ₁ = E _c1 −E _c1
′/F _c −F _c ′ ...(15), so (7), (14) and (15) can be transformed into (13)
Substituting into , U _pb = μ ₁ E _c1 −E _c1 ′/F _c −F _c ′ (F _p F _i ) = μ ₁ K ₁ (F _p F _i ) ……(16).

Now, assuming that the value of the ultraviolet excess is Ure, Ure is the dialysis fluid flow rate F _p minus the dialysate flow rate F _i and is calculated as follows.

Ure＝F _p F _i ……(17) Therefore, the measurement error δ of the ultraviolet excess is calculated by subtracting the expression (17) from the expression (16) as δ＝U _pb −Ure = (μ ₁ E _c1 −E _c1 ′ /F _c −F _c ′−1)(F _p −F _i ) =(μ ₁ K ₁ −1)(F _p −F _i ), and the error rate Δ is Δ=δ/Ure = μ ₁ E _c1 −E _c1 ′/F _c −F _c ′−1=μ ₁ K ₁ −1……(
18) becomes.

In other words, the measurement error of the limit excess depends only on the characteristic values μ ₁ and K ₁ of the flowmeter 16, and
It does not depend on the characteristic value of 7 at all. In other words, the calibration results in a state equivalent to using two flowmeters with exactly the same characteristics.

Now, to explain the case of the previous example, μ ₁ = 95, F _c = 500 ml/min, F _c ′ = 400 ml/min,
Since E _c1 = 5.37 and E _c1 ' = 4.32, Δ = 95 x 5.37 - 4.32 / 500 - 400 - 1 = 0.0025, and the measurement error of the extreme excess amount is -0.25%.

In addition, in the measurement mode, the dialysate flow rate is V _i
, V _p is calculated as the dialysis effluent flow rate using equations (10) and (11), and furthermore, V _p −V _i is calculated in the calculation unit 27, and the result is displayed as the ultraviolet amount in the display unit 28.
to be displayed.

When the ultraoverload measurement device according to the present invention is built into or placed alongside a dialysis machine and enters the preparation mode as a dialysis machine, the above-mentioned calibration mode is also automatically performed, and then the dialysis mode is entered. In this case, only the measurement mode may be performed, or the calibration mode may be automatically performed periodically during the dialysis mode. Alternatively, if necessary, the calibration mode may be manually set to perform the above-described calibration, and then the measurement mode may be manually switched.

FIG. 3 shows an embodiment of the invention using a microcomputer, and parts corresponding to those in FIG. 2 are given the same reference numerals. microcomputer 29
A central processing unit (hereinafter referred to as CPU) 30 performs various processes by decoding and executing programs stored in a read-only memory (hereinafter referred to as ROM) 31, and stores data necessary for the processing,
The data being processed is stored in a readable/writable memory (hereinafter referred to as RAM) 32 as necessary.
The CPU 30 provides a valve control signal to the valve control circuit 34 through the input/output section 33, switches and controls the operation valves 22, 23, 24, 25 based on the output of the valve control circuit 34, and also controls the flow rate through the input/output section 33. Total 16,
17 flowmeter output values V ₁ and V ₂ and the output signals of flow sensors 16a and 17a in the calibration mode, further calculates V ₂ −V ₁ and displays the display unit 2.
The result is supplied to the display circuit 28a of No. 8 and displayed on the display section 28b. Regarding the flowmeter 16, a regression analysis is performed in advance between the sensor output signal at the sample point and the flowmeter output value, and the values of the coefficients μ ₁ and ε ₁ are determined from the regression line, and these values are stored in the ROM 3.
It is stored in 1.

In this embodiment, when booted, ROM3
The calibration mode is entered according to the program fixed in step S1, and the operating valves 22, 23 and 25 are all closed in step _S1 as shown in the flowchart of FIG.
On the other hand, the operating valve 24 is opened, and the dialysate flows through the flow sensor 1.
After passing through 6a, the flow passes through the operation valve 24 and flows through the flow rate sensor 17a without passing through the dialyzer 12. In this state, in step _S2 , the values of the output signals _Ec1 and _Ec2 of the flow rate sensors 16a and 17a for the same flow rate _Fc are loaded into the RAM 32, and then in step _S3 .
According to the program in the ROM 31, the operation valves 22, 2 are controlled by the valve control circuit 34 via the I/O 33.
3 and 24 are closed, and the operation valve 25 is opened. A valve 26 is provided in the flow path of the operating valve 25, which allows an arbitrary flow rate F _c ' to flow, different from the case described above. In this state, in step _S4 , the flow rate F _c ′
Output signals of flow rate sensors 16a and 17a for
E _c1 ' and E _c2 ' are taken into the RAM 32. Next, in step _S5 , the values of the known output value conversion coefficients μ ₁ and ε ₁ for the flowmeter 16 are read from the ROM 31.
Then, in step _S6 , μ _c2 and ε ₂ are calculated based on equations (7) and (8), and in step S ₇ , the values of μ _c2 and ε ₂ are stored in the RAM 32 as output value conversion coefficients of the flowmeter 17 in the measurement mode. Store in.

After processing this calibration mode, CPU30
is controlled by the program in ROM31.
2 and 23, and close the operating valves 24 and 25 to enter the measurement mode.

In the measurement mode, the sensor output signals E _i and E _p of the flowmeters 16 and 17 are transmitted to the signal processing circuit 16, respectively.
b and 17b, the flowmeter output values V _i and V _p are obtained, respectively, by equations (10) and (11) using the output value conversion coefficients obtained in the calibration mode, as in the previous example.
, and is taken into the CPU 30 through the input/output section 33.

Then, V _p −V _i is further calculated, and the result is sent to the display 2 as the limit excess amount via the display circuit 28a.
8b.

Above, the flowmeter 1 is based on the characteristics of the flowmeter 16.
7 is calibrated, however, it is also possible to replace both and calibrate the flowmeter 16 based on the characteristics of the flowmeter 17 in exactly the same manner.

Note that the flowmeters 16 and 17 do not necessarily have to be of the same type; for example, 16 may be an electromagnetic flowmeter, 1
7 may be constructed of another type, such as an ultrasonic flow meter.

Also, two different types of the same flow rate (F _c , F _c ′)
The means for flowing the dialysate to the flowmeters 16 and 17 is not limited to the embodiment. For example, the setting location of the flow rate switching means controlled by the control unit 21, the valve control circuit 34, etc. is not limited to the side passage 18 in the embodiment, but is also between the liquid supply line 11 - the side passage 18 - the drain line 1.
It may be placed elsewhere in the flow path of No. 3. Alternatively, the side passage 18 and the valves 22 to 26 in the embodiment are omitted, and a flow rate switching means controlled in the same manner as described above is provided in the flow path of the liquid supply line 11 - dialyzer 12 - drainage line 13, and in the calibration mode Two different types of dialysate at the same flow rate are passed through the dialyzer 12 to the flowmeter 1.
6 and 17. In this case, in the calibration mode, the pressures in the blood flow path and the dialysate flow path of the dialyzer 12 are controlled to be equal so that no movement of water occurs between the two flow paths.

Further, the liquid flowing in the calibration mode is not limited to dialysate.

<Effects> As described above, according to the present invention, in the measurement of the ultra-overflow amount, which is the difference between the flow rate on the outlet side and the flow rate on the inlet side of the dialyzer, the difference between the flow rate on the outlet side and the flow rate on the inlet side is determined as the ultra-overflow amount, which is avoided when conventionally two flowmeters are used. Measurement errors caused by differences in characteristics between the two flow meters can be eliminated. Therefore, high-precision measurements can be made even if arbitrary flowmeters with completely different characteristics are combined, without using particularly high-precision flowmeters or by combining flowmeters with similar characteristics. becomes possible. Further, the flow path of the flow rate sensor exposed to the dialysis fluid can be cleaned with clean dialysis fluid. Moreover, regarding the characteristic values of flowmeters, it is sufficient to understand only one flowmeter.
The effort required for adjustment can be significantly reduced.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a conventional ultraviolet amount measuring device.
FIG. 2 is a block diagram showing an example of the ultraviolet amount measuring device according to the present invention, FIG. 3 is a block diagram showing an example of the ultraviolet amount measuring device of the present invention using a microcomputer, and FIG. 4 is a flowchart showing an example of the operation of the apparatus shown in FIG. 3 in a calibration mode. 11...Liquid supply line, 12...Dylyzer, 13
...Drain line, 16, 17...Flow meter, 18...
... Side path, 21 ... Control section, 22 to 25 ... Operation valve, 26 ... Valve, 27 ... Arithmetic section, 29 ... Microcomputer, 34 ... Valve control circuit.

Claims (1)

[Claims] 1 Measure the flow rate of the dialysate flowing into the dialyzer with one flowmeter, measure the flow rate of the dialysis fluid flowing out from the dialyzer with another flowmeter, and determine the limit of the difference between the two flow rates as the ultra-overflow amount. In the external excess measurement device, there is provided switching means for switching between an ultra-overflow measurement mode and a calibration mode for calibrating either one of the two flowmeters, and in the calibration mode, a first predetermined flow rate is applied to the two flowmeters. Flow sensor outputs of the two flowmeters obtained when a liquid is caused to flow, then a second predetermined flow rate different from the first predetermined flow rate is caused to flow, and the liquid is caused to flow at the first and second predetermined flow rates. An ultra-overflow measuring device comprising: a calibration means for calibrating the other flowmeter based on the characteristics of the one flowmeter using a signal and a pre-measured characteristic value of the one flowmeter.