JP2946866B2 - Liquid flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a flow rate of a liquid, and more particularly to a flow meter for a liquid chromatograph.

[0002]

2. Description of the Related Art When measuring the flow rate of a liquid in a liquid chromatograph, conventionally, for example, a temperature change is applied to the liquid at the upstream side of the liquid flow path, and this temperature change is provided at the downstream side of the flow path. Sought by detecting. That is, since the temperature change given on the upstream side of the liquid flow path is transmitted to the downstream side after a lapse of time corresponding to the flow rate of the liquid, the flow rate of the liquid is obtained by obtaining the phase difference of this temperature change. Was.

[0003]

However, the conventional apparatus operating as described above is affected by the heat capacity of the temperature detecting element itself such as a thermistor and the thermal resistance between the liquid and the element, so that a measurement error occurs. There is a problem that an accurate flow rate value cannot be obtained easily. In addition, there is a method of calibrating a measurement error, but even in this case, there is a problem that the measurement error is easily affected by a change in room temperature.

The present invention has been made in view of this problem, and has as its object to provide a liquid flow meter capable of measuring the flow rate of a liquid more accurately.

[0005]

In order to achieve the above object, a liquid flow meter according to the present invention is provided at a specific location in a liquid flow path and changes a temperature of a liquid;
One or more electric conductivity measuring units installed at the downstream side of the flow path where the temperature control unit is installed and measuring the electric conductivity of the liquid, and the measurement result of the electric conductivity measuring unit is the temperature of the liquid. And a calculation unit for calculating the flow rate of the liquid based on the fact that the change in the electric conductivity is temporally delayed in accordance with the flow rate of the liquid.

[0006]

The temperature control section is provided at a specific position in the liquid flow path to change the temperature of the liquid in the flow path. The electric conductivity measuring unit is installed at the downstream side of the flow path where the temperature control unit is installed, and measures the electric conductivity of the liquid at one or more points.

[0007] The arithmetic unit determines the flow rate of the liquid based on the fact that the electric conductivity changes in response to the change in the temperature of the liquid and that the change in the electric conductivity delays in time corresponding to the flow rate of the liquid. Ask for. That is, the liquid flow rate is determined by the time difference between when the temperature (or electric conductivity) of the liquid starts changing on the upstream side of the flow path and when the electric conductivity starts changing on the downstream side, and the liquid volume from the upstream side to the downstream side. Measure.

[0008]

The present invention will be described below in more detail with reference to examples. FIG. 1 is a block diagram showing one embodiment of a liquid flow meter according to the present invention. This liquid flow meter has a liquid flow path 1
A temperature control unit 2 installed on the upstream side of the liquid flow path, an electric conductivity measurement unit 3 installed on the downstream side of the liquid flow path 1, and a calculation unit 4 that receives the output of the electric conductivity measurement unit 3 and obtains the liquid flow rate. It is composed of

Here, the temperature control unit 2
Heating unit 2 for heating liquid_-1And heating unit 2_-1Power supply
V, power supply V and heating unit 2_-1Switch to disconnect the connection to
Part 2 _-3And the switch unit 2_-3ON / OFF control of heating
Control unit 2_-2It is composed of Also, electrical conductivity measurement
The part 3 is a sensor 3 for measuring electric conductivity._-1Output
Then, the electric conductivity of the liquid in the liquid flow path 1 is measured.

In the apparatus having the above configuration, the heating control unit 2
_-2 and disconnection of the switch unit 2 _-3 at a constant period, heating of the heating portion 2 _-1 (see FIG. 3 (a)). Therefore, the liquid in the flow path is heated at regular time intervals, and as a result, the electric conductivity of the liquid changes at regular time intervals. However,
Since the liquid in the flow path flows toward the downstream side, the change in the electrical conductivity detected by the electrical conductivity measurement unit 3 on the downstream side is delayed by a time corresponding to the flow rate of the liquid (FIG. 3 (b)). That is, (a) and (b) of FIG.
As shown in FIG. 2, after the temperature of the liquid starts to increase (the electrical conductivity increases) in the temperature control unit 2 on the upstream side, the electrical conductivity actually starts to increase in the electrical conductivity measuring unit 3 on the downstream side. there is a deviation of the time T ₁ in.

Then, the arithmetic unit 4 calculates the time difference T ₁ ,
Based on volume V ₁ of the from the installation point of the temperature control unit 2 to the installation point of the electrical conductivity measuring unit 3, V ₁ / T ₁ the flow F of the liquid
(F = V ₁ / T ₁ ). FIG. 2 is a block diagram showing another embodiment of the flow rate type according to the present invention. This device includes a temperature control unit 2, a calculation unit 3, and first and second electric conductivity measuring units 4 and 5, and is characterized in that two electric conductivity measuring units are provided. is there. Note that 4 _-1 and 5 _-1
Are sensors for measuring conductivity, and the temperature control unit 2 heats the liquid in the flow path at regular intervals, as in the case of FIG. 1 (see FIG. 4A).

In the apparatus shown in FIG. 2, when the capacity between the first and second electric conductivity measuring units 4 and 5 is V ₂ , the electric conductivity in the first electric conductivity measuring unit 4 starts to increase. from the until the electrical conductivity of the second electrical conductivity measuring section 5 begins to increase, resulting a difference of time corresponding to the capacity V ₂ (see FIG. 4 and (b) (c)). Therefore, the calculation unit 3 obtains the time difference T ₂ and obtains the liquid flow rate by calculating V ₂ / T ₂ (F = V ₂ / T ₂ ).

In the case of the embodiment shown in FIG. 2, the measurement results include:
Until the temperature of the actual liquid from the power V is applied to the heating unit 2 _-1 starts to increase, it does not affect the time delay,
The measurement accuracy is higher than in the case of the first embodiment. FIG. 5 illustrates a liquid chromatograph system using the liquid flow meter according to the present invention.

The liquid injected from the pump 21 flows through the liquid flow path 22, and a sample is injected from the siple injector 23 in the process. And they are column 2
After 4 has passed, it is guided to the detector 25 for analysis and reaches the flow meter 26. In addition, high performance liquid chromatography (HPL)
C) usually involves adding a buffer to the mobile phase,
For most HPLC analyses, the liquid flow meter according to the present invention can be used.

[0015]

As described above, in the liquid flow meter according to the present invention, the electric conductivity changes in response to the temperature change, and the electric conductivity changes with time in response to the liquid flow rate. Is used to measure the flow rate of the liquid. The measurement of the electric conductivity does not have a time delay as in the temperature measurement, so that the flow rate measurement with high accuracy can be performed.

Further, this liquid flow meter is used for HPLC GPC.
When used for analysis or the like, the accuracy of molecular weight measurement is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a liquid flow meter according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a liquid flow meter according to another embodiment of the present invention.

FIG. 3 is a view showing waveforms of respective parts of the apparatus of FIG. 1;

FIG. 4 is a diagram showing waveforms at various parts of the apparatus of FIG. 2;

FIG. 5 is a diagram illustrating a configuration of a liquid chromatogram system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Liquid flow path 2 Temperature control part 3 Operation part 4, 5 Electric conductivity measurement part V ₂ Liquid capacity

Claims (1)

(57) [Claims] 1. A temperature control unit which is installed at a specific location of a liquid flow path and changes the temperature of a liquid, and is installed downstream of the installation location of the temperature control unit and measures the electric conductivity of the liquid. One or more electric conductivity measuring units, that the measurement result of the electric conductivity measuring unit changes in accordance with the temperature of the liquid, and that the change in electric conductivity changes in time corresponding to the liquid flow rate. A liquid flow meter comprising: a calculation unit that obtains a flow rate of the liquid based on a temporal delay.