JPH04286948A - Constituent concentration measuring device - Google Patents

Abstract

PURPOSE:To enable a concentration of water contents and constituents of a substance to be measured highly accurately by reducing influence of temperature. CONSTITUTION:High-frequency and low-frequency constant voltage signals are supplied to an object to be measured. Current which flows to the object to be measured is measured along with this voltage signal, admittance at the high frequency and low frequency is calculated from the measured current value and then the difference is calculated. A signal corresponding to the concentration of water contents and constituents is output based on the difference.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a component concentration measuring device that is used as an online moisture or component concentration meter to measure the concentration of components, such as moisture, contained in an object to be measured. The present invention relates to a component concentration measuring device that uses admittance measurement including conductivity in a measuring method.

0002

BACKGROUND OF THE INVENTION There is a component concentration measuring device as a device for measuring the concentration of moisture or components contained in an object to be measured. A method based on permittivity measurement, a method based on admittance measurement including conductivity, etc. are known.

[0003] Among the above-mentioned methods, component concentration measurement by admittance measurement will now be explained. When considering the object to be measured as an admittance, it can generally be represented by an equivalent circuit shown in FIG. Furthermore, when this is expressed as a vector, it becomes as shown in FIG. Now, if the concentration of water or components in the object to be measured changes, the magnitudes of conductance G and susceptance B will change, and the overall absolute value of admittance |Y|=(G2 +B2)1
/2 changes. From this, by measuring the absolute value of admittance |Y|, the concentration of moisture or components in the object to be measured can be determined.

That is, if the voltage applied to the object to be measured is E and the admittance of the object to be measured is Y, then the current value I flowing through the object to be measured is I=Y・E, and the absolute value of each element is |I
It is expressed as |=|Y|·|E|, and by applying a voltage with a constant amplitude to the object to be measured, the absolute value of admittance can be determined from the flowing current value.

[0005]

[Problems to be Solved by the Invention] However, in a device to which the above-mentioned measurement method is applied, it is known that the conductance G changes greatly depending on the temperature of the object to be measured, and therefore there is a problem in that it is necessary to perform temperature correction. was there. In addition, although the device applying the above-mentioned dielectric constant measurement method is suitable for measuring low moisture content in insulating materials, it is difficult to measure components such as moisture in high moisture areas or conductive materials. was there. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a component concentration measuring device that can measure the moisture content of a substance and the concentration of components with high precision while minimizing the influence of temperature. It is about providing.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the component concentration measuring device according to the present invention is a component concentration measuring device for measuring the concentration of water or components contained in a measured object. a signal supply unit that supplies a constant voltage signal at a high frequency and a low frequency to The present invention is characterized by comprising a calculation unit that calculates the admittance at the high frequency and the low frequency, calculates the difference between the admittances, and outputs a signal corresponding to the concentration of the water or component based on this difference.

[0007]

[Operation] The signal supply section supplies a constant voltage signal of high frequency and low frequency to the object to be measured. When a voltage signal is supplied to the object to be measured by the signal supply section, the measuring section measures the value of the current flowing through the object to be measured based on the supply of this voltage signal. Then, the calculation section calculates the admittance at high frequency and low frequency based on the current value measured by the measurement section, further calculates the difference between the calculated admittances, and outputs a signal corresponding to the concentration of water or components.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram showing an embodiment of a component concentration measuring device according to the present invention. The component concentration measuring device according to this embodiment applies a method based on admittance measurement, and is roughly configured with a signal supply section 1, a measurement section 2, and a calculation section 3. We measure the concentration of moisture and components contained in That is, a voltage signal with a constant amplitude is applied to the measured object, the admittance of the measured object at two frequencies fH and fL is calculated from the value of the current flowing through the measured object due to the applied voltage signal, and the difference between these admittances is calculated. is being carried out.

The signal supply section 1 includes a high frequency oscillation circuit 4, a low frequency oscillation circuit 5, an adder 6, a current buffer 7, and a voltage application electrode 8. The high frequency side oscillation circuit 4 has an oscillation frequency fH of 100 kHz to several tens of MHz.
In addition, the low frequency side oscillation circuit 5 receives a signal having DC to
A signal having an oscillation frequency fL of several 100 kHz is output to the adder 6. Adder 6 is high frequency side oscillation circuit 4
and the signals from the low frequency side oscillation circuit 5 are mixed and supplied to the current buffer 7, and the current buffer 7 applies a predetermined voltage to the voltage application electrode 8 based on the supplied voltage signal E.
The voltage is applied to the object to be measured through the

The measuring section 2 includes a current measuring electrode 9, a current measuring circuit 10, a high frequency side pass filter 11, a low frequency side pass filter 12, a high frequency side conversion circuit 13, and a low frequency side conversion circuit 14. There is. The current measuring electrode 9 extracts the current flowing through the object to be measured based on the applied voltage, and the current extracted by the electrode 9 is detected by the current measuring circuit 10. The current measuring circuit 10 converts the detected current into a voltage signal of a predetermined level and outputs the voltage signal to the filters 11 and 12 at the subsequent stage. The high frequency side pass filter 11 outputs a high frequency signal of the voltage signal supplied from the current measurement circuit 10, for example, a signal of 100 kHz to several tens of MHz to the high frequency side conversion circuit 13. Further, the low frequency side pass filter 12 selects a low frequency signal from among the voltage signals supplied from the current measuring circuit 10, for example, from DC to several hundred.
A kHz signal is output to the low frequency side conversion circuit 14. High frequency side conversion circuit 13 and low frequency side conversion circuit 1
4 converts the voltage signal from each filter 11, 12 into a DC signal and outputs it to the calculation section 3.

[0011] The calculation unit 3 includes each conversion circuit 1 in the measurement unit 2.
Based on the signals from 3 and 14, the absolute value of admittance at high frequency fH and low frequency fL |YH
|, |YL | and their admittance difference Δ|Y
|=|YH |−|YL | is being calculated. and,
Based on this difference Δ|Y|, a signal corresponding to the concentration of water and components as shown in FIG. 3 is output. Note that FIG. 3 shows an example of the relationship between the moisture value and the output value when the above-described component concentration measuring device is applied as a moisture sensor for minced fish meat.

Here, the high frequency f avoiding the dielectric dispersion region
The absolute values of the admittance of the object to be measured with respect to H and the low frequency fL are expressed by the following equations. |YH |=(G2 +BH 2)1/2 |YL |=
(G2 + BL 2) 1/2 Note that G is the frequency-independent conductance, and BH and BL are fH and fL
is the susceptance component in each of BH >
BL, that is, |YH |>|YL |.

Therefore, the difference Δ|Y| between |YH| and |YL| can be expressed as follows. Δ|Y|=|YH |−|YL |=(G2 +BH
2) 1/2 - (G2 + BL 2) 1/2 Here, depending on the magnitude of frequencies fH and fL, BH and BL
The temperature coefficient of can have different magnitudes. By selecting appropriate frequencies fH and fL, the temperature coefficients of |YH| and |YL| can be made approximately equal, and the temperature coefficients can be eliminated by finding the difference Δ|Y| between the two. be able to. Also, conductance or capacitance C changes in response to changes in the concentration of water or components, but since BH > BL |
The magnitude of change in YH| and |YL| is different, and Δ|Y| changes. Therefore, by measuring Δ|Y|, it is possible to measure the concentration of moisture and components in the object to be measured.

Next, the operation of the component concentration measuring device having the above-described configuration will be explained. First, a high frequency and a low frequency are set according to the concentration of water and components of the object to be measured, and a constant voltage signal based on the set frequency is applied to the object to be measured via the voltage application electrode 8 in the signal supply section 1. to be applied. When a voltage signal is applied to the object to be measured, a current flows through the object to be measured, and this current is measured by the measuring section 2. That is, the current is measured by the current measuring circuit 10 via the current measuring electrode 9, and then converted into a voltage signal of a predetermined level, passed through the high frequency pass filter 11 or the low frequency pass filter 12, and then sent to the high frequency side conversion circuit 13 or the low frequency side conversion circuit 13. It is output to the frequency side conversion circuit 14. Each of the conversion circuits 13 and 14 converts the supplied voltage signal into a DC signal and outputs it to the calculation section 3. The calculation unit 3 calculates the absolute values of admittance |YH |, |YL | at each of the high frequency fH and low frequency fL based on the signals from each conversion circuit 13 and 14, and calculates the admittance difference Δ |Y| It calculates and outputs a voltage signal corresponding to the concentration of water and components.

Therefore, in the above-mentioned apparatus, the admittance difference Δ|Y|
By measuring this, it is possible to measure the concentration of moisture and components in the object to be measured while sufficiently minimizing the influence of temperature.

Next, FIG. 2 shows an example in which the above-described component concentration measuring device is incorporated into a detection device having a pipeline structure. In this device, connecting flanges 16 for connecting to other pipes are formed at both ends of a stainless steel pipe 15, and a voltage applying electrode 8 and a current measuring electrode 9 are exposed on the inner wall surface at approximately the center of the stainless steel pipe 15. Insulator 1
The above-mentioned component concentration measuring device is held between the tubes 7 and connected by a pipe. The concentration of moisture and components contained in the object to be measured, such as minced fish, flowing through the stainless steel pipe 15 is measured by the method described above. The component concentration measuring device described above can be applied particularly to measuring the concentration of moisture and components in liquid and slurry materials.
For example, it can be used in a wide range of applications, including moisture meters for the manufacturing process of fish paste and paste products.

[0017]

Effects of the Invention As explained above, according to the component concentration measuring device of the present invention, by measuring the admittance difference between high and low frequencies, the influence of the temperature coefficient can be reduced and the concentration of water and components can be measured. Measurements can be made with high precision.

[Brief explanation of the drawing]

[FIG. 1] A schematic configuration diagram showing an embodiment of a component concentration measuring device according to the present invention.

[Figure 2] A diagram showing an example of a configuration in which the same component concentration measuring device is incorporated into a detection device with a pipeline structure.

[Figure 3] A diagram showing an example of the relationship between moisture value and output value when the same component concentration measuring device is applied as a moisture sensor for minced fish meat.

[Figure 4] Diagram showing an equivalent circuit when the object to be measured is considered as an admittance.

[Figure 5] A diagram representing the equivalent circuit shown in Figure 4 using vector representation.

[Explanation of symbols]

1 signal supply section,
2 measurement section 3 calculation section,
4 High frequency side oscillation circuit 5 Low frequency side oscillation circuit, 10
Current measurement circuit 13 High frequency side conversion circuit,
14 Low frequency side conversion circuit

Claims (1)

[Claims] 1. A component concentration measuring device for measuring the concentration of water or components contained in an object to be measured, comprising: a signal supply section that supplies a constant voltage signal at a high frequency and a low frequency to the object to be measured; , a measurement unit that measures the value of current flowing through the object to be measured based on the supply of the voltage signal; and a measurement unit that calculates the admittance at the high frequency and the low frequency based on the measured current value and calculates the difference between the admittances. A component concentration measuring device comprising: a calculation section that outputs a signal corresponding to the concentration of the moisture or component based on the concentration of the moisture or component.