JPS60190873A - Electromagnetic type conductivity meter - Google Patents

Abstract

PURPOSE:To make it possible to stably measure conductivity up to a lower degree, by forming a resonance circuit by connecting a condenser to a detection coil and performing the positive feedback of the resonant voltage thereof to draw the frequency of an oscillator in resonance frequency. CONSTITUTION:An electromagnetic induction current is flowed to a water loop by exciting a magnetic core W1 by the output of an oscillator to induce electromotive force in a detection coil L2. A condenser C5 is connected to the coil L2 to form a resonance circuit and the resonant voltage thereof is supplied to a DC ammeter A through an amplifier Q1 and a detector D1. In this case, the output voltage of the amplifier Q1 is positively fed back to the oscillator through an amplifier Q2 and the oscillation frequency of the oscillator is dawn in the frequency of the resonance circuit consisting of L2 and C5 to eliminate the difference between both frequencies. Therefore, detection can be performed always in a stable state with high sensitivity.

Description

[Detailed description of the invention] This invention relates to an electromagnetic conductivity meter that measures conductivity.

In equipment that handles water, such as boilers and cooling towers, water conductivity measurements are often performed to inspect and manage water negative conditions. In particular, with gaylors, impurities in the feed water and water treatment agents become concentrated as the giler generates steam, and excessive concentration can lead to scale formation, local overheating of the pipe material, and poor can water circulation, so it is important to manage the concentration of can water. , the conductivity of canned water is often measured as an indicator of concentration.

As a means of measuring the conductivity of water, there is the so-called two-electrode method, in which two electrodes are immersed in water and the strength of the current flowing through them is measured, or the so-called two-electrode method, in which two electrodes are immersed between the electrodes and the voltage drop between them is measured. A two-electrode method is known. These electrode methods are simple and good (the former requires a measurement range of 5,000 μs for 7 people or less, and the latter uses a measurement range of 20,000 μs//crn or less); however,
Measurements in high conductivity regions are difficult because they are affected by polarization (polarization does not completely go to zero even when using alternating current) and dirt from deposits, and even if they can be used, the electrodes must be cleaned frequently. It's inconvenient.

Another means of measuring the conductivity of water is an electromagnetic conductivity meter that uses electromagnetic induction current. FIG. 1 is a schematic diagram showing the principle of the excitation ring magnetic core W having a primary coil 1 wound thereon, and a detection ring magnetic core W having a detection coil L2 wound thereon.
2 onto the loop pipe P made of insulator, and
Channel water inside.

When an alternating voltage of a constant magnitude and frequency is applied to the primary coil, the water in the loop pipe P acts like a one-turn coil, and an electromagnetic induction current flows through it as shown by the dotted line in the figure. As a result, an alternating current electromotive force is induced in the υ detection coil L2, the frequency of which is the same as the frequency of the voltage applied to the primary coil, and the magnitude thereof is proportional to the conductivity of the water in the loop pipe P.

Therefore, the electrocardiographic rate of water is measured by measuring the electromotive force induced in the detection coil L2.

FIG. 2 shows a conventional circuit configuration of an electromagnetic induction needle based on such a principle, in which a tuned circuit consisting of the primary coil L1 and the capacitor C4 is connected to the collector circuit of the transistor TRI, and a tuned circuit consisting of the primary coil L1 and the capacitor C4 is connected to the collector circuit of the transistor TRI. An anti-coupling coil L3 wound around W1 is provided in the pace circuit to constitute a collector-tuned oscillator, and the oscillation output excites the magnetic core W, and the electromotive force induced in the detection coil L2 is sent to the operational amplifier Q1 + detector. It is read by a DC ammeter A via the

Electromagnetic conductivity meters do not have polarization like the electrode method mentioned above,
It has the advantage of being almost unaffected by deposits and dirt, but conventionally only the high conductivity region can be used (at: + constant range 1).
0,000 to 100,000 pS/cIn). Therefore, if you want to measure conductivity down to a low level, you will need to increase the size of the coil, strengthen the primary coil input, increase the amplification of the detection coil output, and ultimately increase the power supply capacity. Not only do these methods become complicated and expensive, but when considering noise and other disturbance factors, there is a limit to the methods described above. It was difficult to measure.

An object of the present invention is to provide an improved electromagnetic conductivity meter that has better sensitivity than the conventional one, can stably measure conductivities down to much lower values, and is relatively simple and inexpensive.

In the present invention, a magnetic core around which a primary coil is wound and a magnetic core around which a detection coil is wound are installed interlinked with a loop of a liquid to be measured,
In an electromagnetic conductivity meter that measures the conductivity of a liquid to be measured by applying an AC output of an oscillator to the primary coil and measuring the electromotive force induced in the detection coil, a capacitor is attached to the detection coil. is connected to form a resonant circuit, and the output voltage of the resonant circuit is amplified by positive feedback to the oscillator to pull the oscillation frequency of the oscillator into the resonant frequency of the resonant circuit. It is something to do.

FIG. 3 is a circuit diagram showing an embodiment of the electromagnetic conductivity meter of the present invention. In FIG. 3, Wl and W2 are an excitation ring magnetic core and a detection ring magnetic core, L and L, respectively, which are arranged to interlink with the water loop as shown in FIG.
2ij, the primary coil and detection coil, L, wound on the magnetic cores W1 and W2, respectively, are anti-coupling coils wound on the magnetic core W□. TRI is an oscillation transistor, and its collector circuit is provided with a tuning circuit consisting of the coil L1 and capacitor C1, and its base circuit is provided with an anti-coupling coil L3 to form a collector-tuned oscillator. R1+ R2 and R3 are resistances, C□
and C2 is a pinosu capacitor.

By exciting the magnetic core W1 with the output of the oscillator,
As explained in FIG. 1, an electromagnetic induction current flows through the water loop, and an electromotive force is induced in the detection coil L2. A capacitor C8 is connected to the detection coil L2, and the two form a resonant circuit. This resonant circuit is designed to have a sharp resonance peak at the frequency of the induced electromotive force (ie, the oscillation frequency of the oscillator).

The output voltage of this resonant circuit is the operational amplifier fQ,
The signal is amplified by the wave detector D1 and indicated by the DC ammeter A. R1 and Ra1d, operational amplifier Q
, C3 is the smoothing capacitor, VR,
is a variable resistor for sensitivity adjustment.

By connecting the capacitor Cfi to the detection coil L2' to form a resonant circuit as described above, a significantly higher reception sensitivity can be obtained compared to the case where the capacitor Cfi is not formed.

By the way, the resonance peak frequency of the resonant circuit consisting of Tonori, and 05 and the oscillation frequency of the oscillator tend to deviate from each other due to factors such as changes in the magnetic properties of the foundation stone depending on temperature. However, since the frequency characteristics of the resonant circuit consisting of L2 and C3 are designed to have a steep resonant beat, if a discrepancy occurs between the two frequencies, the reception sensitivity will be greatly reduced. Fluctuation [7 times.

In order to avoid this, in this embodiment, as shown in FIG. 3, the output voltage of the resonance circuit taken out from the operational amplifier Q1 is amplified by the operational amplifier fQ2 via the variable resistor VR2, and the resistor R6, positive feedback to the oscillator via a capacitor C11 to pull the oscillation frequency of the oscillator into the resonant frequency of the resonant circuit consisting of the receiving side beam and Cs, thereby eliminating the deviation between the image frequencies; This enables stable and highly sensitive detection at all times.

The variable resistor VR and the capacitor C7 are used for phase adjustment for such positive feedback, and the resistors R and iIi for setting the amount of positive feedback, and C0 are the capacitors for blocking the DC component.

The prototype device based on this example has a distortion of 500 to 5000 μS/cm, which is difficult to achieve with the conventional circuit configuration as shown in Figure 2.
It is possible to stably measure the electrical conductivity of the oscillator, and even with the use of inexpensive ferrite magnetic cores that are relatively affected by temperature on both the oscillating and receiving sides, sufficiently stable operation was obtained.

As described above, according to the present invention, it is possible to obtain an electromagnetic conductivity meter that is more sensitive and stable than conventional electromagnetic conductivity meters, and is relatively simple and inexpensive. Needless to say, the present invention retains the advantage of the electromagnetic conductivity meter that it is hardly affected by contamination due to deposits.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the principle of an electromagnetic conductivity meter, FIG. 2 is a conventional circuit diagram, and FIG. 3 is a circuit diagram of an embodiment of the present invention. Wl ・W2...Magnetic core, Ll...] Next coil, L2
...Detection coil, C5...Resonance capacitor, C2
...Return amplifier.

Claims (1)

[Claims] The magnetic core around which the primary coil is wound and the magnetic core around which the detection coil is wound are installed interlinked with the loop of the liquid to be measured, and the alternating current output of the oscillator is applied to the primary coil, and the magnetic core is induced in the sensing coil. In an electromagnetic conductivity meter that measures the conductivity of a liquid to be measured by measuring electromotive force, a capacitor is connected to the detection coil to form a resonant circuit, and the output voltage of the resonant circuit is amplified. An electromagnetic conductivity meter characterized in that the oscillation frequency of the oscillator is pulled into the resonant frequency of the resonant circuit by positive feedback to the oscillator.