JP2894704B2 - Electric conductivity meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the electrical conductivity of various liquids such as source water of a pure water production apparatus, pure water or cooling water obtained from a pure water apparatus, and factory drain water. The present invention relates to an electric conductivity meter used when measuring the electric conductivity.

[Prior Art] Conventionally, as an electric conductivity meter of this type, for example, there is one shown in FIG. In this electric conductivity meter, a cell 1 composed of a pair of electrodes 1a and 1b opposed to each other is immersed in a liquid to be inspected, and the resistance between the electrodes 1a and 1b, that is, electric conductivity is measured. When a DC voltage is applied to the electrodes 1a and 1b of the cell 1, electrolysis occurs. Therefore, a rectangular wave voltage of, for example, 500 Hz is applied to the cell 1 by the oscillating unit 2 having a rectangular wave generating function. Electrode 1 of cell 1
The electric conductivity between a and 1b is received by the receiver 3 and the ammeter 4
And the conductivity is read as a current value.

Reference numeral 5 denotes a toggle switch of a three-circuit two-contact system, which is switched to the A side when actually used, and switched to the B side when gain adjustment is performed. When the toggle switch 5 is switched to the B side, the receiving unit 3 is disconnected from the cell 1 and connected to the oscillating unit 2 via the test resistor R5 so that the indicated value of the ammeter becomes a predetermined value. Variable resistor VR for gain control
By adjusting, the conductivity meter is adjusted.

Oscillator 2 has operational amplifier IC1, capacitor C1, resistors R1, R
2, R3 and capacitor C3 (for phase correction of operational amplifier IC1)
The receiving unit 3 is composed of an operational amplifier IC2, a capacitor C2, resistors R4 and R6, a detection diode D1 and a D2 capacitor C4 (for correcting the phase of the operational amplifier IC2),
Each operational amplifier IC1,2 is driven by the voltage of the sum of the second power supply B ₂ consisting of the first power supply B ₁ and batteries consisting of batteries,
For example, the first power supply B ₁ and second power supply B ₂ are each 4.5V, the driving voltage of the operational amplifiers is 9V, operational amplifiers IC1 and operational amplifier IC2
Operates with 4.5V as the reference voltage.

The factory drainage test method is determined by JIS (JIS K 0102), and the electrical conductivity is equivalent to the reciprocal of the electrical resistivity of the solution between the opposed electrodes having a cross-sectional area of 1 cm ² and a distance of 1 cm.
Expressed as S / cm, Ω ⁻¹ / cm, S / m. In the water test, a value of 25 ° C. is used, and the value is expressed in μS / cm in units of one millionth of S / cm. The electric conductivity corresponds to the reciprocal of the electric resistance and is expressed in μS.

[Problems to be Solved by the Invention] By the way, the conventional electric conductivity meter described above has
The operational amplifier IC1 of the receiving unit 3 and the operational amplifier IC2 of the receiving unit 3 are separate integrated circuits. In order to obtain the positive and negative power supplies required for the input of each operational amplifier, a first power supply B1 and a second power supply B2 are used. One power source is required, a large number of battery holders are required, and the entire device becomes large.

The first power supply B1 and the second power supply B2 are common in that they drive two operational amplifiers, but are separate in operation, so that the battery is reduced, and one of the power supplies that can be used sufficiently is also used. There is a waste of having to replace it with the other power source that has reached the end of its life.

An object of the present invention is to reduce the number of power supply batteries by driving and operating a transmission unit and a reception unit with a single power supply. An object of the present invention is to provide an electric conductivity meter that can be reduced in size and can be reduced in size.

[Means for Solving the Problems] The gist for achieving the object of the present invention is as follows.
A cell in which a pair of electrodes are arranged facing each other is immersed in a liquid, and a rectangular wave is applied to a pair of electrodes of the cell from an oscillating unit,
A detection circuit for detecting a current value indicating electric conductivity in the receiving section based on the electric resistance between the pair of electrodes; and a power supply section for applying a power supply voltage to the oscillating section and the receiving section. A total, wherein the detection circuit unit is formed by one integrated circuit containing at least three or more operational amplifiers, and the oscillation unit is configured with one operational amplifier in the integrated circuit as an active element, In addition, the other operational amplifier is used as an active element to constitute the receiving section, and one of the remaining operational amplifiers is used to constitute an active element for voltage distribution, so that the voltage from one operational amplifier driving power supply battery is supplied. The electrical conductivity meter is characterized in that the voltage divider is used to obtain an operating voltage of the operational amplifier of the oscillation section and the reception section by dividing the voltage.

[Operation] The electric conductivity meter configured as described above connects a passive element such as a resistor or a capacitor for forming an oscillating unit, a receiving unit, and a voltage distribution unit to one integrated circuit and a single power supply battery. And the voltage divider divides the driving voltage to obtain operating voltages for the oscillator and the receiver.

EXAMPLES Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

Embodiment 1 FIG. 1 shows a circuit diagram of Embodiment 1 of an electric conductivity meter according to the present invention. Note that the same reference numerals are given to the same portions in the present embodiment and the conventional example, and the description thereof will be omitted.

In the first embodiment, four operational amplifiers OP-1, OP-2, OP
-3, OP-4, using one integrated circuit, the first operational amplifier OP-1 is the amplifier of the oscillating unit 2, the second operational amplifier OP
-2 is used for the amplifier of the receiving unit 3 and the third operational amplifier OP-3 is used for the voltage distribution of the voltage distribution unit 6. The fourth
The operational amplifier OP-4 is not used in this embodiment. Reference numeral 7 denotes a power supply battery composed of, for example, a 9V dry battery (006P), which is connected to the voltage distribution unit 6 by a snap terminal (not shown).
Reference numeral 8 denotes a two-circuit, two-contact toggle switch that switches to the A side when actually used, and switches to the B side when performing gain adjustment.

The voltage distribution unit 6 divides the voltage of the power supply 7 by the resistors R7 and R8, and inputs the divided voltage (V2) to the + side of the third operational amplifier OP-3. Unity gain connection is made to the third operational amplifier OP-3, and the output voltage is set to (V
3) If the negative input voltage is (V1), V2 = V3.

In the present embodiment, since the reference voltage for performing each operation of the operational amplifier is 4.5 V and the voltage of the power supply battery is 9 V, the resistance values of the resistors R7 and R9 are made equal and the divided voltage (V2 )
Is set to half of the voltage of the power supply 7 to obtain an output voltage (V3) of 4.5 V, and this output voltage is supplied to the + and-inputs of the first operational amplifier and the second operational amplifier, respectively. In this integrated circuit, a driving voltage (9 V in this embodiment) is supplied to an external driving terminal, so that the driving voltage is applied to each of the four operational amplifiers.

On the other hand, the oscillating unit 2 and the receiving unit 3 according to the present embodiment include operational amplifiers OP-1 and OP-2 instead of the operational amplifiers IC1 and IC2 of the conventional example.
The operation is the same as in the prior art.

That is, in this embodiment, four operational amplifiers in one integrated circuit are driven by one power supply, and
The voltage of the power supply 7 is divided using two operational amplifiers, and each of the operational amplifiers of the oscillating unit 2 and the receiving unit 3 can be operated using the divided voltage as a reference voltage. In this case, the battery space is reduced and the size can be reduced. In addition, since the power supply battery 7 can be connected with the snap terminal, it is not necessary to provide a battery case particularly in accordance with the outer shape of the battery, so that the structure of the device case can be simplified and the wiring can be simplified.

Furthermore, although two integrated circuits are conventionally used, the present invention requires only one integrated circuit, so that the cost can be reduced accordingly.

In addition, since there is only one power supply, instead of a conventional three-circuit two-contact toggle switch, a two-circuit two-contact toggle switch is sufficient, thereby reducing costs and reducing the number of wirings.

Second Embodiment FIG. 2 is a circuit diagram of an electric conductivity meter according to a second embodiment.

In the first embodiment described above, three of the four operational amplifiers in one integrated circuit are used, and one is used.
In the second embodiment, the idle fourth operational amplifier OP-4 is used as a low-pass filter in the receiving unit 3.

That is, the fourth operational amplifier OP with unity gain connection
-4, a low-pass filter is constituted by the resistor R9 and the capacitor C5, the high-frequency component contained in the signal from the cell 1 is cut, and a signal without noise is output to the second operational amplifier OP-2.

In the present embodiment, the third operational amplifier OP of the voltage distribution unit 6
-3 is provided on the output side with a capacitor C6 to store the operating power and stabilize the operating voltage.

[Effects of the Invention] As described above, according to the present invention, it is possible to reduce the number of power supply batteries to one, and to reduce the number of power supply batteries, thereby effectively using batteries. In addition to this, it is possible to reduce the size of the device and simplify the wiring, and the effect of cost reduction based on these can be significant.

Also, by providing a low-pass filter in the receiver,
Measurement accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of an electric conductivity meter according to the present invention, FIG. 2 is a circuit diagram of a second embodiment of the electric conductivity meter according to the present invention, and FIG. 3 is a circuit of a conventional electric conductivity meter. FIG. 1: Cell, 2: Oscillator 3: Receiver, 4: Ammeter 5, 8: Toggle switch 6: Voltage distributor 7: Power supply battery.

Claims (2)

(57) [Claims] 1. A cell in which a pair of electrodes are arranged opposite to each other is immersed in a liquid, a rectangular wave is applied to a pair of electrodes of the cell from an oscillating section, and reception is performed based on an electric resistance between the pair of electrodes. An electric conductivity meter comprising: a detection circuit for detecting a current value indicating electric conductivity in a section; and a power supply section for applying a power supply voltage to the oscillation section and the reception section, wherein at least three or more operational amplifiers are provided. And the detection circuit section is formed by one integrated circuit containing the same, and the oscillation section is configured with one operational amplifier in the integrated circuit as an active element, and the other operational amplifier is defined as an active element. The receiving unit is constituted, and one of the remaining operational amplifiers constitutes an active element for voltage distribution. The voltage from one operational amplifier driving power supply battery is divided to calculate the operation of the oscillation unit and the receiving unit. Get the operating voltage of the amplifier An electric conductivity meter characterized in that the electric conductivity meter is a voltage distribution section for use. 2. The integrated circuit contains four operational amplifiers, and the remaining one operational amplifier other than the operational amplifiers constituting the oscillating unit, the receiving unit, and the voltage distribution unit is connected to a low-pass filter of the receiving unit. The electrical conductivity meter according to claim 1, wherein the electrical conductivity meter is an active element.