JPS596386B2 - Automatic correction method for electrolyte resistance drop - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for automatically correcting electrolyte resistance drops.

In the electrolytic industry, electrolytic protection, etc., in order to find appropriate electrolytic conditions or anti-corrosion conditions, it is necessary to measure the potential of the electrode to which electrolytic current is applied using a reference electrode. The value obtained by adding the voltage drop (hereinafter referred to as iR drop) caused by the product of the electrolytic current and the electrolytic current is read.

However, in this case, i is the electrolytic current, and R is the electrical resistance of the soil or electrolyte solution. Especially pure water with high electrolyte resistance,
When measuring the potential of an electrode placed in an environment such as freshwater or soil, errors due to iR drop are large, giving erroneous information. Conventionally, as a correction method for iR drop due to electrolyte resistance, the current interruption method (current interruption method) has been used.
erruption method) is known.

This is done by changing the current from the state where the current is applied to the electrode to
The FF is turned on, and the potential response at that time is observed as a waveform using an oscilloscope or a recorder, and the iR drop is separated from the polarization Ed due to the electrode reaction, and the iR drop is corrected. This situation is illustrated in FIG. In other words, the figure a
shows the change over time in the electrolytic current when the electrolytic current i is turned on and off, and b in the figure shows the change over time in the electrode potential E at that time. As shown in Figure b, the time constant of iR drop is the electrode reaction polarization Ed
Based on the principle that Ep-iR is sufficiently fast compared to the time constant of Ep-iR, the electrode potential Ep-iR is obtained by removing the iR drop caused by the electrolyte. However, the conventional current interruption method requires graphical analysis of an oscilloscope, which is complicated to operate and has low accuracy. The present invention aims to eliminate the drawbacks of the conventional iR drop correction method, and uses an electrolytic current switching circuit and a potential calculation circuit to improve the iR drop correction method.
It consists of a circuit that enables high-precision blood connection by outputting a potential with only the drop or with the iR drop removed.

Examples will be specifically described below with reference to the drawings.

FIG. 2 is an example of a block diagram of an electrolytic current switching circuit. In the figure, a current source 1 is coupled to a cell CE of an electrolytic system 3 with a semiconductor switch 2 interposed therebetween. The semiconductor switch 2 is composed of a field effect transistor, triax, or thyristor having a control gate CG. The rectangular wave oscillation circuit 4 is connected to a rectangular wave duty ratio adjustment circuit 5, and is connected to the control gate CG of the semiconductor switch 2 in order to send a rectangular wave having a constant duty ratio to the electrolytic system 3. Electrolytic system 3 is a test electrode TE placed in an electrolyte.
It consists of three electrodes: a counter electrode CE and a reference electrode RE, and the electrolytic current flows between the counter electrode CE and the test electrode TE, and no current flows through the reference electrode RE. A semiconductor switch 2 placed between a current source 1 and an electrolytic system 3 receives a rectangular wave signal with a constant duty ratio at a control gate CG, and in synchronization with this, periodically turns the electrolytic current from 0N to 0FF. Note that the 0N-0FF control signal can be used for other purposes from the terminal CT. When switching the electrolytic current, the electrolytic current is 0FF'
The time TOFF is set to be sufficiently short compared to the time constant of electrode reaction polarization (Ed in FIG. 1).

Specifically, it is preferable that TOFF≦10ms. When the electrolytic current is periodically changed from 0N to 0FF under these conditions, the voltage between the reference electrode RE and the test electrode TE, that is, the electrode potential E, is determined by the voltage at a constant duty ratio obtained from the oscillation circuit through the adjustment circuit. For the rectangular wave shown in Fig. 3a, Fig. 3b
Gives a waveform that is a superimposition of a DC voltage and a rectangular wave, as shown in
The peak-to-peak difference value of the square wave becomes the IR drop, and T
The value of the potential E corresponding to the OFF state is the electrode potential Ep-1R after subtracting the IR drop. An example of an arithmetic circuit for determining IR or Ep-1R in combination with the switching circuit of FIG. 2 will be shown below.

Figure 4 shows the electrolytic current at 0N and 0F with potential E as input.
This is an example of a peak-to-peak difference value calculation circuit for calculating the peak-to-peak difference value of the electrode potential with respect to the F time and providing IR as an output.

The input terminal RE1 is connected to the reference pole RE (FIG. 2), and the input signal passes through a high-pass filter 16 to become an AC rectangular wave, which is further passed through a linear rectifier circuit 7 and a constant multiplier circuit 8. The peak-to-peak difference value is obtained as a DC voltage output. In this case, electrolytic current 0N-0FF
When the duty ratio is 50%, the AC rectangular wave after passing through the high-pass filter 16 becomes symmetrical in both positive and negative directions, and the rectifier circuit 7 can obtain a DC output with less ripple. When the duty ratio is 5070, the constant value in the constant multiplier circuit 8 is 2. FIG. 5 shows an example of a voltage hold circuit for receiving electrode potential E as input and obtaining Ep-1R as output.

However, Ep is the electrode potential when an electrolytic current is applied (at 0N). The input terminal RE2 is connected to the reference pole RE (Fig. 2),
Terminal CT2 is connected to CT (FIG. 2). S is an analog switch with a control end, and when the electrolytic current is 0FF (
TOFF), S is set to 0N. Therefore, capacitor C samples and holds the potential at TOFF so that the voltage output via the voltage follower by operational amplifier 0P2 gives Ep-1R. The voltage follower by operational amplifier 0P1 can be omitted in some cases. At this time, the electrode potential E is 0N-0 of the electrolytic current.
Since it depends on the duty ratio of the FF, it must be kept constant.

In order to find Ep-IR under DC electrolysis conditions,
The larger the TON/TOFF ratio, the better. Example 1 The method of the present invention was tested using an equivalent circuit of an electrolytic system and the electrolytic system as a system to be measured.

FIG. 6 shows an equivalent circuit of a metal electrode placed in an electrolyte, consisting of an electromotive force e1 generated at the interface, a capacitance component Cd, a resistance component Rdl existing in parallel with this, and an electrolyte resistance Re in series.

As a simulation of this, we created the circuit shown in Figure 6 using a dry battery, a resistor, and a capacitor, and conducted an experiment to confirm that when a current of 1 is applied, the drop 1Re due to Re can be directly read without contacting the terminal 10 as shown in Figure 2. and the circuit shown in FIG. Here terminal 9 is the test electrode TE
, the terminal 11 is connected to the counter electrode CE, the reference electrode RE and the input terminal REl.
are connected to each. At this time, output 1 in Fig. 3
R should give IRe. The electrolytic current at 0N is i
= 1mA, Cd = 10PF. ．． Table 1 shows a comparison of the IRe values measured based on the present invention and the calculated values when Rd-100Ω and Re was variously changed, and the two showed good agreement.

Note that the electrolytic current switching frequency was 5 KHz, and the duty ratio was 50%. The time constant CdRdl in this equivalent circuit experiment is 1 msec, which shows good agreement even though it is a much smaller value than the time constant of an actual electrolytic system (usually 1 sec or more).

Therefore, it is expected that electrolytic systems will provide even more accurate values. Example 2 1R drop measurements in an actual electrolytic system were carried out as follows.

Place mild steel or galvanized steel in tap water with a specific resistance of 5 kΩ, use it as the test electrode TE, and use stainless steel as the counter electrode CE.
The electrochemical polarization behavior of TE was determined using a silver/silver chloride electrode as a reference electrode. The results are shown in FIG. 7, where A is the data for mild steel and B is the data for galvanized steel. In FIG. 7, the dotted line is a polarization curve without correcting the IR drop, and the solid line is a polarization curve obtained by determining the IR drop and correcting it according to the present invention. IR drop measurements are completed within 1 second per measurement point and have a reading accuracy of 1m
It was V. The present invention can be implemented with various modifications without changing the gist thereof.

As described above, the present invention periodically applies an electrolytic current to the electrolytic system that is 0N-0FF and whose 0FF time is sufficiently short compared to the polarization time constant of the electrode reaction, thereby increasing the electrode potential. Find the peak-to-peak difference or set the current to 0F
By holding the electrode potential at F, it is possible to correct the IR drop due to electrolyte resistance in an extremely short time and with high precision.

This invention particularly facilitates the management of cathodic protection, as well as the measurement of electrode potential in electrochemistry.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of a conventional current interrupting method, Fig. 2 is a block diagram of an electrolytic current 0N-0FF circuit showing an embodiment of the present invention, and Fig. 3 shows the current and Electrode potential waveform diagram, FIG. 4 is a block diagram showing an example of a peak-to-peak difference calculation circuit for calculating IR from the waveform of FIG. 3b, and FIG. 1R
FIG. 6 is an equivalent circuit diagram of an electrode interface, and FIG. 7 is a diagram showing an example of actual measurement using the present invention. 1... Current source, 2... Semiconductor switch, 3... Electrolytic system, 4... Square wave oscillation circuit, 5... Duty Adjustment circuit, 6...
・High-pass filter 1, 7... Linear rectifier circuit, 8
...Constant multiplier circuit, TE...Test electrode, C
E... Counter electrode, RE... Reference electrode, CG.
... Control end of semiconductor switch.

Claims (1)

[Claims] 1. Electrolyzing with a periodic ON-OFF electrolytic current having a sufficiently short OFF time compared to the time constant of electrode reaction polarization,
An electrolyte resistance drop characterized in that the electrode potential E at that time is given to a peak-to-peak difference calculation circuit to obtain the voltage drop iR due to the electrolyte resistance (where i is the electrolytic current and R is the electrical resistance of the electrolyte) as its output. automatic correction method. 2. The method for automatically correcting electrolyte resistance drop according to claim 1, wherein the peak-to-peak difference detection circuit includes a circuit consisting of a high-pass filter and a linear rectifier circuit. 3 Electrolysis with a periodic ON-OFF electrolytic current having a sufficiently short OFF time compared to the time constant of electrode reaction polarization,
By applying the electrode potential E at that time to a voltage hold circuit only when the electrolytic current is OFF, its output is the electrode potential Ep-iR ( However, Ep is electrolytic current ON
A method for automatically correcting electrolyte resistance drop, characterized in that the electrode potential at