JPH0743404B2 - Attachment for testers that enables direct reading of the electrical resistance of liquids - Google Patents

Description

[Detailed Description of the Invention] Recent agriculture in Japan aims to save labor and increase yields by overly relying on chemical fertilizers and pesticides, resulting in a decrease in organic matter in the soil, contaminated soil and Since the resistance to pests has declined, the old organic farming is gradually being reviewed in recent years.

As a means of determining the degree of soil contamination, make an aqueous solution of the collected soil and measure its pH value (measurement of hydrogen ion concentration) and
The value (electrical conductivity) is used as a guide. For the former, there are direct-reading pH meters and pH indicators that have already been developed, but for the latter, there is the Kauushi Bridge method, but it is unsuitable for agriculture because it is troublesome to handle.

There are endless other things around us that require measurements of soil conductivity. The measurement of ground resistance of electric washing machines, electric refrigerators, microwave ovens, vacuum cleaners, air conditioners, etc. should be obligatory to measure the ground resistance. There is. As is well known, generally, a DC movable wire wheel type instrument is used for measuring the resistance value, and a DC power source (battery) is used as its power source.

However, due to the polarization effect of the liquid, the resistance measurement of the liquid cannot be performed correctly.

In the present invention, DC is used as a power source for resistance measurement,
The measuring instrument (tester or ohmmeter) uses a movable DC wheel type instrument to energize the direct current, and in the aqueous solution, the same amount of electric current as the amount of the electricity energized in the instrument is alternately applied. The current is applied as an alternating current of a rectangular wave with the directions switched to equal amounts. A current (DC) in the same direction is always applied to the ohmmeter or tester in the measured solution. AC is energized.

As an explanation of the circuit here, the circuit caused by the relay is brought out regardless of the SCR because the coil of the relay and its contact point are electrically completely separated and insulated from each other, so that no current is sent or received. Absent. Therefore, it is easily understood that the charge amount flowing through the electrode in the liquid flows into the charge ohmmeter or the tester and does not leak to the other, and is supplied as a direct current with the same charge amount.

If we try to explain this by citing circuit switching SCRs or switching transistors, it will take a considerable amount of time and labor to explain them because they are semiconductors.

Referring to FIG. 1, the operation principle will be described. M is an electric conductivity meter, which has a ohmmeter scale in KΩ units on the lower side and a morometer scale in μ units on the upper side. Ohm Ω and mho are inverse to each other, so 1
Kilo-ohm (1KΩ) is equivalent to 1000 micro mho (1000μ), and (5KΩ) is equivalent to (200μ), so the product of both is always 1. Rm is a parallel resistance for adjusting the sensitivity of the movable loop L, Rk is a series resistance for setting the indicator lens, b is a DC power supply with a built-in meter, and Rj is a pointer (0KΩ) when the conductivity measuring electrodes P1 and P2 are short-circuited. That is, it is a variable resistor that is adjusted to indicate (∞μ).

MB represents an astable multivibrator circuit (hereinafter abbreviated as self-running multi), which is composed of two transistors, and the resistors of each collector circuit are replaced with relays La and Lb. Since each of these transistors operates alternately at the timing of multiplying the product of Ra and Ca and the product of Rb and Cb by 0.69, if the product of the constants of both is equal, the relay
La and Lb are alternately contacted at the same timing a1 and a2, respectively.
And b1 and b2 are alternately conducted. A1 and a2, b1 and
Since the polarity of the circuit is reversed by crossing with b2 and the aqueous solution is energized as an alternating current, the polarization effect due to electrolysis can be prevented.

FIG. 2 illustrates the usage and operation of the present invention. When the push button PB is pressed, one of the transistors TRa and TRb is turned off and the other transistor is turned on.
I don't know which one will conduct first, but that's why it's called an unstable multi or self-propelled matill. If TR
If a is in a conducting state, its collector is at almost zero potential, but Ca is charged through Ra, and when the base potential of TRb becomes (+) potential, TRb becomes conductive and TRb becomes a conducting state. Becomes almost zero potential, and TRa goes back to the cutoff state. Therefore, if Ca and Cb are the same, and Ra and Rb are the same, La and Lb have the same operation time, and the alternating currents become equal. Since the decomposition amounts are canceled by each other, there is no possibility of causing a polarization effect.

Next, in order to perform measurement using this conductivity meter M, first, with the measuring electrode open, the pointer of the instrument is ∞ Ω, immediately 0
In other words, it should be in a position where it cannot be shaken at all even if the push button of PB is pressed, so if it is wrong, the pointer itself is zero-adjusted and the instrument itself is calibrated. Next, short the measuring electrodes P1 and P2 with the short-circuiting clip Sh, and press the push button PB while the pointer of the instrument indicates the full scale 0 KΩ or ∞μ.
Adjust.

Now that the preparation is complete, connect the short-circuit clip Sh to the measuring electrode P1.
And P2. After that, the measuring electrodes P1-P2 are inserted into the aqueous solution to be measured, and the push button PB is pressed to read the instruction of the soil conductivity meter.

Figure 3 shows a commercially available tester with a mortar (μ) scale
It shows an example adapted to be used in a wider range. In this case, it is not always necessary to pass the self-propelled Mathil to measure the resistance not to the electrolytic solution. Also, the measurement of the earth resistance of home electric appliances, power transformers, communication equipment, etc. can be achieved satisfactorily by increasing the number of lens switching resistors shown in Figs. 1 and 2 without using a bridge. You can In the example of FIG. 3, (KΩ) and (μ) and (× 10
) And (× 0.1 mΩ) two-stage switching direct current resistance for setting the instruction range.

[Brief description of drawings]

FIG. 1 is a circuit diagram for explaining the principle of the present invention, FIG. 2 is an explanatory diagram for handling the present invention, and FIG. 3 is an explanatory diagram when the present invention is incorporated in a commercially available tester. .

Claims (1)

[Claims] 1. An attachment to be inserted between a resistance measuring terminal of a tester and a resistance to be measured, wherein two exciting contacts are provided as a collector load of a free-running multi-circuit having two transistors which are alternately turned on and off. The two relays are used, and the exciting contacts of each of the relays are cross-wired to each other so that the relay between the resistance measuring terminal and the probe for the resistance to be measured can be relayed, and each relay exciting contact is equal. A tester attachment capable of measuring the electrical resistance of a liquid, characterized in that a direct current supplied from a tester is made to flow as an alternating current to a resistance to be measured by making it conductive at regular intervals.