JPS6035888Y2 - Moisture meter electrode - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an electrode for measuring the amount of water in powder or granules using capacitance.

Conventionally, there are various methods for measuring the moisture content in granules such as sand, and one of them is a method of converting the moisture content from the amount of change in capacitance.

In this method, a high-voltage electrode and a ground electrode are provided through the object to be measured, and the capacitance between the two electrodes is measured. FIG. 1 shows a conventionally used measuring circuit.

In the measurement circuit shown in Fig. 1, 1 is a high frequency oscillator with a frequency of about 1 to 100 MHz, 2 is a first resonant circuit, 3 is a second resonant circuit, 4 is a coaxial cable, 5 is an electrode, 6 is a detection circuit, and 7 is a Feedback circuit, 8 is a capacitance-voltage conversion circuit, 3-1.8-1 is a variable capacitance diode, 9 is a differential amplifier, 10 is a servo amplifier, 11 is a servo motor, 1
2 is a feedback sampling input terminal.

When an object to be measured is placed on the electrode 5, the capacitance Cx and resistance Rx of the object to be measured are connected in parallel with the second resonant circuit 3, so that the resonance state collapses in accordance with the electrostatic capacitance rX. , this is detected by the detection circuit 6, and a voltage is applied to the variable capacitance diode 3-1.8-1 via the feedback circuit 7 so that a resonant state can be obtained again.

That is, the variable capacitance diode 3- corresponds to the capacitance Cx.
The resonance state is maintained by controlling the capacitance of 1 to decrease.

A variable capacitance diode 8-1 that changes the same capacitance as the variable capacitor diode 3-1 is connected to a capacitance/voltage conversion circuit via a capacitor, and converts the capacitance change of the variable capacitor 8-1 into a voltage. Output.

This output voltage is compared with a reference voltage Eo by a differential amplifier 9, and the difference voltage is taken out as the moisture meter output.

In addition, for the purpose of drift correction, the moisture meter output VO with the electrode 5 left in the air is used as a reference for the servo amplifier 1° in advance, and the moisture meter output is adjusted at the timing when a signal is applied to the feedback sampling input terminal 12. The reference voltage Vo is compared and the servo motor 11 is driven in accordance with the difference to control the reference voltage of the differential amplifier 9.

That is, when no substance to be measured is placed on the electrode 5, a signal is applied to the feedback sampling input terminal 12 to control the reference voltage of the differential amplifier 9 for drift correction, and the servo motor 11 is used as the feedback sampling input. Since the device is in a locked state when no signal is applied to the terminal 12, by performing the above-described drift correction at arbitrary time intervals, it is possible to always accurately measure the moisture content.

However, the conventional electrode 5 has a structure (
1' is a high voltage electrode, 2' is a ground electrode, 3' is an insulator, and 4
′ was a ground electrode fixing metal fitting), so the electrode could not be inserted completely to the base of the electrode into the material to be measured (if the surface of the material to be measured was not smooth), and the apparent moisture content was low. During drift correction when the electrode is being measured or left in space, the substance to be measured when the electrode is inserted into the substance to be measured will be attached to the base of the electrode, and the capacitance will be increased by the amount of adhesion. There is a drawback that incorrect correction is performed when the

The present invention improves the drawbacks of conventional electrodes as described above, and its purpose is to prevent the effects of the electrode not being completely inserted into the substance to be measured and the adhesion of the substance to be measured to the base of the electrode during drift correction. The objective is to eliminate the influence and always be able to stably measure moisture content.

Examples will be described below.

Figure 3 shows the electrodes of one embodiment of the present invention, where 1'' is a high voltage electrode, 2' is a ground electrode, 3' is an insulator, 4' is a ground electrode fixing fitting, and 5' is an electrostatic shield 6'. is the insulator between the high voltage electrode and the electrostatic shield.

In this electrode, a ground electrode is provided at the base of the high voltage electrode 1'', and an electrostatic shield 5' is provided at the same potential as the high voltage electrode 1'' and coaxially with the same diameter as the high voltage electrode 1'', so this electrostatic shield portion 5' Even if a substance to be measured is inserted between the ground electrode 2' and the earth electrode 2', the capacitance between the electrodes will not increase.

Note that it is convenient to make the outer diameter of the insulator 6 the same as that of the high-voltage electrode 1'' and the electrostatic shield 5' so that the substance to be measured does not become boring.

Therefore, when inserting the electrode into the substance to be measured, even if the substance to be measured is not completely inserted to the base of the electrode (as long as it is inserted up to the high voltage electrode part 1"), there is no effect, and the electrode is placed in the air. Even if the electrode is left to stand for a while and drift correction is performed, if the substance to be measured at the base of the electrode is attached to the electrostatic shield portion 5', there will be no effect at all due to this attachment.

The electrode of the present invention has a very large effect in that moisture can be measured stably for a long period of time.

Incidentally, even when a plurality of high-voltage electrodes are used, the same effect as described above can be obtained by applying an electrostatic shield to the base of the high-voltage electrode.

[Brief explanation of the drawing]

Figure 1 shows the circuit of a conventionally used moisture meter, in which 1 is a high-frequency oscillator, 2 and 3 are first and second resonance circuits, and 4 is a high-frequency oscillator.
is a coaxial cable, 5 is an electrode, 6 is a detection circuit, 7 is a feedback circuit, 8 is a capacitance/voltage conversion circuit, 9 is a differential amplifier, 10 is a servo amplifier, 11 is a servo motor, 1
2 is a feedback sampling input terminal, and 13 is an output terminal. In Figure 2, A9 is a conventional electrode, A is a cross-sectional view, and the opening is a plan view, 1' is a high voltage electrode, 2' is a ground electrode, 3' is an insulator,
4' is a ground electrode fixing fitting. Figure 3 A9 shows an example of the electrode of the present invention, A is a cross-sectional view, A is a plan view, 1'' is a high voltage electrode, 2' is a ground electrode,
3' is an insulator, 4' is a ground electrode fixture, 5' is an electrostatic shield, and 6' is an insulator between the high voltage electrode and the electrostatic shield.

Claims (1)

[Scope of utility model registration request] In an electrode that measures the amount of moisture in powder or granules using capacitance, one or more rod-shaped high-voltage electrodes and multiple rod-shaped ground electrodes are arranged around the high-voltage electrodes in parallel. 1. An electrode for a moisture meter, characterized in that the base of the high-voltage electrode is electrostatically shielded via an insulator so that the base of the high-voltage electrode is coaxial with the same diameter as the high-voltage electrode.