JPS60123734A - Level meter for powder - Google Patents

Abstract

PURPOSE:To make operation stable and to improve resolution, by providing a magnetic-field generating means, a magnetic-field detecting part, which converts the change in intensity of the magnetic field due to powder into an electric signal, and a signal processing part, which electrically processes the signal and measures the level of the powder. CONSTITUTION:When a detecting part 1 comprising a magnetic-field generating part 2 and a magnetism detecting element 3 is not covered by powder, the magnetic field is not changed between the element 3, which generates a constant voltage based on a magnetism detecting element driving bridge circuit 4 and a constant-current power source circuit 5, and the generating part 2. When the detecting part 1, the element 3, and the generating part 2 are covered by the powder, the magnetic field is fluctuated and the output voltage of the element 3 is fluctuated. The fluctuating voltage outputted from a DC preamplifier 6 is amplified by a DC amplifier 9. The result is compared with a reference voltage in a hysteresis comparator circuit 10. The state of the presence or absence of the powder is binary-coded. Thus the stable operation is obtained, and the resolution can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder level meter for measuring the content of powder in a hopper, for example, in a powder hopper.

Traditionally, the method of measuring the powder level in the hopper is by measuring the powder level in the hopper.
A method called the capacitance method has been widely used. This capacitance method extracts the change in capacitance when the detection part of a level meter is covered with powder as an electrical signal.
By processing this signal, the powder level can be determined.

However, this capacitance method has the following various drawbacks: (1) Since the electrical signal from the detection section is weak, it is susceptible to electrical noise and is prone to malfunction.

(2) The detection section is easily contaminated by fine particles, etc., and when contaminated, the sensitivity of the detection section is significantly reduced and the response speed is likely to deteriorate, resulting in malfunctions.

(3) Capacitance is greatly affected by changes in the physical properties of the powder to be measured, such as slight changes in moisture, and therefore requires frequent adjustment.

(4) In order to obtain high light sensitivity, it is necessary to increase the area of the detection part, which tends to cause problems in terms of cost and strength, and as the detection part becomes larger, it becomes difficult to use as a level meter. resolution is reduced.

The present invention has been made in view of the above circumstances, and includes a magnetic field generating means that generates a magnetic field, and a magnetic field generating means that is provided opposite to the magnetic field generating means and outputs an electric signal according to a change in the intensity of the magnetic field due to powder. a detection section consisting of magnetic detection means;
The present invention is characterized in that it is equipped with a signal processing section that electrically processes the output signal of the air detection means and measures the powder level in the detection section, and is capable of miniaturization, high resolution, and stable operation. The purpose of the present invention is to provide an inexpensive powder level meter that provides the following.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the circuit configuration of a powder level meter. In the figure, reference numeral 1 denotes a detecting section, which is connected to a magnetic field generating section 2 and a magnetic detecting element 3, which are elastically supported so as to maintain a certain distance from each other and are also magnetically coupled. It is configured. This detection unit 1 is installed, for example, inside the powder body Δ.

The magnetic sensing element 3 is driven by a bridge circuit 4 for driving the magnetic sensing element for temperature compensation and a constant current power supply circuit 5. The output voltage of the magnetic detection element 3 is
It is amplified by a pre-direct current amplifier 6. The preamplifier 6 is set so that the output after amplification by the offset voltage generating circuit 7 is Ov. This makes it possible to extract only the voltage fluctuation of the magnetic detection element 3 after the powder film has entered the p1 powder hopper as the output of the pre-mounted DC amplifier 6. The output of the pre-direct current amplifier 6 is input to a direct current amplifier 9 via a low-pass filter 8 . The low-pass filter 8 prevents, for example, when powder is introduced into the powder horn 4, fluctuations in the output of the magnetic detection element 3 at irregular intervals from being transmitted to the DC amplifier 9 at the subsequent stage. DC amplifier 9
The input signal is amplified to a level sufficient for signal processing. The output of this DC amplifier 9 is input to a hysteresis contorrator circuit 10. A hysteresis comparator circuit differs from a normal controller in that it treats inputs that change at extremely short intervals as continuous and compares them with a reference voltage. That is, this hysteresis conflator circuit 10 compares the output of the DC amplifier 9 with a reference voltage that is properly established in advance according to the physical properties of the powder to be symmetrical, and as a result, determines the state in which the powder is present and the state in which the powder is not present. Binarize into two parts. By combining this hysteresis comparator circuit 10 with the D low/4 filter 8, it is possible to extremely reduce the influence of disturbances. 1) is input. This signal conversion circuit 11 converts an input signal into a standard signal for measuring instruments, that is, an output of 1 to 5 volts of direct current or 4 to 20 mA of the old style.

FIG. 2 shows a concrete structure of a leveling device for powder having the above-mentioned circuit configuration. In the figure, 2 is a flange, and a main body casing 22 is fixed to the soil surface of this flange 2. This main body casing 22 has O
A cap 24 is attached via a ring 23. In addition, there are two vias "2s" on the bottom surface of flange 2.
26 are erected. Vibration prevention ribs 27° and 28 are provided between the pipes 2 and 5 and the nozzle 26. A permanent magnet 29 corresponding to the magnetic field generating section 2 in FIG. 1 is installed inside the lower end of one of the knobs 25. Inside the other Guib 26 is the above pipe:! 5 @
A magnetoresistive element 30 corresponding to the magnetic detection element 3 in FIG. 1' is installed opposite the permanent magnet 29 in FIG. It is fixed within the ship f25°26. There is an insulating spacer inside the main body casing 22?
1 a, , 91 b fI: Set screw 32 through
Yoshimiko circuit board 3. wo is fixed. This electronic circuit board 33 includes a bridge circuit 4 for driving the magnetic extraction element shown in FIG.
, offset voltage generation circuit 7, low-pass filter 8, DC N width 9, hysteresis converter circuit 10
and all electronic circuits of the signal conversion circuit 11 are incorporated.

Main body coolant 22 and 26 pipes, each with flange 2
The inside communicates through a cavity 34 provided at the bottom. The distribution electronic circuit board 33 and the magnetoresistive element 3o are electrically connected by wiring cables 3.5, 46 routed through the cavity 34 of the flange 21 and the groove 26. Wiring~Pull? s, ,? 6 is fixed in the cavity 34 of 7 ranks 2 by a filler 37). The necessary power supply and level output of the electronic circuit board 3 are connected to wiring cables 38, . 99
.

4o, 41Vc are connected to the signal connector 42 disposed on the side wall of the main body casing 22.Next, the operation of the level meter for powder having the above structure will be explained using powder as an example. In FIG. 1, a detection section 1 (in FIG. 2,
If the permanent magnet 29 and the magnetoresistive element 3o) are not yet covered with coal, the magnetic field between the magnetic field generator 2 and the magnetic detection element 3 does not change.

At this time, the magnetic sensing element 3 is connected to the magnetic sensing element driving bridge circuit 42! ! and a constant current power supply circuit, IiK, to generate a certain constant pressure.

This voltage is amplified by the pre-amplifier 6, but in this case, as described above, the output after amplification by the output of the offset voltage generating circuit 7 is Ov7.

As a result, the front DC amplifier 6 outputs only the variation in the output voltage of the magnetic detection element 3.

That is, considering the state in which the detection unit 1 is covered with coal,
In this case, the space between the magnetic detection element 3 and the magnetic field generating section 2 is also filled with coal, so the magnetic field between them changes. As a result, the output voltage of the magnetic detection element 3 fluctuates, and the fluctuating voltage is output from the preamplifier 6. The output of the pre-direct current amplifier 6 is passed through a pass filter 8 and amplified by an amount of light equal to 1 for signal processing by an adjustable gain fx@current amplifier. The output of this DC amplifier 9 is compared with a preset reference voltage by a hysteresis comparator circuit 10, and is binarized into two states: a state in which coal is present and a state in which there is no coal. The 4-digit signal binarized by the hysteresis comparator circuit 1θ is converted into a measuring instrument standard signal by the signal conversion circuit 11VC, and then sent to, for example, a display device, a plant controller, etc. (not shown).

As mentioned above, in the level s-i for powder of the present invention, when the magnetic field generation part and the magnetic detection part are covered with powder, the electric output from the magnetic detection part changes. It detects the B'k of the body and has the following advantages compared to conventional level meters. That is, (a) When compared with level 1 using the capacitance method,
Since the shape and dimensions of the detection section can be made extremely small, the resolution of the level meter is increased.

(b) Since the inside of M, etc. may be of a E-shape, it is difficult for fine powder to adhere, and even if it does, the effect is small, so malfunctions are less likely to occur.

(c) Since it can be miniaturized, it is proven to be strong and the manufacturing cost can be significantly reduced.

(d) Unlike level meters that have mechanically moving parts, failures due to powder intrusion do not cause VC.

As mentioned above, according to the present invention, not only miniaturization is achieved with El performance, but also high W4 performance and stable operation can be obtained77.
We can provide a high-quality powder level meter.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration of a powder level H1 according to a practical example of the present invention, and FIG. 2 is a sectional view showing the specific structure of the level puller. DESCRIPTION OF SYMBOLS 1... Detection part, 2... Magnetic field generation part, 3... Magnetic detection element, 4... Magnetic detection element layer X operation bridge circuit 1
, ri...constant current power supply circuit, 6...front DC amplifier,
7... Offset voltage generation circuit, 8... Low pass filter, 9... W optical amplifier, 10... Hysteresis comparator circuit, 11... No. 1 variable circuit, 22...
...Body casing, 25.26...No9ig, 29
...Permanent magnet 1. ? 0... Magnetoresistive element. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] a detecting section comprising a magnetic field generating means for generating a magnetic field, a magnetic detecting means provided opposite to the magnetic field generating means and outputting an electric signal in accordance with a change in the intensity of the magnetic field due to the powder; A level meter for powder, comprising: a signal processing section that electrically processes an output signal and measures the powder level in the detection section.