KR900005432B1 - Capacitance sensor driver encoder - Google Patents

Abstract

The encoder system for measuring the consumption quantity of the electric power, gas or water remotely detects the rotation angle and transmits the data to a control station through a telephone line. The encoder includes a rotation electode (120), a number of stator electodes (110-119), a capacitance sensor (100) faced to the stator electrode and a part of the stator electrodes, and a microprocessor (200) providing a control signal with a signal processor which consists of analog multiplexers (120,150, 170), and an analog amplifier (400).

Description

Capacitance sensing encoder system

1 is a block diagram of an encoder system according to the present invention.

2a to 2o are waveforms of signals observed at various output terminals of FIG.

3 is a view showing another type of sensor to which the present invention is applied.

4 is a view showing another type of sensor to which the present invention is applied.

5 is an exemplary diagram of a transmission scheme.

* Explanation of symbols for main parts of the drawings

10: register indicating 1 unit 11: register indicating 10 unit

12: register indicating 100 units 13: register indicating 1000 units

100: capacitance sensor 110-119: fixed electrode

120: rotating electrode 150, 170: analog multiplexer

152: channel selection address terminal 200: microcomputer

210-219: Pin 1 of the first port 271: Serial data sending pin

220: pin 310 of the second port, 319: filtering circuit

250: input port 400: amplification circuit

402: AC coupled capacitor 410: operational amplifier

450: Average value circuit 500: Analog-to-digital conversion circuit

600: constant voltage circuit 610: transistor

620: Zener diode 630: full wave rectifier

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoder of a capacitance sensor that enables telemetry of mechanical registers such as electricity, gas, water, lubricator, and television, and more particularly, the position, direction, speed, and acceleration of the rotation angle of the rotating body. Microcomputer and analog-to-digital converter which apply the driving signal to the pattern sensor for measuring the back and receive the output signal from the sensor and process the position of the rotation angle of the rotating body through the 2-wire transmission line. It relates to an encoder system using.

The principle related to the capacitance sensor according to the present invention is disclosed in Japanese Patent Application Laid-Open Nos. 86-8456 ('86. 11. 15) and 87-6388 ('87. 7. 11). The encoder circuit related to the sensor is disclosed in Japanese Patent Laid-Open Publication No. 87-5252 (`87. 5 Publication) and the above-mentioned Patent Publication No. 87-6388. The encoder circuit uses a gate-level digital device, which is expensive to manufacture a substrate, has low reliability, and is difficult to control quality. It is best to design and manufacture the encoder circuit as a single chip, but at the current level of technology, the price will increase.

The research results of performing the control function of the encoder circuit by the microcomputer were presented by the inventors at the Fall Conference of the Korean Institute of Electronics Engineers on October 2, 1986. However, even though a microcomputer is used, it is not an efficient circuit and has low reliability because it adopts a complex circuit using a square wave oscillation circuit, an analogplexer and an OR circuit to generate an input signal.

An encoder circuit similar to the present invention is described in US Pat. No. 4,471,4109, issued to Anason on September 11, 1984. This is also using a capacitance sensor and a microcomputer, but in order to increase the capacitance of the sensor, pressure is applied by a spring so that the rotating electrode and the fixed electrode are in close contact. Therefore, since a friction force exists between the rotating electrode and the fixed electrode, high sensitivity such as an integrated power meter is obtained. It cannot be used where it is required or where high precision is required. Since the pulse method is used in the measurement, the resolution of the system is limited by the number of fixed electrodes, which is extremely low.

That is, the rotating electrodes are rotated around the fixed electrodes (the range occupied by one fixed electrode 36 °) arranged in concentric circles by equally dividing the original plate into 10 discs, thereby being detected by any one of the divided fixed electrodes. Since the position of the rotating body is determined using the pulse signal, the angle of the detectable rotating body, that is, the resolution, is only 36 ° corresponding to one fixed electrode, making precise measurement impossible.

On the other hand, in order to improve the resolution, an increase in the number of fixed electrodes may be considered, but the number of encoder circuits has to be increased correspondingly with an increase in the number of fixed electrodes, so that the structure becomes very complicated and the cost is high. Will rise. In addition, as the number of fixed electrodes increases, the area occupied by one fixed electrode is also reduced in inverse proportion, and the area of the rotating electrode must be made smaller at the same time, so that the detection signal becomes weak and the occurrence of an error cannot be avoided.

It is therefore an object of the present invention to provide an encoder system that greatly simplifies the encoder circuit while significantly increasing the reliability of the measurement data without increasing the manufacturing cost.

It is another object of the present invention to provide an encoder that can have various functions that can provide advantages such as peak time measurement or load control simultaneously with telemetering of an electric meter.

Still another object of the present invention is to provide an encoder system having a greatly improved resolution by overcoming the disadvantage that the resolution of the capacitance sensor is limited by the number of fixed electrodes. In order to achieve the above object, first, a plurality of fixed electrodes are disposed on a rotating electrode disposed on a part of a rotating surface of the rotating body and a fixed surface of the fixed body having a surface that is always parallel to the rotating surface, so that Accordingly, a capacitance sensor capable of distinguishing rotation angles of the rotating body by the opposite fixed electrode by forming a capacitance facing a portion of the fixed electrode, and generating and applying an input signal required for the sensor. Means, third means for obtaining and amplifying analog signals from said capacitance sensor, fourth means for converting said amplified analog signals into digital signals, and fifth means for supplying and accepting signals required for supplying and receiving necessary signals. Done by a microcomputer.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention connected to a mechanical register 10 (hereinafter, abbreviated as a register) of one unit of the four-digit mechanical registers 13, 12, 11, and 10 of the integrated power meter. A block diagram of the capacitor sensor 100 and the encoder circuit is shown.

The capacitor sensor 100 is attached to the resistor 10 and rotates at the same speed, and is disposed on the fixed body by being arranged concentrically opposite and arranged point-symmetrically with respect to the center of the concentric circles. Fixed electrodes 100-119 are provided. In the present embodiment, the area of one rotating electrode 120 is one such that the rotating electrode 120 (shown in dashed lines in FIGS. 3 and 4) corresponds to one of the two fixed electrodes. Approximately twice the area of the fixed electrode. In addition, the rotating electrode 120 forms a capacitance opposite to two fixed electrodes 114 and 115 immediately adjacent to each other according to the rotation angle of the rotating body, and when the input signals are sequentially applied to the ten fixed electrodes, It is connected to an encoder circuit so as to obtain an output signal from a fixed electrode in the immediate neighborhood. In addition, when the resistor 10 indicates 0, the fixed electrodes 110 and 111 face the rotating electrode 120 and 1 indicates that the fixed electrodes 111 and 112 indicate 2. The fixed electrodes 112 and 113,... … In order to form the capacitance to face the rotating electrode 120.

The embodiment of FIG. 1 shows a case in which the indicator number of the register 10 is 4, and the numbers of the fixed electrodes constituting the capacitance opposite to the rotating electrode 120 are (114) and (115). Therefore, output is obtained from the fixed electrode 115 only while an input signal is applied to the fixed electrode 114.

The microcomputer 200 is a single chip device having a real time clock, a ROM, and a RAM therein, and also having a port for transmitting and receiving data in series with dozens of input / output ports. These features include 8048 or 8051, a product of Intel Corporation, addressed at 3065, Santa Clara-Baches, California, USA, and their characteristics are described in the company's microcontroller handbook.

In order to apply an input signal to each of the ten fixed electrodes of the capacitor sensor 100, ten of the pins of the input / output port of the microprocessor 200 are first port 210, 211, 212, 213, 214, 214, 216, 217, 218, and 219, each of which has a program stored in the ROM to sequentially output square waves of a P cycle having a frequency of F.

An input can be applied by directly connecting the output port to the fixed electrode. However, since a square wave includes harmonic components, even high frequency components, a circuit for processing an output signal should use a wideband amplifier. There are many good circuits in the broadband amplifier's circuit, but complex circuits must also be designed to achieve large gains. In the present invention, filtering circuits 310, 311, 312, 313, 314, 315, 316, 317, 318, and 319 are connected to each pin of the first port to convert square waves into analog signals. The output terminal of the sensor is connected to an electrode having the same end of the fixed electrode, so that an analog signal is applied to the sensor so that the output signal of the sensor becomes an analog signal, thereby easily designing and manufacturing a circuit for processing the output signal. To save money. As the filtering circuit, various filters such as low pass, band pass, and the like may be used, but when the cycle P is small, it is preferable to use an integrator rather than the above filter, especially in FIG. It is recommended to use the dual integrator shown.

In this embodiment, each channel of the analog multiplexer 150 is removed in order to obtain an output signal from a fixed electrode having a higher number while the input signal is applied to one fixed electrode in the capacitor sensor 100. Connect as shown in Fig. 2.

Since the output signal of the sensor is an analog waveform, the multiplexer 150 should be to multiplex the analog signal. The channel selection address terminal 152 of the analog multiplexer 150 is connected to the second ports 220,... Of the microcomputer 200. In order to select a pin of the first port, the microcomputer 200 may obtain an output by first outputting a number greater than the number of the pin to the second port. A resistor 402 and a capacitor 404 are commonly connected to the output terminal of the analog multiplexer 150. The other terminal of resistor 402 is grounded. The resistance value when the channel of the analog multiplexer 150 is in a conductive state should be negligible compared to the resistance value of the resistor 402, and compared with the resistance value when the channel of the analog multiplexer 150 is in a blocking state. The resistor 150 must be determined such that the resistance value of the resistor 402 can be ignored. That is, since the resistance value when the channel of the analog multiplexer 150 is in a conductive state is 0 in an ideal state but is not actually 0, the resistance value at this time is r, and the resistance when the channel of the analog multiplexer 150 is in a blocking state. The value is infinite in the ideal state, but cannot be infinite due to leakage current, so the resistance value R at this time is satisfied. When the resistance value of the resistor 402 is R402, the condition of r << R402 << R is satisfied. Value of the resistor 402 should be set.

Capacitance and resistance 402 between the rotating electrode and the fixed electrode are circuits for differentiating an input signal, but since the input signal is a sinusoidal signal that is very close to analog waveform, it is not operated as a differential circuit but operated as a divided circuit. will be.

In order to increase the terminal voltage of the resistor 402, the higher the frequency of the input signal is, the better, but it is selected according to the selection of a circuit and an element to amplify the voltage. The terminal voltage of the resistor 402 is amplified by the amplifying circuit 400, and it is preferable to adjust the output voltage of the amplifying circuit 400 to be 3 V or more. Capacitors 412 and 422 are AC coupled capacitors whose impedances should be short-circuited as compared to the impedance of the capacitance defined in capacitance sensor 100 above.

Since the input signal of the capacitance sensor 100 is a sine wave signal, the waveform of the output signal obtained from the sensor 100 is maintained in the sine wave. Accordingly, the operational amplifier 410 processing the output signal obtained from the sensor 100 can use an operational amplifier having a narrow frequency bandwidth but having a very large gain. The operational amplifier suitable for the present invention is operated by a single power source, and there are 1900, 2900, 3900, etc., which are manufactured by National Semiconductor, Inc., which is located at 2900, Santa Clara City Semicontacter, California. These characteristics are described in the linear data book generated by the company, the maximum gain is 60 decibels or more, the frequency is reduced to tens of thousands of Hz and the gain is drastically reduced as the frequency is higher. These op amps can benefit greatly from circuits that are simple to amplify pulse waveforms.

Although the output of the amplification circuit 400 can be directly connected to an analog-to-digital converter, the output voltage of the amplifying circuit 400 can be converted into a binary digital number. The analog-digital converter 500 may then be connected and converted to digital numbers. By using the Schmitt circuit or the level detector in the analog-to-digital converter 500, one-bit digital number can be obtained and can be manufactured with a simple circuit. In this case, the resolution of the whole system is determined by the number of fixed electrodes. Therefore, it is better to use a long bit-to-bit analog-to-digital converter in order to obtain a good resolution while reducing the number of fixed electrodes.

Here, an 8-bit analog-to-digital converter is used to obtain a system with a resolution of 0.14 degrees. Suitable devices for this include ADC0817 or ADC0831, which are manufactured by National Semiconductor Corporation, and the characteristics thereof are described in the linear data book issued by the company. The output terminal of the analog-to-digital converter 500 is connected to the third port of the microcomputer 200. The microcomputer 200 reads the value input from the analog-digital converter 500 into the third port several times while applying an input signal to one fixed electrode and measuring the output from the fixed electrode of the larger number. When the average value is calculated or the same value is matched more than a predetermined number of times, it is inputted as an output signal of the selected fixed electrode, and the selected fixed electrode is stored in the memory address of the RAM corresponding to the number. When the microcomputer 200 executes the measurement of all the fixed electrodes of the capacitor sensor 100 and completes, the number of the measured value fixed electrodes stored in the RAM is the number indicated by the register 10.

FIG. 2A shows a time for sequentially selecting pins 0 to 9 of the first shift of the microcomputer 200, and at the same time, a number larger than this number is output to the second port. Figures 2b-2k show the output waveforms that appear on each pin of the first port. When one pin is selected, it outputs a square wave signal of P cycle with frequency F by alternately outputting "1" and "0" to the pin.

FIG. 2A is a waveform appearing on the output terminal by the channel of the analog multiplexer 150. In the above example, since the number of the register 10 is 4, the fixed electrodes 114 and 115 are rotated. Since it is coupled by an electrode, as shown in FIG. 2A, an output signal appears at the output terminal of the analog multiplexer 150 only while pin 4 is selected at the first port and 5 is output to the second port. Since the unit of capacitance between the fixed electrode and the rotating electrode is F, the level of the output signal is V. FIG. 2m illustrates that the output signal of the amplifier 400 is amplified because it is 3V or more.

Fig. 2n is a DC component obtained from the waveform of Fig. 2m.

Figure 2o shows the state and the output signal sampled by the analog-to-digital converter 500. While one pin is selected at the first port, two samplings are performed. If the two values are the same, input the correct measurement value or input the average value as the correct measurement value. As can be seen in FIG. 1, the number of pins of the output port of the microcomputer 200 is much more than 60 to read the 6-digit indicating number using a sensor having 10 fixed electrodes. Although this type of output port is commercially available, reducing the number of fills required can greatly reduce the cost of the encoder system.

3 is described in detail in the above-mentioned Patent Publication No. 87-6388 as a structure of a sensor suitable for this purpose, and by using this, the number of pins of the output port required for generating the input signal of the sensor is 24. Or it can be greatly reduced to five.

In the sensor of FIG. 1, the pins of the output port of the microcomputer must be connected to all 10 fixed electrodes. However, in the sensor of FIG. 3, there are 4 groups of 4 electrodes among the 5 groups of electrodes A, B, C, D, and E. Since the input signal is applied only to the electrode of the microcomputer, the output port of the microcomputer is possible with four pins.

That is, as shown in FIG. 3, first, five fixed electrodes A, B, C, D, and E are selected from ten fixed electrodes, and the five fixed electrodes A, B, C, D, and E are selected. ) And connected to the fixed electrodes (A, B, C, D, E) denoted by the same reference numerals that are filtered in two in the same direction and combined into five fixed electrode groups (AA, BB, CC, DD, EE). The area of one rotating electrode 120 is formed to be approximately twice the area of the one fixed electrode so that the rotating electrode 120 is opposed to at least two adjacent fixed electrodes.

In addition, four fixed electrodes A, B, C, and D of the five fixed electrode groups AA, BB, CC, DD, and EE are selected, and the filtering circuits 310, 311, 312, shown in FIG. The output port 210 of the five fixed electrode groups AA, BB, CC, DD and EE is connected to the output ports 210 to 213 of the microcomputer 200 through 313. The analog multiplexer shown in FIG. 1 is selected by selecting four fixed electrodes B, C, D, and E to include one fixed electrode E of the fixed electrode group EE not connected to It is connected to four input terminals of 150, and the rest of the overall configuration is the same as that shown in FIG.

According to such a configuration, first, when the square wave of the P cycle having the frequency F is output from the input / output port 210 of the microcomputer 200 and input to the fixed electrode A through the filtering circuit 310, the analog multiplexer 150 By scanning the fixed electrodes B to E by multiplexing the analog signal, any of AB, AC, AD, and AE formed of the electrodes B, C, D, and E adjacent to the fixed electrode group AA may be rotated and It is detected whether the object is facing, and the resulting signal is processed in the same process as the description of FIG. After that, when the square wave signal of the P cycle having the frequency F is output from the input / output port 211 of the microcomputer 200 and is input to the fixed electrode B through the filtering circuit 311, the analog multiplexer 150 is performed in the same process as described above. When the square wave signal is applied to the fixed electrodes of B, C, and D), the fixed electrodes of B, C, D, and E are sequentially scanned while the signal is applied to any one of the fixed electrodes. When the detection is completed in the electrode neighboring the BB pair of fixed electrode group by the square wave signal is again output from the input / output port 212 of the microcomputer 200 is input to the fixed electrode (C) and the B to The analog multiplexer 150 sequentially scans the fixed electrode of E to detect a signal at an electrode neighboring the fixed electrode group of the CC pair. Subsequently, a square wave signal is input to the fixed electrode of D, and a signal is detected from an electrode neighboring the fixed electrode group of D-D by the above-described process. That is, when the square wave signals are sequentially applied to the fixed electrodes of A, B, C, D, and E in the microcomputer 200, B, C, D, and E while the signal is applied to any one of the fixed electrodes. While sequentially scanning the fixed electrodes of, a detection signal indicating which electrode group is opposed to the rotating body 120 is detected.

Thus, these detected fixed electrode groups are for example AB = 7, CA-6, AD = 0, AE = 9, BB = X, BC = 5, DB = 4, DE = 8, CB = X, CC = X When the microcomputer 200 processes CD, CD = 3, EC = 2, DB = X, DC = X, DD = X, and DE = 1, the position of each fixed electrode facing the rotating body 120 is determined. (The first of the letters indicating two fixed electrode groups is the fixed electrode to which the signal is applied, and the second indicates the fixed electrode to which the detection signal is detected.)

4 illustrates an embodiment of an analog multiplexer in which a fixed electrode is connected to one output terminal at the same time when a sensor in which the area of the rotating electrode is twice the area of the fixed electrode is obtained. It is shown. The rotating electrode is provided with a connecting means of an external circuit formed by forming a cylindrical conductor inside the mandrel hole at the center of the rotating body and connecting the cylindrical conductor to the rotating electrode. While an input signal is applied through the input / output port 210 of the computer 200, five groups of A, B, C, D, and E are connected to the analog multiplexer 150, so that the second ports 220,... In accordance with the channel selection signal from), only two groups of fixed electrodes of the five groups of fixed electrodes may be connected to the output terminal.

Since the output terminal is connected to the input terminal of the operational amplifier 410 through the capacitor 404, the analog multiplexer 170 and the operational amplifier 410 is operated as an add amplifier, so that the two fixed to the output terminal of the amplifier circuit 400 The signal from the electrode is added and amplified.

In this case, even when the radius of the sensor is small, by increasing the ratio of the area of the rotating electrode to the fixed electrode, the same effect as using a sensor with a larger radius is obtained, making the configuration of the encoder circuit easier.

The measured data of the rotation angle of the rotating body can be transmitted so that it can be used elsewhere by using the function of the serial data transmission and reception terminal and the transmission line in the microcomputer. An example of a circuit that can achieve this purpose is shown in FIG. According to this, the power supply voltage required for the encoder circuit can be supplied only when it is necessary to read data from the outside, and since the power supply line and the line transmitting and receiving data are the same, a telephone line or a power line can be used.

The microcomputer 200 outputs 0V or 5V to the serial transmission sending pin 217 according to the transmitted data. The constant voltage circuit 600 receives 10-20V and supplies a constant voltage of 5V to the entire system. The current required for the microcomputer 200 is 3-10. The transistor 610 absorbs current, and the amount of current absorbed varies according to a signal coming from the microcomputer 200. The zener diode 620 drops as much as the zener voltage when the zener voltage is higher than the zener voltage, and supplies the excess voltage to the element connected in series with the zener diode 620. The rectifier 630 is for supplying the positive voltage at all times to the circuit regardless of the sign of the voltage coming into the input terminal. When supplying a voltage to the system from the transmission line side, if a voltage lower than the zener voltage is applied, it appears to be an open circuit due to the zener diode 620, and if a voltage higher than 10 V is higher than the zener voltage, the constant voltage circuit 600 operates so that the microcomputer The 200 may transmit data through the transmission path.

Since the current flowing through the transistor 610 varies depending on the data, the terminal voltage of the resistor 810 in series with the DC power supply at the receiving location of the data changes in accordance with the data of the microcomputer 200, and thus this change is detected. This completes the data transfer.

As described above, according to the present invention, it is possible to easily control the generation of the input signal and the connection method of the sensor by using various functions of the microcomputer, good input / output ports and fast processing speed, so that the configuration of the encoder circuit is simple, but measurement is possible. The data processing method can be improved so that a reliable encoder system is supplied. In addition, since the waveform of the input signal is made of a sinusoidal waveform by using the filtering circuit, an analog amplifier using an operational amplifier can be used to amplify the output of the sensor. Thus, an 8-bit analog-to-digital converter is used. Encoder systems that can greatly improve resolution and enable precise measurements will be provided.

Claims (4)

One rotating electrode arranged to be arranged on a part of the rotating surface of the rotating body and a plurality of (N) fixed electrodes are arranged to be arranged on a fixed surface of the fixed body installed in parallel to the rotating surface, and the rotating electrode and the plurality of fixed electrodes A capacitance sensor formed so that some of the electrodes (M out of N) face each other, a signal processing means for processing a detection signal of the capacitance sensor, and an input signal sequentially supplied to the capacitance sensor, and controlled to the signal processing means. An encoder system having a microcomputer for applying a signal and input and processing an output signal of a signal processing means to measure a position, a speed direction, etc. of a rotating body, wherein the signal processing means comprises an analog multiplexer (150, 170) and an analog. An amplifier 400, wherein the output of the capacitance sensor 100 is the analog multiplexer 120 and the analog An encoder system, characterized in that connected to the input terminal 250 of the microcomputer (200) through the amplifier (400). 2. The method of claim 1, wherein the output terminal of the microcomputer in which the input signal is generated is connected to an input of the filtering circuits 310-319 so that an analog waveform is supplied to the sensor from the output terminal of the filtering circuit. An encoder system characterized by the above. 3. The encoder system according to claim 2, wherein the filtering circuit is a double integrator circuit. 4. The encoder system according to any one of claims 1, 2, or 3, wherein an average value circuit (450) is provided between the analog amplification circuit (400) and the analog-digital converter (500).

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