JP2640310B2 - Information transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information transmission system for converting information detected by a remote terminal into an electric current and transmitting the electric current to a measuring load via a transmission cable.

[0002]

2. Description of the Related Art For example, in a petroleum plant, a terminal device equipped with a sensor for detecting information such as water content, temperature, pressure and the like of crude oil is installed in a tank at a remote point where crude oil is stored, and the sensor detects the information. The terminal device converts the obtained information into a current value of 4 to 20 mA in the terminal device, and transmits, for example, a moisture meter, a thermometer of a central information monitoring system,
It is sent to a measuring load, which is a measuring device such as a pressure gauge, to constantly monitor whether or not the crude oil in the tank is kept in an appropriate state.

FIG. 7 shows a basic configuration of such a conventional information transmission system. Information S such as the amount of water, temperature, and pressure detected by a sensor of a terminal device (not shown) is input to the information / voltage conversion and voltage amplification circuit 10, and after the information S is converted into a voltage, a voltage of an appropriate magnitude is applied. It is amplified to V.
The voltage V corresponding to the information S is input to the constant current circuit 11. The constant current circuit 11 includes an operational amplifier OP, a transistor Tr, and a resistor R connected to the emitter of the transistor Tr. A voltage V corresponding to information S from the information / voltage conversion and voltage amplifying circuit 10 is applied to the operational amplifier. It is supplied to one input (+) of the OP. Operational amplifier OP
Is amplified by a transistor Tr, the amplified output of which flows through a resistor R connected to its emitter to generate a voltage VR across the resistor R. This resistance R
Generated between both ends of the constant current circuit 11 corresponds to the input voltage V of the constant current circuit 11. Since the resistance R has a constant value, the current I1 flowing through the transistor Tr and the resistance R is determined by the input voltage V.

After the information S detected by the sensor is converted into an appropriate current value of 4 to 20 mA, a current signal corresponding to the information S from the terminal device is transmitted to the transmission cable 20.
The information S is supplied to the measurement load 21 which is a measurement device such as a moisture meter, a thermometer, or a pressure gauge of the central information monitoring system through the central processing unit.

On the other hand, a central information monitoring system, for example, 2
The power supply voltage Vdd generated from the 4V power supply 22 is applied to the constant current circuit 11 and the information / voltage conversion and voltage amplification circuit 10 via the transmission cable 20. As a result, the current I flowing from the power supply 22 through the transmission cable 20 is equal to the load of the constant current circuit 11, that is, the current I1 flowing to the transistor Tr and the information / voltage conversion and voltage amplification circuit 10
The current (I1 + I2) flows through the transmission cable 20 to the measurement load 21 and returns to the power supply 22.

Here, when the information / voltage conversion and voltage amplification circuit 10 is composed of a simple analog circuit or the like and the flowing current I2 is constant, no problem occurs in the basic configuration of FIG. If the detection output is digital data, a digital-to-analog converter is required, and in order to minimize explosion-proof safety, the current consumption of terminal devices is reduced as much as possible. Often, IC chips such as digital-analog converters and analog-digital converters are used. In this case, if the circuit becomes complicated and there is a load fluctuation or a load current flowing through the circuit fluctuates due to information, That will cause a large error.

[0007]

FIG. 8 shows a conventional basic structure which is generally used to solve the above problem. That is, the difference from the basic configuration of FIG. 7 is that the power supply voltage Vdd supplied from the power supply 22 of the central information monitoring system to the information / voltage conversion and voltage amplification circuit 10 of the terminal equipment is changed to a constant current and current / voltage conversion circuit. 12. As a result, the current I2 flowing through the information / voltage conversion and voltage amplification circuit 10 becomes constant, and the above problem is solved.

However, in the configuration shown in FIG. 8, it is unreasonable to provide a double constant current circuit, and the circuit configuration becomes complicated, the terminal equipment becomes large, the cost increases, and the current consumption increases. There are drawbacks. Furthermore, since this type of terminal equipment is used as a transmitter installed on site, there are strict restrictions on size, price, environmental stability, explosion-proof safety, etc. It is desired to increase the environmental stability by lowering the current consumption, reduce the current consumption, and increase the explosion-proof safety.

Accordingly, an object of the present invention is to provide an information transmission system in which the circuit configuration of a terminal device is simplified, the size and cost are reduced, and the current consumption is reduced.

[0010]

The above object is achieved by an information transmission system according to the present invention. In summary, the present invention has a sensor for detecting information on an object to be measured, an information / voltage converting means for converting information from the sensor into an analog voltage, and a voltage signal from the information / voltage converting means. Terminal equipment including voltage / current conversion means for converting to a current signal, transmission means for transmitting a current signal from the terminal equipment to a load for measurement, the information / voltage conversion means and the voltage / current through the transmission means And a power supply for supplying a predetermined operating voltage to the conversion means, wherein the operating voltage from the power supply is
The voltage / current converting means and the information / current converting means are connected through an impedance element connected to the current amplifying means of the current converting means.
This is an information transmission method characterized in that the information is supplied to voltage conversion means.

[0011]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a basic configuration of an embodiment of an information transmission system according to the present invention. Also in this embodiment, information S such as the amount of water, temperature, and pressure detected by a sensor (not shown) of the terminal device is input to the information / voltage conversion and voltage amplification circuit 10, and after the information S is converted into a voltage, Is amplified to a voltage V of an appropriate magnitude. The voltage V corresponding to the information S is input to the constant current circuit 11. The constant current circuit 11 includes an operational amplifier OP, a transistor Tr, and a transistor T
r comprising a resistor R connected to the collector of
The voltage V corresponding to the information S from the voltage conversion and voltage amplification circuit 10 is supplied to one input (+) of the operational amplifier OP. The output signal from the operational amplifier OP is the transistor Tr
And the amplified output is taken directly from its emitter.

After converting the information S detected by the sensor into an appropriate current value of 4 to 20 mA, the information S
Is supplied from the terminal device through the transmission cable 20 to the measuring load 21 which is a measuring device such as a moisture meter, a thermometer, or a pressure gauge of the central information monitoring system through the transmission cable 20, and the information S is displayed. Become.

On the other hand, the central information monitoring system, for example, 2
In this embodiment, the power supply voltage Vdd generated from the 4V power supply 22 is applied to the resistor R of the constant current circuit 11 via the transmission cable 20, but the constant voltage is applied to the information / voltage conversion and voltage amplification circuit 10. It is configured to be applied further through the resistor R of the current circuit 11. Therefore, the current I flowing from the power supply 22 through the transmission cable 20 flows through the resistor R of the constant current circuit 11 as it is.
The current I1 flows through one transistor Tr and the current I2 flows through the load of the information / voltage conversion and voltage amplification circuit 10. Of course, the current (I1 + I2) flowing through the circuits 10 and 11 flows through the transmission cable 20 to the measurement load 21 and returns to the power supply 22.

With this configuration, both the current I1 flowing to the transistor Tr of the constant current circuit 11 and the current I2 flowing to the load of the information / voltage conversion and voltage amplification circuit 10 flow through the resistor R. When there is a load change in the voltage amplifier circuit 10 or the load current I2 flowing through the circuit 10 fluctuates due to information, the load current I1 flowing through the transistor Tr of the constant current circuit 11 increases or decreases by the amount of the change. The current I (that is, I1 + I2) transmitted from the device to the measurement load 21 of the central information monitoring system is always kept constant.

Therefore, according to the present embodiment, it is possible to prevent the occurrence of measurement errors without complicating the circuit configuration by providing a double constant current circuit in the terminal equipment. Therefore,
Measurement accuracy is improved. Further, since the circuit configuration of the terminal device can be simplified, the size and cost can be reduced, and the current consumption can be significantly reduced. For this reason, environmental stability can be greatly increased, and explosion-proof safety can be further enhanced. In addition, it is possible to cope with a case where the detection output of the sensor is digital data, and it is possible to use a microcomputer which consumes less current, an IC chip such as a digital-analog converter, an analog-digital converter, or the like.

Next, a specific example of the information / voltage conversion and voltage amplifying circuit 10 of the present embodiment corresponding to the case where the detection output of the sensor is digital data will be described.

For example, as a sensor for detecting the concentration of a certain component in a liquid phase such as the amount of water in crude oil, a moisture (gas) sensor having an electric characteristic of a capacitance change type, an electric sensor of a resistance change type, Moisture (gas) sensors with characteristic properties are often used. As shown in FIGS. 2 and 3, these sensors include, for example, two serially connected inverters 51 and 52 such as a C-MOS type Schmitt inverter, and a resistor R1 inserted in a feedback circuit of the preceding inverter 51. When,
Similarly, it is used as an oscillation frequency determining element of the CR oscillation circuit 50 composed of a capacitance element (capacitor) C1 connected to the input side of the inverter 51 in the preceding stage.

That is, in FIG. 2, a capacitance change type sensor Ch whose capacitance changes according to a change in the concentration of an object to be measured such as moisture is connected to the input side of the inverter 51 in the preceding stage and the capacitance element. CR oscillation circuit 5
0, the oscillation frequency of the CR oscillation circuit 50 is correspondingly changed by changing the capacitance of the sensor Ch in accordance with the change in the concentration of the object to be measured. The microcomputer sends the detected frequency to a pulse signal corresponding to the concentration of the measured object and outputs the pulse signal.

In FIG. 3, a resistance change type sensor Rh whose electric resistance changes in accordance with a change in the concentration of an object to be measured, such as moisture, is connected to the CR oscillation circuit 50 described above.
The resistor R1 inserted in the feedback circuit of the inverter 51 in the previous stage
Instead, insert it as a resistor for determining the oscillation frequency,
A CR oscillation circuit 50 is formed, and the electric resistance of the sensor Rh changes according to the change in the concentration of the object to be measured.
The oscillation frequency of the R oscillation circuit 50 is changed correspondingly, and from this oscillation output, that is, the frequency signal, C
An oscillation frequency of the R oscillation circuit 50 is detected, and a pulse output corresponding to the frequency is provided.

Further, as shown in FIG. 4, a sensor GS having electric characteristics in which a capacitance component C and an electric resistance component R change according to a change in the concentration of an object to be measured such as moisture is used. The first, second and third switches X of the configuration,
When the sensor GS is used as a sensor of the capacitance change type by Y and Z, as shown in FIG. 2, the sensor GS is connected in series between the input side of the inverter 51 at the previous stage and the capacitance element C1. When the sensor GS is used as a variable resistance type sensor, as shown in FIG. 3, the sensor GS is switched and connected so as to be inserted instead of the resistor R1 in the feedback circuit of the inverter 51 in the preceding stage. 2 and the CR oscillation circuit 50 shown in FIG. 3 are also proposed.

The first, second and third switches X, Y,
Z has one movable contact XC, YC, ZC and two fixed contacts X0 and X1, Y0 and Y1, Z0 and Z1, respectively. The first switch X has a movable contact XC having a resistor R2 for removing a DC voltage. The first fixed contact X0 is not connected, and the second fixed contact X1 is connected to the input side of the inverter 51 in the preceding stage. The second switch Y has a movable contact YC connected to the other terminal of the sensor GS, and a first fixed contact Y0 connected to a connection point between the DC voltage removing resistor R2 and the capacitance element C1. , The second fixed contact Y1 is connected to the third switch Z
Is connected to the second fixed contact Z1. In addition, the third
The switch Z is provided with an inverter 5 whose movable contact ZC is in the preceding stage.
1 and the first fixed contact Z0 is connected to the resistor R1
It is connected to the.

In the above configuration, three switches X,
When the movable contacts XC, YC, ZC of Y and Z are connected to the first fixed contacts X0, Y0, Z0 as shown, the resistor R1 is inserted into the feedback circuit of the inverter 51 in the preceding stage, A sensor GS is connected in series with the capacitance element C1 on the input side of the inverter 51 at the preceding stage, and the sensor G
A resistor R2 for removing a DC voltage is connected in parallel between both ends of S. A capacitance measurement type circuit configuration is provided, and the CR whose oscillation frequency changes corresponding to the capacitance value of the sensor GS same as that in FIG. An oscillator 50 is configured.

On the other hand, the movable contacts XC, YC, ZC of the three switches X, Y, Z are the second fixed contacts X1, Y.
1, when connected to the Z1 side, the sensor GS is inserted into the feedback circuit of the preceding inverter 51 instead of the resistor R1, and the DC voltage removing resistor R2 on the input side of the preceding inverter 51 is connected to the first stage. Shorted by one switch X,
Since the capacitance element C1 is connected to the input side of the preceding inverter 51 through the first switch X, the CR oscillator 50 in which the oscillation frequency changes in accordance with the electric resistance value of the same sensor GS as in FIG. Is done.

The oscillation output from the CR oscillation circuit 50, that is, the frequency signal is sent to the microcomputer 60, where it is subjected to arithmetic processing to detect the oscillation frequency, and this detected frequency is converted into a pulse signal corresponding to the concentration of the measured object. Convert and output.

Normally, C-
A MOS Schmitt inverter is used, and a pulse signal whose frequency changes in response to a change in the capacitance value or a change in the electric resistance value of the sensor GS is output from the CR oscillation circuit 50 and sent to the microcomputer 60. . The microcomputer 60 is, in this example, the counter unit 61 for counting the number of pulses of the frequency signal F _C or F _R that is input
And a storage unit 62 including a ROM (Read Only Memory) storing an arithmetic processing program, and a storage unit 6 based on the number of pulses within a certain time counted by the counter unit 61.
2, an arithmetic processing unit 63 for detecting the frequency and converting the detected frequency into a pulse signal corresponding to the concentration of the DUT, and transmitting control commands from the arithmetic processing unit 63 to respective control lines LX, LY, LZ. each analog switch X through, Y, a control port 64 for controlling the connection mode of the switches is supplied to the Z, parallel input port for outputting a pulse signal P ₀ and the strobe signal STR from the arithmetic processing section 63 (I / O port) 65.

The operation of the C-MOS type Schmitt inverters 51 and 52 will be briefly described.
Both Schmitt inverter has two threshold voltage of the high level of the threshold voltage V _TH and a low-level threshold voltage V _TL, when the input voltage is lower than the threshold voltage V _TH of the high levels generates an output voltage V _H of the high-level When the input voltage reaches the high-level threshold voltage V _TH , the output voltage switches from the high level V _H to the low level V _L , and keeps the low level until the input voltage drops to the low-level threshold voltage V _TL. and holding the output voltage V _L, the input voltage is an output voltage when the drop of the low-level threshold voltage V _TL operates to switches from the low level V _L to the high level V _H. Therefore, C
From the R oscillation circuit 50, a pulse voltage having a cycle corresponding to the charging and discharging of the capacitance of the capacitance element C1 or the series circuit of the capacitance element C1 and the sensor GS is output.

The pulse signal P ₀ and the strobe signal STR output from the parallel I / O port 65 of the microcomputer 60 are converted to analog voltage signals by a simple digital-to-analog converter which consumes very little current as shown in FIG. Is sent to the operational amplifier OP of the constant current circuit 11 of FIG.

The parallel I /
O port 65, in this embodiment, the pulse signal P ₀ corresponding to the concentration of the object of the water content and the like in the crude oil are output at fixed intervals, and output the strobe signal STR the same period at the same time. The pulse signal P ₀ is a diode D11 and a resistor R
11 and stored in the capacitor C11. That is, the capacitor C11 is charged with the electric charge through the resistor R11 only during the section where the pulse output voltage is at a high level. The diode D11 is a diode for preventing a reverse current for preventing the charge stored in the capacitor C11 from being discharged when the pulse output is at a low level.

On the other hand, the strobe signal STR is supplied to a first one-shot multivibrator MM1. Since the first one-shot multivibrator MM1 is activated when the strobe signal STR changes from a high level to a low level, that is, when it falls, the output of the first one-shot multivibrator MM1 is low when the strobe signal STR is supplied. Therefore, the same operation is performed (however, the operation is performed when the output of the first one-shot multivibrator MM1 changes from the high level to the low level). The output of the second one-shot multivibrator MM2 is also at the low level. Therefore, the first and second switches SW1 and SW
2 is in the off state as shown.

Now, assuming that the pulse width of the pulse signal P ₀ is t 1 (high-level time) and the voltage value at the high level is V, 1
Assuming that the capacitor C11 is charged by the two pulses and its voltage becomes Vc, the following equation is established.

Vc = V (1−e− ^{t1 / C11 · R11} ) (1) ^{Assuming that} t1 << C11 · R11, the above equation (1) can be expressed as follows.

Vc = V (t1 / C11 · R11) (2) When N pulses are output in one cycle, if it is assumed that Expression (2) is similarly satisfied, the voltage of the capacitor C11 is obtained. Vc1 can be expressed by the following equation.

Vc1 = V (Nt1 / C11 · R11) = N (Vt1 / C11 · R11) (3) Accordingly, the voltage Vc1 proportional to the pulse number N is accumulated in the capacitor C11.

When N pulses are output, the strobe signal STR changes from a high level to a low level. The falling of the first one-shot multivibrator MM
1 is detected, and one pulse Vs1 having a pulse width of time constant t2 = R12 · C12 is output. Due to the output pulse Vs1 from the one-shot multivibrator MM1, the first switch SW1 is turned on for a time t2, and a part of the charge stored in the capacitor C11 is transferred to the capacitor C14. Assuming that the voltage of the capacitor C14 at that time is Vc2, the total charge Q is as follows: Q = C11 · Vc1 = (C11 + C14) · Vc2 (4), and if C11 >> C14, Vc2 = Vc1. This means that the charging voltage Vc1 of the capacitor C11 has been transferred to the capacitor C14 as it is.

Since the capacitance of the capacitor C14 is very small, the voltage of the capacitor C14 changes due to the leakage current of the first switch SW1, the capacitance between the contacts, the input impedance of the amplifier circuit AMP, and the influence of the bias current. Care must be taken in their selection. For example, it is necessary to select a switch having the smallest leakage current between the contacts and the smallest capacitance between the contacts.

Also, a one-shot multivibrator M
It is also necessary to take sufficient time such that the time during which the voltage of the capacitor C14 changes by minimizing the time of the pulse width t2 of M1. For example, assuming that the voltage Vc2 of the capacitor C14 in the previous cycle is Vc2 >> Vc1, when the first switch SW1 is in the ON state, the total charge Q 'of the capacitors C11 and C14 becomes the first charge.
C when the switch SW1 is turned on.
11, assuming that the voltage of C14 is Vc3, Q '= C11 · Vc1 + C14 · Vc2 = (C11 + C14) · Vc3 (5) In this case, too, in order to hold the voltage of the capacitor C11 by the capacitor C14, That is, Vc1
In order to satisfy = Vc3, it is necessary to use in a voltage range (Vc1 to Vc2) in which C11.Vc1 >> C14.Vc2 is satisfied.

However, for example, when the measurement is performed continuously, the value does not change suddenly but changes gradually. Therefore, it is not always necessary to satisfy the above equation (5). Only the condition of> C14 may be satisfied.

First one-shot multivibrator M
When the output pulse of M1 falls, the first switch SW
1 is turned off, and at the same time, the second one-shot multivibrator MM2 operates, and the time constant t3 = R13 · C
One pulse Vs2 having a pulse width of 13 is output. The output pulse Vs2 from the one-shot multivibrator MM2 turns on the second switch SW2 for the time t3, the electric charge charged in the capacitor C11 is rapidly discharged, and the voltage of the capacitor C11 becomes 0V. This is because the capacitor C1 is output by the pulse output of the next cycle.
Since 1 is recharged, the zero point is corrected. It should be noted that the first switch S
Since the second switch SW2 is turned on at the same time when W1 is turned off, there is a possibility that the charge of the instantaneous capacitor C14 is discharged by this operation. Therefore, it is preferable to insert, for example, a CR delay circuit in a stage preceding the control line for the second switch SW2. As with the first switch SW1, it is necessary to select the second switch SW2 that has the smallest leakage current between the contacts and the smallest capacitance between the contacts.

The above-mentioned signal STR, the waveform of P _0, the one-shot multivibrator MM1, MM2 of the output waveform V
FIG. 6 shows s1, Vs2 and voltage waveforms Vc1, Vc2 of the capacitors C11, C14.

The analog signal Vc2 converted by the simple digital-analog converter in this manner is amplified to an appropriate size by the amplifier circuit AMP, and is amplified by the constant current circuit 11
Is supplied to one input (+) of the operational amplifier OP.

As described above, the information detected by the sensor is represented by C
The signal is converted into a pulse signal by the R oscillation circuit 50, the frequency of the pulse signal is detected by the microcomputer 60, and converted into a binary pulse signal corresponding to the concentration of the object to be measured such as the amount of water, which is output at regular intervals. However, if this pulse data is configured to be directly converted to an analog voltage output using a simple digital-to-analog converter having an extremely simple circuit configuration, the circuit configuration of the terminal device is greatly simplified.
Therefore, it is possible to reduce the size and cost,
The current consumption is extremely reduced. By the way, the current consumption of the conventional digital-analog converter is several mA to several tens mA, whereas the digital-analog converter of this example is less than 1 mA at the maximum. Thus, by adopting the configuration of this specific example, there are remarkable effects such as greatly increasing the environmental resistance stability of the terminal device, and further improving the explosion-proof safety.

In the above embodiment, the case where the present invention is applied to a petroleum plant has been mainly described. However, it goes without saying that the information transmission system according to the present invention is not limited to this. In addition, not only information such as the amount of water in crude oil, but also the concentration of water in the gas phase such as humidity, the concentration in the liquid phase such as the amount of water in lubricating oil, and various other gases and liquids. The present invention is also applicable to measuring the concentration of a certain component. Further, the above-described embodiments are merely examples of the present invention, and the circuit configuration, elements used, and the like can be arbitrarily changed as necessary.

[0044]

As described above, according to the information transmission system of the present invention, it is not necessary to provide a double constant current circuit in the terminal equipment, and it is possible to reliably prevent the occurrence of measurement errors. Therefore, the measurement accuracy is increased, and the circuit configuration can be simplified, so that the size and cost can be reduced, and the current consumption can be significantly reduced.
As a result, there is a remarkable effect that the environmental stability is greatly increased and the explosion-proof safety can be further improved. Furthermore, it is possible to cope with the case where the detection output of the sensor is digital data. In this case, the circuit configuration can be simplified by using a microcomputer with low current consumption, a simple digital-analog converter, etc. And cost reduction, and the current consumption can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing a basic configuration of an embodiment of an information transmission system according to the present invention.

FIG. 2 is a circuit diagram showing a specific example of a CR oscillation circuit including a sensor applicable to the information / voltage conversion and voltage amplification circuit of the information transmission method of the present invention shown in FIG. 1 as an oscillation frequency determining element.

3 is a circuit diagram showing another specific example of a CR oscillation circuit including a sensor applicable to the information / voltage conversion and voltage amplification circuit of the information transmission method of the present invention shown in FIG. 1 as an oscillation frequency determining element.

4 is a circuit configuration diagram showing still another specific example of the CR oscillation circuit including a sensor applicable to the information / voltage conversion and voltage amplification circuit of the information transmission system of the present invention shown in FIG. 1 as an oscillation frequency determining element. is there

FIG. 5 is a simplified digital type used in the information / voltage conversion and voltage amplification circuit of the information transmission system of the present invention shown in FIG.
FIG. 3 is a circuit diagram illustrating a specific example of an analog converter.

FIG. 6 is a waveform chart showing voltage output in each part of the digital-analog converter of FIG.

FIG. 7 is an overall configuration diagram showing an example of a basic configuration of a conventional information transmission system.

FIG. 8 is an overall configuration diagram showing another example of the basic configuration of the conventional information transmission system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Information / voltage conversion and voltage amplification circuit 11 Constant current circuit 20 Transmission cable 21 Measurement load 22 Power supply 50 CR oscillation circuit 51, 52 Schmitt inverter 60 Microcomputer OP Operational amplifier R Resistance Tr Transistor AMP Amplifier circuit MM1, MM2 One shot multi Vibrator SW1, SW2 switch

Claims (3)

(57) [Claims] An information / voltage conversion means for converting information from the sensor into an analog voltage, and a voltage signal from the information / voltage conversion means as a current signal. A terminal device including a voltage / current conversion unit for converting, a transmission unit for transmitting a current signal from the terminal device to a measurement load, and the information / voltage conversion unit and the voltage / current conversion unit through the transmission unit. A power supply for supplying a predetermined operating voltage, wherein the operating voltage from the power supply is supplied to the voltage / current converting means and the information / voltage converting means through an impedance element connected to the current amplifying means of the voltage / current converting means. An information transmission method characterized in that the information transmission method is supplied to a means. 2. The information / voltage conversion means detects a CR oscillation circuit including the sensor as a frequency determining element, a frequency of an oscillation output of the oscillation circuit, and uses the detected frequency as information of the device under test. A control signal for converting the pulse signal voltage output from the calculation control means into a voltage signal by accumulating the pulse signal voltage output from the calculation control means for each cycle. 2. An information transmission system according to claim 1, further comprising digital-analog conversion means for amplifying the signal and outputting the signal as an analog voltage signal. 3. The sensor according to claim 2, wherein the capacitance component, the electric resistance component, or both components change in accordance with the concentration of a certain component in a gas phase or a liquid phase. Information transmission system.