Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
  • G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
  • G01N27/223—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance for determining moisture content, e.g. humidity
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/26—Oils; viscous liquids; paints; inks
  • G01N33/28—Oils, i.e. hydrocarbon liquids
  • G01N33/2835—Oils, i.e. hydrocarbon liquids specific substances contained in the oil or fuel
  • G01N33/2847—Water in oil

Definitions

• the present invention relates to a measuring device for detecting the amount of water contained in various liquids such as lubricating oils such as insulating oils and refrigerators, solvents, fuels and petroleum products such as petrochemical raw materials, that is, a water concentration.
• liquid moisture measuring device for detecting the amount of water contained in various liquids such as lubricating oils such as insulating oils and refrigerators, solvents, fuels and petroleum products such as petrochemical raw materials, that is, a water concentration.
• electrical insulating oil is dehydrated by a suitable means such as a dehydrating agent or vacuum oil purifier when shipped at a refinery because it does not like to contain moisture in the oil.
• a suitable means such as a dehydrating agent or vacuum oil purifier when shipped at a refinery because it does not like to contain moisture in the oil.
• aluminum anodic oxide film type moisture sensors have been studied as sensors suitable for such products.
• the feature of this sensor is that it is compact and can be used directly in liquid.
• the detection principle of the aluminum anodic oxide film type moisture sensor is that when a sensor is placed in the liquid to be detected, the moisture adsorbs to the interface between the sensor and the liquid, generating electric capacitance.
• the capacitance corresponds to the amount of adsorbed water molecules, and the amount of adsorbed water corresponds to the concentration of water in the liquid. This sensor can be used to detect water in the liquid.
• the output signal of such a moisture sensor for example, an electric signal such as capacitance, resistance, impedance, etc., is converted into another parameter (phase, frequency, voltage, etc.) corresponding to that in a certain electric circuit. ), And its output form is an electrical signal, either analog or digital, and is ultimately converted to concentration (PPm) by appropriate conversion means.
• the problem with this series of processes is that the relationship between the magnitude of the capacitance generated from the moisture sensor and the moisture concentration is not linear. In other words, the temperature varies depending on the temperature, and the relationship differs for each sensor due to the difference in characteristics between the sensors.
• a data table of capacitance C and moisture concentration W is created, or another electric signal J obtained by converting the capacitance C and a data table of moisture concentration W are created. And write them to ROM and incorporate them into the measurement circuit.
• the PGM (programming) of the computer the water concentration W corresponding to the signal C or J is appropriately extracted and processed by an appropriate electric circuit to display the concentration (PPm).
• an object of the present invention is to provide a low-cost liquid moisture measuring apparatus that is small, has high accuracy, and is easy to calibrate.
• Another object of the present invention is to eliminate a measurement error due to a variation in the quality of a capacitance or a temperature dependency provided in a detection circuit for protecting a moisture sensor, and to eliminate a temperature dependency.
• An object of the present invention is to provide a liquid moisture measuring device that enables highly accurate measurement.
• Still another object of the present invention is to simplify the circuit configuration of a terminal device, to reduce the size and cost, to reduce the current consumption, and to reduce the current consumption in the device in a transient state when the device is powered on.
• Mic mouth Computer malfunctions and damage to the power supply circuit can be prevented, and abnormal current values exceeding the original transmission amount can be prevented to prevent damage to measuring equipment.
• Information transmission method Another object of the present invention is to provide a liquid moisture measuring device.
• the present invention provides a capacitance type moisture sensor for detecting moisture in a liquid, and outputs the capacitance type moisture sensor according to a change in capacitance of the capacitance type moisture sensor.
• a sensor signal processing section having a CR transmitting circuit whose frequency changes, and an arithmetic processing for converting an output frequency (F) from the sensor signal processing section into a moisture concentration (L) according to the following arithmetic expression (1)
• a moisture value display section for displaying a moisture concentration output from the microcomputer. is there.
• the output frequency (F) from the sensor processing unit is converted into a water concentration by the following equation (2).
• the constants A, B, 0 are externally manipulated.
• the data relating to the constants X, ⁇ , and ⁇ ⁇ are stored in the storage unit of the microphone computer, and are input to the above-described arithmetic expression (1) or (2) when the power is turned on. Is calculated.
• the sensor signal processing unit includes a protective capacitance provided in series with the capacitance-type moisture sensor, and a change in capacitance value of the moisture sensor. Means for switching between a circuit configuration in which the oscillation frequency changes in accordance with the oscillation frequency and a circuit configuration in which the oscillation frequency is determined by the protection capacitance, and the difference between the oscillation frequencies obtained in both circuit configurations is determined.
• the water concentration (L) can be calculated based on the oscillating frequency obtained by the measurement.
• a terminal device including: an information Z-voltage conversion circuit that converts the voltage into a current signal; and a voltage-Z current conversion circuit that converts a voltage signal from the information Z-voltage conversion circuit into a current signal.
• FIG. 1 is a schematic configuration diagram of one embodiment of a liquid moisture measuring apparatus according to the present invention.
• FIG. 2 is a schematic configuration block diagram of an embodiment of the apparatus for measuring water in liquid according to the present invention.
• FIG. 3 is a flow chart showing the operation procedure of one embodiment of the apparatus for measuring water in liquid according to the present invention.
• FIG. 4 is a diagram showing an example of a Langmuir-type adsorption isotherm.
• Figure 5 shows an example of the relationship curve between the liquid moisture concentration and the capacitance.
• Figure 6 shows the characteristics of the moisture sensor.
• Figure 7 shows the characteristics of the moisture sensor.
• Fig. 8 is a diagram showing the relationship between the liquid moisture concentration and the output frequency of the moisture sensor.
• FIG. 9 is a diagram showing the relationship between the output of the liquid moisture measuring apparatus according to the present invention and the value actually measured by the Karl Fischer method.
• FIG. 10 is a diagram illustrating the principle of the calibration method according to the present invention.
• FIG. 11 shows the output of the liquid moisture measuring apparatus according to the present invention before and after calibration in the liquid moisture measuring apparatus according to the present invention. Is a diagram showing the relationship between and the measured value by the Karl Fischer method.
• FIG. 13 is a circuit configuration diagram showing one embodiment of a moisture content measuring device provided with a moisture sensor according to the present invention.
• FIG. 14 is an overall configuration diagram showing a basic configuration of an embodiment of an information transmission method according to the present invention.
• FIG. 15 is a circuit configuration diagram illustrating the microcomputer portion shown in FIG.
• FIG. 16 is a circuit diagram showing a specific example of a simplified digital-to-analog converter used in the information / voltage conversion and voltage amplification circuit of the information transmission method of the present invention shown in FIG.
• FIG. 17 is a waveform diagram showing the voltage output at each section of the digital-to-analog converter of FIG.
• the liquid moisture measuring apparatus of the present invention is basically a capacitance type for detecting the amount of water in oil, for example, an aluminum anodic oxide film.
• a sensor signal processing unit 10 having a moisture sensor S such as a mold sensor and a CR transmission circuit whose output frequency changes in accordance with a change in the capacitance of the capacitance type moisture sensor S 10 And a micro computer 20 having an arithmetic processing unit for converting the output frequency (F) from the sensor signal processing unit 10 into a moisture concentration (L) according to a predetermined arithmetic expression.
• a moisture value display section 30 for displaying the moisture concentration output from the micro computer 20 of the present invention.
• the present inventors believe that the amount of water adsorption affects the dielectric constant that governs the capacitance in a range where the water concentration in the oil is low, and the relationship between the amount of water in the oil and the capacitance is also a Langmuir type. We thought that the curve might become ,
• the output capacitance (C) of the moisture sensor in the oil rises from the low concentration region as shown in FIG. 5 and gradually asymptotically as shown in FIG. Approaches a certain value.
• This phenomenon is completely different from moisture detection in the gas phase. This is probably because multi-molecule adsorption is performed in the gas phase on the sensor surface, while single-molecule adsorption is performed in oil.
• n number of adsorption sites occupied by one oil molecule when one water molecule occupies one adsorption site
• N total number of adsorption sites
• K Equilibrium constant In the above formulas (4) and (5), A 2 is the oil activity, but it is 1 because it is practically abundant, and A, is the water activity in the oil. Although the water concentration is low, it can be replaced with the concentration L.
• the capacitance C actually obtained by the LCR meter measurement is, as shown in Fig. 5, the Xc component that changes with the moisture concentration, and the sensor when the moisture concentration is zero.
• XB component (base volume), and a crotch from X s components ing corresponding to the X c component at saturation is understood to have.
• the surface coverage e xc / Xs (this is based on the assumption that the amount of change in capacitance Xc is constant when the dielectric constant of water at the oil-Z solid interface is constant.
• (9) can be rewritten into the above equation (3), which has the same form as the Langmuir-type adsorption isotherm. If the Lang If mu-type single molecule adsorption is established, a linear relationship should be obtained by plotting LX c with respect to L in this equation (3).
• the present invention measures the concentration of a component that performs Langmuir-type single molecule adsorption at the interface between individual Z liquids and also has a large difference in dielectric constant from the liquid, in addition to water in oil, for the above-described reason.
• the magnitude of the equilibrium constant K differs depending on the individual difference of the sensor and the type of oil. If the results of experiments, for example, oil is mineral oil, 0.0 1 5 to 0.0 5 1 der is, 1 in synthetic lubricating oils such or ester. 5 X 1 0- 3 ⁇ 5 . 4 X 1 0 — 3 .
• FIG. 1 shows a sensor signal processing unit 10 having a conversion circuit to which a shunt circuit is applied.
• a CR transmission circuit in principle, and in this embodiment, for example, a C-M0S type shunt inverter 11 and A fixed resistor R, which is a pulse frequency determining element connected between the input and output of the inverter 11 (feedback circuit), and a capacitance element C connected to the input side of the inverter 11 And a capacitive sensor S, which is another pulse frequency determining element connected in series between the capacitive element C and the input side of the shunt inverter 11. And outputs a pulse signal whose frequency (F) fluctuates in response to changes in the capacitance (C) of the sensor S caused by the amount of water in the oil.
• a C-M0S type shunt inverter 11 and A fixed resistor R which is a pulse frequency determining element connected between the input and output of the inverter 11 (feedback circuit), and a capacitance element C connected to the input side of the inverter 11
• a capacitive sensor S which is another pulse frequency determining element connected in series between
• the resistor R 'connected in parallel with the sensor S is for preventing the DC voltage component from being applied to the sensor S.
• a sensor made of aluminum oxide or the like is used as a moisture sensor. Therefore, when a DC voltage component is applied, deterioration of sensor characteristics due to polarization, dielectric breakdown, etc. This is to prevent this from occurring because it tends to occur.
• the pulse signal from the pulse generation circuit is converted into an output voltage of the same frequency, the pulse waveform of which is inverted by a second C-M0S type Schmitt inverter 12, and Supplied to computer 20.
• the micro computer 20 counts the frequency F from the sensor signal processing unit 10 and the signal from the count unit by a predetermined arithmetic expression. It has an arithmetic processing unit that calculates and converts to the water concentration PP m.
• both of the Schmitt invertors have a high threshold voltage V ⁇ H and a low threshold voltage VT.
• the CR oscillation circuit outputs a periodic pulse voltage corresponding to the charging and discharging of the capacitance of the series circuit of the capacitance element C ′ and the sensor S.
• the relationship between the frequency output from the conversion circuit 10 and the capacitance in the present embodiment is represented by the following equation (10).
• X t, X 2 for example high density (L,), medium concentration (L 2), low concentration (L 3) frequency value F obtained each actually measured at a water concentration of 3 points ,, F 2 , and F a can be obtained by substituting into the equation.
• L high density
• L 2 medium concentration
• L 3 low concentration
• F frequency value
• FIG. 9 shows the results of detection and measurement of the amount of water by the apparatus for measuring water in liquid according to the present invention, and the results of measurement by the Karl Fischer method. It can be seen that there is a correlation between the two measurement results.
• the liquid moisture measuring apparatus inputs the measured values L i, L 2 , L 3 , F,, F 2 , and F 3 to obtain the above formula (1 2 )
• equation (1 2) instead of equation (1 2), the following equation (1
• L is the liquid water concentration (PPm)
• the characteristics of the measuring device move from curve b 'to curve 1.
• the characteristics of the measuring device move from curve 2 to curve 2.
• the characteristic of the measuring device is that the curve 2 moves in parallel and moves to the target curve a '. This eliminates the gap between the measured moisture concentration and the display of the measuring device. That is, the relationship between the measured moisture concentration and the display of the measuring device is corrected so that b matches the target a.
• the liquid moisture measuring apparatus of the present invention can function extremely effectively.
• the constants A, B, and 0 in the above equation (13) are calculated values from the water concentration at any two points in the water concentration range to be measured and the output frequency of the liquid water measuring device at that time. Obtainable. That is, each of the moisture concentration and frequency L a, L b, F a , when the F b, the following equation (1 4).
• X, Y is zeta, the cormorants I described above, any water concentration, such as high density (L,), medium concentration (L 2), and low density (L 3), that the Kino frequency It is a constant related to the type of liquid calculated from the output, F 2 , and F 3, and is obtained by the following equation (15), as described above.
• Fig. 11 and Fig. 12 show the relationship between the measured moisture concentration by Karl Fischer method and the display of the detector when measuring the translucent oil, ester, etc. by applying the above calibration method. Is shown. From these figures, it was found that the measured value and the measured value by the Karl Fischer method were measured for a micro computer having an arithmetic processing unit including the calculation algorithm according to the above equation (13). By adjusting the numerical values so that the display on the device matches, and inputting the correction coefficients A, B, and 0 with the setting switches, the measuring apparatus of the present invention can be used. It can be suitably calibrated, and thus can be applied to water detection of various liquids.
• FIG. 3 shows an embodiment of a flow chart showing the operation procedure of the apparatus for measuring water in liquid according to the present invention.
• step 1 when the power of the device is turned on or reset (step 1), the device is initialized (step 2), and the arithmetic expression (12) or Is input by operating the setting switch 40 provided in the apparatus, or by inputting the X, Y, and of (13), or by inputting the constants L i and ⁇ stored in advance in R 0 ⁇ of the storage unit. It is calculated from L 2 , L 3 , F 1 , F 2 , and F 3 .
• the setting mode is necessary. If necessary, the constants ⁇ , ⁇ , and ⁇ are input using a setting switch 40 provided in the device. If you want to prevent the operator or the like from inputting constants from outside at this time, install an internal switch inside the device, and when this switch is OFF, use the external switch. Input can be disabled. Also, the setting mode can include alarm settings (HI, L0), and can be configured to generate an alarm when the moisture value is out of the allowable range.
• the setting mode can include the setting of the sample time, and if the setting of the constants A, B, 0 and the alarm has been completed or is not necessary, the setting of the sample time is then performed. Do it (Step 5). For example, the sample time is 1 second.
• step 6 measurement is performed in step 6, and the number of pulses per second is sent from the sensor processing unit 10 to the micro computer 20.
• a signal of number (F) is input, and the frequency is counted at the counter.
• the oil temperature is measured with a temperature sensor (such as a thermistor) at the same time as the water content measurement, and the measurement result is input to the micro computer 20 and Temperature correction of the signal from one signal processing unit 10 is performed (step 7).
• a temperature sensor such as a thermistor
• the arithmetic unit of the micro computer 20 is operated by using the arithmetic expression (12) or (13) (step 8), and the sensor signal processing unit 10 is operated.
• the signal of the moisture sensor S input to the computer 20 via the controller 20 is finally displayed on the moisture value display section 30 by the moisture concentration (PPm) (Step 9).
• all of the constants A, B, / 3 and X, Y, ⁇ ⁇ may be input by external operation, or all may be stored in advance in the storage section of the micro computer.
• the calculation unit may be automatically set when the power is turned on so that the calculation can be performed.
• the apparatus for measuring moisture in liquid uses the CR transmission circuit according to the change in the capacitance of the capacitance-type moisture sensor for detecting the moisture in the liquid. And the signal is calculated by a micro computer to output the water concentration in PPm, so that it is compact, highly accurate, and easy to calibrate. Yes, it has the feature of low cost.
• Example 2
• the temperature dependency of the sensor signal processing unit 10 is particularly eliminated to detect the moisture content in the subject with high accuracy.
• FIG. 13 is a circuit configuration diagram of the moisture measuring apparatus of the present embodiment.
• the moisture measuring apparatus of the present embodiment has a sensor signal processing section basically serving as a CR oscillation circuit, that is, a moisture detecting circuit 10 as in the measuring apparatus described with reference to FIG. .
• the moisture detecting circuit 10 is provided between the input / output of the C-M0S type shunt-inverter 11 and the inverter 11 as described above.
• the fixed resistor R which is a pulse frequency determining element inserted in the feedback circuit, and the other pulse frequency determining element, which is connected between the input side of the inverter 11 and the ground.
• the capacitive sensor S generates a pulse signal having a frequency related to the amount of water in the subject. That is, this pulse generation circuit outputs a pulse signal whose frequency (F h ) fluctuates as the capacitance value C of the sensor S changes according to the change in the amount of water.
• Second C one MOS type shoe mitt up inverter 1 2 is Ri Monodea inverting the pulse waveform of the pulse generation circuit or these pulse signals, the output frequency (F h) does not change.
• a resistor R ' is connected in parallel with the sensor S, and a protective capacitance C' is connected between the sensor S and the ground.
• a protective capacitance C' is connected between the sensor S and the ground.
• the output frequency (F h ) from the moisture detection circuit 10 is
• the output frequency (F) from the moisture detection circuit 10 is sent to the micro computer 100, and the count within the micro computer 100 is performed.
• the count is performed by the unit 101 and input to the memory unit 102 and the arithmetic processing unit 103.
• a switch means for example, an on / off switch SW is connected in parallel with the sensor S. That is, one end of the switch SW is connected to the input side of the inverter 11, and the other end is connected to a connection between the sensor S and the capacitance C ′.
• the switch SW is connected to a control port 104 of the micro computer 100, and its on / off is controlled.
• the moisture detection circuit 10 has a circuit configuration in which the oscillation frequency changes in accordance with a change in the capacitance value C of the moisture sensor S by switching the switch SW, and the protection circuit. Switch to a circuit configuration in which the oscillation frequency is determined by the You.
• This pulse generation circuit 10 does not operate as a device for use, and outputs a pulse signal of a frequency (F.) by a resistor R and a capacitance C ′. This output frequency (F.)
• the output frequency (F 0) from the moisture detection circuit 10 is sent to the micro computer 100 and the counter section 2 in the micro computer 100 is sent. It is counted at 1 and input to the storage unit 102 and the arithmetic processing unit 103.
• the output frequency (F h ) from the previous moisture detection circuit 10 stored in the storage unit 102 is referred to as an arithmetic processing program stored in the storage unit 102.
• the output frequency (F.) is called and the subtraction processing of both is performed.
• the frequency (F) after the arithmetic processing from the micro computer 100 is
• this frequency (F) from the arithmetic processing unit 103 is input to the computer 20 shown in FIG.
• the water content (L) corresponding to (F) is calculated and output.
• the output frequency (F) after the arithmetic processing does not include the frequency component due to the capacitance C ′, that is, the capacitance C Therefore, the influence of the capacitance C ′ can be completely eliminated from the moisture content output data.
• the CR oscillation circuit includes a circuit configuration in which the oscillation frequency changes in accordance with a change in the capacitance value of the moisture sensor, and a protection electrostatic device. Switch to the circuit configuration where the oscillation frequency is determined by the capacitance, and calculate the amount of water in the subject based on the difference between the oscillation frequencies obtained by both circuit configurations, thus protecting the moisture sensor. This eliminates measurement errors due to variations in quality or temperature dependence of the protective capacitance provided in the water content detection circuit, and enables highly accurate measurement without temperature dependence. .
• liquid moisture measuring apparatus described in the first embodiment, a liquid moisture equipped with an information transmission method for transmitting a signal from a sensor installed at a remote location to a measuring instrument via a transmission cable is used.
• An embodiment of the measuring device will be described.
• FIG. 14 shows a basic configuration of the information transmission method according to the present embodiment.
• a sensor S which constitutes a terminal device, is provided.
• the sensor-signal processing unit 10 and the micro computer 20 obtain the water content (concentration L) in the liquid.
• the configurations and operations of the sensor signal processing unit 10 and the micro computer 20 are the same as those described in the first embodiment.
• the detected moisture concentration information L is input to the information Z voltage conversion and voltage amplification circuit 110, and after the moisture concentration information L is converted into a voltage, it is amplified to a voltage V of an appropriate magnitude. You.
• the voltage V corresponding to this information L is input to the voltage-Z current conversion circuit, that is, the constant current circuit 120.
• the constant current circuit 120 has an operational amplifier 0 P, a transistor Tr, and a resistor R connected to the collector of the transistor Tr. According to this, the protection resistor RR is inserted between the emitter of the transistor Tr and the ground.
• the voltage V corresponding to the information L from the information voltage conversion and voltage amplification circuit 110 is supplied to one input (+) of the operational amplifier 0 P of the constant current circuit 120, and the output signal from the operational amplifier 0 P is the current amplification I by the preparative La Njisuta T r, the amplified output and it is removed from the E Mi jitter DOO La Njisuta T r through the resistor R R.
• a current signal corresponding to the information L is transmitted from the terminal device to the transmission cable 20. Through 0, it is supplied to a current measuring device such as the moisture display section 30 of the central information monitoring system, that is, the measuring load 210, and the information L is displayed.
• the power supply voltage V p applied to the constant current circuit 120 via the transmission cable 200 is equal to the operating voltage V dd of the information / voltage conversion and voltage amplification circuit 110.
• This is applied via the resistor R of the constant current circuit 120. Therefore, the current I flowing from the power supply 220 through the transmission cable 200 flows through the resistor R of the constant current circuit 120 as it is, and then flows into the transistor T of the constant current circuit 120. r and the current I flowing through the protection resistor R R, and the current I 2 flowing through the load of the information-to-voltage conversion and voltage amplification circuit 110.
• both circuits 1 1 0 and 1 2 0 flow current (I, + 1 2) flows through the transmission cable 2 0 0 on the measuring load 2 1 0 Te Tsutsu, and this Returns to the power supply 2 2 0 become.
• both the current I flowing through the transistor Tr of the constant current circuit 120 and the current I 2 flowing through the load of the information-to-voltage conversion and voltage amplification circuit 110 are resistances. If the flow through R Runode, Ri had information Z voltage conversion and load variation in the voltage amplifying circuit 1 1 0, the load current I 2 flowing by Ri to the circuit 1 1 0 information is varied, a constant by the fluctuation The load current I, flowing through the transistor Tr of the current circuit 120 increases and decreases, and the current I transmitted from the terminal device to the measurement load 210 of the central information monitoring system (i.e., I, + I 2 ) is always kept constant.
• the present embodiment it is possible to prevent a measurement error from occurring without making the circuit configuration complicated by providing a double constant current circuit in the terminal device. Therefore, measurement accuracy is improved. Also 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, the environmental stability can be greatly increased, and the explosion-proof safety can be further enhanced. In addition, it can handle the case where the sensor's detection output is digital data, and it uses micro-computers, digital-to-analog converters, and analog-to-digital converters that consume less current. IC chips, etc., can be used.
• a protection resistor R R is inserted between the emitter of Tr and ground.
• the protective resistor R R is an action to prevent the flow of excessive current in the transient state when device power is turned on preparative La Njisuta T r. Therefore, the sizes of the protection resistor R R and the resistor R can be determined as follows.
• the operating voltage V dd of the circuit 110 fluctuates depending on the transmitted current I, and is expressed by the following equation.
• V d d V p-R * I
• V dd the required minimum voltage value of V dd
• I MAX the maximum transmitted current value
• V d M I N V-R * I M A X
• the protection resistance R R is set so as to satisfy the following conditions. You.
• V p 5.0 V
• V dd 4.5 V
• IMAX 20 mA
• the insertion of the protection resistor RR having the above-mentioned size effectively prevents excessive current from flowing through the transistor Tr and the resistor R when the power is turned on.
• the protection resistor R R prevents overcurrent from flowing in the device.
• the oscillation output from the sensor signal processing unit 10, that is, the frequency signal F is sent to the micro computer 20, where it is calculated.
• the oscillation frequency is detected by processing, and the detected frequency is used as a pulse signal P corresponding to the concentration L of the device under test. And output.
• the micro computer 20 includes a counter section 21 for counting the number of pulses of the input frequency signal F, and an R 0 M (reader) storing an arithmetic processing program.
• the frequency is calculated from the number of pulses within a certain time counted by the storage unit 22 including the memory (d-only) and the counter unit 21 according to the program of the storage unit 22.
• An arithmetic processing unit 23 for detecting and converting this detection frequency to a pulse signal corresponding to the concentration of the DUT, and a control signal from the arithmetic processing unit 23 is sent to the sensor signal processing unit 10 through each control line.
• a control port 24 for supplying analog switches and the like to control the connection of these switches, and a pulse signal P from the arithmetic processing unit 23.
• a parallel input / output port (1-0 port) 25 for outputting a strobe signal STR.
• the operation mode of the C-MOS type shunt inverters 11 and 12 of the sensor signal processing unit 10 described above is as described above, and the operation from the CR oscillation circuit is static. Capable of charging and discharging the capacitance of the series circuit of capacitance element C 'and sensor S A periodic pulse voltage is output.
• the strobe signal STR is converted to an analog voltage signal by a simple digital-analog converter with extremely low current consumption shown in FIG. 16 and converted to a constant current circuit 120 in FIG. It is sent to the operational amplifier OP.
• the pulse signal P corresponding to the water concentration in the oil is provided. Are output at regular intervals, and at the same time, a strobe signal STR having the same period is output.
• Norse signal P. Is stored in the capacitor CI 1 via the diode D 11 and the resistor R 11. That is, only during the period when the pulse output voltage is at the high level, the capacitor C I 1 is charged with the electric charge through the resistor R 11.
• the diode D 11 is a diode for preventing a reverse current for preventing the charge stored in the capacitor C 11 from being discharged when the pulse output is at a low level.
• the strobe signal STR is supplied to the first shot multi-noiser MM 1. Since the first short-circuit multivibrator MM1 is activated when the strobe signal STR changes from a high level to a low level, that is, when the strobe signal STR falls, the strobe signal MM1 is activated. When STR is provided, its output is low, and therefore performs the same operation (except that the output of the first short-cut multivibrator MM1 is changed from high to low). (Activates when the level changes to low level.) The output of the second short-circuit multivibrator MM2 is also low. Because of the level, the first and second switches SW1 and SW2 are in the off state as shown.
• the pulse width of the pulse is t 1 (high level time)
• the voltage value at the high level is V
• the capacitor C 11 is charged by one pulse to change the voltage. Assuming V c, the following equation holds.
• V c V (i- e - tl / cll - R 11 ) ( 3-1 ) If 1 ⁇ C 11 ⁇ R 11, the above equation ( 3-1 ) can be expressed as follows. You.
• V c V (t l / C l l-R l l) (3-2)
• the voltage Vc1 of the capacitor C11 can be expressed by the following equation, assuming that Equation (32) holds.
• V c l V (N t l / C l l-R l l)
• the strobe signal STR changes from the high level to the low level.
• the first switch SW1 is turned on for the time t2, and the capacitor C11 is charged. A part of the stored charge is transferred to the capacitor C14. Capacitor C at that time If the voltage of 14 is V c 2, the total charge Q is
• the capacitance of the capacitor C14 is very small, the leakage current of the first switch SW1, the capacitance between the contacts, and the input impedance and the bias current of the amplifier circuit AMP are determined. Careful attention must be paid to the selection of the capacitors C14, since the voltage of the capacitors C14 varies depending on the influence. For example, it is necessary to select a switch that has the smallest leakage current between contacts and the smallest capacitance between contacts.
• the output pulse Vs2 from the short-circuit multivibrator MM2 turns on the second switch SW2 for the time t3, and charges the capacitor C11. The charged charge is discharged rapidly, and the voltage of the capacitor C 11 becomes 0 V. This is to correct the zero point because the capacitor C 11 is recharged by the pulse output of the next cycle.
• the second switch SW2 when the first switch SW1 is turned off, the second switch SW2 is turned on at the same time as the first switch SW1 is turned off. There is a possibility that the charge of C14 may be discharged. Therefore, it is preferable to insert a delay circuit using, for example, a CR before the control line for the second switch SW2. Note that the second switch SW2 also has the smallest leakage current between the contacts, as with the first switch SW1. In addition, it is necessary to select one having a small inter-contact capacity.
• Figure 17 shows the output waveforms of the MM1 and MM2 and the voltage waveforms Vcl and Vc2 of the capacitors C11 and C14. Show.
• the analog signal Vc2 converted by the simple digital-to-analog converter in this way is amplified to an appropriate level by the amplifier circuit AMP, and the operational amplifier of the constant-current circuit 120 is amplified. Supplied to one input (+) of OP.
• the information detected by the sensor S is converted into a pulse signal by the CR oscillation circuit of the sensor signal processing unit 10, and the frequency of the pulse signal is detected by the micro computer 20. It converts it to a binary pulse signal (P.) corresponding to the moisture concentration (L), outputs it at regular intervals, and uses this pulse data with a simple digital-to-analog converter with an extremely simple circuit configuration. If it is configured to directly convert the analog voltage output to analog voltage output, the circuit configuration of the terminal equipment will be greatly simplified, and therefore, miniaturization and cost down will be possible, and the current consumption will be extremely low. Fewer. By the way, the current consumption of the conventional digital-to-analog converter was several mA to several 10 mA, while the digital-to-analog converter of this embodiment was less than 1 mA at the maximum. .
• the operating voltage of the terminal device for transmitting information from the sensor to the measuring device is increased by the current amplification of the voltage-Z current conversion circuit.
• the current signal as information from the voltage-to-Z current conversion circuit is transmitted from the terminal device to the measuring device via the protection resistor element connected to the current amplifying means.
• the circuit configuration of the terminal equipment can be simplified, the size and cost can be reduced, and the current consumption can be reduced. This prevents malfunctions of the micro computer and damage to the power supply circuit, and also prevents the transmission of abnormal values exceeding the original transmission volume, thereby avoiding damage to measuring equipment. it can.
• the apparatus for measuring moisture in liquid according to the present invention uses the CR transmission circuit according to the change in the capacitance of the capacitance-type moisture sensor for detecting the moisture in the liquid. And the signal is calculated by a micro computer to output the water concentration in PPm, so that it is compact, highly accurate, and easy to calibrate. Yes, it has the feature of low cost.
• Such an apparatus for measuring water in liquid according to the present invention can be used for measuring the amount of water contained in various liquids such as lubricating oils such as insulating oils and refrigerators, solvents, fuels and petroleum products such as petrochemical raw materials. It is suitably used as a measuring device for detecting concentration.

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• 1994
  • 1994-05-26 WO PCT/JP1994/000839 patent/WO1994028400A1/ja active Application Filing
  • 1994-05-26 DE DE4493593T patent/DE4493593T1/de not_active Ceased

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