KR101475710B1 - Capacitance press sensor - Google Patents

Abstract

The present invention relates to a capacitance pressure sensor. The capacitance pressure sensor has a correction value input terminal, to which a correction value for controlling output specifications is inputted, so that the output of the capacitance pressure sensor can satisfy various output specifications that customers require when the capacitance pressure sensor is shipped.

Description

[0001] Capacitance press sensor [0002]

The present invention relates to pressure measurement techniques, and more particularly to capacitive pressure sensors.

The pressure sensor converts the mechanical displacement generated by the pressure into an electric signal and outputs the electric signal. The pressure is measured by measuring the intensity of the electric signal outputted. A capacitive pressure sensor as disclosed in Korean Patent Publication No. 10-2001-0039983 (2001. 05. 15), etc., converts a mechanical displacement into a capacitance, outputs the capacitance, and the pressure is measured by detecting the capacitance change .

Capacitive pressure sensors have nonlinear characteristics to the applied pressure and are temperature-sensitive. Therefore, in order to satisfy various output specifications required by customers, the output specification of the capacitive pressure sensor at the time of delivery must be adjusted to the customer's requirements . Accordingly, the present inventor has studied a capacitive pressure sensor having an adjustment value input terminal to which an adjustment value for adjusting an output specification of a pressure sensor is inputted.

Korean Patent Publication No. 10-2001-0039983 (2001. 05. 15)

SUMMARY OF THE INVENTION The present invention has been made under the above-mentioned circumstances and has an object to provide a control apparatus for an internal combustion engine, which is capable of outputting an output of a capacitive pressure sensor when a capacitive pressure sensor is shipped, The present invention has been made in view of the above problems, and it is an object of the present invention to provide a capacitive pressure sensor capable of improving reliability.

It is still another object of the present invention to provide a capacitive pressure sensor capable of improving the sealing efficiency by forming a stepped portion in a groove into which an O-ring for sealing is inserted, thereby increasing the close contact surface of the O-ring.

According to an aspect of the present invention, there is provided a sensor module comprising: a sensor module to which a plurality of wires connecting a capacitive pressure sensor to a sensing signal are connected; A circuit part to which the wire is bonded; A connector having a terminal electrically connected to the circuit unit; A housing having an inlet hole through which the medium flows in one end and a space in which the sensor module is assembled in fluid communication with the inlet hole at the other end; The terminal comprising: a power input terminal; A ground terminal; An adjustment value input terminal to which an adjustment value for adjusting an output specification of the sensor module is inputted; A sensor output terminal for outputting an output value of the sensor module; .

According to a further aspect of the present invention, the housing is provided with a groove into which the O-ring for sealing is inserted, and the groove is formed with a step for increasing the contact surface of the O-ring.

According to a further aspect of the present invention, the O-ring is distorted such that the close contact surface is enlarged corresponding to the stepped portion.

According to a further aspect of the present invention, there is provided a sensor module comprising: a Cp output terminal for outputting an output value of a capacitance Cp formed by the main electrode of the sensor module; A Cr output terminal for outputting an output value of a capacitance Cr formed by the reference electrode of the sensor module; A common terminal which is a virtual ground terminal; .

The present invention provides an adjustment value input terminal to which an adjustment value for adjusting an output specification is input so that the output of the capacitive pressure sensor at the time of shipping the capacitive pressure sensor can satisfy various output specifications required by customers, There is an effect.

In addition, the present invention has an effect of improving the sealing efficiency by forming a stepped portion in the groove into which the O-ring for sealing is inserted to increase the close contact surface of the O-ring.

1 is a perspective view of a capacitive pressure sensor according to the present invention.
2 is a cross-sectional view of a capacitive pressure sensor according to the present invention.
3 is an exploded perspective view of a capacitive pressure sensor according to the present invention.
4 is a view showing an example of a sensor module of the capacitive pressure sensor according to the present invention.
5 is a view showing an electrode shape of a sensor module of a capacitive pressure sensor according to the present invention.
6 is a schematic diagram of a circuit part of a capacitive pressure sensor according to the present invention.
7 is a circuit diagram showing a configuration of an embodiment of a circuit portion of the capacitive pressure sensor according to the present invention.
8 is a timing chart of the main control section for adjusting the output specification of the circuit section of the capacitive pressure sensor according to the present invention.
9 is a switching timing diagram of the capacity-voltage conversion portion of the circuit portion of the capacitive pressure sensor according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The terms used throughout the specification of the present invention have been defined in consideration of the functions of the embodiments of the present invention and can be sufficiently modified according to the intentions and customs of the user or operator. It should be based on the contents of.

1 is a perspective view of a capacitive pressure sensor according to the present invention. 2 is a cross-sectional view of a capacitive pressure sensor according to the present invention. 3 is an exploded perspective view of a capacitive pressure sensor according to the present invention.

1 to 3, the capacitive pressure sensor 1 according to the present invention includes a sensor module 10, a circuit portion 20, a connector 30, and a housing 40 .

The sensor module 10 is provided with a plurality of terminals 21c for extracting sensing signals. 4 is a view showing an example of a sensor module of the capacitive pressure sensor according to the present invention. 5 is a view showing an electrode shape of a sensor module of a capacitive pressure sensor according to the present invention.

As shown in FIGS. 4 and 5, the sensor module 10 may include a dielectric substrate 11 and an electrode pattern 12. The dielectric substrate 11 is a portion where mechanical deflection occurs due to pressure. The electrode pattern 12 formed on one side of the dielectric substrate 11 is composed of a main electrode 12a and a reference electrode 12b and is connected to the terminal 21c through a lead portion (not shown).

The main electrode 12a and the reference electrode 12b act on the conductor plate 12c formed on the other side of the dielectric substrate 11 to form a capacitance Cp formed by the main electrode and a capacitance Cr formed by the reference electrode, . The conductor plate 12c operates as a ground and is connected to the terminal 21c through a lead portion (not shown).

When a mechanical displacement occurs due to the application of pressure to the dielectric substrate 11, the distance between the main electrode 12a and the reference electrode 12b formed on the dielectric substrate 11 changes, and the capacitance Cp and the capacitance of the capacitance Cr change do. The sensor module 10 converts the capacitance change of the capacitance Cp and the capacitance Cr into an electric signal and outputs the electric signal so that the pressure is measured.

The terminal 21c includes a Cp output terminal 21c-1 for outputting an output value of a capacitance Cp formed by the main electrode 12a of the sensor module 10 and a reference electrode 12b- A Cr output terminal 21c-2 for outputting the output value of the capacitance Cr formed by the capacitor C1, and a common terminal 21c-3 serving as a virtual ground terminal. The Cp output terminal 21c-1 is connected to the main electrode 12a, the Cr output terminal 21c-2 is connected to the reference electrode 12b, and the common terminal 21c- (12c).

The circuit portion 20 is bonded to the terminal 21c. Meanwhile, the circuit unit 20 may include a PCB 21 and an FPCB 23 connected thereto. The connection between the PCB 21 and the FPCB 23 can be achieved by soldering the FPCB 23 to the pad 21a formed on the PCB 21. [

The PCB 21 may be a ceramic substrate, a FR4 substrate, a BT substrate, or the like. The PCB 21 is fixed to the sensor module 10 by an adhesive or the like. A circuit pattern is formed on the PCB 21 so that the circuit component 22 is mounted. The circuit component 22 may be an application specific integrated circuit (ASIC) including a measurement circuit or the like. The PCB 21 on which the circuit component 22 is mounted receives a weak signal sensed by the sensor module 10 and amplifies the weak signal.

In the FPCB 23, four terminal holes 23b corresponding to the respective terminals are formed to be electrically connected to the terminals 31 of the connector 30. [ A pad is formed on the outer circumferential surface of the terminal hole 23b so that the terminal 31 is inserted into the terminal hole 23b and is electrically connected to the connector 30 through the FPCB 23, Lt; / RTI > The FPCB 23 can be formed by forming a pattern such as a copper foil on the surface of the polyimide film.

The circuit unit 20 is separated from the PCB 21 and the FPCB 23. Since the circuit components 22 are mounted only on the PCB 21 and are not mounted on the FPCB 23, the FPCB 23 is simpler and easier to manufacture than the conventional products, and the material cost can be reduced. If the FPCB 23 is damaged in the handling process before assembling, the FPCB 23 can be replaced without the loss of the circuit component 22, thereby reducing manufacturing costs. In addition, since the product is mounted on the PCB 21, the product is relatively strong against vibration or shock, thereby improving the reliability of the product.

The circuit unit 20 may further include a grounding piece 23a that extends from both sides of the FPCB 21 and electrically connects the FPCB 21 to the housing 40. The grounding piece 23a is electrically connected to the housing 40 made of a metal and is grounded, thereby preventing malfunction of the capacitive pressure sensor according to the present invention due to electromagnetic interference (EMI). The portion 30d of the connector 30 may be cut so that the grounding piece 23a can be connected to the housing 40. [

6 is a schematic diagram of a circuit part of a capacitive pressure sensor according to the present invention. 6, a capacitance Cp formed by the main electrode 12a of the sensor module 10, a capacitance Cr formed by the reference electrode 12b, a power input terminal Vcc, It can be seen that the stage (Gnd) and the sensor output stage (Vout) are connected.

On the other hand, it can be seen that the main control section for controlling the output specification adjustment is connected to the measurement circuit, and the adjustment value input terminal for inputting the adjustment value for adjusting the output specification is connected to the main control section. The adjustment value is stored in a memory connected to the main control unit. A specific circuit configuration of the circuit unit 20 will be described later in detail with reference to FIG.

The connector (30) has a terminal (31) electrically connected to the circuit part (20). At this time, the terminal 31 has a power input terminal 31a, a ground terminal 31b, an adjustment value input terminal 31c to which an adjustment value for adjusting an output specification of the sensor module is inputted, And a sensor output terminal 31d that outputs the output signal.

The power input terminal 31a is connected to the power input terminal Vcc of FIG. 6, the ground terminal 31b is connected to the ground terminal Gnd, and the adjustment value input terminal 31c is connected to the adjustment value input terminal And the sensor output terminal 31d is connected to the sensor output terminal Vout.

Meanwhile, the connector 30 can be manufactured by insert molding a synthetic resin material such as polybutylene terephthalate (PBT). Referring to FIGS. 2 and 3, a coupling groove 30a is formed at one end of the connector 30, to which an object (not shown) on which a capacitive pressure sensor is mounted is coupled. The other end of the connector 30 is provided with a receiving groove 30b for receiving the sensor module 10 and the circuit unit 20 to fix the sensor module 10 and the circuit unit 20. The four terminals 31 protruding into the coupling groove 30a and the receiving groove 30b are electrically connected to the circuit portion 20 at one end and to the pins of the connector of the object It serves as input / output.

The housing 40 has an inlet hole 40c through which the medium is introduced at one end and a space 40a through which the sensor module 10 is assembled in fluid communication with the inlet hole at the other end.

A pressure measurement medium such as an automobile coolant that has entered the housing 40 through the inflow hole 40c applies pressure to the sensor module 10 assembled in the space 40a. A thread 40d may be formed on the outer peripheral surface of the housing 40. [ The housing 40 is fastened to the object through an air conditioner pipe nut or the like through the thread 40d. The thread 40d may be formed on the inner circumferential surface instead of the outer circumferential surface.

After the connector 30 is assembled in the space 40a of the housing 40, the end of the housing 40 is closed to seal the periphery of the sensor module 10 when the connector 30 is brought into close contact with the housing 40. [ Can be formed by bending the portion. However, the present invention is not necessarily limited to this, and the interference fit structure of the housing 40 and the connector 30, the engagement jaw structure, or the like may be used. The material of the housing 40 is preferably a metal such as aluminum for the purpose of thread formation, bending, and the like.

According to the present invention, the output of the capacitive pressure sensor at the time of shipment of the capacitive pressure sensor is provided with an adjustment value input terminal to which the adjustment value for adjusting the output specification is inputted so as to satisfy various output specifications required by customers The reliability can be improved.

According to a further aspect of the present invention, the housing 40 is provided with a groove 40b through which an O-ring 50 for sealing is inserted into the space 40a, and the groove 40b is provided with an O- The stepped portion 40b-1 for increasing the close contact surface of the stepped portion 40b-1 is formed.

At this time, the O-ring 50 may be distorted so that the close contact surface is enlarged corresponding to the stepped portion 40b-1. For example, the distortion may be such that the upper outer side of the O-ring 50 is inserted into the stepped portion 40b-1.

The O-ring 50 is for sealing the surroundings of the sensor module 10 by preventing the entry of water, moisture and the like from the outside, and is provided with a stepped portion 40b-1 in a groove 40b into which an O- So that the sealing efficiency can be improved by increasing the close contact surface of the O-rings.

The detailed circuit configuration and operation of the circuit unit 20 will be described with reference to FIG. 7 is a circuit diagram showing a configuration of an embodiment of a circuit portion of the capacitive pressure sensor according to the present invention.

7, the circuit unit 20 includes a capacity-voltage conversion unit 200, a first compensation device 300, and a compensation control unit 400. As shown in FIG.

The capacitance-to-voltage converter 200 converts the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance change of the capacitance Cr formed by the reference electrode into an output voltage and outputs the output voltage. For example, the capacitance-voltage conversion unit 200 may include a switch unit 210, an integrator 220, a power input unit 230, and a feedback unit 240.

The switch unit 210 controls the charging and discharging operations of the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance Cr formed by the reference electrode.

3, the switch unit 210 includes six switches (two P1 switches that are simultaneously turned on at the start of phase 1 and are off at phase 2, and a phase 2 One P2d switch that is turned on at the start of P2 and is in the off state at phase 1, one P1d switch that is turned on after a specific time delay after P1 switch turn-on at phase 1, And one P2d switch that is turned on after a certain time delay after turning on).

A capacitance Cp formed by the main electrode of the capacitive pressure sensor and a capacitance Cr formed by the reference electrode are connected in series between the two P1-P2 switch connectors. A common terminal Ccom is formed by branching between a capacitance Cp formed by the main electrode connected in series and a capacitance Cr formed by the reference electrode, and a terminal P1d and a switch P2d are connected in parallel at the terminal end of the common terminal Ccom.

The P1 switch of the P1-P2 switch connector to which the capacitance Cr formed by the reference electrode is connected is connected to the output terminal of the power input section 230, and the P2 switch is connected to the ground. The P1 switch of the P1-P2 switch connector to which the capacitance Cp formed by the main electrode is connected is connected to the ground, and the P2 switch is connected to the output terminal of the feedback section 240. [ The P1d switch, which is connected in parallel to the common terminal Ccom, is connected to the inverting input terminal of the integrator 220, and the P2d switch is connected to the ground.

The integrator 220 receives the capacitance Cp and the current discharged from the capacitance Cr and outputs it as an output voltage. The integrator 220 integrates the error correction signal in the control loop until the error approaches zero.

As shown in FIG. 3, the integrator 220 may be implemented to include an operational amplifier and an integral capacitor CF. The noninverting input terminal of the op amp is connected to ground for input bias current compensation. The error of the integration result due to the input bias current can be reduced by connecting the non-inverting terminal to the ground and equalizing the resistance between the two input terminals and the ground.

On the other hand, the inverting input terminal of the operational amplifier receives a capacitance Cp formed by the main electrode of the capacitive pressure sensor and a current discharged by the capacitance Cr formed by the reference electrode through the common terminal Ccom.

On the other hand, an integral capacitor CF is connected between the inverting input terminal and the output terminal of the operational amplifier. The integral error of the integrator 220 is inversely proportional to the open DC gain of the operational amplifier. Compensating only the input offset voltage when an op amp is used can ensure sufficient accuracy.

The power input unit 230 supplies a constant power to the capacitance Cp and the capacitance Cr. For example, the power input unit 230 may be implemented as a buffer used when the output voltage needs to be kept constant regardless of a change in the load.

The buffer outputs the voltage inputted through the input terminal as it is through the output terminal to supply a constant power to the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance Cr formed by the reference electrode.

The feedback unit 240 amplifies the output voltage output from the integrator 220 and outputs a capacitance Cp formed by the main electrode of the capacitive pressure sensor, a capacitance Cr formed by the reference electrode, and a power input unit 230, Lt; / RTI >

The voltage outputted by the integrator 220 and amplified by the amplifier is applied to the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance Cr formed by the reference electrode by the switching operation of the switch unit 210 . Also, the amplifier applies the output voltage, which is output and fed back by the integrator 220, to the input terminal of the power input unit 230. [

At this time, the fixed resistor ROF may be connected between the inverting input terminal and the output terminal of the amplifier to adjust the gain of the amplifier, and the variable resistor ROI may be connected between the inverting input terminal of the amplifier and the output terminal of the integrator 220 .

The gain of the amplifier indicates how much the output voltage is amplified compared to the input voltage, and the gain (input voltage V _out Output voltage V _bdge ratio) can be expressed as a variable resistance ROI resistance value versus a fixed resistance ROF resistance value ratio (ROI / ROF).

Meanwhile, a second compensator 600 for adjusting an output voltage offset of the capacity-voltage converter 200 to be described later may be connected to the non-inverting input terminal of the amplifier.

Meanwhile, a fixed resistor R _LinF is used between the amplifier output terminal and the input terminal of the power input unit 230 to adjust the output voltage of the amplifier fed back to the power input unit 230.

The first compensator 300 may have an output voltage nonlinearity due to a change in output voltage depending on a temperature of the capacitance-voltage converter 200 or a capacitance Cp and a capacitance Cr of the capacitance-voltage converter 200 Selectively compensate.

For example, the first compensation element 300 is connected in series between the power input and the ground, and is connected to the fixed resistor R _Lin1 for applying a voltage to the capacitance-to-voltage converter 200 and the variable resistor R _Lin2 . &_Lt; / RTI >

The power input can be applied to the non-inverting input terminal of the buffer which is branched from the series connection connection point of the fixed resistor R _Lin1 and the variable resistor R _Lin2 and used as the power input part 230. In addition, the non-inverting input terminal of the buffer is connected to the output terminal of the feedback unit 240, and the inverting input terminal of the buffer can be connected to the output terminal of the buffer.

A power supply input voltage in which the output voltage change depending on the temperature or the output voltage nonlinearity due to the capacitance Cp and the capacitance Cr is selectively compensated by the resistances R _Lin1 and R _Lin2 and the output voltage fed back by the feedback unit 240 are And is applied to the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance Cr formed by the reference electrode by the switching operation of the switch unit 210 held at the output voltage of the buffer as it is, The capacitance Cp formed by the main electrode of the positive pressure sensor and the capacitance Cr formed by the reference electrode are charged.

Therefore, the output voltage nonlinearity due to the temperature-dependent output voltage change or the capacitance Cp and the capacitance Cr can be determined by _comparing the resistance values of the two variable resistors R _Lin1 and R _Lin2 included in the first compensation device 300 to the compensation control unit 400, So that it is possible to adjust the output voltage of the capacitive pressure sensor, so that the output specification of the capacitive pressure sensor can be adjusted.

The compensation controller 400 selectively adjusts an electrical characteristic value for compensating an output voltage variation or an output voltage nonlinearity compensation according to a temperature of the first compensator 300. For example, the electrical characteristic value may be a resistance value of a variable resistor for selectively compensating for an output voltage change according to temperature or an output voltage non-linearity.

For example, the compensation controller 400 may be implemented to include a BGR (BandGap Reference) 410, a MUX 420, an AD converter 430, and a characteristic value setting unit 440.

The BGR (BandGap Reference) 410 is a circuit most commonly used in an IC without being influenced by a power supply voltage or temperature, and is a proportional to absolute temperature (PTAT) A CTAT (Complementary To Absolute Temperature) characteristic in which the thermal voltage is constantly changed in inverse proportion to the absolute temperature can be used.

The MUX 420 selectively outputs the output voltage of the BGR 410 or the output voltage fed back from the capacity-voltage converter 200 according to an applied signal level.

For example, when the applied signal level is high, the MUX 420 selects and outputs the output voltage of the BGR 410, and when the applied signal level is low, the MUX 420 May be implemented to select an output voltage that is output from the capacity-voltage converter 200 and is fed back. At this time, the signal level applied to the MUX 420 may be controlled by the main control unit 500 to be described later.

The AD converter 430 converts the output voltage of the BGR 410 selectively output by the mux 420 or the output voltage fed back from the capacity-voltage converter 200 into an analog-digital signal, Generate a pressure code.

When the output voltage of the BGR 410 is selected and output by the MUX 420, the A / D converter 430 converts the output voltage of the BGR 410 into an analog-digital signal to generate a temperature code, The AD converter 430 converts the output voltage of the AD converter 430 into an analog signal and generates a pressure code.

The temperature code is a code referred to when selecting an electrical characteristic value for compensating for an output voltage change according to temperature, and the pressure code is a code referred to when selecting an electrical characteristic value for output voltage nonlinearity compensation.

The characteristic value setting unit 440 selects a resistance value corresponding to a temperature code or a pressure code generated by the AD converter 430 as an electrical characteristic value and sets a resistance value of the variable resistance R _Lin2 to a selected resistance value Setting. The selection of the electrical characteristic value of the characteristic value setting unit 440 will be described later.

Therefore, according to the present invention, the output voltage of the capacitor-voltage converter 200 can be compensated for by changing the output voltage according to the temperature, or by compensating the output voltage nonlinearity caused by the capacitance Cp and the capacitance Cr of the capacitor- The output specifications of the capacitive pressure sensor can be adjusted by adjusting the resistance values of the two variable resistors R _Lin1 and R _Lin2 included in the 1 compensator 300 through the compensation controller 400. [

The circuit unit 20 may further include a main control unit 500. The main control unit 500 applies a low or a high level signal to the mux. Accordingly, when the applied signal level is high, the MUX 420 selects and outputs the output voltage of the BGR 410. When the applied signal level is low, the MUX 420 420 selects and outputs an output voltage that is output from the capacity-voltage converter 200 and is fed back.

For example, as shown in FIG. 8, the main control unit 500 first outputs a signal (MUX_SENSE) level to be applied to the mux during a specific time, and then changes the signal level applied to the mux (High), thereby compensating for the output voltage change according to the temperature first, and then compensating the output voltage non-linearity caused by the capacitance Cp and the capacitance Cr.

The circuit unit 20 may further include a second compensator 600. The second compensator 600 adjusts an output voltage offset of the capacitance-voltage converter 200.

At this time, the second compensator 600 is connected in series between the power input and the ground, and is branched at the series connection connection point to apply a voltage to the non-inverting input terminal of the amplifier of the feedback unit 240, two variable to regulate the output voltage offset (offset) of the voltage conversion unit 200, a resistance R _of1 and the variable resistance can be implemented to include the R _of2.

The output voltage of the voltage converting part 200 - the two variable resistors R _of1 and the variable resistance R is amplified by the amplifier of the feedback unit 240 according to _of2 value because the voltage level is fed back to the power input unit 230 determines the capacity The offset can be adjusted, thereby adjusting the output specification of the capacitive pressure sensor.

The circuit unit 20 further includes a memory 510 in which information is referred to when setting the electrical property values of the first compensating element 300 and the second compensating element 600 in the main control unit 500 . For example, the memory 510 may be an EEPROM or a control register.

For example, the characteristic value setting unit 440 may search the value written in the control bit of the control register and select a resistance value corresponding to a temperature code or a pressure code as an electrical characteristic value.

Meanwhile, the main controller 500 searches the value written in the control bit of the control register to select the resistance values of the two variable resistors R _of1 and R _of2 included in the second compensator 600 as electrical characteristic values Can be implemented.

Therefore, by setting a control bit value of the memory 510 by connecting a PC or the like to the adjustment value input terminal, electrical characteristic values for adjusting the output specification of the capacitive pressure sensor can be set.

7, a programmable gain amplifier (PGA) 700 is a circuit for amplifying the output voltage of the capacitance-to-voltage converter 200, and a polarity inversion amplifier (PIA) 800 is connected to the PGA 700 And the clamping circuit 900 is a circuit for limiting the output voltage amplified by the PGA 700 to a specific level and the clock generator 920 is a circuit for limiting the output voltage amplified by the output And a POR (Power On Reset) circuit 940 is a circuit for resetting the main control unit.

The operation of the circuit portion 20 of the capacitive pressure sensor shown in Fig. 7 will be described in detail with reference to Fig. 9 is a switching timing diagram of the capacity-voltage conversion portion of the circuit portion of the capacitive pressure sensor according to the present invention.

As shown in Fig. 9, six switches (two P1 switches, two P2 switches, one P1d switch, one P2d switch) are turned on at phases 1 and 2 that do not overlap with each other ) And turn-off.

The two P1 switches are simultaneously turned on at the start of phase 1, and remain simultaneously off at phase 2, and the P1d switch is turned on after a delay of a predetermined time after the P1 switch is turned on.

On the other hand, the two P2 switches are simultaneously turned on at the start of phase 2 and remain off simultaneously in phase 1, and the P2d switch is turned on after a delay of a predetermined time after the P2 switch is turned on.

The two non-overlapping phase control signals for the six switch control are output by an oscillation drive gating circuit (not shown). Six switches are on or off controlled by these two non-overlapping phase control signals.

The main control unit 500 determines whether the output voltage varies according to the temperature of the capacity-voltage conversion unit 200 or the capacitance Cp of the capacity-voltage conversion unit 200 using the electrical characteristic value recorded in the control bit of the memory 510 Linearity of the output voltage caused by the capacitance Cr is selectively compensated and the output voltage offset of the capacitance-voltage converter 200 is adjusted.

The output voltage V _out of the integrator 220 and the amplification voltage V _bdge of the amplifier of the feedback unit 240 are given by the following equations.

(Equation 1)

When the power input is V ₊ , the voltage between the variable resistors Rof ₁ and Rof ₂ is:

(Equation 2)

At phase 1, the P1 and P1d switches are turned on, the P2 and P2d switches are turned off, and in phase 2, the P2 and P2d switches are turned on and the P1 and P1d switches are turned off.

Although the P1d switch and P2d are each turned on in phase 1 or phase 2, the on state of both switches is delayed with a specific time interval to the on time of the P1 switch or P2 switch.

During Phase 2 where the P2 switch and the P2d switch are turned on, the capacitance Cp formed by the main electrode is charged to the V _bdge voltage amplified by the amplifier through the P2 switch, and the capacitance Cr formed by the reference electrode is connected to another P2 switch To the ground.

The common terminal Ccom branching between the capacitance Cp formed by the main electrode and the capacitance Cr formed by the reference electrode is discharged to the ground through the switch P2d. The capacitance Cp formed by the main electrode is charged by V _bdge x Cp. The capacitance Cr formed by the reference electrode is not charged at the ground potential. The negative charges are immediately accumulated at the common terminal _Ccom by -V _bdge x Cp.

Then, the P2 switch is turned off after the P2d switch is turned off. No charge transfer occurs at the common terminal Ccom during a period between phase 2 and phase 1.

Then, at the start of phase 1, the capacitance Cp (charged with the V _bdge voltage at phase 2) formed by the main electrode is discharged to ground via the P1 switch, and the capacitance Cr formed by the reference electrode reaches P1 And is charged to the voltage V _L which is the buffer output voltage of the power input unit 230 through the switch.

The common terminal Ccom, which is branched at the phase 1 between the capacitance Cp formed by the main electrode and the capacitance Cr formed by the reference electrode, is connected to the inverting input terminal of the integrator 220 through the switch P1d, The inverting input terminal is connected to ground.

The charge during phase 1 is accumulated by V _L x Cr in the capacitance Cr formed by the reference electrode. This immediate negative charge accumulates at the common terminal Ccom by -V _L x Cr. -V _bdge x Cp = -V _L Cr, the negative charge of the common terminal Ccom is equal between the two phases and there is no charge supply / recovery to the integrator 220. Thus, the output voltage V _out of the integrator 220 is constant during two phase operations. In this condition, the circuit is considered to be in equilibrium.

The voltage V _bdge amplified and outputted by the amplifier of the feedback unit 240 can be obtained by _modifying the charge charged in Cp during phase 1 and the charge charged in Cr during phase 2.

(Equation 3)

However,

(Equation 4)

And V _L x Cr / C p represents the change in capacitance due to the pressure applied to the capacitive pressure sensor.

However, unintended ripple at the output terminal of the integrator 220, capacitance Cp formed by the main electrode and nonlinear characteristics of the capacitance Cr pair formed by the reference electrode and single end power supply operation And it is difficult to use it in the above-mentioned case.

In the control loop, the integrator 220 does not only operate as an error integrator, but also as an output amplifier. This allows the integrator 220 to be input via the common terminal Ccom at the ground potential. In the unbalanced state, Cr × V _L is not equal to Cp × V _bdge . The error charge is integrated by the integrator 220 until it reaches equilibrium through successive periods.

When the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance Cr formed by the reference electrode are connected to the capacitance-to-voltage converter 200 for pressure measurement, the Cr / Cp value relative to the pressure is nonlinear. That is, the decreasing Cr / Cp ratio relative to increasing pressure is not constant.

Also, since the capacitance Cp formed by the main electrode of the capacitive pressure sensor and the capacitance-voltage conversion unit 200 for converting the capacitance change of the capacitance Cr formed by the reference electrode into the output voltage are sensitive to temperature, The output voltage varies.

Thus, in the absence of linearity adjustment and correction for temperature-dependent output voltage changes, the output voltage versus the pressure can not, in most cases, meet the tolerances allowed for the production of various pressure sensors.

The circuit unit 200 selectively adjusts an electrical characteristic value for compensating an output voltage change or an output voltage nonlinearity according to the temperature of the first compensator 300 through a compensation controller 400, Adjust the specifications.

The voltage V _bdeg amplified by the amplifier of the feedback unit 240 and the power source input V ₊ are inputted to the first input terminal of the power source input unit 230 as the first resistors R _Lin1 and R _Lin2 , the feedback resistor R _LinF , The equation of the buffer output voltage V _L can be derived.

Preservation of the current at the junction between the fixed resistor R _Lin1 and the variable resistor R _Lin2 follows the following relationship. The amount of current flowing from the amplifier of the feedback unit 240 to the buffer of the power input unit 230 and from the power supply input V ₊ to the buffer of the power supply input unit 230 is the current flowing from the branch point between the fixed resistor R _Lin1 and the variable resistor R _Lin2 to the ground .

(Equation 5)

,

(Equation 6)

If we transpose this equation,

(Equation 7)

, And by substituting the above equation into this equation,

(Expression 8)

. In the above equation, 1 / R _Lin2 selectively adjusts the output voltage according to the temperature of the capacity-voltage converter 200 and the nonlinearity due to Cr / Cp. That is, by controlling the resistance value, which is the electrical characteristic value of the variable resistor R _Lin2 included in the first compensator 300, through the compensation controller 400, the output voltage change according to the temperature of the capacitance- The output voltage non-linearity caused by the capacitance Cp and the capacitance Cr of the capacity-voltage converter 200 is selectively compensated.

Next, a ripple reduction operation is examined. As shown in Fig. 9, there are switch control waveforms of two phases. The switching operation of the P1 switch and the P2 switch is not overlapped, and the P1d switch is delayed and turned on in the P1 switch on interval, and the P2d switch is delayed and turned on in the P2 switch on interval. At the beginning of the P2 switch-on period of phase 2, the current is charged from the amplifier of the feedback unit 240 to the capacitance Cp formed by the main electrode, and discharged from the capacitance Cr formed by the reference electrode to ground. The P2d switch-on state is delayed until the current transient state (unbalanced state) reaches the steady state (equilibrium state).

The P1 switch is turned on at phase 1 after the P2d switch and P2 switch are turned off and the non-overlapping section has elapsed. At the start of the P1 switch-on period, the current is charged from the buffer, which is the power input part 230, to the capacitance Cr formed by the reference electrode, and discharged from the capacitance Cp formed by the main electrode to the ground. The P1d switch-on state is delayed until the current transient state (unbalanced state) reaches the steady state (equilibrium state).

When the P1d switch is turned on, the unbalanced (error) charge is supplied / recovered to the integrator 220. This unbalance condition continues until the error reaches zero. When reaching equilibrium, no current will flow when the P2d switch or P1d switch is turned on.

As the turn-on is delayed until the P1d switch and the P2d switch respectively reach a steady state, errors or ripples injected into the integrator 220 are prevented or avoided. Without these P1d and P2d switch turn-on delays, not only will the measurement not be accurate, but the output voltage V _out and ripple will be larger.

Integrator 220 has the advantage of using virtual ground to detect capacitance changes in capacitive pressure sensors. The charge supplied / recovered from the integrator 220 is supplied / recovered only by the common terminal Ccom which is the virtual ground terminal, and the capacitance Cp formed by the reference electrode or the capacitance Cp formed by the main electrode is divided into stray capacitance Does not affect the output of the integrator 220.

The operation of the common terminal Ccom, which is the virtual ground terminal of the integrator 220, is exactly done at the ground potential. The + input of the integrator 220 is connected to ground to stabilize the bias current or leakage current occurring between the two inputs.

According to Equations 1 and 2, it can be seen that the output voltage V _out of the capacity-voltage converter 200 is related to the variable resistors Rof ₁ and Rof _2, and therefore the output of the capacity-voltage converter 200 The voltage offset can be adjusted according to the resistance values of the variable resistors Rof ₁ and Rof ₂ .

That is, by controlling the resistance values, which are the electrical characteristic values of the variable resistors Rof ₁ and Rof ₂ included in the second compensator 600, through the main control unit 500, the output voltage offset of the capacitance- ) Can be adjusted.

Accordingly, the output voltage change, nonlinearity, and output offset according to the temperature of the capacitive pressure sensor can be easily adjusted through the circuit unit 200 when the capacitive pressure sensor is shipped, and various output specifications required by customers can be satisfied.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. .

The present invention is industrially applicable in the field of pressure measurement technology and its application technology.

10: sensor module 20:
30: connector 40: housing
50: O ring

Claims (4)

A sensor module to which a plurality of wires for fetching a sensing signal are connected;
A circuit part to which the wire is bonded;
A connector having a terminal electrically connected to the circuit unit;
A housing having an inlet hole through which the medium flows in one end and a space in which the sensor module is assembled in fluid communication with the inlet hole at the other end;
Including,
Said terminal comprising:
A power input terminal;
A ground terminal;
An adjustment value input terminal to which an adjustment value for adjusting an output specification of the sensor module is inputted;
A sensor output terminal for outputting an output value of the sensor module;
Wherein the capacitive pressure sensor comprises a capacitive pressure sensor. The method according to claim 1,
Said housing comprising:
Wherein a groove is formed in the space for inserting an O-ring for sealing, and the groove is formed with a step for increasing the contact surface of the O-ring. 3. The method of claim 2,
The O-
And the tight contact surface is distorted so as to correspond to the stepped portion. The method according to claim 1,
Said wire comprising:
A Cp output terminal for outputting an output value of a capacitance Cp formed by the main electrode of the sensor module;
A Cr output terminal for outputting an output value of a capacitance Cr formed by the reference electrode of the sensor module;
A common terminal which is a virtual ground terminal;
Wherein the capacitive pressure sensor comprises a capacitive pressure sensor.

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