JPH0815070A - Pressure detecting device - Google Patents

Abstract

PURPOSE:To provide a pressure detecting device by which temperature compensation can be made when the device detects a pressure. CONSTITUTION:When an atmospheric pressure value ATM is measured based on the output of a pressure sensor 10, a CPU 1 instructs a sensor driving circuit 9 to drive a magnetic sensor 11 with a constant current and temperature data are prepared from the output signal of the sensor 11 driven with the constant current by means of the circuit 9 through a temperature conversion table. Then temperature compensation is made on the atmospheric pressure value ATM based on the temperature data. Therefore, the temperature compensation can be performed at the pressure detecting time by means of the magnetic detecting means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure detecting device.

[0002]

2. Description of the Related Art Conventionally, there has been known a pressure detecting device which detects a geomagnetism by using a magnetic sensor and measures an azimuth based on the detected geomagnetism. Such a pressure detecting device is mounted on, for example, an electronic watch (electronic wristwatch) or the like, and has been put into practical use as a product for measuring and displaying the "direction" in addition to a normal timekeeping function. Further, in recent years, a watch equipped with a function of measuring and displaying "atmospheric pressure", "altitude", "water depth" and the like by using a pressure sensor in an electronic watch has been known in accordance with the user's outdoor life orientation.

[0003]

As the pressure sensor mounted on the above-mentioned watch, a semiconductor pressure sensor in which a Wheatstone bridge is formed by a diffusion resistance having a piezoresistive effect is often used. In this type of pressure sensor, the temperature characteristics can be compensated to some extent by connecting the diffusion resistors to the bridge, but if there is a slight variation in the resistors forming the bridge, complete temperature compensation cannot be performed. Therefore, in order to perform highly accurate measurement of "atmospheric pressure" (or measurement of "altitude", "water depth", "wind pressure", etc.), a temperature detecting means for detecting temperature is separately provided in the watch. It becomes necessary to temperature-compensate the output of the semiconductor pressure sensor according to the output of.

By the way, if the temperature detecting means is newly mounted on the watch, there are disadvantages such as an increase in cost and an increase in size of the product itself, which is not preferable. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pressure detection device that can perform temperature compensation during pressure detection.

[0005]

In order to achieve the above object, in the invention described in claim 1, a magnetic detecting means for detecting magnetism using a magnetoresistive element and a pressure detecting means for detecting pressure. In a device for measuring azimuth and pressure, a conversion unit that measures the resistance value of the magnetoresistive element and converts it into temperature information; and a pressure conversion unit that measures the pressure by the pressure detection unit. Compensation means for compensating the temperature using the obtained temperature information is provided.

According to the second aspect of the invention, the compensating means stores in advance a compensating value associated with the temperature information and the pressure value as a compensating table, and is supplied from the converting means. The compensation value is read from the compensation table according to the temperature information and the pressure value measured by the pressure detection means.

[0007]

As a result, it becomes possible to perform temperature compensation at the time of pressure detection by the pressure detection means without providing new temperature detection means.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. A. Configuration of Embodiment FIG. 1 is a block diagram showing a configuration of a multi-function watch to which a pressure detection device according to an embodiment of the present invention is applied. The multi-function watch shown in this figure includes a control unit 100 and a measurement unit 20.
0, and the structure of each of these parts will be described in sequence below.

(A) Configuration of Control Unit 100 The control unit 100 is composed of components 1 to 6. A CPU 1 controls each part of the watch, and its operation will be described later. The CPU 1 has a function of generating a timer clock obtained by dividing the oscillation clock, and sequentially counting the timer clock (for example, 1/16 second) to measure the time. Reference numeral 2 is a ROM that stores various control programs read by the CPU 1, conversion tables, and the like.

In the ROM 2, an output signal (magnetic sensor data D _MR ') output when a magnetoresistive element 11 (MR element) 11b of the magnetic sensor 11 described later is driven with a constant current is converted into temperature data D _T. A temperature conversion table CT for conversion and a table for correcting the pressure value measured based on the temperature data are provided. This temperature conversion table CT
Details of will be described later. Reference numeral 3 denotes a RAM as a work area of the CPU 1 in which various calculation results, register values, or flag data are temporarily stored, and the register configuration will be described later.

The operation switch 4 is provided with a display changeover switch DS, a mode changeover switch SW1 and a measurement start switch SW2 (not shown).
A switch signal corresponding to the operation of S, SW1 and SW2 is generated. A display unit 5 includes an LCD panel and an LCD driver. The display unit 5 displays the time, direction, and atmospheric pressure on the LCD panel (not shown) arranged on the front surface of the watch according to the display data supplied from the CPU 1 according to the display mode. The display mode referred to here means a display mode set according to the operation of the mode changeover switch SW1, and its details will be described later.

Reference numeral 6 is an input / output interface circuit composed of registers 6a and 6b, and the pressure data Dp, the magnetic detection data D _MR or the magnetic sensor data D _MR 'supplied from the A / D converter 13 is sent to the RAM 3 side. To send
Various control signals supplied from the CPU 1 are output to the measuring unit 200 side. Input / output interface circuit 6 to measurement unit 2
Signals BS, S1, S2 and S3 are supplied to the 00 side. The signal BS is a signal for switching and controlling the resolution of the A / D conversion circuit 13 described later. In addition, signals S1 and S2
And S3 are signals for ON / OFF controlling the switching elements described later.

(B) Structure of the measuring unit 200 The measuring unit 200 is composed of the constituent elements 8 to 13. 8
Is a waveform synthesizing circuit, which controls switching of the resolution of the A / D conversion circuit 13 in accordance with the signal BS supplied from the input / output interface circuit 6, and also signals S1, S2 and S.
The sensor to be driven is designated according to 3. Reference numeral 9 denotes a sensor driving circuit, which drives a sensor designated based on the control signal supplied from the waveform synthesizing circuit 8 and inputs the sensor output to the amplifying circuit 12. Reference numeral 12 amplifies the output of the pressure sensor 10 or the magnetic sensor 11 which will be described later and supplies the amplified output to the A / D conversion circuit 13 in the next stage. The A / D conversion circuit 13 converts the output of the amplification circuit 13 into a digital signal with the resolution indicated by the waveform synthesis circuit 8, and corresponds to the pressure data Dp corresponding to the output of the pressure sensor 10 or the output of the magnetic sensor 11. Generates magnetic detection data D _MR (magnetic sensor data D _MR ').

The pressure sensor 10 forms a Wheatstone bridge with diffusion resistances Ra to Rd having a piezoresistive effect. The magnetic sensor 11 is configured by connecting magnetoresistive elements in a bridge shape, aligning the sensitivity axes of two opposing magnetoresistive elements, and arranging the sensitivity axes of two adjacent magnetoresistive elements at right angles to each other. And two more around this
A set of coils is wound.

Here, the structure of the magnetic sensor 11 will be described with reference to FIGS. Figure 2 (a)
11a is a substrate of alumina or the like, and a magnetoresistive element 11b formed by patterning vapor deposition of permalloy (Ni—Fe alloy) is formed on the substrate 11a. The stripe pattern portion in the figure is the element 11b, and each has a sensitivity to a magnetic field in a direction orthogonal to the stripe. FIG. 11B shows a state where the substrate 11a is held by the resin molding holder 11c.

Although not shown in FIG. 2B, two sets of coils C orthogonal to each other are provided in the recess of the holder 11c.
1, C2 are wound. Magnetic sensor 1 for geomagnetism
These coils C1 and C so as to cancel the output generated by 1
By supplying the drive current to 2, the direction of the geomagnetism is determined.

In the magnetic sensor 11 having such a structure,
As shown in FIG. 3, the resistance value of the magnetoresistive element 11b has a temperature coefficient. In the example shown in this figure, room temperature (25
It has a resistance of about 800 Ω at a temperature of ° C) and a temperature coefficient of about 3000 ppm / ° C. That is, in the case of this example, the resistance value linearly increases by 2.4Ω each time the temperature rises by 1 ° C, and the temperature and the resistance are in a proportional relationship in a predetermined temperature range with reference to room temperature. Therefore, if the temperature characteristics of the magnetoresistive element 11b are tabulated in advance in a predetermined temperature range, the resistance value at that time can be converted into a temperature value. That is, the level data (magnetic sensor data D _MR ') output when the magnetic sensor 11 described later is driven with a constant current and the temperature value corresponding thereto are measured in advance, and this is used as the temperature conversion table CT in the ROM 2 Register in.

(C) Structure of Sensor Unit Next, the structure of the sensor unit formed of the above-mentioned sensor drive circuit 9, pressure sensor 10 and magnetic sensor 11 will be described with reference to FIG. In this figure, 17 to 3
Reference numeral 4 denotes a transfer gate (hereinafter abbreviated as TG) including a switching element, which is the control signal S described above.
ON / OFF control is performed according to S1 and S2. Of these, TG1
7 to TG25 are on / off controlled according to the control signal S1, and TG26 to TG34 are on / off controlled according to the control signal S2. 35 to 48 are voltage dividing resistors, and 49 is a variable resistor. The variable resistor 49 connected to the output end of the pressure sensor 10 is for trimming and adjusting the variation of the offset voltage applied to the pressure sensor 10.

Reference numerals 50 to 56 are switching transistors, which form a switch matrix for controlling the direction of the drive current supplied to the two sets of coils C1 and C2 wound around the magnetic sensor 11. In this matrix,
The transistors 53 to 56 are on / off controlled according to the control signal S3 supplied from the waveform synthesizing circuit 8 via the buffers 62 to 65. On the other hand, the transistors 50 to 52
Are turned on / off based on the output of the operational amplifier 59 via the TGs 28 to TG 34 which are turned on / off according to the control signal S2. 57 is TG17,18,19
Constant current drive of the magnetic sensor 11 according to the on / off state of
Alternatively, the operational amplifier 58 is driven by a constant voltage, and 58 is an operational amplifier that drives the pressure sensor 10 by a constant current.

(C) Register Configuration Next, the register configuration of the RAM 3 described above will be described with reference to FIG. In this figure, E1 is a display register, which is an area for temporarily storing various display data to be supplied to the LCD driver. E2 is a time register in which time data TIME representing the current time is stored. E3 is a mode register in which an operation mode MODE and switch flags SWF1 and SWF2 are stored as data. The operation mode MODE represents a "timekeeping mode" for displaying the time when the value is "0", a "atmospheric pressure measurement mode" when the value is "1", and a "direction measurement mode" when the value is "2". The details of the “atmospheric pressure measurement mode” and the “azimuth measurement mode” will be described later.

The switch flags SWF1 and SWF2 are flag values corresponding to ON / OFF operations of the mode changeover switch SW1 and the measurement start switch SW2 described above. E4 is a control register for temporarily storing various control data generated by the CPU 1, in which status flags corresponding to the above-mentioned signals BS, S1, S2 and S3 are set. E5 is the A / D conversion circuit 13
The sampling buffer temporarily stores the pressure data Dp output from the device for a plurality of sampling cycles. E6
Is a sampling buffer for temporarily storing the magnetic detection data D _MR (or the magnetic sensor data D _MR ′) output from the A / D conversion circuit 13 for a plurality of sampling cycles.

E7 is the atmospheric pressure value A converted based on the pressure data Dp read from the sampling buffer E5.
This is an area for storing TM. E8 is an area for temporarily storing the temperature data D _T. The temperature data D _T is data that is read out from the temperature conversion table CT described above using the magnetic sensor data D _MR ′ output when the magnetic sensor 11 is driven with a constant current as a read address. E9 is an area for storing the azimuth angle AZ converted based on the magnetic detection data D _MR read from the sampling buffer E6.

B. Operation of the Embodiment Next, the operation of the embodiment having the above configuration will be described with reference to FIGS. Here, the operation of the main routine will be first described as an overall operation, and subsequently, the operation of the atmospheric pressure measurement processing routine and the azimuth measurement processing routine called in this main routine will be sequentially described.

Main Routine Operation (Overall Operation) (a) Timekeeping Mode First, when the battery is mounted on the multi-function watch having the above-mentioned configuration, the CPU 1 reads the control program from the ROM 2 and loads it into itself, and then secures it in the RAM 3. The registers and flags to be initialized are initialized, the main routine shown in FIG. 6 is started, and the process proceeds to step SA1. In step SA1, it is determined whether or not it is in a standby state. Here, it is assumed that the timer clock is input from the clock circuit 5 (see FIG. 1). Here, the CPU 1 advances the processing to the next step SA2 at the timing of timing (for example, 1/16 sec).

In step SA2, a time counting process of counting the supplied timer clock and incrementing the value of the time register E2 is executed. Then, in step SA3, if the mode is the time display mode, the step is advanced. The displayed time is displayed on the display unit 6 as the current time, and the process returns to step SA1 described above. Thereafter, every time the timer clock is input, steps SA1 to SA3 are repeated to measure the current time.

(B) Atmospheric pressure measurement mode / azimuth measurement mode Next, when the mode changeover switch SW1 is operated while the CPU 1 is in the standby state of step SA1, the CPU
The process of 1 proceeds to step SA4. In step SA4, it is determined whether the value of the operation mode MODE is "1" or "2". Here, when the mode switch SW1 is operated to specify the "atmospheric pressure measurement mode", the CPU 1 advances the processing to step SA5, and executes the atmospheric pressure measurement processing described later. On the other hand, when the mode changeover switch SW1 is operated to specify the “azimuth measurement mode”, the CPU 1 advances the process to step SA6 and executes the wind speed measurement process described later.

Operation of Atmospheric Pressure Measurement Processing Routine (a) Measurement of Atmospheric Pressure Data ATM Next, the operation of the atmospheric pressure measurement processing routine will be described with reference to FIG. As described above, when the processing of the CPU 1 proceeds to step SA5, the atmospheric pressure measurement processing routine shown in FIG. 7 is executed, and the processing proceeds to step SB1. First, in step SB1, the output of the pressure sensor 10 is fed to the amplifier circuit 1
The control signal S1 for turning on the TG 24 and the TG 25 shown in FIG.

As a result, the output of the pressure sensor 10 is supplied to the A / D conversion circuit 13 via the amplifier circuit 12. Next, when proceeding to step SB2, the CPU 1 executes the A /
The pressure data Dp output from the D conversion circuit 13 is sampled via the register 6a and sequentially stored in the register area E5 of the RAM 3. And the pressure data Dp
Is sampled a fixed number of times, the next step SB
In step 3, the sampled pressure data Dp are averaged, and the averaged pressure data Dp is converted into an atmospheric pressure data ATM by an engineering value.

(B) Measurement of magnetic sensor data D _MR 'When the atmospheric pressure data ATM is obtained in this way, the CPU 1 first proceeds to step SB4 to temperature-compensate the atmospheric pressure data ATM, and then proceeds to step TG24 and TG25 described above.
Generates a control signal S1 for turning off the pressure sensor 10
The output line of is cut from the amplifier circuit 12 side. Next, in Step SB5, the TG 18 is set to ON and the TG is set.
A control signal S1 for turning off 17 and TG 19 is generated. As a result, the operational amplifier 57 supplies a constant current corresponding to the potential of the non-inverting input terminal and the load resistor 35 to the magnetic sensor 11.

(C) Temperature compensation of atmospheric pressure data ATM When the operational amplifier 57 enters a state in which the magnetic sensor 11 is driven with a constant current, the CPU 1 proceeds to step SB6 and TG22.
Then, the TG 23 is turned on, and the drive line of the magnetic sensor 11 is connected to the amplification circuit 12 side. As a result, the drive line of the magnetic sensor 11 is input to the amplification circuit 12 side, and in this case, the magnetic sensor 11 outputs the magnetic sensor data D _MR 'in correspondence with the constant current drive. The magnetic sensor data D _MR 'is level data corresponding to the resistance value of the magnetoresistive element 11b and is known within a predetermined temperature range.

Subsequently, in step SB7, the magnetic sensor data D _MR ′ output from the A / D conversion circuit 13 via the amplifier circuit 12 is sampled, and this is sampled in the RAM3.
Is temporarily stored in the register area E6. And after this,
Magnetic sensor data D _MR 'stored in register area E6
The corresponding temperature data D _T is read from the temperature conversion table CT stored in the ROM 2 by using as a read address.

Next, the CPU 1 proceeds to step SB8.
And read the temperature data D Regis based on T
Temperature compensation of atmospheric pressure data ATM read from the data area E5
Then, the result is displayed in step SB9. What
Oh, temperature compensation is temperature data D Barometric pressure data based on T
Compute the ATM to correct the atmospheric pressure value, or
Temperature data D_TAnd barometric pressure data ATM
The corrected values are stored as a compensation table, and this compensation
Also as a mode to read the corrected atmospheric pressure value from the table
good.

Operation of Azimuth Measurement Processing Routine Next, the operation of the azimuth measurement processing routine will be described with reference to FIG. (A) Initialization As described above, when the processing of the CPU 1 proceeds to step SA6, the azimuth measurement processing routine shown in FIG. 8 is executed, and the processing proceeds to step SC1. In step SC1, first, the transfer gate (TG) 1 is operated to drive the operational amplifier 57 (see FIG. 4) at a constant voltage prior to the direction measurement.
7 and TG19 are turned on, and a control signal S1 for turning off TG18 is generated. As a result, both ends of the load resistor 35 (see FIG. 4) are short-circuited, the operational amplifier 57 operates as a voltage follower, and a constant level corresponding to the voltage division ratio of the voltage dividing resistors 36 and 37 is applied to the magnetic sensor 11. It will be.

(B) Magnetic Detection Data D _MR Sampling When the magnetic sensor 11 is driven at a constant voltage, the CPU 1 advances the processing to step SC2 to generate a control signal S1 for turning on both TG20 and TG21, and the magnetic sensor 11 is generated.
Is connected to the amplifier circuit 12 side. Then, the magnetic detection data D _MR output from the A / D conversion circuit 13 via this circuit 12 is sampled, and this is sampled in the RAM 3
It is stored in the register area E6.

(C) Direction detection Then, when proceeding to the next step SC3, the CPU 1 controls signals S2 and S for supplying drive currents in predetermined directions to the coils C1 and C2 wound around the magnetic sensor 11, respectively.
3 is generated. The control signals S2 and S3 are TG26 to TG.
34 (see FIG. 4) and switching transistor 50
ON-OFF control of ~ 55, and by this, coils C1, C2
A drive current in a predetermined direction is supplied to the coils C1,
The horizontal magnetic field component (N component and E component) of the geomagnetism corresponding to the magnetic detection data D _MR is offset by the current magnetic field generated by C2.

When the coils C1 and C2 are thus excited so as to cancel the magnetic detection data D _MR , the CPU 1 advances the processing to step SC4, and the coils C1 and C2 are processed.
Direction data AZ is calculated based on the direction of the current supplied to the
Is displayed on the display unit 6.

As described above, according to this embodiment, it is based on the finding that the resistance value of the magnetoresistive element forming the magnetic sensor 11 is proportional to the temperature in the predetermined temperature range with reference to room temperature. Since the temperature conversion table CT in which the magnetic sensor data D _MR 'outputted when the magnetic sensor 11 is driven at a constant current is associated with the temperature data D _T in advance is registered in the ROM 2, after the atmospheric pressure data ATM is acquired,
The temperature data D _T corresponding to the magnetic sensor data D _MR ′ obtained by driving the magnetic sensor 11 at a constant current is read from the temperature conversion table CT, and the atmospheric pressure data ATM can be temperature-compensated.

In the embodiment described above, the temperature data D _T is read from the temperature conversion table CT using the magnetic sensor data D _MR ′ as a read address, and the atmospheric pressure data ATM is temperature-compensated based on this. However, instead of this, for example, two-dimensional table data for reading out the atmospheric pressure compensation data using the magnetic sensor data D _MR and the atmospheric pressure data ATM as the read addresses may be used. By doing so, the processing can be further simplified and the processing speed can be increased.

When applied to a multi-function wristwatch as in this embodiment, the temperature data D _T read from the temperature conversion table CT may be displayed in degrees Celsius. In a multi-function wristwatch or the like in which the mounting volume is restricted, the temperature can be measured without the temperature detection means, so that the mounting efficiency is improved. Further, in the above-mentioned embodiment, the case where the invention is applied to the multifunctional wristwatch is described, but it is not limited to this, and it is needless to say that the invention can be applied to, for example, a portable outdoor sports equipment.

[0040]

According to the present invention, when the atmospheric pressure value is measured based on the output of the pressure detecting means, the atmospheric pressure value is temperature-compensated according to the temperature information obtained by supplying the output signal of the magnetic detecting means to the converting means. Even if the temperature detecting means is not newly provided, the temperature can be compensated at the time of pressure detection by the magnetic detecting means. As a result, highly accurate barometric pressure measurement can be performed without providing the temperature detecting means, and in a multifunctional wristwatch or the like that has a limited mounting volume, the temperature can be measured without the temperature detecting means. The effect that the mounting efficiency is improved can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a multi-function watch to which an embodiment of the present invention is applied.

FIG. 2 is a diagram for explaining the structure of a magnetic sensor 11 in the same embodiment.

FIG. 3 is a diagram showing an example of a temperature coefficient of a magnetic sensor 11 in the example.

FIG. 4 is a circuit diagram showing a circuit configuration of a sensor unit in the embodiment.

FIG. 5 is a memory map for explaining the register configuration of the RAM 3 in the embodiment.

FIG. 6 is a flowchart showing an operation of a main routine in the embodiment.

FIG. 7 is a flow chart showing an operation of an atmospheric pressure measurement processing routine in the embodiment.

FIG. 8 is a flowchart showing an operation of an azimuth measurement processing routine in the embodiment.

[Explanation of symbols]

 1 CPU (converting means, compensating means) 2 ROM (converting means) 3 RAM 4 Operation switch 5 Display section 6 Input / output interface circuit 8 Waveform synthesizing circuit 9 Sensor drive circuit 10 Pressure sensor (pressure detecting means) 11 Magnetic sensor (magnetic detection) means)

Claims (2)

[Claims] 1. An apparatus for measuring azimuth and pressure, comprising magnetic detection means for detecting magnetism using a magnetoresistive element and pressure detection means for detecting pressure, wherein the resistance value of the magnetoresistive element is measured. And a compensating means for compensating the temperature using the temperature information obtained by the converting means when the pressure is measured by the pressure detecting means. Detection device. 2. The compensating means stores in advance a compensating value associated with the temperature information and the pressure value as a compensating table, and the temperature information supplied from the converting means and the pressure detecting means are measured. The pressure detection device according to claim 1, wherein the compensation value is read from the compensation table according to the pressure value.