JPS61243339A - Pressure detector - Google Patents

Abstract

PURPOSE:To facilitate the correction of temperature along with an increase in the output sensitivity, by arranging a plurality of pressure sensors different in the property to determine the product of resistance ratios as pairs after the computation thereof. CONSTITUTION:A plurality of semiconductor pressure sensors RA, rB, Ra, rb which are different in the resistance change with respect to the hydrostatic pressure are provided in a pressure container 1 sealed with a pressure transmission medium 2. The outputs of the pressure sensors are drawn from leads 4-7 to compute resistance ratios as proper pairs (for example, RA/rB) of the pressure sensors. THen, the product of the outputs of the resistance ratios as pairs is determined. The value of the product is converted into a logarithmic value, which is divided by a temperature signal T obtained from a temperature detection element TC to obtain the outputs of the pressure sensors with the corrected temperature. This can increase the final output thereby facilitating the correction of the temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention [Field of Industrial Application] The present invention relates to improving the pressure detection sensitivity of a pressure detection device using a semiconductor.

[Conventional technology]

Most pressure detection devices using semiconductors as sensors utilize piezoresistance effects. In a sensor that utilizes this piezoresistance effect, stress changes occur within the semiconductor crystal due to strain caused by external force, and this changes the energy level of electrons. As a result, the resistance value changes.

Therefore, in order to obtain sufficient detection sensitivity for the pressure to be measured, the key point in designing a pressure detection device is how to apply distortion to the semiconductor pressure sensor. In general, a method in which a semiconductor piezoresistance element is bonded to a metal diaphragm is often used.

[Problem that the invention seeks to solve]

However, since the conventional pressure detection device described above uses a diaphragm, the mechanical structure is complicated, and an overpressure protection mechanism is required, which makes the structure even more complicated. .

In addition, if a semiconductor with pressure-sensitive characteristics is used as a pressure sensor, the configuration becomes simpler, but if a normal semiconductor is used as a pressure sensor, the resistance changes little with respect to the measured pressure, so the detection sensitivity will be insufficient and it will not be practical. It cannot be submitted to the public.

An object of the present invention is to provide a pressure detection device that can double the output sensitivity by combining a plurality of semiconductors having pressure-sensitive characteristics.

``Structure of the Invention'' [Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a pair of pressure sensors ( For example, a plurality of pairs of pressure sensors such as Ra and rB are provided, and these are placed in a pressure vessel filled with a pressure transmission medium, and the resistance ratio (for example, R^/ra) of the paired pressure sensors is calculated. The first effect of temperature is removed by n o + T 2 ・exp (
-One! 9-) T;? Furthermore, by calculating the product of the outputs of each pair of resistance ratios and logarithmically converting the value of the product, the temperature correction calculation of 1/T is facilitated, and the final output is It is designed to provide multiple times the sensitivity of a pressure sensor.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a diagram showing an example of the main part configuration (pressure detection end) of a pressure detection device according to the present invention. In the figure, 1 is a pressure vessel. Reference numeral 2 denotes a pressure transmission medium sealed in the pressure vessel 1, and for example, in the embodiment, silicone oil, which is an incompressible fluid, is used.

RA and Ra are pressure sensors made of a pressure-sensitive semiconductor material whose resistance value changes according to changes in applied hydrostatic pressure. In addition, each resistance value of this pressure sensor is RA,
It is written as Ra.

rB and rb are pressure sensors made of a pressure-sensitive semiconductor material whose resistance value changes according to a change in applied hydrostatic pressure, and have different change characteristics from the resistance change of the pressure sensors RA and Ra. It is something that you have. The resistance value of each pressure sensor is rB.

It is written as rb.

TC is a temperature detection element, such as a thermocouple. The above four pressure sensors R^ to rb and the temperature detection element TO are arranged inside the pressure vessel 1. Note that since the temperature detection element TC is for measuring the temperature of the pressure sensor RA, j%b, the temperature detection element TC does not necessarily have to be placed inside the pressure vessel 1.

10 is a hermetic seal part, and pressure sensor RA-
Lead wires 4 to 8 electrically connected to rb are connected to pressure vessel 1.
This is to prevent the pressure transmission medium 2 from leaking when taken out to the outside.

Although the pressure to be measured is applied to the portion 1a of the pressure vessel 1, a diaphragm that is corrosion resistant and has a wide elastic range is provided to prevent the pressure transmission medium 2 sealed therein from flowing out.

FIG. 2 shows an electric circuit to which the lead wires 4 to 8 in FIG. 1 are connected, and it is possible to obtain a signal eo u L corresponding to the pressure applied from the output terminal of this circuit. Second
In the figure, 20 and 21 are constant voltage sources, and U+ and U2 are amplifiers. RA to rb are pressure sensors also shown in FIG. M is a multiplier, C is a logarithmic variable yA unit, D is a divider,
F is an adder.

Pressure sensor rB is connected to the inverting input terminal of amplifier U1, and pressure sensor RA is connected between the output terminal and the inverting input terminal of the amplifier. The other end of pressure sensor r9 and amplifier U
A constant voltage source 20 is connected between the two non-inverting input terminals.

The signal between the output terminal and the non-inverting input terminal of amplifier U1 @e1
is introduced into multiplier M.

In addition, pressure sensors Ra and rb, an amplifier U, and a constant voltage source 2
1 is the same as the above-mentioned pressure sensor RA, amplifier U+, etc., so the explanation thereof will be omitted.

The output e3 of the multiplier M is introduced into the logarithmic converter C, and the output voltage e4 of the logarithmic converter C and the output voltage (-A) of the adder F are
are connected in series and introduced into the divider. Further, a signal 1/T based on the temperature detection element TC is introduced into another input terminal of the divider.

The operation of the pressure detecting device in which the pressure detecting end shown in FIG. 1 and the electric circuit shown in FIG. 2 configured as described above are combined will be described below.

Assuming that the pressure sensors shown in FIGS. 1 and 2 are intrinsic semiconductors sensitive to hydrostatic pressure, the electrical conductivity σ1 of the pressure sensors RA and Ra can be expressed as r9. The conductivity σ2 of rb is (
2) It is expressed by the formula.

σ+”'ni+ ・q・(μe, 10 μp + >
(1) σz=niz ・q・(μC20μP 2
) (2) Here, q is the electron elementary charge μe is the electron mobility μp is the hole mobility 0), and njl and n□2 in equation (2) are the intrinsic carriers llr! of the semiconductor material, respectively. 1, and is expressed by the following formula.

n,, 2=no2-7zexp (”L) (4)
KT Here, not, n02 is a material constant EQl that is not related to temperature or band energy, and EQ2 is band gap energy. The resistance value, that is, the conductivity changes with respect to the hydrostatic pressure of the semiconductor material, mainly due to the band gap energy. This is because Eo changes depending on the pressure P. Therefore, pressure sensor RA~
The resistance value of rb is expressed by equations (5) to (8).

Note that ROI~Roa is a constant C+”C determined by the dimensions and structure.
2- is a constant determined by the geometrical shape of the resistance element, R,
,,p −J,−,I =L−.

S Scr: Length, S: Area When the pressure sensors RA to rb are immersed in silicone oil as shown in FIG. 1 and a pressure change is applied, the resistance value changes depending on the band gap energy Ea. In this case, since the volume of the pressure vessel 1 is small, there is no temperature distribution within the vessel 1, and temperature changes affect these pressure sensors equally. The pressure sensors are RA, 'aqRa and rb as shown in Figure 2.
The pairwise combination of amplifiers U1. When connected to U2 and amplified there, amplifier LI1. The output e of LI2 and C2 are expressed by equations (9) and 00).

RA e + --He o (9)
C2=-kidney eo (1■eo is the voltage of the constant voltage source 20.21 If the temperature inside the pressure vessel 1 shown in Fig. 1 is uniform, (9
), (to) expressions are (+I
), it can be rewritten as formula 04.

e + = -臂eo -eXI' (Spring ([EGIC
P) EQI(P) ) )...(11) e 2--toeo -exp pot(E, 1(P) -E
, CP)) )...0a eI + C2 is introduced into the multiplier M, and the signal e3 shown by equation (13) is multiplied by 1.

C3=el-C2=肚"e o" eXD (,,,,(Ec+CP)
-E(,2(P))-38...(13) When the output e3 of the multiplier M is input to the logarithmic transformation 3C, a signal e4 expressed as a set is obtained.

ea = ln l ez I -8 -F-,, -r E,, (P,) -'Eb
z(P)))
'υIn addition, if we add a constant signal of (-8) from adder F to this e4 signal, the input to the divider is 5〒(E,, (P) −E, □(P)). When this signal is divided by the temperature signal (1/T) from the temperature detection element TC, the signal expressed by the Q formula 8e.ut is fl.

eo ut =C・2 (E41(P)E6z(P)
) 'J9 From the above, it can be seen that by using two or more sets of semiconductor elements with different hydrostatic pressure sensitivities, it is possible to obtain a sensitivity that is 2IrEI or more of the hydrostatic pressure sensitivity obtained when using one set. In addition, the temperature characteristics of the signal from the pressure sensor can be easily corrected.

This will be explained using a specific example. For example, pressure sensor 1A, R
Assume that black phosphorus is selected for a, and InSb is selected for pressure sensors rB and rb.

The pressure sensitivity for one set can be expressed as equation 04 using equation 10.

-F-Chi=Kichi・An (E, 1(P) -EQ□CP))
(14Here, black phosphorus is +(E(,1(P)) = 24X 10-
'``%a-Yes'' is as follows.

-0.9x10-3/bar, that is, 90 with a change of 0~1000 ttg/Cm"
% change. Therefore, by using two sets (pairs),
The changes are as follows.

-2X O,9x 1-0-3/bar= 1,8X
IP Co/bar Therefore, by using two sets (pairs) of pressure sensors, the pressure sensitivity can be doubled.

Note that although the above example has been explained using two sets (pairs), the sensitivity is not limited to two sets, and sensitivity can be improved by using a plurality of sets. For example, if there are 0 sets (pairs), the pressure sensitivity can be increased by n times.

In addition, in FIG. 2, pressure sensor r9 is connected between the inverting input terminal of amplifier U and constant voltage source 20, and pressure sensor RA
Although the explanation has been made assuming that the pressure sensor RA+'a is connected between the input and output terminals of the amplifier U, it is clear that the present invention can be applied even if the connection arrangement of the pressure sensor RA+'a is changed.

(Effect of the Invention J As described above, according to the present invention, output sensitivity can be doubled by combining a plurality of semiconductors having pressure-sensitive characteristics.Furthermore, the temperature characteristics of a semiconductor pressure sensor can be doubled. Can be easily corrected.

[Brief explanation of drawings]

jf! Figure 1 is a diagram showing an example of the main part configuration of the pressure detection device according to the present invention, and Figure 2 is a diagram showing each lead wire 4 to 8 shown in Figure 1.
FIG. 2 is a diagram showing an electric circuit to which the 1...Pressure vessel, 2...Pressure transmission medium, 4-8...
・Lead wire, 10...Hermetic seal part, RA-
rb...Pressure sensor, ゛C...Temperature detection element, U
+, U2...amplifier, M...multiplier, C...logarithmic converter, D...divider, F...adder. Figure 1 Figure 2 A

Claims (2)

[Claims] (1) A pair consisting of a pressure vessel to which the pressure to be measured is applied and a pressure transmission medium sealed inside the vessel, and a semiconductor placed within the pressure vessel and having different resistance changes with respect to hydrostatic pressure. A pressure detection device comprising: a plurality of pairs of pressure sensors; a means for calculating a resistance ratio of the pressure sensors constituting each pair; and a means for calculating a product of the resistance ratios. (2) comprising a temperature detection element for detecting the temperature of the pressure sensor; and means for logarithmically converting the output signal of the means for calculating the product; 2. The pressure detection device according to claim 1, wherein the temperature component of the signal from the conversion means is corrected.