JPH0640042B2 - Pressure detector - Google Patents

Description

Detailed Description of the Invention a. [Object of the Invention] [Industrial field of use] The present invention relates to improvement in sensitivity and improvement in temperature compensation means of a pressure detection device using a semiconductor.

[Conventional technology]

Most pressure detection devices using a semiconductor as a sensor utilize the piezoresistance effect. In the sensor using the piezoresistive effect, a stress change occurs in the crystal of the semiconductor due to the strain due to the external force, and the energy order of the electrons changes due to the stress change. As a result, the resistance value changes.

Therefore, in order to obtain sufficient measurement sensitivity of the pressure to be measured, how to devise so that the semiconductor pressure sensor is strained is a design point of the pressure detection device. Further, generally, as shown in FIG. 3, many means are used such that the semiconductor piezoresistive element 10 is bonded to the diaphragm 11.

[Problems to be solved by the invention]

However, since the conventional pressure detecting device as shown in FIG. 3 is used as one semiconductor sensor, it will be described later. and It is difficult to eliminate the term of (is difficult to compensate for temperature),
In addition, there is a problem in that it is impossible to obtain a sufficient change in pressure-conductivity (insufficient pressure sensitivity).

It is an object of the present invention to provide a pressure detection device having a simple structure in which two pressure sensors each composed of a semiconductor are combined and whose temperature can be easily corrected.

B. [Structure of the Invention] [Means for Solving the Problems] In order to solve the above problems, the present invention uses two pressure sensors each formed of a semiconductor whose polarities of resistance change with respect to hydrostatic pressure are different from each other. It is arranged in a pressure vessel filled with a transmission medium, and the resistances of two pressure sensors are ratio-calculated and divided by a temperature signal to remove the influence of temperature and obtain a signal proportional to pressure. .

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a configuration example (a pressure detection end) of a main part of a pressure detection device according to the present invention. In the figure, 1 is a pressure vessel. Reference numeral 2 is a pressure transmission medium enclosed in the pressure vessel 1, and in the embodiment, for example, silicone oil which is an incompressible fluid is used. R ₁ is a pressure sensor made of a pressure-sensitive semiconductor material whose resistance value changes to a positive polarity in response to a change in hydrostatic pressure applied. R ₂ is a pressure sensor made of a pressure-sensitive semiconductor material whose resistance value changes to a negative polarity in response to a change in applied hydrostatic pressure.
TC is a temperature detecting element, such as a thermocouple. The above pressure sensors R ₁ and R ₂ , the temperature detection element T
C is arranged in the pressure vessel 1. The temperature detecting element T
Since C is for measuring the temperature of the pressure sensors R ₁ and R ₂ , the temperature detecting element TC does not necessarily have to be arranged in the pressure vessel 1. Reference numeral 4 denotes a hermetic seal portion, which is used to take out the lead wires 5a to 7b electrically connected to the pressure sensors R ₁ and R ₂ to the outside of the pressure vessel 1.
This is for preventing the pressure transmission medium 2 from leaking out. A pressure-measurement target pressure is applied to the portion 1a of the pressure vessel 1, but a diaphragm having a wide corrosion resistance and a wide elastic range is provided so that the pressure transmission medium 2 sealed inside does not flow out.

FIG. 2 shows an electric circuit to which the lead wires 5a to 7b in FIG. 1 are connected, and a signal e _out corresponding to the applied pressure can be obtained from the output terminal of this circuit. Second
In the figure, 20 is a constant voltage source and U is an amplifier. R ₁ ,
R ₂ is the pressure sensor shown in FIG. C is a logarithmic converter, D is a divider, and F is an adder.

The pressure sensor R ₁ is connected to the inverting input terminal of the amplifier U,
A pressure sensor R ₂ is connected between the output terminal and the inverting input terminal of the amplifier. A constant voltage source 20 is connected between the other end of the pressure sensor R ₁ and the non-inverting input terminal of the amplifier U. The output terminal and the non-inverting input terminal of the amplifier U are connected to the logarithmic converter C. The output voltage e ₂ of the logarithmic converter C and the output voltage (−A) of the adder F are connected in series and introduced into the divider D.
The signal from the temperature detecting element TC is introduced to the other input terminal of the divider D.

The operation of the pressure detecting device having the pressure detecting end shown in FIG. 1 and the electric circuit shown in FIG.

Assuming that the pressure sensor shown in FIGS. 1 and 2 is an intrinsic semiconductor having hydrostatic pressure sensitivity, the conductivity σ ₁ and σ ₂ of the pressure sensors R ₁ and R ₂ are expressed by the equations (1) and (2). It is represented by.

σ ₁ = n _i1 · e · (μ _e1 + μ _p1 ) (1) σ ₂ = n _i2 · e · (μ _e2 + μ _p2 ) (2) where e is electron elementary charge μ _e is electron mobility μ _p is the hole mobility, and n _i1 and n _i2 in the equations (1) and (2) are the intrinsic carrier concentrations of the semiconductor material, respectively, and are represented by the following equations.

Here, n _o1 and n _o2 are material constants E _G1 and E _{G2 that} are not related to temperature and band energy. Band gap energy The resistance value, that is, the conductivity changes with the hydrostatic pressure of the semiconductor material. This is because the gap energy E _G changes with pressure. The resistance values of the pressure sensors R ₁ and R ₂ (represented by R ₁ and R ₂ ) are represented by equations (5) and (6).

When the pressure sensors R ₁ and R ₂ are immersed in silicone oil as shown in FIG. 1 to change the pressure, the resistance values R ₁ and R ₂ change. When this is amplified by the amplifier U of FIG. 2, the output e _{1 of the} amplifier U is expressed by the equation (7).

e _o is the voltage of the constant voltage source 20, if the temperature inside the pressure vessel 1 shown in FIG. 1 is uniform, (7)
The equation can be rewritten as equation (8) using equations (5) and (6).

As described above, by taking the resistance ratio (R ₂ / R ₁ ), the influence of the first temperature It is possible to obtain a signal e _{1 in} which

When e ₁ is passed through the logarithmic converter C, a signal e represented by the equation (9) is obtained.
₂ is obtained.

In addition, When a constant signal of −A− is added from the adder F to this e ₂ signal, the input to the divider D is Becomes When this signal is divided by the temperature signal (1 / T) from the temperature detecting element TC, the signal e expressed by the equation (10) is obtained.
_out is obtained.

e _out = C · (E _G2- E _G1 ) (10) Here, as one pressure sensor, Is a positive polarity, choose a semiconductor material with a large absolute value, and as the other pressure sensor, Select a semiconductor material with a negative polarity and a large absolute value. As a result, the hydrostatic pressure (E
The value of _{G2 -E G1)} is made to the addition of both absolute value, the magnitude of e _out to pressure changes is increased than when using a single semiconductor material. In addition, the temperature signal (1 /
The effect of the second temperature can also be eliminated by dividing by T).

Fig. 4 shows various semiconductor materials Here are examples of positive and negative values.

By the way, the semiconductor silicon is in the order of -0.3 to -1.5, and the sensitivity is lower than that of the material shown in FIG. 4 by one digit or more.

If the material shown in FIG. 4 is selected, the rate of change in resistance with pressure is expressed by equation (11).

ρ is the specific resistance P is the pressure E _G is the band cap will be described using a specific example. Figure 5 is the change in resistance due to the pressure of the black phosphorus, FIG. 6 is a variation of resistance due to the pressure of I _n S _b. The a-axis and the b-axis in FIG. 5 are due to the difference in the crystal direction of black phosphorus. The black phosphorus to the pressure sensor _{R 1,} and chose _I n _{S b} to the pressure sensor _{R 2.} The black phosphorus and I _n S _b, because the change the polarity of the resistance to pressure is reversed, (10)
E _out of the formula is about 0 for a change of 0 to 1000 kgf / cm ^2.
~ 50% change. This change is large and sufficient as the sensitivity of pressure measurement.

In the above, as the pressure sensors R ₁ and R ₂ , Although it has been described that semiconductors having different signs (plus-minus) and a large absolute value are used, in order to obtain a temperature compensation effect, if one pressure sensor is an intrinsic semiconductor, Does not have to be large.

That is, if the semiconductor material is represented by the equations (5) and (6), the equations (8), (9) and (10) can be easily realized, and the temperature compensation can be performed more easily than a single semiconductor material. Become. For a single material, for example, Term or Terms cannot be easily erased.

Further, if the bridge is assembled as shown in FIG. 7, the amplifier is not required in FIG. In FIG. 7, R ₁ , R ₂
Is a pressure sensor.

In FIG. 2, the pressure sensor R ₁ is connected between the inverting input terminal of the amplifier U and the constant voltage source 20, and the pressure sensor R ₂ is connected between the input and output terminals of the amplifier U.
It is clear that the present invention can be realized even if the connection arrangement of the pressure sensors R ₁ and R ₂ is replaced.

[Effects of the Invention] As described above, according to the present invention, the following effects can be obtained.

Temperature compensation can be easily performed by using two semiconductor materials as the resistance element and determining the change in the ratio.

The pressure converter such as a diaphragm is not required, and the mechanical structure is simplified.

Since two semiconductors having opposite polarities are used, pressure sensitivity can be increased.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a main part of a pressure detecting device according to the present invention, FIG. 2 is an electric circuit diagram to which the lead wires 5a to 7b shown in FIG. 1 are connected, and FIG. 3 is a diaphragm. 11 is a view showing a conventional means constituted by bonding the semiconductor piezoresistive element 10 to 11,
Fig. 4 shows various materials Shows the data, FIG. 5 and FIG. 6 shows an example of a change due to the pressure P of the band gap energy E _G FIG, 7
The figure shows an example in which the amplifier U is not required. 1 ...... pressure vessel, 2 ...... pressure transmission medium, 4 ...... hermetic seal portion, 5A～7b ...... _lead, R 1, _{R 2} ...... pressure sensor, TC ...... temperature detecting element, U ...... amplifier, C ...
... Logarithmic converter, D ... Divider, F ... Adder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Aga 2-932 Nakamachi, Musashino-shi, Tokyo Inside Yokogawa Hokushin Electric Co., Ltd. (56) Reference JP-A-54-81088 (JP, A) JP JP-A-56-140229 (JP, A) JP-A-53-149778 (JP, A) JP-A-55-146020 (JP, A) Actually developed JP-A-59-67433 (JP, U)

Claims (2)

[Claims] 1. A pressure vessel in which a pressure to be measured is applied and a pressure transmission medium is enclosed therein, and a semiconductor which is arranged in the pressure vessel and whose polarities of resistance change with respect to hydrostatic pressure are different from each other. A pressure detecting device comprising: two pressure sensors; and means for calculating a resistance ratio of the two pressure sensors. 2. A temperature detecting element for detecting the temperature of the pressure sensor, and a means for logarithmically converting an output signal of the means for calculating the resistance ratio, wherein a signal based on the signal obtained by the temperature detecting element is provided. The pressure detecting device according to claim 1, wherein the temperature component of the signal from the logarithmic converting means is corrected by using the pressure detecting device.