JPH0556815B2 - - Google Patents

Description

[Detailed Description of the Invention] A. Object of the Invention [Field of Industrial Application] The present invention relates to a differential pressure gauge using a semiconductor.

[Conventional technology]

There are various types of differential pressure gauges used for process control. For example, a diaphragm or bellows is used as a pressure receiving element, and a movable part converts the pressure difference into displacement, which is then converted into an electrical signal. Generally, it works to obtain . In such devices, a protection mechanism is provided to prevent movable parts and the like from exceeding displacement limits and being destroyed when excessive pressure is input.

[Problem that the invention seeks to solve]

As mentioned above, conventional differential pressure gauges have a movable part that is displaced by differential pressure and a protection mechanism that protects this movable part from excessive pressure, resulting in a physically large size and a complex configuration. It's getting old.

SUMMARY OF THE INVENTION An object of the present invention is to provide a differential pressure gauge that is compact and has a simple configuration without moving parts.

B "Structure of the Invention" [Means for Solving the Problems] In order to solve the above problems, the present invention has two recesses separated by a partition, and pressure is applied to each of the two recesses. The apparatus includes a container equipped with a pressure-receiving diaphragm that encloses a transmission medium, a semiconductor provided in each pressure transmission medium, and means for measuring the amount of electricity flowing between the semiconductors.

〔Example〕

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

FIG. 1 is a diagram showing an embodiment of the present invention.
In the figure, 1 is a container, which has two recesses separated by a partition wall 1a. Pressure transmission media 4 and 5 are sealed in these two recesses by pressure receiving diaphragms 2 and 3. Pressures P _A and P _B to be measured for differential pressure are applied to the pressure receiving diaphragms 2 and 3. 6 and 7 are semiconductors provided in the pressure transmission media 4 and 5, respectively. 8 is an ammeter that measures the current flowing between the two semiconductors 6 and 7.

The device shown in FIG. 1 configured as described above operates as follows.

As will be explained in detail later, the electron density of a semiconductor changes depending on the pressure. The semiconductors 6 and 7 are configured to have the same electron density (hole density) under the same temperature and pressure environment. If these two semiconductors 6 and 7 are connected via an ammeter as shown in the figure, no current will flow under the same temperature and pressure environment.

However, if there is a difference in the pressures P _A and P _B applied to the pressure receiving diaphragms 2 and 3, 2
A difference occurs in the electron density (hole density) of the two semiconductors 6 and 7. Therefore, since charge moves through the ammeter 8 in order to equalize the fermi levels of the two semiconductors, the pressure difference can be measured from the deflection of the ammeter. Note that the semiconductors 6 and 7 are connected via the partition wall 1a side.
No current flows between them.

FIG. 2 is a diagram showing an example in which the ammeter 8 in the semiconductor differential pressure gauge of FIG. 1 is replaced with an integrator or the like. In this figure, the same elements as in FIG. 1 are given the same element numbers. The difference from Figure 1 is that
A resistor R is connected between the semiconductors 6 and 7 in place of the ammeter 8, the voltage generated across this resistor R is amplified by a buffer 10, and the output of this buffer 10 is integrated by an integrator 11. It is something.

In Figure 1, the ammeter 8 operates when P _A ≠ P _B
This is during a short period of time when a pressure of is easy. However, in this case, since the output currents from the semiconductors 6 and 7 are at a small level, the integrator 11 is required to be highly accurate.

The semiconductor differential pressure gauge of the present invention operates as described above. Next, it will be explained that the carrier number (electron concentration or hole concentration) of the semiconductor changes depending on the pressure.

In an intrinsic semiconductor to which no impurities are added, the electron concentration n and the hole concentration p are equal, and their values are given by equation (1).

n=p=√ _{C V} exp (-E _g /2kT) (1) where N _C , N _V : Effective density of states in conduction band and valence band E _g : Energy gap k : Boltzmann constant T : Absolute When pressure P is applied to a temperature semiconductor, an energy gap occurs.
Since E _g changes, let its rate of change be S = ∂E _g / ∂P (2) Therefore, the carrier concentration n changes with pressure and becomes ∂n / ∂p = -√N _C N _V / 2kT・exp(−E _g /2kT)・S=
K・S (3) However, K=−√N _C N _V /2kT・exp(−E _g /2kT (4).

In order for the number of carriers to change significantly due to pressure, S must be large and K must be large. In order for K to be large, the energy gap E _g must be small, and such a semiconductor is called a narrow gap semiconductor. An example of this is mercury cadmium tellurium cd _x H _g1-x T _e .
Here, the ratio of cadmium and mercury is cd:E _g =
x: (1-x).

Figures 3 and 4 show that regarding cd _x E _g1-x T _e , the specific resistance when the pressure is P is ρ(p), the specific resistance when the pressure is 0 is ρ(o), and this Taking the ratio on the vertical axis,
The horizontal axis is data when pressure is used. This data is from s.narita etal apply.phys.2 pp151−156 (1973)
This is an excerpt from. Fig. 3 shows the case when x<0.09, and Fig. 4 shows the case when x>0.09, both of which treat changes in carrier concentration as changes in resistivity.

C. “Effects of the present invention” As described above, according to the present invention, FIG.
Since there are no displaceable parts as shown in FIG. 2, there is no need to provide a protection mechanism against excessive pressure, and the structure is very simple. Therefore, the problems of conventional means can be solved. Furthermore, since the pressure difference can be directly converted into an amount of electricity without converting it into displacement, it is advantageous in terms of linearity and the like.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams showing an example of the configuration of a semiconductor differential pressure gauge according to the present invention, and Figures 3 and 4 are CD _x H _g1-x
FIG. 3 is a diagram showing pressure-specific resistance changes with respect to T _e . DESCRIPTION OF SYMBOLS 1... Container, 1a... Partition wall, 2, 3... Pressure receiving diaphragm, 4, 5... Pressure transmission medium, 6, 7...
...Semiconductor, 8...Ammeter, R...Resistance, 10...
Batsuhua, 11...Integrator.

Claims (1)

[Scope of Claims] 1. A container having two recesses separated by a partition wall, in which a differential pressure to be measured is applied via a diaphragm to a pressure transmission medium sealed in each of the two recesses. and a semiconductor disposed in each of the pressure transmission media, and a means for measuring the amount of electricity flowing between the semiconductors, the semiconductor disposed in each of the pressure transmission media being connected to these semiconductors. A semiconductor differential pressure gauge, characterized in that the semiconductor differential pressure gauge is configured to measure the differential pressure by utilizing a difference in carrier concentration depending on the applied pressure difference.