JPS60259922A - strain sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a strain sensor that receives the pressure of a liquid or the like through a diaphragm and converts the strain into an electrical signal using a strain-sensitive resistor set on the diaphragm.

BACKGROUND ART Conventionally, pressure sensors have been widely used to measure the pressure of liquids, etc., which receive pressure with a diaphragm and extract strain as a change in electrical resistance using a strain-sensitive resistor formed on the diaphragm. In addition to metal gauges and semiconductor gauges, strain-sensitive resistors include those having a diaphragm made of a silicon semiconductor and a diffused resistance layer formed on the diaphragm. When the strain-sensitive resistor is a semiconductor such as silicon, the resistance and gauge factor are particularly strongly affected by the operating temperature, so it is necessary to compensate for temperature more strictly. It has the advantage of being 10 times more sensitive.

FIG. 8 shows an example of a conventional pressure sensor, and is a sectional view of a main part in which a semiconductor gauge is attached on a diaphragm.

A strain-sensitive resistor 3.5 is formed on the diaphragm.

4.6 shows the electrode portions at both ends of the strain-sensitive resistor, respectively. In order to compensate for the temperature, the strain-sensitive resistor is usually used by connecting a Wheatstone bridge (hereinafter simply referred to as a "bridge") circuit as shown in FIG. In FIG. 9, 11° and 12 are strain-sensitive resistors, 13 and 14 are metal resistors, and +5 is a constant voltage power source. The power supply 41 is connected to the bridge end ^,C, and the bridge voltage output is obtained from s,d.

Furthermore, if there is a difference in the resistance temperature characteristics of the strain-sensitive resistors,
It is known to compensate for temperature-induced fluctuations in the zero point of the voltage between the output voltages of the IJ and d by connecting metal resistors in series and parallel as necessary to the resistor parts that make up the IJ. ing.

- The force output sensitivity is proportional to the gauge factor of the strain-sensitive resistor, but since the gauge factor is affected by the ambient temperature, it is necessary to compensate for the operating temperature. For example, as shown in FIG. The resistance-temperature characteristic of the thermistor element is the resistance-temperature characteristic of the strain-sensitive resistor. It is quite complicated and time-consuming to make precise adjustments to match the
For example, in a wide operating temperature range such as -40''C to +20'C, it is often difficult to obtain sufficient sensitivity compensation.
There is also the inherent problem of giving a zero point fluctuation in the horn output voltage, and there are many cases where this zero point fluctuation cannot be ignored. or,
The desired thermistor element cannot necessarily be made small, and there are drawbacks such as the overall shape of the sensor becomes large.

OBJECTS OF THE INVENTION Therefore, in view of the above, an object of the present invention is to facilitate temperature compensation of sensitivity while keeping the zero-point fluctuation of the output voltage of a bridge composed of strain-sensitive semiconductor resistors to a minimum. The first thing to do is to provide a small strain sensor.

Structure of the Invention The present invention provides a strain-sensitive semiconductor resistor connected to a diaphragm in a bridge circuit, and a bridge output voltage zero point that is temperature-compensated. This is a strain sensor in which a resistance consisting of It is characterized by a bridge IJ connected in parallel with a horn circuit and connected to a constant voltage power supply.It is a compact IJ that facilitates temperature compensation of sensitivity while keeping the zero point fluctuation of the bridge output voltage to a minimum. strain sensors.

Embodiment FIG. 1 shows a sectional view of the main parts of an embodiment of the strain cell according to the present invention. In Figure 1, 1 is a metal diaphragm made of stainless steel, 2 is an electrical insulating layer made of resin, ceramic, glass, etc., and 3, 5.7 is a strain-sensitive semiconductor such as germanium or the like formed on the insulating layer. Shows a resistor. The strain-sensitive resistors 3 and 5 are strain sensor sections that receive strain generated in the diaphragm 1, and electrical resistance changes due to strain are extracted from electrodes 4.6 at both ends of the resistors 3 and 5. The resistor 7 is a temperature-sensitive sensor portion formed in a portion of the diaphragm 1 that is not subjected to strain, and approximately senses the temperature of the strain-sensitive resistors 3 and 5, and detects the change in electrical resistance at the electrodes 8 at both ends of the resistor 7. Take it out.

The resistors 3.5.7 are formed of the same semiconductor material on the same diaphragm and can be easily miniaturized.

Figure 2 shows an example of the bridge circuit connection in Figure 1, where 21.22 is a strain-sensitive semiconductor resistor, 23.24 is a metal resistor, and 25 is a temperature-sensitive resistor made of the same material as the strain-sensitive semiconductor resistor. Reference numerals 43 and 43 respectively indicate constant current power supply sections.

In Fig. 2, the metal resistor connection part for temperature compensation at the bridge voltage output zero point is omitted from the figure, but b, d
It is assumed that the zero point temperature compensation of the bridge output voltage between the two is sufficient. The dotted line portion 20 indicates a portion that is integrated as a strain sensor and is used at the same ambient temperature.

FIG. 3 shows the relationship between the bridge output voltage 1 in FIG. 2 and the pressure P applied to the diaphragm, using the ambient temperature T as a parameter.

In the figure, To indicates 20°C. FIG. 4 shows the relationship between the voltage (2) between both ends C1e of the resistor 25 and the temperature T in FIG. As shown in FIG. 3, the zero point fluctuation of the bridge output voltage due to the ambient temperature is suppressed to a sufficiently low level. Also, the bridge output voltage VI with respect to the pressure P is α, β
It is expressed as Vr 2a (1-β(T-To))P, where is a constant.

Also, from Fig. 4, the voltage V1 is expressed as ■2; V with Vo and γ as constants.
It is expressed as oe''T. Therefore, if the voltages V, , V, are totaled by θ11, then P2V, /α(1-β(T-To))
Therefore, the pressure applied to the diaphragm can be calculated. Voltage V+ +Vt (7) A microcomputer or the like can be used to measure M1 and calculate pressure P. Calculation can also be performed by storing the voltages V, V, and values at each temperature in a microcomputer, if necessary.

FIG. 5 shows another embodiment of the Britno circuit connection in FIG. In the figure, 31.32 is a strain-sensitive semiconductor resistor, and 33
．． 34.3G is a metal resistor, 35 is a temperature sensitive resistor, and 45
Each indicates a constant voltage power supply section. (Similar to Figure 2, the metal resistor connection part for temperature compensation at the bridge voltage output zero point is omitted, but it is assumed that the zero point temperature compensation for the bridge output voltage between b and d is sufficient.) Dotted line part 3
0 indicates a part that is integrated as a strain sensor and used at the same ambient temperature. In the case of FIG.
The relationship between the voltage and the voltage between 1 and 2 has the same characteristics as in FIGS. 3 and 4.

Therefore, by measuring the voltages V, , V, the value of the pressure P can be calculated. If necessary, in order to linearize the resistance-temperature characteristics of the temperature-sensitive resistors 25 and 35 in FIGS. It is also possible to add resistors 26.27 and 38.39 in series and parallel.

Although this example shows the case where the diaphragm is made of metal,
Similar excellent effects can be obtained when a semiconductor such as silicon single crystal is used for the diaphragm.

Further, in the embodiment of the present invention, the power source applied to the temperature sensitive resistor section is the same as the power source for the strain sensitive resistor section, but it goes without saying that each may be driven by a separate power source.

Effects of the Invention As described above, the present invention provides a strain sensor in which a strain-sensitive semiconductor resistor is connected to a diaphragm in a bridge circuit, and the Brisono output voltage zero point is temperature compensated. A strain sensor in which a resistor made of the same material is used as a temperature-sensitive resistor. It is characterized by a circuit connected in parallel with a Brisono circuit and connected to a constant voltage power supply.It is a compact design that facilitates temperature compensation of sensitivity while keeping the zero point fluctuation of the bridge output voltage to a minimum. The present invention provides a strain sensor.

The strain sensor according to the present invention is particularly effective and exhibits its characteristics when used in a measurement/control/stem system using a Funbuter.

[Brief explanation of the drawing]

FIG. 1 shows a sectional view of the main parts of an embodiment of the strain sensor of the present invention. FIG. 2 shows an example of the bridge circuit connection in FIG. 1. FIG. 3 shows the relationship between the bridge output voltage VI and the pressure P applied to the diaphragm in FIG. 2 using the ambient temperature T as a parameter, where the vertical axis shows the output voltage and the horizontal axis shows the pressure. FIG. 4 shows the temperature characteristics of the voltage V between the m-sensitive resistors in FIG. 2, where the vertical axis shows the voltage and the horizontal axis shows the temperature. 5, 6 and 7 respectively show examples of bridge circuit connections of other embodiments of the strain sensor of the present invention. FIG. 9 and FIG. 1O show examples of Blitzno circuit connections of conventional strain sensors. 21, 22.31.32・・・・・・・・・・・・・・・
...Strain-sensitive semiconductor resistors 25, 35...
・・・・・・・・・・・・・・・・・・Temperature-sensitive resistor 41,
42.43.44.45.4G... Constant voltage power supply part 2 Figure 20 (L-=-=, -1 --J Fang 3 I → Baka (P) Samurai 4 open 5th I ￥l Fang G Shame 0 "' 廿 ■1 Tsuji G L--1---1---~-1" /+8 Shouga OI Shinkyu )0 Seki l'7

Claims (3)

[Claims] (1) In a strain sensor in which a strain-sensitive semiconductor resistor is connected in a bridge circuit on a diaphragm and the zero point of the bridge output voltage is temperature compensated, a resistor made of the same material as the strain-sensitive resistor is formed on a portion of the diaphragm that is not subjected to strain. A strain sensor characterized by using a temperature-sensitive resistor as a temperature-sensitive resistor. (2) The temperature-sensitive resistor described in l is connected in series with the above circuit and connected to a constant current power supply, or a series circuit with a metal resistor is connected in parallel with a bridge circuit and then connected to a constant voltage power supply. The strain sensor according to claim 1, characterized in that: (3) The strain sensor according to claim 1 or 2, wherein the temperature-sensitive resistor is formed by connecting a metal resistor in series and parallel to the temperature-sensitive resistor.