JPH01109231A - Pressure 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 [Field of Industrial Application] The present invention relates to a pressure sensor that detects pressure by detecting displacement of a diaphragm using a strain gauge.

[Conventional technology]

As shown in Fig. 4, four strain gauges 2 are attached to the diaphragm 1, and the four strain gauges 2 are connected in a bridge circuit as shown in Fig. 5, so that the output voltage v out acts on the diaphragm 1. Pressure sensors that detect pressure are known.

In other words, when diaphragm 1 is displaced by pressure, 4
Pressure is detected by utilizing the strain deformation of the two strain gauges 2.

[Problem that the invention seeks to solve]

In such a pressure sensor, its output voltage has nonlinearity due to the characteristics of the diaphragm 1 and the characteristics of the strain gauge 2.

For example, as shown in Figure 6, pressure and output voltage theoretically change along a straight line (A), but in reality they change along a curve (B).
, and the shaded area is the error.

For this reason, pressure cannot be detected with high accuracy.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a pressure sensor that can accurately detect pressure by making the output voltage match a theoretical value.

[Means and actions for solving the problem] The voltage applied to the bridge circuit is divided into a power supply voltage between a correction variable resistor whose resistance value changes depending on the pressure applied to the diaphragm and a correction resistor whose resistance value does not change with pressure. As a value, the nonlinearity of the output voltage can be canceled by the amount of change in the applied voltage.

(Example of implementation) As shown in FIG. 1, four strain gauges 111 to 114 are placed on a portion 10a of the diaphragm 10 that is displaced by pressure.
A correction strain gauge 12 is attached to the diaphragm 10, and a correction resistor 13 is attached to the non-displaceable portion 10b of the diaphragm 10. Four strain gauges 111 to 114 are connected in a bridge circuit as shown in FIG. A variable compensation resistor that changes, such as a compensation strain gauge 12, and a compensation resistor 13 whose resistance value does not change with pressure are connected in series to the power supply V, and one end of a bridge circuit is connected between the compensation resistor 13 and the compensation strain gauge 12. This is to correct the output voltage V out.

That is, the output voltage VΔR(p) of a pressure sensor in which four strain gauges 111 to 114 are connected in a bridge circuit is the resistance change of the strain gauge due to pressure, and R is the resistance of the strain gauge.

The resistance change ΔR(p) of the strain gauge includes nonlinearity, and can be expressed as ΔR(p)φ and XI)+ as 2Xp2. However, P is pressure and K 1 + K 2 is a constant.

Therefore, the output voltage V out of the pressure sensor is as follows, where the first term is a linear term and the second term is a nonlinear term.

Therefore, as shown in FIG. 2, the applied voltage Vp
If we divide the power supply voltage V by the resistance value of the correction resistor v3, which does not change with pressure, and the resistance value of the correction strain gauge 12, which changes with pressure, p, the applied voltage Vp becomes a voltage that changes with pressure, and this change is By setting the resistance value so as to cancel the nonlinearity shown in FIG. 6, the output voltage v ou
t can be made to match the theoretical value.

More specifically, the applied voltage Vp is determined by the correction gauge 1.
The characteristics of the resistance value rp of 2 appear, and the resistance value ``p'' becomes rp-rpo (1+N Xp).

Therefore, the output voltage V out of the pressure sensor configuring the bridge circuit shown in FIG. can be matched.

Here, K2 + K1 * j! Since is a constant value that cannot be adjusted, rl and rpQ are adjusted.

Note that the correction resistor 13 may be attached anywhere as long as it does not displace, but it is preferably in a position close to the correction strain gauge 12, and the correction resistor 13 and the correction strain gauge 1
2. In the case of a vapor-deposited semiconductor pressure sensor, the strain gauges 11° to 114 can be formed of the same thin film, so the temperature coefficient of resistance value is almost the same, and the entire pressure sensor consists of the correction resistor 13 for nonlinearity compensation and the correction strain gauge 12. There is no change in the temperature characteristics of

The correction strain gauge 12 and the correction resistor 13 are constructed by arranging a large number of resistance plates 12a and 13a concentrically and connecting them with Al electrodes 12b and 13b, as shown in FIG. It is made to be drawn out to the outside by wire bonding 14.

〔Effect of the invention〕

The applied voltage Vp of the bridge circuit becomes a voltage that changes depending on the pressure, and this change can cancel out the nonlinearity of the output voltage of the bridge circuit, so the output voltage can be made to match the theoretical value and the pressure can be adjusted with high precision. Can be detected.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of the present invention, FIG. 2 is a bridge circuit diagram, FIG. 3 is a front view showing a specific example of a correction resistor, FIG. 4 is a front view of a conventional example, and FIG. The bridge circuit diagram,
FIG. 6 is a chart showing the relationship between pressure and output voltage. 10 is a diaphragm, 111 to 114 are strain gauges, 13
is the correction resistance. Applicant Komatsu Ltd. Representative Patent Attorney Masaaki Yonehara

Claims (1)

[Claims] Four strain gauges 11_1 attached to the diaphragm 10
11_4 is connected in a bridge circuit, and the voltage obtained by dividing the power supply voltage V between a correction variable resistor whose resistance value changes depending on the pressure acting on the diaphragm 10 and a correction resistor whose resistance value does not change due to pressure is set as the applied voltage Vp, and A pressure sensor characterized in that pressure is detected using an output voltage Vout of a bridge circuit.