JPS6125015A - Characteristics correcting apparatus for sensor - Google Patents

Abstract

PURPOSE:To make it possible to perform high speed response without using high-speed, highly accurate A-D and D-A converters and logic operation circuits, by converting a physical quantity group other than a physical quantity to be measured into an electric signal, and correcting the characteristics of a detecting circuit by the corresponding control quantities. CONSTITUTION:The output voltage of a pressure detecting circuit 10 is outputted to the outside through an amplifier circuit 106. The output of a temperature detecting circuit 20 is inputted to a logic operation circuit 60 through a preamplifier circuit 40 and an A/D converter 50. A zero-point control quantity, a sensitivity control quantity and a non-linear-error control quantity are outputted to registers 70, 80 and 90. The outputs of the registers 70, 80 and 90 are imparted to a zero-point control circuit 76, a sensitivity control circuit and a non-linear control circuit 96. The zero point, the sensitivity and the non-linearility of the output of the pressure detecting circuit 10 are corrected.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a sensor characteristic correction device, and particularly to sensor characteristics suitable for digitizing a correction circuit such as a pressure sensor using a semiconductor pressure-sensitive element. This invention relates to a correction device.

[Background of the invention]

Conventionally, as a characteristic correction device for a digital sensor, there is a method disclosed in U.S. Pat.
There is one proposed in Publication No. 99. The configuration of these conventional pressure sensing devices includes a pressure sensing circuit that converts applied pressure into an electrical signal, including a pressure sensing element, and a temperature sensing circuit that includes a temperature sensing element installed near the pressure sensing element. a temperature detection circuit that detects and converts it into an electrical signal, a memory circuit that stores in advance the relationship between the applied pressure and the output signals of the pressure detection circuit and temperature detection circuit, and the outputs of the pressure detection circuit and temperature detection circuit. a logic operation circuit that reads out the relationship between applied pressure and the signal from the storage circuit and calculates the applied pressure; an A-D converter that converts the output signals of the pressure detection circuit and the temperature detection circuit into digital signals; and the logic operation circuit. The configuration includes a DA conversion circuit that converts the calculation result of the circuit into an analog signal.

The operation is as follows. First, the output signals of the pressure detection circuit and the temperature detection circuit are converted into digital signals by an A-D converter and input into a logic operation circuit. The logic operation circuit reads the relationship between the applied pressure values corresponding to the input signals from the pressure detection circuit and the temperature detection circuit from the storage circuit, and calculates the applied pressure. This calculation corrects temperature effects and nonlinear errors on the zero point and sensitivity that occur in the pressure detection circuit. The applied pressure value determined here is converted into an analog signal by a DA converter and output.

As described above, the applied pressure signal passes through the A-D converter, logic operation circuit, and D-A converter in sequence after exiting the pressure detection circuit, so the response time, resolution, accuracy, etc. of the pressure detection device, etc. The performance of the digital signal processor depends on the performance of the digital signal processing section, which includes AD and DA converters, logical operation circuits, and the like.

For this reason, conventional pressure detection devices require a high-speed, high-resolution digital signal processing section, regardless of the temperature influence value or nonlinear error of the pressure detection circuit. In other words, the number of bits corresponds to the reciprocal of the allowed error,
For example, processing circuits for o and is require 10 bits, and processing circuits for o and oi* require 13.5 to 14 bits.

[Purpose of the invention]

The present invention has been made in view of the above, and its purpose is to enable high-speed response without using high-speed, high-precision A-D, D-A converters or logic operation circuits, and to An object of the present invention is to provide a sensor characteristic correction device capable of digitally correcting sensor characteristics.

[Summary of the invention]

The present invention focuses on the fact that the sensitivity of the sensor to the physical quantity to be measured is greater than the sensitivity to other physical quantities that are disturbances, and has a configuration in which only the detection signal of the physical quantity other than the physical quantity to be measured is digitally processed and corrected. a second detection circuit that converts into electrical signals a group of physical quantities other than the physical quantities to be measured that affect the first detection circuit that converts the physical quantities to be measured into electrical signals; An A-D conversion circuit that converts the output into a digital signal;
A logical operation that inputs a digital signal from a conversion circuit and converts the group of physical quantities that have an effect according to the digital signal into a control amount necessary for correcting the influence value that it has on the output characteristics of the first detection circuit and outputs the control amount. The present invention is characterized in that it has a configuration consisting of a circuit and a correction means for correcting the output characteristics of the first detection circuit by inputting the output of the logic operation circuit.

[Embodiments of the invention]

The present invention will be explained in detail below using the embodiments shown in FIGS. 1 and 2.

FIG. 1 is a block diagram showing an embodiment of a physical quantity detection device equipped with a sensor characteristic correction device according to the present invention, and illustrates a pressure detection device using a semiconductor strain gauge. In FIG. 1, 1o is a pressure detection circuit, and a pressure sensing element 1 consisting of a semiconductor strain gauge whose resistance value changes depending on the applied pressure.
1 to 14 constitute a bridge circuit. Reference numeral 20 denotes a temperature detection circuit for detecting the temperature of the pressure detection circuit 10, and a bridge circuit is formed by a temperature sensing element 21 whose resistance value changes with temperature and resistors 22 to 24. Note that the temperature sensing element 21 is formed on the same semiconductor substrate as the pressure sensing elements 11 to 14, or is formed separately, and is installed near the pressure sensing elements 11 to 14. 30 is a pressure detection circuit 10 and a temperature detection circuit 20
It is a reference power supply that supplies voltage to the components of each circuit, including the circuit. 40 is a preamplifier that amplifies the output signal of the temperature detection circuit 20; 50 is an A-D converter that converts the analog signal amplified by the preamplifier 40 into a digital signal;
60 is a zero point control amount for inputting a digital signal from the A-D converter 50 and setting the zero point of the pressure detection circuit 20 to a predetermined voltage, which is stored in advance in the storage circuit 61 and corresponds to the digital signal; This is an operational amplifier that reads out the sensitivity control amount for setting the sensitivity to a predetermined value and the nonlinear error control amount for reducing the nonlinear error to zero, and outputs them to the registers 70, 80, and 90, respectively.

71 is a D-A converter, and 72 to 75 are resistors, which constitute a zero-point control circuit 76, which adjusts the zero-point output voltage of the pressure detection circuit 10 to a predetermined voltage based on the input data of the D-A converter 71. to control.

81 is a D-A converter, 82 to 85 are resistors, 86 is an operational amplifier, and 87 is a MOS transistor, which constitutes a sensitivity control circuit 88. Based on the input data of the D-A converter 81, The current flowing through the pressure detection circuit 10 is controlled, and the sensitivity of the pressure detection circuit 10 is controlled.

91 is an operational amplifier, 92 to 95. R, ~R, is resistance, S
1 to S are switches, which control the nonlinearity control circuit 96.
The non-linear error of the pressure detection circuit 10 is controlled by the output data of the register 90.

101 is an operational amplifier, 102 to 105 are resistors, and these constitute an amplifier circuit 106 that amplifies the output of the pressure detection circuit 10.
It consists of

Next, the operation will be explained. First, the pressure detection circuit 10
When pressure is applied to pressure sensitive elements 11 to 14, the resistance values of pressure sensitive elements ii and ta decrease, and the resistance values of pressure sensitive elements 12 and 14 increase, causing the bridge circuit to become unbalanced and the output voltage to decrease. occurs. This output voltage is amplified by the amplifier circuit 106 and output to the outside.

On the other hand, the resistance value of the temperature sensing element 21 of the temperature detection circuit 20 changes when the ambient temperature changes, causing the bridge circuit to become unbalanced and generate an output voltage according to the change in the ambient temperature. This output voltage is amplified by a preamplifier circuit 40, converted to a digital signal by an A-D converter 50, and then sent to a logic operation circuit 60.
be taken in. The logic operation circuit 60 controls a zero point control amount to make the zero point corresponding to the digital signal a predetermined voltage, a sensitivity control amount to make the sensitivity a predetermined value, and a nonlinear error to make the nonlinear error zero. The control amount is read out and output as a digital signal to the registers 70, 80 and 90, respectively.

Next, the operation of the zero point control circuit 76 will be explained. When the contents of the register 70 change and the output voltage of the DA converter 71 changes, the voltage at the output point A changes due to the voltage division between the resistor 72 and the output resistance of the pressure detection circuit 10 viewed from the output point A. Therefore, the data set in the register 70 controls the output OUT of the pressure detection device when the pressure is zero. Here, the resistor 73 to 750 circuit has an output of O
This is used to determine the reference voltage when controlling the UT. The resistance value of the resistor 73 is made equal to that of the resistor 72, and the voltage at the connection point between the resistors 74 and 75 and the DA converter 7
When the output voltages of output points A and B are equal, the output points A and B form a symmetrical circuit, so the voltage changes at the output points A and H are equal, and the voltage at the output OUT does not change. As a result, the output OU
The reference voltage used to control the zero point of 'l' reaches the voltage at the connection point between resistors 74 and 75.

Next, the operation of the sensitivity control circuit 88 will be explained. When the contents of the register 80 change and the output voltage of the DA converter 81 changes, the voltage at the (g) input terminal of the operational amplifier 86 changes. Therefore, the voltage at the connection point between the resistor 85 and the MOS transistor 87 changes, and the current flowing through the bridge circuit forming the pressure detection circuit 10 changes. Since the output of this bridge circuit is proportional to the applied voltage or current, the data set in register 80 controls the sensitivity of the pressure sensing device.

Next, the operation of the nonlinearity control circuit 96 will be explained.

The operational amplifier 91, the resistors 92 to 94, R1 to R111, and the switches S and -S constitute an inverting amplifier whose amplification factor changes depending on the contents of the register 90. Here, the output OUT
When the voltage at the output point C of the inverting amplifier increases, the voltage at the output point C of the inverting amplifier decreases, and the current in the pressure detection circuit 10 increases. As a result, the sensitivity increases as the output voltage of the pressure detection device increases, and nonlinearity can be imparted to the amplification. For this reason,
Nonlinearity is controlled by the data set in register 90 since changing the contents of register 90 changes the sensitivity of the inverting amplifier.

As described above, according to the embodiment of the present invention, the amount of characteristic correction of the pressure detection circuit 10 is digitally controlled, but since the amplification is performed by amplifying an analog signal, high-speed response is possible. Further, since the control range for characteristic correction is limited to the error of the pressure detection circuit 10, the number of bits required for digital signal processing can be reduced. Furthermore, since characteristic correction control only needs to respond to temperature changes, a high-speed response circuit is not required.

FIG. 2 is a block diagram corresponding to FIG. 1 showing another embodiment of the present invention, and the same parts as in FIG. 1 are designated by the same reference numerals, and the explanation thereof will be omitted here. The difference from FIG. 1 is the configuration of the sensitivity control circuit 88 and the nonlinearity control circuit 96.

The sensitivity control circuit 88 controls the switches P1 to P1 using the output data of the register 80 to control the resistors Z1 to Z.

By switching the resistance connected to the source of the MOS transistor 87, the current flowing through the pressure detection circuit 10 is changed to control the sensitivity.

Further, the nonlinearity control circuit 96 controls the switches S, ~S, with the output data of the register 90, and outputs fF'OUT.
The value of the feedback resistor fed back to the sensitivity control circuit 88 is changed to control the non-linear error.

According to the embodiment shown in FIG. 2, in addition to the same effect as in FIG. 1, the voltage at the feedback point of the nonlinearity control circuit 96 does not change depending on the control amount of the sensitivity control circuit 88, so An additional advantage is that there is no mutual interference between circuit 96 and sensitivity control port 88.

Note that in each of the embodiments described above, the pressure detection circuit 10
Although the bridge circuit is composed of four pressure-sensitive elements, if the bridge circuit includes one or more pressure-sensitive elements, pressure changes can be converted into voltage signals.

In addition, although the temperature detection circuit 20 is shown using a temperature sensing element 21 whose resistance value changes depending on the temperature, PN
A temperature sensing element that utilizes the temperature dependence of the forward voltage of a junction may be used.

Further, although the pressure detection circuit 10 is driven by constant current, it goes without saying that it may be driven by constant voltage.

〔Effect of the invention〕

As explained above, according to the present invention, high speed.

High-speed response is possible without using high-precision A-D, D-A converters or logical operation circuits, and sensor characteristics can be digitally corrected (1'J). This has the effect of reducing the number of pits required for signal processing.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of a physical quantity detection device equipped with a sensor characteristic correction device according to the present invention, and FIG. 2 is a block diagram corresponding to FIG. 1 showing another embodiment of the present invention. be. 10...Pressure detection circuit, 20...Temperature detection circuit, 4
0... Preamplifier, 50... A-D converter, 60...
. . . logical operation circuit, 61 . . . memory circuit, 70, 80.
90...Register, 76...Zero point control circuit, 88...
...Sensitivity control circuit, 96...Nonlinearity control circuit, 10
6...Amplification circuit.

Claims (1)

[Claims] 1. In a physical quantity detection device equipped with a first detection circuit that converts a physical quantity to be measured into an electrical signal, a group of physical quantities other than the physical quantity to be measured that affects the first detection circuit is a second detection circuit that converts the output into a signal; an A-D conversion circuit that converts the output of the second detection circuit into a digital signal; a logic operation circuit that converts and outputs a control amount necessary for correcting the influence value that the group of influencing physical quantities has on the output characteristic of the first detection circuit; and an output of the logic operation circuit that inputs the output. A sensor characteristic correction device comprising: a correction means for correcting an output characteristic of the first detection circuit. 2. The control amount is a zero point control amount to make the zero point of the output of the first detection circuit a predetermined voltage, a sensitivity control amount to make the sensitivity a predetermined value, and a nonlinear error to zero. Non-linear error control amount, wherein the correction means is configured to control offset voltage, amplification factor and non-linearity by inputting digital signals corresponding to each of the control amounts, respectively. A sensor characteristic correction device according to scope 1. 3. The first detection circuit includes a bridge circuit using an element that converts a change in the physical quantity to be measured into a resistance change, and the correction means includes an amplifier circuit that amplifies the output from the first detection circuit. , a control circuit that controls the current or voltage applied to the bridge circuit by a digital signal corresponding to a control amount from the logic operation circuit; and a feedback circuit that feeds back the output of the amplifier circuit to the current or voltage applied to the bridge circuit. A sensor characteristic correction device according to claim 1 or 2, comprising a quantity control circuit.