Data processing: measuring – calibrating – or testing – Calibration or correction system – Sensor or transducer
Reexamination Certificate
1999-04-19
2002-04-16
Bui, Bryan (Department: 2857)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Sensor or transducer
C702S085000, C702S098000
Reexamination Certificate
active
06374191
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a self-calibrating sensor having a sensor element for electrically detecting a change in physical amount of a workpiece, a signal output means for detecting the change of the sensor element and outputting an electric signal, a processor for conducting calibration calculation of the electric signal for adjusting to the physical amount of the workpiece, and a memory for storing a calibration value to conduct calibration calculation by the processor. The present invention can be applied to, for example, a self-calibration pressure sensor having ASIC (Application Specific Integrated Circuit) including CPU (Central Processing Unit), in which a deformation of a diaphragm in accordance with pressure change of a workpiece can be detected as a change in electro-capacitance.
2.Description of Related Art
Conventionally, a sensor having a sensor element for electrically detecting a change in a physical amount of a workpiece and a signal output means for detecting the change of the sensor chip and outputting an electric signal is used. For example, an electro-capacitance type sensor having a diaphragm deforming in proportion to a change in pressure of the workpiece, a movable electrode formed on the diaphragm, a fixed electrode opposed to the movable electrode and a signal output means for detecting the change of the sensor element as a change in electro-capacitance between the movable electrode and the fixed electrode to output as a capacitance signal is known as such a sensor.
As a specific example, a pressure detector
90
using an electro-capacitance pressure sensor is shown in FIG.
10
.
In the figure, the pressure detector
90
has a base member
91
which has a fitting
92
fixedly screwed to a portion to be detected. The fitting
92
is provided with a pressure inlet
93
to which pressure is introduced from an inside of the portion to be detected. The base member
91
has a greatly enlarged diameter remote from the fitting
92
and a pressure sensor
1
is installed thereon to cover the enlarged opening. A sealing member
94
such as an O-ring is inserted between the pressure sensor
1
and the base member
91
in order to ensure sealability therebetween.
The pressure sensor
1
has a diaphragm
1
A on a surface facing the pressure inlet
93
, the diaphragm
1
A receiving the pressure from the pressure inlet
93
to displace in a direction intersecting the surface. The pressure sensor
1
outputs the displacement of the diaphragm
1
A by an internal electrode (not shown) as a change in electro-capacitance.
A processor
5
is mounted on the pressure sensor
1
on a side opposite to the fitting
92
. The processor
5
is connected to an electrode of the pressure sensor
1
through a through-hole etc. provided on the pressure sensor
1
to receive a signal showing the change in the electro-capacitance and to output to the outside after amplifying and conducting predetermined arithmetic processing etc.
An output substrate
95
is provided for outputting the signal from the processor
5
to the outside. The processor
5
and the output substrate
95
are wired by wire-bonding etc. and a durable cable
96
is wired to connect the output substrate
95
and the outside.
The base member
91
is covered by a cover member
97
, in which all of the pressure sensor
1
, the processor
5
, the output substrate
95
etc. are accommodated.
The change in the pressure of the workpiece and the capacitance signal do not always linearly correspond within the entire measurement range. Furthermore, slight deviation is caused to respective products when the sensors are mass-produced as consumer products.
Accordingly, calibration work is conventionally conducted for every electro-capacitance pressure sensor so that highly accurate measurement is possible irrespective of the electro-capacitance sensor employed and the measurement range.
However, an outside adjusting apparatus such as potentiometer and trimming apparatus as well as the sensor is necessary for such calibration work and the calibration work is necessary to be done to individual electro-capacitance pressure sensor, thereby largely increasing the cost required for the calibration work after manufacturing the sensor.
In view of the above, a self-calibration pressure sensor is proposed, in which an electro-capacitance pressure sensor has ASIC including CPU which performs the above calibration work.
FIG. 11
shows an example of the conventional self-calibrating sensor.
Self-calibrating sensor
100
has a sensor element
101
including a diaphragm, a signal output means
102
for outputting a change in electro-capacitance in accordance with the pressure change of the sensor element
101
as a capacitance signal S
1
, a processor
103
for conducting calibration calculation of the capacitance signal S
1
to adjust to the pressure of the workpiece, and a memory
104
for storing calibration value for conducting calibration calculation by the processor
103
.
When the pressure of the workpiece is measured by the self-calibrating sensor
100
, the processor
103
obtains the calibration value for conducting calibration calculation from the memory
104
simultaneously with activation of a power supply unit
105
connected to the self-calibrating sensor
100
. Subsequently, the processor
103
conducts calibration calculation of the capacitance signal S
1
outputted from the signal output means
102
based on a predetermined calculation formula for outputting signal of pressure converted value P.
When the calibration value of the self-calibrating sensor
100
is calculated, a known calibration pressure P
0
is applied to the sensor element
101
and the capacitance signal S
1
outputted by the signal output means is detected. The calibration value is set so that the pressure converted value P equals P
0
in the calculation formula for obtaining pressure converted value P based on the outputted capacitance signal S
1
.
For calibrating the self-calibrating sensor
100
, a pressure generator
110
is connected to the sensor element
101
of the self-calibrating sensor
100
and the processor
103
of the self-calibrating sensor
100
and a controller (not shown) of the pressure generator
110
are electrically connected to a computer
120
, as shown in FIG.
11
.
A control signal S
2
for outputting calibration pressure P
0
is outputted from the computer
120
to the pressure generator
110
and the capacitance signal S
1
outputted from the self-calibrating sensor
100
is received by the computer
120
through the serial interface
106
. The computer
120
sets the calibration value of the self-calibrating sensor
100
by processing the calibration pressure value P
0
based on the outputted control signal S
2
and the received capacitance signal S
1
. The determined calibration value is outputted to the self-calibrating sensor
100
from the computer
120
and is stored in the memory
104
through the serial interface
106
.
However, following disadvantage occurs in the conventional self-calibrating sensor.
For outputting the calibration value set by the computer
120
to the self-calibrating sensor
100
, an exclusive I/O (input/output) line has to be provided. Specifically, as mentioned above, the serial interface
106
and the like has to be connected to the self-calibrating sensor
100
by a serial and parallel cable for outputting the calibration value, or digital signal has to be coupled to a power supply line to transmit the calibration value.
In the actual pressure measurement, the computer
120
checks whether the calibration value is stored in the memory
104
through the exclusive I/O line to determine which one of the actual measurement and calibration work should be done according to presence of the calibration value. Accordingly, though the aforementioned exclusive I/O line is only used for the calibration work or the check before conducting measurement, the serial interface
106
has to be separately provided and the computer
120
and the self-calibrat
Ogawa Shigemitsu
Tsuchiya Munenori
Yamagishi Kazuya
Bui Bryan
Flynn ,Thiel, Boutell & Tanis, P.C.
Nagano Keiki Co. Ltd.
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