Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
2002-05-17
2004-07-27
Le, N. (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S686000, C338S195000
Reexamination Certificate
active
06768320
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of regulating a resistance value in a sensor circuit, and more particularly to the method of regulating the resistance value in the sensor circuit for enabling the resistance value in the sensor circuit provided with an electrostatic capacitance sensor or the like to be regulated easily.
Referring to
FIGS. 3
to
5
, a related method for regulating a resistance value in a sensor circuit of this type will be described. In
FIG. 3
, a switch device
1
includes a pair of first electrodes
3
mounted on a base plate
2
, and a C-shaped second electrode
4
is circumferentially arranged around the first electrodes
3
so as to be outwardly apart therefrom. The first electrodes
3
and the second electrode
4
are covered with a resist
5
, and a pair of carbon electrodes
6
are provided on an upper face of the resist
5
and above the first electrodes
3
.
Moreover, there is provided a click rubber
7
above and opposed to the first electrodes
3
and the second electrode
4
. The click rubber
7
has a substantially cylindrical body
8
and a flexible leg
9
extending downwardly from an outer peripheral part of the cylindrical body
8
at a lower end thereof. In addition, a conductive rubber
10
substantially in a disc-like shape is provided in a center part of the lower end of the cylindrical body
8
. The conductive rubber
10
, the first electrodes
3
and the second electrode
4
constitute an electrostatic capacitance sensor
13
.
Further, a button
11
is mounted on an upper face of the click rubber
7
. An upper cover
12
for covering an upper part of the click rubber
7
, the first electrodes
3
and the second electrode
4
, is provided to press down at a bottom part of the flexible leg
9
of the click rubber
7
, so that an upper part of the button
11
projects through an opening
12
a
which is formed in an upper part of the upper cover
12
.
FIG. 4
shows a sensor circuit
14
of the switch device
1
. The sensor circuit
14
includes a resistor
16
, for setting a resistance constant, which is connected to a line extending from a clock power source
15
. The resistor
16
is composed of a high resistance element
17
having a relatively high resistance value and a pre-set variable resistor
18
capable of regulating the resistance value connected in series. The pre-set variable resistor
18
is connected to one of input terminals of an ENOR (Exclusive NOR) gate
19
. Then, an end of the electrostatic capacitance sensor
13
is connected to the line between the pre-set variable resistor
18
and the ENOR gate
19
. The electrostatic capacitance sensor
13
is composed of a capacitor
20
and a switch
21
connected in series, and the other end of the electrostatic capacitance sensor
13
is grounded.
On the other hand, a resistor
22
for setting a resistance constant is connected to another line extending from the clock power source
15
. The resistor
22
is composed of a high resistance element
23
having a relatively high resistance value and a pre-set variable resistor
24
capable of regulating the resistance value connected in series. The pre-set variable resistor
24
is connected to the other input terminal of the ENOR gate
19
.
In this state, the capacitor
20
corresponds to a circuit constituted by the conductive rubber
10
, the first electrodes
3
and the second electrode
4
, while the switch
21
corresponds to a circuit constituted by the conductive rubber
10
and the carbon electrodes
6
.
Incidentally, when the button
11
is depressed, the flexible leg
9
of the click rubber
7
is flexed so that the conductive rubber
10
is brought into contact with the carbon electrodes
6
to establish electrical continuity between the carbon electrodes
6
. As the button
11
is further pushed down, the conductive rubber
10
is pushed against the first electrodes
3
and the second electrode
4
which are covered with the resist
5
. According to the pressure contact, electrostatic capacitance in the conductive rubber
10
is varied so that output from the conductive rubber
10
is thereby changed.
In other words, after the switch
21
has been turned on in the circuit
14
, the output at the ENOR gate
19
is changed in accordance with the variation of the electrostatic capacitance of the capacitor
20
.
FIG. 5
is a graph showing relationship between input pressure of the electrostatic capacitance sensor
13
provided by bringing the conductive rubber
10
into contact with the resist
5
and the output level thereof. As shown by a solid line, the output level rises substantially in proportion to an increase of the input pressure.
However, as shown by dotted lines in
FIG. 5
, there exists dispersion in the outputs of the respective electrostatic capacitance sensors
13
with respect to the input. The dispersion may incur instability of the output level of the electrostatic capacitance sensor
13
so that reliability as the electrostatic capacitance sensor
13
may be deteriorated.
Under the circumstances, the dispersion in the output levels has been adjusted by regulating the resistance values of the pre-set variable resistors
18
and
24
. However, costs for components of the pre-set variable resistors
18
and
24
are relatively high, and regulation of the resistance values through the use of the pre-set variable resistors
18
and
24
takes a relatively long working time.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method and a structure for regulating a resistance value in a sensor circuit in which the resistance value in the sensor circuit can be easily regulated with a low cost.
In order to achieve the above object, according to the present invention, there is provided a method of regulating a resistance value in a pressure sensitive sensor circuit comprising the steps of:
providing a pressure sensitive sensor circuit including;
a first conductive path having a first resistor which has a first resistance value; and
a second conductive path having a second resistor which has a second resistance value lower than the first resistance value of the first resistor, and the second resistor connected to the first resistor in series; and
a third conductive path having an open circuit which is connected to the second resistor in parallel;
inspecting a relationship between input pressure and output level in the pressure sensitive sensor circuit; and
short-circuiting the open circuit of the third conductive path based on the result of the inspection.
In the above method, the second resistance value of the second resistor can be decreased by short-circuiting the open circuit of the third conductive path, so that the second resistance value in the pressure sensitive sensor circuit can be easily regulated with a low cost.
According to the present invention, there is also provided a sensor circuit comprising:
a first resistor having a first resistance value;
a second resistor having a second resistance value lower than the first resistance value of the first resistor, and connected to the first resistor in series; and
an adjuster for regulating a resistance value in the sensor circuit, including a pair of lands separated from each other for a solder joinable distance, and the pair of lands connected to the second resistor in parallel.
In the above structure, the second resistance value of the second resistor can be decreased by short-circuiting the pair of lands, so that the second resistance value in the sensor circuit can be easily regulated with a low cost.
Further, according to the present invention, there is also provided a sensor circuit comprising:
a first resistor having a first resistance value;
a second resistor having a second resistance value lower than the first resistance value of the first resistor, and connected to the first resistor in series; and
an adjuster for regulating a resistance value in the sensor circuit, including;
a first land, branched from upstream of the second resistor; and
a second land branched from dow
Dole Timothy J
Le N.
Mitsumi Electric Co. Ltd.
Whitham Curtis & Christofferson, P.C.
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