Horology: time measuring systems or devices – Power supply details – Electrical
Reexamination Certificate
1995-10-13
2002-10-15
Roskoski, Bernard (Department: 2841)
Horology: time measuring systems or devices
Power supply details
Electrical
Reexamination Certificate
active
06466521
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a sensor function-equipped portable device for detecting physical information, such as water depth and altitude, and displaying such information or issuing a warning.
BACKGROUND ART
Although sensor function-equipped portable devices having a single function, such as dive computers, altimeters, and depth gauges, have been used in, for example, marine sports and mountaineering, sensor function-equipped electronic clocks have recently been manufactured that, in addition to their ordinary functions, e.g., basic time display function, alarm function, and timer function, also have sensor functions that use sensors to measure constantly changing physical information such as air pressure, water pressure, and temperature, and that display this information via a signal processor circuit; this kind of electronic clock has become more common.
With these sensor function-equipped portable devices, it is necessary to convert the physical information obtained as analog values into digital values in order to display the physical information detected by the sensors in a digital fashion; a 3 V high voltage power source means, for example, is required for this A/D conversion; in the past, a 3 V coin-type lithium cell has been used, or two or three 1.5 V button-type silver cells have been used.
However, a coin-type lithium cell or two or three buttontype silver cells result in a bulky clock element, which increases costs, so that for portable devices such as electronic clocks that have limited electronic circuit housing space and that must be inexpensive, operation with a single 1.5 V button-type silver cell is desired.
Prior art is described below with reference to accompanying drawing.
FIG. 2
is a block diagram of a conventional sensor signal processor used in a sensor-equipped portable device.
In
FIG. 2
,
101
is an air pressure sensor adapted to output an air pressure signal S
1
proportional to an air pressure P,
102
is a sensor drive circuit adapted to drive the air pressure sensor
101
by causing constant current to flow in the air preasure sensor
101
,
103
is an amplifier circuit that amplifies the air pressure signal S
1
using an operational amplifier not shown in the figure, and that outputs the result as a signal S
1
′,
104
is an A/D converter circuit that subjects the signal S
1
′ output from the amplifier circuit
103
to A/D conversion and outputs the resulting product as data Dc,
105
is a sensor information data processor circuit that processes the data Dc and outputs the result as sensor information data Dj,
106
is a display unit that digitally displays the air pressure value on the basis of the sensor information data Dj output from the sensor information data processor circuit
105
,
107
is a constant-voltage power source circuit that generates a −2.6 V power source voltage Vreg, and
109
is a coin-type lithium cell that generates a −3.0 V power source voltage Vss.
FIG. 7
is a diagram depicting the internal structure of the sensor drive circuit
102
.
The sensor drive circuit
102
comprises a resistor
102
a
with a resistance value Rs and an operational amplifier
102
b
whose power source is a −3.0 V power source voltage Vss. The negative input terminal of the operational amplifier
102
b
has the same potential Vs as the positive input terminal due to imaginary shortening with the air pressure sensor
101
as feedback resistance. A constant current Is, expressed by Formula (1) consequently flows in the resistor
102
a
, and the air pressure sensor
101
is thereby driven by the constant current Is.
Is=Vs/Rs
(1)
FIG. 9
is a diagram depicting the internal structure of the constant-voltage power source circuit
107
.
The constant-voltage power source circuit
107
comprises a constant-voltage generator
171
and a basic reference voltage generator
107
a l composed of a resistor RO and a constant-current circuit
173
. The constant-current circuit
173
allows a constant current Ir to flow through the resistor RO, so that a reference voltage Vr is generated due to the voltage drop across the resistor R
0
, and the reference voltage Vr is applied to the constant-voltage generator
171
. The constant-voltage generator
171
subjects the reference voltage Vr to voltage/current amplification, and the resulting
−2.6 V power source voltage Vreg is supplied to the amplifier circuit
103
and the A/D converter circuit
104
.
A conventional sensor signal processor having the aforementioned circuit structure operates as described below.
A voltage Vss of a coin-type lithium cell
109
serves as the power source, and when the air pressure sensor
101
is subjected to constant-current driving by the sensor drive circuit
102
, an air pressure signal S
1
proportional to the air pressure P applied to the air pressure sensor
101
is output. As shown in
FIG. 10
, the air pressure signal S
1
is amplified by the amplifier circuit
103
, with a voltage of Vreg/2 that is half of the power source voltage Vreg that serves as the reference, resulting in a signal S
1
′. As far as this amplified signal S
1
′ is concerned, the difference between the voltage Vreg/2 and the signal S
1
′ is subjected to digital conversion by the A/D converter circuit
104
, with the voltage Vreg/2 serving as the reference, to produce digital data Dc. The digital data Dc is converted into a sensor information signal Dj by the sensor information processor circuit
105
, and the display unit
106
displays the air pressure value (e.g., 1013 hPa) based on this sensor information signal Dj. The signal S
1
′ that has been amplified by the amplifier circuit
103
varies within a range between the voltage Vreg/2 and the voltage Vreg shown in
FIG. 10
, the potential difference between Vreg and Vreg/2 is taken as the dynamic range, and, for a given air pressure range, the resolution of the A/D converter circuit
104
can be increased for a larger dynamic range, so that the air pressure value display resolution can be increased. Since the number of bits per unit display air pressure can be increased, it is also possible to reduce the variation in the air pressure value display that is caused by bit errors due to poor A/D conversion reproducibility.
As described above, when display resolution and bit errors during A/D conversion are taken into account, it is sometimes necessary to increase the dynamic range of the signal S
1
′ amplified by the amplifier circuit
103
. For this reason, the power source voltage Vreg must be about −2.6 V to generate such a Vreg, and the constant-voltage power source circuit
107
must have a power source voltage Vss that is −3.0 V or less, and the cell
109
must be of a voltage of 3 V or more.
To maintain a power source voltage of 3 V or more, however, either a coin-type lithium cell with a large diameter or a plurality of 1.5 V button-type silver cells must be used; as far as portable devices such as electronic clocks with limited electronic circuit element housing space are concerned, the size of the module becomes considerable, and this is disadvantageous in terms of design and cost.
The present invention was devised in light of the aforementioned situation, and its objective is to provide a sensor function-equipped portable device that can maintain A/D conversion resolution and reproducibility using only a single small and inexpensive 1.5 V button-type silver cell.
DISCLOSURE OF THE INVENTION
To achieve this objective, the present invention provides a sensor function-equipped portable device comprising a sensor for detecting physical information, a sensor drive circuit for driving the sensor, an amplifier circuit for amplifying the sensor signal from the sensor, an A/D converter circuit for converting the output signal of the amplifier circuit into digital information, a sensor information data processor circuit for preparing sensor information data from the digital information output from the A/D converter circuit, and a display
Citizen Watch Co. Ltd.
Roskoski Bernard
Thompson & Coburn LLP
LandOfFree
Sensor function-equipped portable device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Sensor function-equipped portable device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sensor function-equipped portable device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2994256