Data processing: measuring – calibrating – or testing – Measurement system – Pressure
Reexamination Certificate
2001-01-19
2004-01-13
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Pressure
C702S098000, C702S150000, C702S138000, C073S384000
Reexamination Certificate
active
06678629
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an altimeter for measuring altitude based on pressure sampled at prescribed intervals and particularly to a highly portable altimeter.
2. Description of the Prior Art
This kind of portable altimeter is, for example, incorporated into the body of a wristwatch and has become widely publicized together with the recent increase in participation in outdoor activities. A block view of the essential parts of the configuration of this kind of related portable altimeter is shown in FIG.
27
. The related portable altimeter shown in
FIG. 27
is provided with a pressure sensor
100
for measuring pressure, an A/D converter
101
for converting an analog output for pressure from the pressure sensor
100
into a digital signal, a measurement controller
102
for controlling the pressure sensor
100
and the A/D converter
101
, a pressure/altitude calculator
103
for calculating altitude based on pressure converted at the AID converter
101
, a display altitude calculator
104
for subjecting the altitude calculated by the pressure/altitude calculator
103
to offset compensation, a switch
105
for carrying out an arbitrary instruction, a display panel
106
for displaying altitude, etc., a ROM
107
for storing programs for processing altitude measurements, a RAM
108
for temporarily storing measured values, etc., and a controller
109
for controlling each part.
A flowchart of an altitude measuring process for a related portable altimeter of this kind of configuration is shown in FIG.
28
. As shown in FIG.
28
, in this altitude measuring process, first, pressure is measured by the pressure sensor
100
(step S100) and altitude is calculated based on this pressure (step S101). This altitude calculation is carried out using equation (1) in the following so as to conform to the International Standard Atmosphere as specified by the International Civil Aviation Organization (ICAO).
Altitude
in
an
ideal
gas
(
m
)
=
44332
×
{
1
-
(
pressure
(
hPA
)
/
1013.25
)
0.1903
}
(
Equation
1
)
However, equation (1) is fulfilled for conditions where (a) an equation of state is fulfilled for an ideal gas, (b) where the pressure is 1013.25 hPa and the temperature is 15 degrees at a location 0 m above sea level, and (c) where temperature falls by 6.5 degrees for a rise of 1000 m. However, in reality, errors occur due to reasons such as, (d) the Earth's atmosphere is not an ideal gas, (e) atmospheric pressure usually fluctuates and is therefore not fixed at 1013.25 hPa at 0 m above sea level, and (f) measuring errors occur within the pressure measuring system itself.
In order to resolve this error, an operation assigning an offset value to the altitude (hereinafter referred to as the “ideal gas altitude”) calculated in accordance with the above equation is carried out at the display altitude calculator
104
, a final displayed altitude (hereinafter referred to as “displayed altitude”) is decided upon (step S102), and this process ends (step
103
). The decided displayed altitude is then displayed at the display panel
106
. This offset value is a sum of the aforementioned errors, and is a correction value obtained by the user inputting the current altitude. This relationship is shown in the following equation (2).
displayed altitude (
m
)=offset value (
m
)+ideal gas altitude (
m
) (2)
However, it is of course preferable to provide an accurate way of measuring altitude without the user having to input current altitudes one by one to carry out offsetting. Altimeters have therefore also been proposed in the related art to resolve this kind of problem by identifying the presence or absence of actual changes in altitude.
In, for example, Japanese Patent Laid-open Publication No. Hei. 8-285582 and Japanese Patent Laid-open Publication No. Hei. 8-261755, it is proposed to provide, for example, a vibration sensor or a position sensor for detecting the presence or absence of movement of the altimeter and then maintain a fixed displayed altitude while ignoring changes in pressure when no movement of the altimeter is detected by these sensors (when the altimeter is not moving). Alternatively, it has also been proposed to obtain a change in altitude per unit of time, compare this altitude change with a prescribed reference change, and then determine that there has been a change in altitude only when this change in altitude exceeds a reference change in altitude (Please refer to Japanese Patent Laid-open No. 6-137976 and Japanese Patent Laid-open No. 6-501553, although the object of these reference examples differs from that of this application).
However, when movement detection is carried out as described in the former case, it is necessary to provide new sensors, etc., the cost of manufacturing the altimeter increases accordingly, and the device itself also becomes large. This is a major problem, particularly for portable altimeters where device miniaturization is sought.
Further, in the latter case where the altitude change is compared with a reference change, just one reference change can be set and there are therefore cases where there is no correspondence with actual changes in altitude. In other words, with this method, when the reference change is exceeded, it is determined immediately that there has been an actual change in altitude, and when the reference change is fallen below, it is immediately determined that there has actually been no change in altitude. However, in reality, there are also intermediate situations where there is actually no change in altitude when the reference change is exceeded, and also, on the contrary, cases where there has actually been a change in altitude when the reference change has been fallen below. If this kind of situation cannot be reliably determined, then measurement errors cannot be resolved.
SUMMARY OF THE INVENTION
In order to resolve the aforementioned problems, it is the object of the present invention to provide a portable altimeter capable of maintaining device portability, and precisely determine the presence or absence of actual changes in altitude to give highly accurate altitude measurements.
FIG. 1
is a block view of essential parts of a configuration for a portable altimeter of a first embodiment of the present invention. In
FIG. 1
, in addition to substantially the same basic structure as the related art, this portable altimeter is provided with a movement determining unit
12
for determining whether or not the altimeter is at a standstill or is moving by comparing an amount of change in altitude with a prescribed standstill threshold value 20 and a movement threshold value 30.
A portable altimeter of the present invention therefore comprises a pressure sensor for measuring pressure,
a pressure/altitude calculating unit for calculating altitude from pressure measured by the pressure sensor,
an altitude variation calculating unit for calculating a difference in altitude between the altitude calculated by the pressure/altitude calculating unit and another altitude for prior to calculation of the altitude, and
a movement determining unit constituted by a first determining unit for determining whether or not the altitude difference calculated by the altitude variation calculating unit is at a standstill, and a second determining unit for determining whether or not there is movement from the altitude difference calculated by the altitude variation calculating unit.
Determinations can therefore be made without using newly provided sensors etc. to determine whether the altimeter is moving or at a standstill, and measurement precision is improved.
In the present invention, the portable altimeter also has a movement duration timer for measuring a duration or number of durations occurring in a moving mode.
Moving states can therefore be measured, moving states can be more accurately determined, and measurement precision is i
Adams & Wilks
Seiko Instruments Inc.
Vo Hien
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