Data processing: measuring – calibrating – or testing – Measurement system – Dimensional determination
Reexamination Certificate
2001-03-13
2003-08-26
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Dimensional determination
C073S861120
Reexamination Certificate
active
06611785
ABSTRACT:
TECHNICAL FIELD
This invention relates to a flowmeter and control method thereof to measure flow rate of fluid by using a pulse signal having a frequency corresponding to a flow rate from a sensor, a flow detecting switch and control method thereof to compare a measured flow rate and a preset flow rate value and to output a digital output corresponding to a comparison result toward an external apparatus, and a recording medium having recorded a control program.
And, the present invention relates also to a flowmeter to measure an injection rate of each fluid so that a plurality of fluids to be measured can be fixed in a fixed percentage in one tank or to measure an injection rate of each fluid so that a plurality of fluids with different temperature or the like can be mixed in one tank, a control method thereof, and a recording medium having recorded a control program.
BACKGROUND ART
Some kinds of liquids are often transferred, mixed and saved in a liquid tank in a fixed percentage in a manufacturing process using liquid medicine and in a cleaning process after the manufacturing process in a semiconductor manufacturing facility, a liquid crystal manufacturing facility, and the like.
An outline of such a conventional liquid mixing system is shown in FIG.
42
.
In
FIG. 42
, the liquid mixing system
100
has reservoirs
101
A-
101
C to reserve respective liquids to be mixed, a liquid tank
102
to mix the liquids, solenoid valves
103
A-
103
C provided on respective flow-channels between the reservoirs
101
A-
101
C and the liquid tank
102
in order to carry out injection/injection stop of the respective liquids, a plurality of flowmeters
104
A-
104
C provided on respective flow-channels between the solenoid valves
103
A-
103
C and the liquid tank
102
in order to output flow detection signals FA-FC, for example analog signals, having current values of 4-20 [mA] corresponding to respective flow rate values every fixed measuring period, a plurality of totalizers
105
A-
105
C to output on/off control signals SC for opening and closing the respective solenoid valves
103
A-
103
C when fixed integrated batch flow rates are obtained, and a concentrated monitor
106
to receive the batch output signals BA-BC and to output reset signals SR to reset the integrated batch flow rates of the totalizers
105
A-
105
C. The plurality of totalizers
105
A-
105
C also integrate the respective flow rates on the basis of the flow detection signals FA-FC and output respective batch output signals BA-BC to inform of the completion of the integrating when the respective fixed integrated batch flow rates are obtained. Here, in this specification, the words related to “integrate” mean almost the same as of “totalize”. A pump M in
FIG. 42
is controlled by a sequencer
106
A.
The concentrated monitor
106
has the sequencer
106
A to carry out the control of the whole liquid mixing system
100
and a display touch panel
106
B to carry out the input of various data and the indication of data.
And, the above totalizers
105
A-
105
C are set on a local monitoring board
107
provided at the flowmeters
104
A-
104
C side (i.e. local side).
Summary of operation of this liquid mixing system
100
is described hereinafter. Here, only a liquid system of the reservoir
101
A will be described because operation of each liquid system is the same. And, it is assumed that a liquid injection rate (i.e. an integrated batch flow rate) has been preset to the totalizer
105
A in advance.
When the sequencer
106
A of the concentrated monitor outputs the reset signal SR, the integrated batch flow rate of the totalizer
105
A is reset, and this totalizer
105
A outputs on/off control signal SC to the solenoid valve
103
A.
By this, ON signal the solenoid valve
103
A comes to an opened state, and the liquid reserved in the reservoir
101
A is injected in the liquid tank
102
.
With this, the flowmeter
104
A outputs the flow detection signal FA corresponding to the flow rate to the totalizer
105
A.
When the integrated batch flow rate reaches the preset integrated batch flow rate, the totalizer
105
A outputs the on/off control signal SC to the solenoid valve
103
A, and the solenoid valve
103
A comes to a closed state with this off signal. And, the injection of the liquid to the liquid tank
102
stops, and the batch output signal BA is outputted to the sequencer
106
A of the concentrated monitor
106
.
As a result, the sequencer
106
A indicates the liquid injection having closed on the display touch panel
106
B.
By the way, a frequency meter, a rotation speedometer, a pulse counter and the like are known as devices to measure a signal from a sensor which outputs a pulse signal based on measurement of a physical quantity.
For example, a capacitance type pressure sensor forms an oscillator and generates a signal with a frequency corresponding to the pressure. Then, pressure can be measured by measuring the frequency of the signal from this pressure sensor. And, in a vane wheel type flow sensor a magnetized vane wheel is rotated by a flow, and a secured Hall element detects the magnetism thereby to output a pulse signal having a frequency corresponding to the flow rate. The flow rate can be measured by measuring the frequency of this pulse signal.
There is a Karman vortex type flow sensor as a flow sensor of the above flowmeter or as one of such a physical quantity measuring apparatus. The Karman vortex type flow sensor detects the frequency of Karman vortexes by means of a supersonic wave sensor or a pressure-electricity element sensor in order to measure the flow rate of the fluid such as gas or liquid.
The flow measurement range and the frequency of Karman vortexes corresponding to the above flow rate are decided by a diameter of a flow-channel and material of the pipe portion of the flow sensor.
Here, an instantaneous flow rate value Q is obtained from the next linear expression (1) by using the frequency value f.
Q=a×f+b
(1)
And, because the expression (1) does not give an accurate result, the following expression (2) is applied, wherein the flow measurement range is divided into a plurality of sections n, and a linear expression for each section i (i=1−n) is defined thereby to secure nearly a full scale accuracy ±1%. (Japanese Patent Application Laid-open NO. 60-238720)
Q=ai×f+bi
(2)
For further improving the accuracy, the following expression (3) is proposed thereby to secure a full scale accuracy ±0.5%, wherein the above ai value and bi value are decided for each device and the individually decided values, i.e. corrected coefficients, Ai(s) and Bi(s) (i=1−n) are stored in a RAM or an EEPROM. (Japanese Patent Application NO. 9-345742)
Q=Ai×f+Bi
(3)
And, as for the above frequency value f, the measuring accuracy should be studied. Generally, when the frequency of a pulse signal is measured, the pulse number inputted during a fixed time-period (a gate-time) is counted, or the frequency is calculated from the reciprocal number of the measured period of the input pulse. However, in the flow measurement, the frequency of the generated pulse is high (the period is short) in a large flow and is low (the period is long) in a small flow. Accordingly, a sufficient measuring accuracy has to be obtained in each of the large and small flows.
Therefore, a frequency measuring apparatus having a counter controlling means to control a count operation with a timer, a clock generator, a clock counter, and a clock and a processing means to detect and count a pulse signal and to carry out a fixed arithmetic control is proposed. (Japanese Patent Application Laid-open NO. 5-297036)
According to this frequency measuring apparatus, a time not less than 2 times of the period of a measurement bottom frequency is set to the above timer, and the detection and the count of the pulse signal is started. And, when a pulse signal is detected, the above counter controlling means is controlled so
Kitamura Akinori
Nakahara Seiichi
Yamanaka Hidemi
Barlow John
Butzel Long
Kabushiki Kaisha Saginomiya Seisakusho
Sun Xiuqin
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