JPH02213736A - Pressure measuring instrument - Google Patents

Abstract

PURPOSE:To obtain the pressure measuring instrument with which zero point correction can be executed in a short period of time by providing a differential pressure detecting means, 3-port valve and control device. CONSTITUTION:The 3-port valve 11 is so switched as to select the pipeline connecting a 2nd measuring port 5 and a 1st measuring point P1 when the timing for the zero point correction arrives. The same pressure at a measuring point P1 is applied on both of the 1st measuring port 4 and the measuring 5 in this way. The differential signal S outputted from the differential pressure detecting means 3 is stored 10 as a correction value in the control device 9. The control device 9 shifts to an ordinary pressure difference measuring mode and the valve 11 is so switched as to select the line connecting the measuring port 5 and the measuring point P2 upon ending of the storage processing. The pressures of the measuring points P1, P2 are eventually applied to the measuring ports 4, 5 in this way and the differential signal S corresponding to the pressure difference is obtd. The differential signal S is subtracted by as much as the correction value component previously stored in the control device 9 and the corrected value is used as the correct pressure difference value, i.e., the air flow rate value for the input data for the purpose of control by the control device 9.

Description

[Detailed description of the invention] Meaning! BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure measuring device for measuring a pressure difference between two different points in an object to be measured such as gas or liquid. This pressure measuring device is used to measure various physical quantities that can be converted based on pressure differences, such as gas flow rate.

2. Description of the Related Art Pressure measurement devices that measure the pressure difference between two different points in gases, etc., are already known. In order to accurately measure the pressure difference with this pressure measuring device, the pressure difference value measured when the pressures at the two points above are the same must be exactly zero, that is, the zero points must match exactly. Must be.

However, this zero point changes depending on the ambient temperature around the pressure measuring device, changes over time in the characteristics of the pressure measuring device itself, and the like. Therefore, it is necessary to correct the zero point change.

Conventional zero point correction methods include the following. After several tens of minutes have passed since the pressure measuring device was started and the pressure measuring device has reached a stable state, the same pressure is applied to the two pressure measuring ports of the pressure measuring device, and at this time, the pressure is not zero from the pressure measuring device. If a certain value is output, this is manually adjusted to zero. This zero point correction method has the problem that it is difficult to apply it to automatic control because the zero point cannot be adjusted in a short period of time and requires manual intervention.

Additionally, zero point changes may also occur while the device is in operation.
In such a case, it is necessary to temporarily stop pressure measurement, perform zero point correction over a long period of time, and then restart measurement, which is extremely troublesome work.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pressure measuring device that can perform zero point correction in a short time without using human hands.

Another object of the present invention is to provide a pressure measuring device that can be applied to a control system that performs automatic control using pressure measurement values.

for The above problem is solved by the following pressure measuring device.

In a pressure measuring device that measures the pressure difference between a first measurement point and a second measurement point on an object to be measured, a first measurement port to which the pressure at the first measurement point is applied and a second measurement port to which the pressure at the second measurement point is applied. and a differential pressure detection means that outputs an electrical signal according to the difference in pressure applied to the measurement ports, and a second measurement device that measures the pressure at the first measurement point that is applied to the first measurement port. and pressure transmission means leading to the mouth.

The pressure at the first measuring point is changed to the second 'f' by operating the pressure transmitting means.
By guiding it to the iR fixed port, the pressure at the first measurement point is applied to both the first measurement port and the second measurement port, the output value from the differential pressure detection means at that time is stored as a correction value, and the pressure at the first measurement point is and a control means for correcting the output value from the differential pressure detection means when the pressure at the second measurement point is individually applied to the first measurement port and the second measurement port, using the correction value. This is a pressure measuring device.

In the above configuration, the configuration of the differential pressure detection means is not limited to any particular one as long as it outputs an electrical signal according to the difference in pressure applied to each of the two pressure measurement ports. For example, one that utilizes pressure changes in a resistance wire can be used.

The pressure transmitting means is constituted by an auxiliary pipe 12 and a three-port valve 11 in the embodiment. However, at the timing of zero point correction, the pressure at one measurement point is
Any other means can be used as long as it can simultaneously apply pressure to two pressure measurement ports.

During normal pressure measurement, the pressure at the first measurement point (Pl) is applied to the first measurement port (4) of the differential pressure detection means (3), and the pressure at the second measurement point (Pl) is applied to the first measurement port (4) of the differential pressure detection means (3).
A pressure of 2 [11 J at the fixed point (P2) is applied to the second measurement port (5). At this time, the differential pressure detection means outputs an electrical signal (S), current, voltage, etc. corresponding to the pressure difference.

At the time of zero point correction, the same pressure at the same measurement point, for example, the first measurement point (Pl), is applied to both measurement ports of the differential pressure detection means (3). At this time, the electrical signal output from the differential pressure detection means (3) is stored in the storage means (1o), and is used as a correction value for zero point correction.

FIG. 1 is a schematic diagram of one embodiment. The pressure measuring device 2 according to this embodiment is used to measure the flow rate of air flowing through the blast pipe 1. This pressure measurement device 2 is equipped with differential pressure detection means 3. This differential pressure detection means 3 has a first measurement port 4 and a second measurement port 5.
The pressure at the first measurement point P1 of the air flow is increased by the suction pipe 6.
On the other hand, the pressure at the second measurement point P2 of the air flow is guided to the second measurement port 5 by the second suction pipe 7.

An orifice 8 is provided between the first measurement point P1 and the second measurement point P2, so the flow rate of air flowing through the blast pipe 1 can be measured by measuring the pressure difference between Pl and P2.

The differential pressure detection means 3 individually measures the pressure applied to the first measurement port 4 and the second measurement port 5, calculates the pressure difference between them, and outputs an electric signal corresponding to the pressure difference as a difference signal S. It is output to the control bag W9 as This difference signal S is essentially a signal indicating the air flow rate.

Any device can be used as the differential pressure detection means 3 as long as it fulfills the above-mentioned function. For example, a pressure gauge is connected to each of the first measuring port 4 and the second measuring port 5, and the outputs of those pressure gauges are connected to a comparator, and the output of each pressure gauge is connected by this comparator. It is possible to calculate the difference between the output values and output a signal corresponding to the difference as the difference signal S.

The control device 9 controls a blower (not shown) or the like based on the difference signal S to adjust the flow rate of air flowing through the blow pipe 1 . This control device 9 may be an automatic control element with a built-in microcomputer, or may be a simpler control circuit. However, in order to execute the zero point correction function described later, an appropriate storage means 1 is provided inside.
0, for example, RAM.

When the pressures applied to the first measurement port 4 and the second measurement port 5 are the same, the differential pressure detection means 3 must output a difference signal S of zero.

However, due to changes in ambient temperature or changes over time, a value that should originally be zero may take on a certain value. In such a case, zero point correction is performed by the method described below.

First, the second suction pipe 7 is provided with a three-boat valve 11. An auxiliary pipe 12 extending from the first suction pipe 6 is connected to one input boat of the three-boat valve 11. This three-boat valve 11 is operated by a command from the control device 9 to select one of the pipes connecting the second measuring port 5 and the second measuring point P2, and the pipe connecting the second measuring port 5 and the first measuring point P1. Choose one. As can be understood from the above explanation, when normal pressure difference measurement is being performed, the 3-boat valve 11
A conduit connecting the measurement port 5 and the second measurement point P2 is selected.

When the timing for zero point correction arrives in the control device 9, the three-boat valve 11 is switched to select the pipe line connecting the second measurement port 5 and the first water fixed point P1. This allows the first
The same pressure at the first measurement point P1 is applied to both the measurement port 4 and the second measurement port 5. At this time, the differential pressure detection means 3
The difference signal S output from the control device 9 is stored in the storage means 10 in the control device 9 as a correction value.

When the above storage process is completed, the control device 9 shifts to the normal pressure difference measurement mode in a timely manner, and the three-boat valve 11 selects the pipe connecting the second measurement port 5 and the second measurement point P2. Switch. As a result, the pressures at the first measurement point P1 and the second measurement point P2 are applied to the surface measurement ports 4 and 5, respectively, and a difference signal S corresponding to the pressure difference therebetween is obtained. However, this difference signal S includes an error component corresponding to the change in the zero point. The difference signal S containing this error component is first stored in the storage means 10 in the control device 9.
The correction value stored in the memory is subtracted. This corrected value is the correct pressure difference value.

That is, it is used as input data for control by the control device 9 as an air flow rate value.

In this way, zero point correction can be performed in a short time without any manual effort. Furthermore, it becomes possible to use the difference signal S as input data for automatic control by the control device 9.

As explained above, the zero point correction is performed when the timing for that purpose arrives in the control device 9. How to set this timing can be considered in various ways depending on the situation. For example, this can be done automatically and repeatedly at regular intervals. Further, when the previous correction value was large, the next correction timing can be advanced, and conversely, when the correction value was small, the next correction timing can be delayed.

In the above explanation, for convenience, the upstream measurement point of the orifice 8 was referred to as the 19J fixed point P1, and the downstream measurement point was referred to as the second measurement point P2. There are no inconveniences.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of one embodiment. 1...1st measurement point 2...Second measurement point ...First measurement port ...Second measurement port ···electoronic signals ・・・Differential pressure detection means 1...3 boat valve 2... Auxiliary pipe ···Control device 1st figure

Claims (1)

[Claims] In a pressure measuring device that measures a pressure difference between a first measuring point and a second measuring point on an object to be measured, a first measuring port and a second measuring point, to which pressure at the first measuring point is applied, are provided. a second measurement port to which pressure is applied; differential pressure detection means for outputting an electrical signal according to the difference in pressure applied to the measurement ports; and a first measurement point to be applied to the first measurement port. pressure transmitting means for guiding the pressure at the first measuring point to the second measuring port; and by operating the pressure transmitting means to guide the pressure at the first measuring point to the second measuring port, a Apply the pressure at one measurement point, store the output value from the differential pressure detection means at that time as a correction value, and apply the pressure at the first measurement point and the second measurement point to the first measurement port and the second measurement port, respectively. A pressure measuring device comprising: a control means for correcting the output value from the differential pressure detection means when the pressure is applied, using the above correction value.