SU657287A2 - Pressure variation rate measuring device - Google Patents

Description

one

The invention relates to the field of measuring tachniki and can be used in automatic pressure control systems.

A device for measuring the rate of change of pressure is known by the author. .at. No. 336549. The device sotsderzhit pressure difference, the dynamic cavity of which communicates with the input pressure directly, and statically - through a normally closed solenoid valve differentiating element, the threshold circuit and the memory circuit. The signal from the output of the differential pressure sensor is fed to the input of the threshold circuit and the differential link. The output signal of the latter, proportional to the rate of change of pressure, is fed to the output of the device. When the pressure differential between the sensor cavity reaches the threshold value, the solenoid valve is opened under the action of the impulse of the seam. Before opening the electrovalve, the output signal of the differentiating link is memorized by the memory circuit, while the electrovalve is open, arrives from the MWB to the output of the device. In memory mode, the rate of pressure change is not measured by the device. When pressure

in the VOLUME X, the differential sensors connected by the solenoid valve equalize, the electrovalve closes, after which the memory stops. The device is switched to the measurement mode, and the signal to

 the output of the device comes directly from the output of the differentiating link. In the memory mode, an error occurs that is proportional to the duration of the memory mode.

 A disadvantage of the known device is the considerable time required to equalize the pressure in the cavity of the differential sensor when the electro-valve is triggered.

Q

The aim of the invention is to reduce the time of the pressure equation in the cavities of the differential pressure sensor when the solenoid valve is triggered. This is achieved by the fact that in the proposed device, the sensor cavity, connected to the source of the measured pressure through the electrovalve, is divided by metallic partitions into a series of communicating cells between each other. Fig. 1 shows a schematic diagram of the device described, its pressure differential sensor 1, a normally closed electro-valve 2, a differential link 3, a threshold circuit 4, a relay 5 and a storage capacity 6. Sensor 1 consists of a dynamic 7 and a static 8 cavities, cut by an elastic membrane 9, and a transducer 1O intermingling the rigid center of the membrane 9 into an electrical signal. The dynamic 7 and static 8 cavities of the sensor 1 are interconnected by a capillary 11. In addition, the static cavity 8 is divided by metal partitions 12 into a series of communicating cells 13 between each other.

The proposed device when closed solenoid 2 works similarly to the known device. FIG. Figure 2 shows a timing diagram of the output signal of the differential pressure sensor 1, which is proportional to the differential pressure across the cavity between cavities 7 and 8 when the electronicwiHa 2 is triggered.

In the initial state, the differential pressure is equal to the initial value of the DR.

At time i, the solenoid valve 2 opens and the differential pressure drops to zero. At time ij, the electric control valve 2 closes and the differential AR increases to a certain steady-state value ДРч, DRO of the same sign as n d PO, although the input pressure P remains unchanged. . This is evidence of a change in pressure f in a static cavity 8.

Until the process of pressure change in the static cavity 8 has been completed, the device

The device cannot be transferred from the memory mode to the measurement mode. A reduction in the duration of the memory mode can be achieved by reducing the duration of the process of pressure change in the static cavity 8.

The reason for the change in pressure in the static cavity 8 was established by experimental studies, the results of which were theoretically substantiated. Experiments have shown that (the pressure described in the pressure in the static cavity 8 cannot be caused by the movement of the locking element of the solenoid 2 at

8, after closing the solenoid valve 2, is explained as follows.

When the solenoid valve 2 is opened, as a result of a change in the amount of air in the static cavity 8, there is a change in its internal energy, which is characterized by a simultaneous change in its pressure and temperature. Due to the resulting temperature difference between the air and the inner surface of the static cavity 8, heat exchange begins between them. After closing the solenoid valve 2, the change in air temperature in the closed jjj of that static cavity 8 as a result of this heat exchange leads to a change in pressure in it.

The duration of the heat exchange process is determined by the thermal inertia.

35 static cavity 8 and depends on its volume, as well as on thermal conductivity and the area of its inner surface in contact with the air contained in it. The volume V cannot be chosen arbitrarily. It influences the gain and non-linearity of the characteristic of the differential sensor 1 and, therefore, is chosen based on the given values of these parameters.

Total oscillograms of the output signal of the differential sensor 1 for various designs and various materials of the internal surface of the static cavity 8

50 at the same size of its volume. The waveforms in FIG. For and 36 obtained on the sensor 1 differential without additional devices that reduce thermal inertia. According to the waveforms,

Claims (1)

53% heat transfer rate 1.2s. The waveforms in FIG. Sv is obtained for sensor 1, the static cavity of which is divided by partitions 12 of metal with high thermal conductivity into a series of communicating actuations. Although the movement of the locking element causes a change in pressure, however, it has a constant value, it occurs in hundredths of a second and, moreover, its direction depends on the direction of movement of the locking element and does not depend on the sign of the difference in differential pressure before opening the solenoid valve 2 in about 1 second and its value depends on the initial value of DS j and its direction depends on the sign of A if before opening of the solenoid valve 2 and does not depend on the direction of movement of the locking element, Pressure change pon static FIG. 3 shows experimentally with each other 13 cells and has a Shui contact area with the air contained in it. Wherein; duration of heat exchange: 5; 0.1 s. The oscillogram (Fig. 3g) shows the output signal of the differential sensor 1, the static cavity of which is made of plastic. The duration of heat transfer in this case, Q with. The waveforms in FIG. 3 confirms the possibility of reducing the duration of the memory mode of the device for measuring the rate of change of pressure by reducing the duration of heat exchange. In the proposed device, the static cavity 8 is divided by partitions 12 of metal with high thermal conductivity into a series of interconnected cells 13. Due to the large surface area of the partitions 12 in contact with the air contained in the static cavity 8, a reduction of the length of 766 is achieved. heat exchange between the air and partitions 12 and the corresponding reduction in the duration of the regime should be saved. Apparatus of the Invention A device for measuring the rate of change of pressure according to the authors. A certificate, NO 336549, characterized in that, in order to reduce the time to equalize the pressures in the cavities of the differential pressure sensor when the electroglot valve triggers, the sensor cavity is connected. with a source of measured pressure through an electrovalve, divided by metal partitions into a series of interconnected cells. Sources of information taken into account in the examination 1, USSR Author's Certificate number 336549, cl. Q 01 L 11/00, 1971. -1 | -LADHALH SL / V / / / / / W AAAA / VVVV AAAAAL / UU. / UUCHA / UCH / uuu // uuuuuuuh. VX / AAA2S UZ / UAAL / ULAAA LC yra MS