Two-wire system multiple sensors liquid level transmitting instrument

Abstract

The two-wire multi-sensor liquid level transducer includes the upper absolute pressure sensor for measuring the gas pressure over the liquid surface; the lower absolute pressure sensor for measuring the total pressure in the measured point inside liquid; and signal processing unit for processing data from the upper sensor and the lower sensor. All the upper sensor, the lower sensor and the signal processing unit are connected, and the lower sensor has sealing structure in the wiring terminal. Compared with traditional liquid level measuring devices, the present invention has the advantages of no dewing, excellent sealing, etc.

Description

technical field [0001] The invention relates to an input type multi-sensor liquid level measuring device. Background technique [0002] The traditional liquid level measuring instrument uses a single differential pressure sensor with a back pressure tube. The differential pressure sensor is installed at the bottom of the probe rod or cable. The pressure difference value between the two is transmitted to the signal processing device, and the signal processing device obtains the required liquid level value according to the liquid pressure formula P=ρgh. Because the use and installation of this liquid level measuring instrument is very simple and convenient, it is widely used in many fields such as hydraulic power, electric power, metallurgy and sewage treatment. However, since the back pressure tube of the differential pressure sensor of this liquid level measuring instrument must be connected to the atmosphere when it is used, it is necessary to use a cable with an air guide...

AI Technical Summary

Problems solved by technology

However, since the back pressure tube of the differential pressure sensor of this liquid level measuring instrument must be connected to the atmosphere when it is used, it is necessary to use a cable with an air guide tube for electrical connection with the differential pressure sensor, so there is a problem of condensation:

[0003] (1) There is often residual water vapor in the air duct. When the temperature drops, the water vapor will condense into water droplets and drop to the surface of the differential pressure sensor, causing the differential pressure sensor to fail to work normally;

[0004] (2) If there is a lot of water vapor remaining in the air duct, when the temperature drops, the water droplets condensed by the water vapor will accumulate together to form a water column, and the pressure of this section of the water column will be added to the back pressure side of the differential pressure sensor together with the atmospheric pressure. lead to inaccurate measurement

[0007] 1. Since there is a vent pipe in the air guide cable, there is a serious problem of condensation;

[0008] 2. Since there is a vent tube in the air guide cable, the locking force during sealing is limited, thus affecting the sealing effect;

[0009] 3. Since only one differential pressure sensor is used to feel the pressure, the density of the measured liquid medium must be a constant value in order to accurately measure and convert the liquid level value and transmit the output. Once the liquid density in the container changes, then The liquid level output by the transmission will no longer be the real liquid level, and there will be no measurement accuracy when the medium density is unstable;

[0010] 4. Due to the limitations of the differential pressure sensor itself, it can only measure and control the liquid level of the open container, and the measurement function is single

[0011] 5. It can only measure the change of hydraulic pressure passively, and cannot know the pressure value above the liquid surface and the total pressure value below the liquid surface

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