CN204612780U - A kind of low-temperature liquid level measuring system - Google Patents

Abstract

The utility model discloses a low-temperature liquid level measurement system, which is used to realize the simultaneous measurement of two low-temperature liquid levels, and the first container and the second container containing the two liquids are separated by vacuum. The measurement system includes A resistive probe inserted into the first container and a capacitive probe inserted into the second container; a low-temperature liquid level measuring instrument is installed on the capacitive probe, which is connected with the resistive probe by a cable, and the low-temperature liquid level is measured The instrument includes a communication module for communicating with terminal equipment. According to the low-temperature liquid level measuring system realized by the utility model, the system is compact in structure, small in size, portable, and can use the detected current value to calculate the resistance, use the detected frequency value to calculate the capacitance, and use the terminal equipment after calibration The value of the liquid level is calculated, which can realize the real-time and accurate measurement of the liquid level of the cryogenic liquid.

Description

A low-temperature liquid level measurement system

technical field

The utility model belongs to the field of low-temperature liquid level measurement, and more particularly relates to a low-temperature liquid level measurement system.

Background technique

Cryogenic liquids are very dangerous due to their low temperature. They are often sealed in sealed canned containers. Accurately monitoring the liquid level in the container plays a very important role in controlling their danger. Other equipment such as super The magnetizer needs to rely on a certain liquid level to maintain its superconducting properties, so it is necessary to accurately judge the liquid level of the cryogenic liquid. However, the cryogenic liquid is sealed in the container, which is difficult to measure with the naked eye or manually, and cannot use the current popular liquid level measurement methods, such as laser distance measurement, ultrasonic distance measurement and other non-contact distance measurement and traditional contact liquid surface measurement method.

The ILM ²⁰⁰ from Oxford Instruments, the low-temperature liquid level measuring instrument from AMI, and the liquid nitrogen and liquid helium liquid levels are measured by capacitive and resistive measurement methods. The low-temperature liquid measuring instruments used are all desktop instruments. The instrument itself has complete measurement and calibration functions, and the user operates through the panel buttons. At the same time, the cryogenic liquid level measuring instrument must be used with a cryogenic liquid probe. The probe is installed in a cryogenic liquid container, and the cryogenic liquid measuring instrument is placed on the desktop, On the load such as the floor, it is connected with the probe through a cable.

The above-mentioned liquid level measuring instrument has the following problems: 1) In order to avoid the influence of the parasitic capacitance of the cable itself, a converter needs to be installed on the upper end of the probe to realize the conversion between the probe measurement signal and the stable measurable signal; 2) The cryogenic liquid measuring instrument takes up a lot of space; 3) The method of cable connection is likely to bring new problems in some specific occasions, for example, when the measured low liquid container is a strong magnetic field or the container is large in volume, the connection cable The length will reach tens of meters, which is likely to bring safety hazards; 4) The existing cryogenic liquid measuring instrument uses RS232 to communicate with the computer, and can only obtain the reference value of the liquid level measurement data. In the case of uncalibrated measurement results The real result of the liquid level cannot be accurately obtained; 5) The existing cryogenic liquid measuring instrument does not have functions such as early warning and remote monitoring, and the acquisition of measurement data can only be performed manually on site, and the state of the liquid level cannot be obtained in real time.

Utility model content

Aiming at the above defects or improvement needs of the prior art, the utility model provides a low-temperature liquid level measurement system, which aims to provide a compact structure, no need for an installation platform, and can realize real-time monitoring and accurate measurement of the low-temperature liquid level.

In order to achieve the above purpose, according to one aspect of the utility model, a low-temperature liquid level measurement system is provided, which is used to realize the simultaneous measurement of the liquid levels of two low-temperature liquids, and the first container and the second container containing the two liquids separated by a vacuum, characterized in that the measurement system includes a resistive probe inserted into the first container and a capacitive probe inserted into the second container; a cryogenic liquid level measuring instrument is installed on the capacitive probe , which is connected to the resistance probe with a cable, and the cryogenic liquid level measuring instrument includes a communication module for communicating with terminal equipment.

Generally speaking, compared with the prior art, the above technical solutions conceived by the utility model can achieve the following beneficial effects:

(1) The low-temperature liquid level measurement system realized according to the utility model has a small and simple structure, can be powered by a lithium battery or an external power supply, and can be directly installed on the liquid level sensor without an installation platform. Liquid level sensors such as liquid helium and liquid nitrogen are separated from each other and can be carried with you, which is portable;

(2) Use two coaxial stainless network tubes to form a liquid nitrogen sensor, use a superconducting resistance wire and a heating resistor to form a liquid helium sensor, use a single-chip microcomputer to directly measure the frequency of the conversion output of the liquid nitrogen sensor to measure the liquid nitrogen liquid level, and use the control current The method of size and current time outputs pulse current to drive the liquid helium sensor;

(3) The output end of the constant current source driven by the liquid helium sensor is connected in series with a controllable, low-resistance switch, so that the leakage current of the low-temperature liquid level measuring instrument is less than 1uA when it is not working, so that the use of the liquid level measuring instrument can greatly increase the volatilization of liquid helium reduce to a minimum;

(4) The cryogenic liquid level measuring instrument uses human-computer interaction mode, and can connect terminal control equipment through CAN bus or Ethernet (holding line conforms to standard IEEE802.3 and wireless WIFI conforms to standard IEEE802.b/n/g). It operates a low-temperature liquid level measuring instrument, and can remotely monitor the real-time state of the liquid level, making the low-temperature liquid level measurement system compact in structure, small in size, and portable.

Description of drawings

Fig. 1 is the schematic diagram that the cryogenic liquid liquid level measuring system realized according to the utility model is installed in the liquid container to be tested;

Fig. 2 is a schematic diagram of hardware modules of the cryogenic liquid level measurement system realized according to the utility model.

Throughout the drawings, the same reference numerals are used to designate the same elements or structures, wherein:

1-First cryogenic liquid 2-First cryogenic liquid container 3-Capacitive probe 4-Second cryogenic liquid 5-Second cryogenic liquid container 6-Resistive probe 7-Connecting cable 8-Threaded connector 9-Cryogenic liquid Liquid level measuring instrument 10-voltage conversion circuit 11-current monitoring circuit 12-low resistance switch 13-controllable constant current source 14-capacitance-frequency conversion circuit 15-MCU processor 16-OLED screen 17-alarm sound and light indication 18- Ethernet transceiver 19-CAN bus transceiver 20-computer terminal equipment 21-mobile platform terminal equipment 22-cable connector

Detailed ways

In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute conflicts with each other.

The schematic diagram of the low-temperature liquid level measuring system of the present invention being installed in the liquid level container is shown in Figure 1, in the equipment (such as superconducting magnet) that uses the first low-temperature liquid 4 that temperature such as liquid helium is less than 10K, for To reduce the volatilization rate of the expensive first low-temperature liquid 4, a second low-temperature liquid container 2 is often placed outside the first low-temperature liquid container 5 for holding the low-temperature liquid, for holding the second low-temperature liquid 1, and the low-temperature liquid container 5 and the low-temperature The liquid containers 2 are separated by vacuum.

In order to measure the liquid level heights of the second cryogenic liquid 1 and the first cryogenic liquid 4 at the same time, the resistance probe 6 of the cryogenic liquid level measuring instrument is inserted into the first cryogenic liquid 4 through the first cryogenic liquid container 5, and the cryogenic liquid level is measured A capacitive probe 3 is inserted into the second cryogenic liquid 1 through the second cryogenic liquid container 2 .

The low-temperature liquid level measuring instrument 9 is connected to the capacitive probe 3 of the low-temperature liquid level measuring instrument through a threaded connector 8, so that the low-temperature liquid level measuring instrument 9 is directly installed above the capacitive probe 3 of the low-temperature liquid level measuring instrument, and can be Easy to disassemble and assemble. The resistance probe 6 of the low-temperature liquid level measuring instrument is very close to the low-temperature liquid level measuring instrument 9 , and is directly connected to the low-temperature liquid level measuring instrument 9 through a short connection cable 7 .

As shown in Figure 2, according to the schematic diagram of the hardware of the low-temperature liquid level measuring system realized by the utility model, wherein, the MCU processor 15 is the central processing unit of the low-temperature liquid level measuring instrument, and completes the control and data processing of peripheral equipment, and Communicate with the computer terminal 25 or the mobile platform terminal 26 .

Driven by the internal DAC of the MCU processor 15, the controllable constant current source 13 outputs a specified current as the working current for the sensing of the resistive probe. The current flows through the low-impedance switch 12. When the MCU processor 15 is connected to the When the terminal device 20 or the external command of the mobile platform terminal device 21 measures the liquid level of the first cryogenic liquid 4, the MCU processor 15 controls the low-resistance switch 12 to be turned on so that the current can flow smoothly, otherwise the low-resistance switch 12 is turned off. , so that the quiescent current output by the low-temperature liquid level measuring instrument is almost 0 when it is not working, and the consumption of the first low-temperature liquid 4 is minimized, because the low-resistance switch is completely in the non-working state of the low-temperature liquid level measuring instrument In the closed state, the current of the measuring circuit should be close to 0 in theory. If the MCU processor still detects abnormal output current during this period, the cryogenic liquid level measuring instrument will make corresponding alarm actions in time.

The output current enters the resistive probe 6 of the cryogenic liquid level measuring instrument through the cable connector 7, forms a voltage at both ends of the resistive probe 6 of the cryogenic liquid level measuring instrument, and returns to the voltage conversion circuit 10 and The current monitoring circuit 11 has two branches. The output of the voltage conversion circuit 10 is sampled by the internal ADC of the MCU processor 15, and the MCU processor 15 can obtain accurate voltage values at both ends of the resistive probe 6 of the cryogenic liquid level measuring instrument. The output of the current monitoring circuit 11 is sampled by the internal ADC of the MCU processor 15, and the MCU processor 15 can obtain an accurate output current, thereby accurately calculating the resistance value of the resistive probe 9 of the cryogenic liquid level measuring instrument. In this case , The measurement of resistance is calculated based on the precise measurement value rather than the theoretical output value, which can better improve the measurement accuracy of resistance.

In the standby state, the MCU processor 15 is still constantly measuring the current flowing through the resistive probe 6 of the cryogenic liquid level measuring instrument through the current monitoring circuit 11. When the current is abnormal, the MCU processor 15 will pass through the Ethernet transceiver. 18. The CAN bus transceiver 19 sends alarm information to the computer terminal equipment 20 and the mobile platform terminal equipment 21, and at the same time displays the alarm on the OLED screen 16 connected to the MCU processor 15 and the alarm sound and light indicator 17.

The capacitive probe 3 of the cryogenic liquid level measuring instrument is connected to the capacitance-frequency conversion circuit 14 inside the cryogenic liquid level measuring instrument 9 through the threaded connector 8, and converts the capacitance value measured by the capacitive probe 3 of the cryogenic liquid level measuring instrument is the frequency value, and the frequency value is collected and calculated by the internal timer of the MCU processor 15, and the accurate capacitance value of the capacitive probe 3 of the cryogenic liquid level measuring instrument is calculated.

The MCU processor 15 communicates with the computer application terminal equipment 20 and the mobile platform terminal equipment 21 through the Ethernet transceiver 18 and the CAN bus transceiver 19, and the MCU processor 15 collects the capacitance value of the capacitive probe 3 of the low temperature liquid level measuring instrument collected by it. and the resistance value of the resistance probe 6 of the cryogenic liquid level measuring instrument are uploaded to the computer terminal equipment 20 and the mobile platform terminal equipment 21, and the capacitance value and the resistance value are calibrated by the computer terminal equipment 20 and the mobile platform terminal equipment 21, and the calibration value is passed The Ethernet transceiver 18 and the CAN bus transceiver 19 send to the MCU processor 15, and the MCU processor 15 further accurately calculates the liquid level percentage height of the first cryogenic liquid 4 and the second cryogenic liquid 1, and the percentage value together with the resistance value , and the capacitance value are uploaded to the computer terminal equipment 20 and the mobile platform terminal equipment 21 together, and displayed on the OLED screen 16 at the same time, the use of the computer terminal equipment, etc., can grasp the height of the cryogenic liquid level in real time, and get an alarm at the first time information to gain time for timely handling of dangerous situations.

In a word, according to the cryogenic liquid level measurement system of the present invention, it has the following prominent features:

1) The cryogenic liquid level measuring instrument 9 uses a circuit structure of a multifunctional MCU processor 15, a current source 13, and a capacitance-frequency conversion method. , a controllable constant current source 13, a resistive probe 6 of a low-temperature liquid level measuring instrument, a capacitance-frequency conversion circuit 14, and a capacitive probe 3 of a low-temperature liquid level measuring instrument;

2) The cryogenic liquid level measuring instrument 9 is directly connected to the capacitive probe 3, and the cryogenic liquid level measuring instrument 9 is connected to the resistive probe 6 using a very short connecting cable 7, and the cryogenic liquid level measuring instrument 9 can measure both A low-temperature liquid surface, compact structure, small volume, can be directly installed on the low-temperature liquid container, and has portable features;

3) Using the current monitoring circuit 11 to achieve accurate measurement of the output current, instead of taking the theoretical output current as the basis for calculation, a higher accuracy of liquid level measurement is achieved;

4) The use of the low-resistance switch 12 reduces the leakage current output of the low-temperature liquid level measuring instrument 9, and at the same time, the current monitoring circuit 11 realizes real-time monitoring of the leakage current, ensuring the safety of the low-temperature liquid level measuring instrument 9;

6) The cryogenic liquid level measuring instrument 9 can communicate with the computer terminal equipment 20 and the mobile platform terminal equipment 21 using CAN bus or Ethernet, and the transmitted data includes the cryogenic liquid level measuring instrument resistive probe 6, the cryogenic liquid The actual measurement value of the capacitive probe 3 of the surface measuring instrument and the converted liquid level percentage value make the measurement results meet the requirements of various application occasions.

7) The application of computer terminal equipment 20 and mobile platform terminal equipment 21 enables the cryogenic liquid level measuring instrument 9 to have the ability to monitor the liquid level of the measured cryogenic liquid in real time, and the alarm has a visual feature.

Those skilled in the art can easily understand that the above descriptions are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements and modifications made within the spirit and principles of the utility model Improvements and the like should all be included within the protection scope of the present utility model.

Claims (1)

1. A low-temperature liquid level measuring system, which is used to realize the simultaneous measurement of two low-temperature liquid levels, and vacuum isolation is used between the first container (5) and the second container (2) containing the two kinds of liquids. It is characterized in that the measuring system comprises a resistive probe (6) inserted into the first container (5) and a capacitive probe (3) inserted into the second container (2); on the capacitive probe (3) A low-temperature liquid level measuring instrument (9) is installed, which is connected with the resistance probe (6) by cables, and the low-temperature liquid level measuring instrument (9) includes a communication module for communicating with terminal equipment.