Liquid Level Detection System Research Articles

Design of liquid level detection circuit based on sampling probe structure capacitance.

Liquid level detection system is an essential core functional component of automatic clinical medical testing instrument. The conventional liquid level detection method has low detection accuracy and sensitivity, and may have the problem of false detection, which may lead to the inaccurate test results. This paper presents a high sensitivity liquid level detection system based on the principle of variable capacitance. When the sampling probe contacts the liquid level, the probe capacitance will change. The liquid level detection circuit board judges whether the probe contacts the liquid level by sensing the change of probe capacitance. When judging the liquid level signal, the combination of slope detection and amplitude detection is used. The liquid level detection circuit board takes the phase-locked loop(PLL) circuit as the center to detect the change of the capacitance. The reference signal of the PLL is set as a square wave of 375kHz. The double tube probe is used as a part of the tuning capacitor of the voltage controlled oscillator to control the frequency of the output signal, which can realize the rapid phase locking. The experimental results show that the system has accurate detection results, high sensitivity, stable and reliable operation, good dynamic response performance in the case of large and small liquid volume. Compared with other liquid level detection methods based on machine vision, ultrasonic, optics and so on, the proposed liquid level detection system has simpler structure and lower cost, it can avoid the problems of collision, carryover contamination and empty suction by controlling the depth of sampling needle inserted into liquid.

Magnetic Float Liquid Level Detection Method for High-Temperature Superconducting Flux-Pinning Maglev System

High temperature superconducting (HTS) flux-pinning maglev system uses the flux-pinning characteristics of HTS bulk to achieve self-stable levitation, but the superconductivity of HTS bulk depends on low temperature maintained by liquid nitrogen. It can be seen that the real-time detection of liquid nitrogen level is an essential safety detection in the HTS flux-pinning maglev system. However, the liquid nitrogen level measurement of Dewar is limited by many conditions, such as small available size of Dewar, small liquid nitrogen capacity, low temperature characteristics of liquid nitrogen, etc. These conditions require the liquid level detection system to be able to withstand low temperature, have sufficient identification accuracy and have no significant impact on the cold insulation performance of Dewar. All of these bring difficulties to the design of real-time liquid level detection in the maglev system. Based on the structural characteristics of Dewar, a new type of magnetic float liquid level detection device is studied in this paper. The device can realize liquid nitrogen level detection function and low-level alarm function. Its technical principle is to use Hall sensor array to detect the position of the magnetic float in real time, and transmit the data to the onboard computer for data storage and data monitoring. The experimental results show that the proposed liquid nitrogen level detection method can meet the requirements of liquid nitrogen level detection and alarm with certain accuracy, and will not bring additional heat leakage to affect the Dewar performance.

Design of an Infusion Monitoring System Based On Image Processing

At present, infusion monitoring heavily relies on nursing rounds or supervision. In many cases, nursing staff fail to remove patients’ cannula in a timely manner after intravenous infusion due to negligence, which leads to serious swelling and blood backflow at the chosen venipuncture area over time, causing pain and even endangering patient lives. This study designed a smart real-time liquid level detection system based on image processing to solve this difficulty. By running the canny edge detection algorithm and Hough Transform (HT) algorithm on a Raspberry Pi computer with an industrial camera, the system extracted and calculated the image’s pixels for judgment. As the number of pixels in the detected area reaches the alarm value, the system shall issue an alarm. In this experiment, a 62mm drip chamber was selected, and the system could achieve a high success rate of 98% with a set detection width of 5mm. The experimental results showed that whether the liquid level reached the alarm level could be accurately and effectively-identified utilizing the system. The information could be transmitted to the receiving end promptly with a high success rate, which verified the system’s effectiveness. Given its real-time performance and high accuracy, the system has excellent application prospects.

High precision on-line liquid level detection system based on microwave penetration method

In order to meet the high precision and low cost of liquid level detection for bottled drinks in industrial production line, based on microwave transmission principle a liquid level detection method was designed on the basis of radar level meter. The rectangular microstrip antenna sent and received specific microwave signals. The signal was processed by the embedded ARM(Advanced RISC Machines) processor and digital signal processing method, and finally the data was transmitted. It was verified by experiments that the microwave penetration method can be used for liquid level detection, and the detection accuracy can reach ±1mm. Due to the use of microwave for measurement, the system has high stability and can be applied to the liquid level detection of bottled drinks on the production line.

Particle Filter With Unknown Statistics to Estimate Liquid Level in the Silicon Single-Crystal Growth

In the process of silicon single-crystal growth, the detection of melt level is an important step to ensure that the grown silicon single crystal is of high quality. Since there exist many mechanical motions, chemical interactions, thermal convection, and so on, it is extremely difficult to obtain the noise statistics of the liquid-level data. To attain a high-accuracy detection of liquid level with unknown noise statistics, we present an extended set-membership-based particle filter (PF). The key points are as follows. We construct a nonlinear state-space model for liquid-level detection system based on the kinematic principle and laser triangulation measurement principle and cast the detection problem of the liquid level into a state estimation problem. Based on this model, we use the extended set-membership estimation theory to generate an ellipsoid set that contains the true value of the liquid-level state. To overcome the difficulty of drawing particles under the case of unknown statistics noise, we draw particles from a Gaussian distribution in the obtained ellipsoidal set. In order to resample particles when the measurement noise statistic is unknown, we introduce a cost function to obtain the weights of the particles, and the ultimate estimation of liquid level is calculated by the weighted particles after the resampling procedure. Comparing with the extended Kalman PF (EPF) and the cost-reference PF (CRPF), the proposed algorithm has higher estimation accuracy. Some simulation and experiment results are presented to illustrate the effectiveness of the proposed method.

The Liquid Level Detection System Based on Pressure Sensor.

Micro-liquid distribution operation has been a core part of the fully automatic liquid handling platform in clinical testing. Accurate and fast automatic detection of liquid level with disposable tip is the precondition to ensure the stability of the whole operation of liquid handling platform. By further research on the liquid level sensing technology of pressure sensor, in this paper we designed a new type of accurate and stable micro-liquid level detection system and verified its stability, instantaneity and accuracy by setting up a small reagent distribution platform. It was shown that the liquid level detection system designed in this paper has reliable stability, good instantaneity and high accuracy, with the liquid level detecting accuracy up to 100%, the response speed after detecting the liquid level reaching millisecond and the depth in the liquid level less than 0.3 mm. Besides, there is no limit on the physical and chemical properties of the liquids to be tested, which is consistent with the technical indicators of the liquid handling platform.

Real-time Liquid Level and color Detection system using Image Processing

Detecting the level of the liquid is very essential for any chemical study in research labs. The objective of this paper is to design real-time liquid level detection system using image processing. Besides, this system is able to indicate the color of the liquid during chemical reaction. The proposed system was developed using vision assistant tools in LabVIEW and webcam. Regarding to webcam resolution, the average accuracy of the system is approximately 99%.

The Hardware Design and Implementation of Liquid Level Detection System for Lead-Acid Battery

The hardware structure of a liquid level detection system for lead-acid battery was briefly introduced. The system adopts AT89C51 MCU as host module, combined with display storage, extended storage and the watch dog technology. The slave module adopts AT89C2051 MCU, which driver the linear CCD to realize non-contact measurement in acidic and corrosive conditions. The infrared transmission module uses RS-232 serial-to-infrared technology to realize wireless data delivery. The damage due to sensor corrosion could be avoided in this system. Compared with other similar equipments, this system has the advantages of simple structure, small volume, low cost, high measure precision and convenient maintenance.

Research of the Liquid Level Detection System for Integral Stereolithography System

To improve the dimension accuracy of integral stereolithography (SL) system, the resin liquid level in SL system need controlled. Based on the measuring principle of laser triangulation, a laser liquid level detection system for SL system has been developed. The laser liquid level detection system consists of light source, Position Sensitive Detectors (PSD), PSD signal processing circuit and data acquisition system. According to the principle that electrical signal of PSD changes when resin liquid level vary, a PSD is employed to detect the liquid level height in the liquid level detection system. Confirmation experiment is conduct to test the accuracy of the detection system, and the experiment results indicated that deviation is 0.34% in the range of 6mm, and satisfy the accuracy requirement of integral SL system.

The Design of Liquid Level Detection System for Oil Tank

The basic principle of liquid level measurement with capacitive sensor is described. According to differences in dielectric constant between oil and water, a liquid level detection system for oil tank is designed. The system includes capacitive sensor, signal processing circuit, FPGA logic circuit and the software of computer. Results show that the system has characteristics of easy operation, high precision. It can detect the change of liquid level accurately and effectively.

Fiber optical liquid level sensor under cryogenic environment

Abstract This paper reports a preliminary experimental investigation and characterization of an optical fiber-based liquid level detection system for applications in cryogenic environment. The sensor system comprises a multiplexed array of point liquid probes. Two different designs of the probe were fabricated and tested. Probe tests were conducted in water–air, liquid–gas nitrogen environments. The multiplexing of multiple liquid probes using an optical time domain reflectometer (OTDR) device was successfully demonstrated. In addition, response time of the liquid probe was measured and compared experimentally.

Non-contacting liquid level detection system

A transmitting transducer is mounted on the outside wall of a vessel and supplies bursts of ultrasonic energy. If liquid is present, the energy is coupled to the other side of the vessel. Otherwise, the energy is attenuated. A receiving transducer (which may be the same as the transmitting transducer) is positioned to receive the ultrasonic energy if liquid is present. It is gated to be active only when such energy should arrive in the presence of liquid. The receiving transducer therefore generates an electrical signal indicating presence or absence of liquid in the vessel at the level at which the transducers are mounted.

Simple, Inexpensive Solid State Liquid Level Detection and Control1

AbstractLiquid level detection and control is commonly used in agronomic and soil science research. Various mechanical, electromechanical, and solid state systems have been devised for this purpose. Of these, the solid state systems are the most versatile and reliable but also the most expensive to purchase or complex to construct. The function and construction of a very simple, inexpensive, sensitive, and versatile solid state liquid level detection and control system is described here. The detection circuit consists of an integrated circuit plus two capacitors and a simple bielectrode probe. Indicator, alarm, and control functions are available with the inclusion of as few as one to three additional components.