Differences between radar, ultrasonic, and radio frequency admittance level gauges

Ultrasonic level gauges determine distance based on the reflection time of ultrasound and are not suitable for use in high-temperature environments. Radar measures distance by using the strength of echoes, while radio frequency admittance level gauges operate on the principle of high-frequency bridges to accurately measure the admittance of sensors installed in the container being measured. In direct-acting mode, the output of the instrument increases as the level rises. Simple reply: Please forgive me

RF admittance level control technology is a type of level control technique that evolved from capacitive level control technology. It offers better performance in preventing sensor clogging (the material that adheres to the sensor is referred to as clogging), greater reliability, more accurate measurements, and broader applicability. In “RF admittance,” “admittance” refers to the reciprocal of impedance in electricity; it is composed of resistive, capacitive, and inductive components. “RF” stands for high frequency, so RF admittance technology can be understood as a method of measuring admittance using high-frequency currents. The key difference between point RF admittance technology and capacitance technology lies in the use of three-terminal technology and the diversity of measurement parameters. The measurement signal at the center of the circuit unit is connected to the center conductor of the coaxial cable, and then connected to the center of the sensor. At the same time, the shield of the coaxial cable remains at a level that is extremely low and very stable; it is at the same potential as the measurement signal, in the same phase and at the same frequency, but there is no direct electrical connection between them – in other words, they are isolated from each other. The effect of this is equivalent to the measurement signal passing through a non-inverting amplifier with a gain of “1” and high driving capacity, with the output being connected to the shield of the coaxial cable and then to the shield of the sensor. The ground wire is another separate conductor in the cable. Due to the aforementioned relationship between the center conductor of the coaxial cable and its outer shielding layer, there is no potential difference between them; as a result, no current flows, meaning no current leaks from the center conductor. In other words, there is no capacitance between them or the capacitance is zero. Therefore, the temperature effects of the cable, as well as the installation of capacitors, have no impact. The issue of adhered material on the sensor is known as the contamination problem. A new sensor structure, a five-layer concentric design, is employed: the innermost layer consists of the central probe, the middle layer is a shielding layer, and the outermost layer features grounding mounting threads; these various components are separated from one another by insulating layers. As is the case with coaxial cables, there is no potential difference between the central probe and the shielding layer; even if the impedance of the material attached to the sensor is low, no current will flow. The electronic instruments measure only the current flowing from the center of the sensor to the opposite tank wall (ground). Since the shielding layer prevents current from flowing back along the sensor toward the container wall, the current to ground can only pass through the end of the sensor, via the material being measured, to reach the opposite container wall. That is, the U-center probe = U-shielding layer; the I-center probe to the shielding layer = (U-center probe – U-shielding layer) × YL = 0. Although there is a potential difference between the shielding layer and the container wall, and current flows between them, this current is not measured and does not affect the measurement results. This protects the measurement end from being affected by the hanging material. Only when the material inside the container actually rises and comes into contact with the central probe can a current flow between the material under test, the central probe, and the ground; the instrument detects this current and generates a valid output signal. RF admittance technology improves the signal-to-noise ratio of the instruments by introducing measurement parameters other than capacitance, particularly resistance parameters, thereby significantly enhancing the resolution, accuracy, and reliability of the instruments ； The diversity of measurement parameters has also significantly expanded the reliable application areas of instruments.

Radar level gauges use a non-contact measurement method. Non-contact measurement methods have been the primary approach for level measurement in recent years, and the more mature non-contact measurement techniques currently available include ultrasound, nuclear radiation, and microwaves. In process industries such as chemicals and petrochemicals, the media to be measured are often subject to complex conditions such as high temperature, high pressure, corrosion, volatilization, and condensation; moreover, explosion-proof requirements apply to the measuring instruments used. Compared to ultrasonic waves, the inherent properties of microwave propagation determine the advantages of radar level gauges: 1) Directed propagation. 2) Quasi-optical properties. 3) Good transmission characteristics. 4) The microwave absorption by a medium is proportional to the dielectric constant of the medium. Due to its inherent properties, radar level gauges offer the following advantages in use: 1) Continuous and accurate measurement: Since radar level gauges do not come into contact with the medium being measured, they are minimally affected by factors such as temperature, pressure, and gases. 2) Easy maintenance and simple operation: The radar level gauge features fault alarm and self-diagnosis functions. 3) Wide range of applications: non-contact measurement, good directionality, low transmission loss, and capable of measuring a variety of media. 4) Simple installation: In various industrial applications, radar level gauges can be directly installed on the top of storage tanks, making the installation process very simple.

The transmission pulse of ultrasonic waves consists of one or more electrical \"transmission\" pulses, which are supplied to the scanning relay. This relay then activates as required, sending transmission pulses to the ultrasonic probe connected to the terminals of the ultrasonic electronic control unit. For each electrical pulse provided, the probe emits an acoustic \"transmission\" pulse. After each session, sufficient time is provided before the next pulse (if applied) is emitted, to allow for the reception of the echo (the reflection of the emitted signal). After all transmission pulses have been sent, the processed combined echo is added back. Echo processing: The echo processing process includes echo enhancement, selection of the true echo, and confirmation of the selected echo. Echo enhancement is achieved by filtering and shaping the echo envelope (the digital signal representing the received echo signal). The selection of true echo signals is accomplished by establishing criteria that the partial echo envelope must meet in order to be considered a true echo (an echo reflected from the target being measured). The sound speed in the transmitting medium is affected by the type, temperature, and pressure of the gas or vapor present. Currently, ultrasonic sensors generally assume that the gas in the container is air at 20°C. Unless otherwise specified, the speed of sound used for distance calculations is 334.1 m/s. Sensor installation: 1. The sensor should be installed above the maximum level of the medium being measured, with at least a certain distance from the material surface to ensure there is a blind zone. 2. When measuring liquid levels, the surface where the sensor is installed should be perpendicular to the liquid surface. When measuring the solid level, a sighter is used to assist the sensor in achieving accurate positioning. 3. Do not tighten it too much during installation. In most applications, it is sufficient to simply screw the solid in by hand. A protective chain connects the sensor to the component to ensure reliable installation. When using flange-type sensors, or when a fast temperature response is required, or for use in high-temperature containers, it is advisable to consider using temperature sensors. 4. In applications with strict pressure requirements, turn the sensor by an additional 1/2 to 1 turn when installing it by hand. PTFE sealing tape or other suitable sealants can be used to seal the threads. 5. Take some special protective measures when necessary to protect the sensor surface from damage. 6. Do not expose the cable. The best method to resist electrical noise is to run the cables separately inside grounded metal conduit. Seal all threaded connections to prevent moisture from entering. 7. Do not run cables near high-voltage or high-current wiring, current contactors, or SCR control drivers. In high-voltage environments, turn the sensor’s screw hand-tight by an additional half turn when securing it. 8. In high-pressure environments, PTFE sealing tape or other suitable sealants can be used to seal the threads.

Friends, be sure to support me after watching!

Thank you for your hard work, beautiful! 6# mf1109

This post was last edited by tqg8888 on 2009-5-8 23:22. The views expressed in the second comment and by that MM are not fully supported, for the following reasons: 1. Both ultrasonic and radar level gauges determine distance based on the time difference between the emission and reflection of ultrasonic or radar waves; it is not the case that radar waves use the strength of the echoes to measure distance. 2. Radio frequency admittance level gauges operate on the principle of high-frequency bridges. Admittance is the reciprocal of impedance, which includes resistive, inductive, and capacitive components. Radio frequency refers to high-frequency self-oscillating waves; changes in liquid level lead to changes in capacitive reactance, which in turn alters the oscillation frequency. 3. It cannot be said that radar level gauges use a non-contact measurement method. There are two types of radar level gauges: one type has an antenna and is non-contact; it emits radar waves through the antenna. The other type features a wave guide, which is what we refer to as guided-wave radar; this is a contact-type gauge, with radar waves traveling along the wave guide and returning when they encounter the liquid surface or interface. 4. Ultrasound is a type of mechanical wave, a vibration wave, whereas radar is an electromagnetic wave, a form of radio wave. Ultrasound has greater penetration power and directionality compared to electromagnetic waves; this is where the difference between the two lies. 8# zxdslh

9# tqg8888 ^_^ Brother, you’re absolutely right; I used to work in this field!

I disagree with the person on floor 9; can ultrasonic waves be used at temperatures above 80 degrees? Radar and ultrasound each have their own applicable scenarios and operating conditions in industrial settings; for example, in environments with high steam levels, is ultrasound a viable option? Well, the selection depends on the specific parameters and conditions at the site. If you trust me, you can contact me via QQ: 107433171