The intelligent external ultrasonic liquid level meter (hereinafter referred to as“liquid level meter” or “meter”) utilizes advanced signal processing technology and a high-speed signal processing chip. Its signal penetrates the wall of the tank and ultimately achieves completely non-contact measurement of liquid height in hermetic tanks.
The ultrasonic sensor (probe) is installed at the bottom of the tank’s external surface without the need for drilled holes in the tank. This allows for quick, simple installation that does not interrupt the tank’s operation. The liquid level meter can be placed on a portable moving tool such as a cart for convenient moving measurement. The instrument can be powered by mobile power bank.
Because of the non-intrusive nature, the meter can be used to acquire accurate liquid level measurements for high-pressure hermetical tanks containing toxic, highly acidic or alkaline, and various types of pure liquids. The liquid level meter has no special requirements related to the material of the tank, and it is explosion proof as designed. Its robust, engineered design allows it to be used in a wide variety of applications and conditions.
Features
l Non-Contact Liquid Level Measurement
The ultrasonic sensor (probe) is designed to be installed on an external surface of a tank wall without the need to drill holes on the measured tank.
l Self-Calibration
This function eliminates accuracy loss due to long term usage.
l Infrared Debugging During Operation
This function is especially suitable for conditions where it is dangerous to open the meter cover to debug, making the debugging process simple.
l Self-Test
The liquid level meter can self-test its own operating status and hardware conditions, ensuring reliability and stability.
l One-Key Recovery
If the liquid level meter is not functioning properly, the user can press the one-key recovery button on the remote control to allow the liquid level meter to return to normal working condition.
Working Principle
The system kernel of the liquid level meter is based on special ultrasonic processing technology capable of high-speed digital signal processing. After processing, the liquid volume percentage value is precise enough that additional CPU analyzing, comparing or judging is unnecessary. Once the CPU acquires the liquid level value, the value is transmitted directly to NVRAM for storage and display. In addition, the liquid level meter can output a 4～20mA standard signal or transmit measurement results to a computer ( or secondary meter ) via an RS-485 interface.
As shown in Fig. 1, during the process of measuring liquid level height, the modulated acoustic signal is transmitted from the probe and echoed from the liquid surface. The probe then detects the echoed signal. After going through preprocessing, processing and post-processing, this signal provides the accurate time t directly. The CPU then calculates the liquid level height value through a mathematical model.
h = act/2
h：Liquid level height
a：Correction factor
c：Ultrasound transmitting velocity in liquid
t：Time duration between transmission and reception of ultrasound signal
Parameters
Measuring range | 3m, 5m, 10m, 20m, 30m |
Display resolution | 1mm |
Short time repetition | 1mm |
Measurement error | ±1‰FS(Excessive wall thickness and temperature/pressure instability may affect measurement precision.) |
Span shift | ±10 m |
Current output | 4～20mA，Max load 750Ω |
Communication interface | RS-485, IrDA |
Operating ambient temperature for liquid level meter | -30℃～+70℃ |
Operating ambient temperature for ultrasonic probe | -50℃～+100℃ (A probe with wider temperature range can be provided upon request） |
Operating ambient humidity | 15%～100%RH |
Explosion proof mark | Ex d ⅡC T6 Gb |
Housing ingress protection | IP 67 |
Volume percentage display | 4 digit OLED display |
Power supply | DC24V |
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