Daviteq Radar Liquid Level (RDW) Sensor
RDW
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1. Giới thiệu
Daviteq Radar Liquid Level (RDW) sensor is a built-in pulse radar sensor to measure the water level in hydrological applications such as rivers, canals, lakes, and damp... Pulse radar sensor provides distance measurement based on the direct measurement of the running time of microwave pulses transmitted to and reflected from the surface of the product being measured.
The RDW sensor can be integrated into the wireless transmitter from Daviteq, such as Sub-GHz WS433, LoRaWAN WSLRW, and Sigfox WSSFC, to build the complete Wireless Radar Liquid Level sensor.
The RDW is also powered by the solar panel and chargeable batteries in the wireless transmitter.
Specifications
Technology: Pulse radar
Frequency: 26GHz∼±250MHz, PULSE radar emission pulse time <3ns
Range of level measuring: 0.40∼30m/ 0.60∼70m
Resolution: 1 mm
Level Measuring Accuracy: ±5mm for 30m range/ ±10mm for 70m range
Beam Width: 6°∼18° (with antenna)
Dielectric constant range: 2.5∼100, Medium viscosity <1000cp
Process Temperature: -40∼100℃/ -40∼320℃ (Distribution pipe flange)
Process Pressure: -0.1∼4MPa; / OR -1∼32MPa (Distribution pipe/ quartz isolation flange)
2. Nguyên tắc hoạt động
Radar level sensor measures the distance from the transmitter/sensor (located at some high point) to the surface of a process material by measuring the time-of-flight of a traveling wave and then determine the level of the process material. It is regarded as continuous level measurement device because it continues to measure level. Radar level sensor uses radio waves, electromagnetic in nature (comprised of alternating electric and magnetic fields), with very high frequency in the microwave frequency range – GHz.
To measure the level of a liquid in this type of radar sensor, radar signals are transmitted from the antenna of a radar sensor located at the top of the tank/bridge/chamber as shown below:
The radar sensor uses the pulse radar technique, pulse radar sends out a microwave signal that bounces off the product surface and returns to the gauge. The transmitter measures the time delay between the transmitted and received echo signal and the on-board microprocessor calculates the distance to the liquid surface using the formula:
Distance = [Speed of microwave signal * Time Delay]/2
To calculate liquid level (L), the transmitter is programmed with the reference gauge height of the application– usually the bottom of the tank or chamber. The liquid level is then calculated by the microprocessor in the transmitter.
3. Hiệu chuẩn
The Daviteq radar level sensor measures the distance by taking the air speed of microwaves signals in the ambient air so the calibration is not required.
However, in most level measurement applications, customers need to get the level value instead of distance. To do so, the coefficient A & B value is calculated from the height of the tank/chamber/structure as per the below instructions.
DB: Dead band (This is a short range in front of the sensor can not measure distances)
H: Maximum measuring distance (Span)
D: Distance
How to determine H value?
Method 1: Based on the design drawing of the trashbin or actual measurement
Method 2: Read the sensor's measurement value when the tank/chamber is empty (L0). Then H = L0
Note: a₁, b₁ of sensor must be as default when use Method 2. (Default value a₁ = 1, b₁ = 0)
How to determine the new coefficients A and B?
The calibration formula is L = a x D + b. Calibration at 2 points: L = 0 when D = H and L = H - DB when D = DB
The result is A = -1 and B = H and the level formula is L = H - D
4. Ghi chú ứng dụng
5. Installation Notes
Make sure the installation environment does not emit gases that harm the transducer or the device housing (usually made from Polycarbonate);
Make sure the measured distance must be within the detection range of the sensor;
Do not place the transducer upward to the sky for outdoor application as the rain drops can cause malfunctioning;
Make sure there is no impact on the transducer surface; it will cause the transducer to get damaged;
Do not install the sensor in the closed compartment with solvent vapor or steam; it will cause the wrong measurement.
Do not install the sensor in the dirty environment. It will cause the wrong measurement.
6. Troubleshooting
7. Maintenance
There are no moving parts or consumed parts in the RDW radar level sensor. Therefore there is no need to do maintenance.
However, depending on the installation environment, the transducer must be checked and cleaned periodically for accurate measurement.
8. Cấu hình mặc định
This RDW radar level sensor has the default configuration. The user can change the configuration on the wireless transmitter so that the complete sensor (transducer + wireless) delivers the proper output value.