Capacitive level Transmitter

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Xi'an Kacise Optronics Tech Co., Ltd.

Shaanxi, China

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The capacitive intelligent liquid level sensor is a liquid level (material level) transmitter that can be used for liquid, oil, solid, interface, and measurement. There are no moving parts, the reliability is greatly improved, it is not affected by water vapor, dust, or condensation, and has the advantages of stable and reliable long-term operation, high sensitivity, good linearity, high-temperature resistance, high-pressure resistance, etc. The intelligent liquid level meter is a two-wire (loop powered) 4~20mA DC measurement signal, easy to adjust, wireless transmission, 485 transmissions, etc.
Capacitive level transmitter Structure
Capacitive liquid level sensors have different structures due to different application occasions and parameters, but in general, their main structure can be roughly divided into two parts, namely the sensor part and the transmitter part.

A in the picture shows the sensor, which directly probes into the container equipment or measures
in the measured medium of the meter tube
B and C in the figure are the gas phase and liquid phase connection flanges of the liquid level measurement and control instrument, which are used for the connection of the equipment flanges, and the liquid and pressure in the equipment are drawn to the measuring cylinder.
D in the figure shows the measuring cylinder of the liquid level measurement and control instrument, which can form a capacitance with the sensor electrode.
E shown in the figure is the sewage flange, which can regularly discharge the dirt in the liquid level measurement and control instrument to the outside, keep the inside of the measuring tube of the liquid level measurement and control instrument clean, and prevent the sensor from adhering to the dirt.
F shown in the figure is the Capacitive level transmitter, which is a conversion device from capacitance to standard current signal and is the central part of the entire liquid level measurement and control instrument.

Its main function is to receive the capacitance change increment caused by the liquid level change sent by the sensor, and then After conversion, it outputs the 4-20mADC standard current signal. This transmitter adopts military integrated devices, with low power consumption, high-temperature resistance, strong reliability, and meets the requirements of intrinsic safety.
Note: There is a sealing part between the transmitter and the measuring tube, which is composed of several seals, which can ensure that the measured medium is in contact with the sensor but will not leak out, causing harm. This section is an important sealing part, please do not disassemble it without the consent of the manufacturer to avoid accidents.
Capacitive level transmitter Calibration
Although the analog adjustment has been made before the product leaves the factory, in order to allow the user to further experience the performance of our product before use, it is recommended that the user perform a simple verification. You can remove the whole set of instruments for calibration. (But do not disassemble the parts of our products)
The calibration of the external liquid level measurement and control instrument is shown in the figure :
The Capacitive level transmitter verification steps are as follows:
1) Prepare a transparent water pipe, mark it with a scale, or fix it with a ruler, so that the actual liquid level can be observed and calibrated during calibration. In addition, prepare an ammeter (DC) with a precision of more than three digits, several rubber stoppers, and enough test medium (which can be replaced by water).
2) Connect one end of the transparent water pipe to the liquid phase port of the liquid level measurement and control instrument, block the sewage outlet, keep the gas phase port unobstructed, and then turn on the power after confirming that the wiring is correct.
3) Add the medium from the upper end of the transparent tube, the medium flows through the liquid phase tube into the liquid level measurement and control instrument, and the liquid level is added to several points with different heights because at this time the liquid level in the transparent tube is measured with the liquid level measurement and control instrument. The liquid level in the metering cylinder is exactly in line. At this time, read the value of the ammeter, and then compare the height ratio corresponding to the output standard 4-20mA signal with the collected current value to check the accuracy of the level meter (Note: In order to It is easy to calculate. Generally, several points are taken at 0%, 25%, 50%, 75%, and 100% respectively, and the corresponding currents are 4mA, 8mA, 12mA, 16mA, and 20mA respectively. The capacitive level transmitter range should correspond to the center of the liquid phase and gas phase respectively).

                                                            Detection range
                                                            0.1～30m
                                                        
                                                            Capacitance measurement range
                                                            10PF～500PF
                                                        
                                                            Accuracy
                                                            0.1 class, 0.2 class, 0.5 class, 1 class
                                                        
                                                            Pressure range
                                                            -0.1MPa～32MPa
                                                        
                                                            Probe temperature resistance
                                                            -50～250℃
                                                        
                                                            Ambient temperature
                                                            -40～85℃
                                                        
                                                            Power supply voltage
                                                            5～36V DC
                                                        
                                                            Level sensor material
                                                            316 stainless steel, 1Gr18Ni19Ti or PTFE
                                                        
                                                            Long-term stability
                                                            ≤0.1%FS/year,
                                                        
                                                            Temperature drift
                                                            ≤0.01%FS/ ℃ (within the range of 0～70 ℃)
                                                        
                                                            Explosion-proof grade
                                                            ExibIICT6
                                                        
                                                            Protection level
                                                            IP67
                                                        
                                                            Storage temperature
                                                            -55℃～ 125℃
                                                        
                                                            Output signal
                                                            4～20mA, 485 communication, etc.
                                                        
                                                            The communication distance of the wireless output level sensor
                                                            is less than 200 meters, and the power supply voltage is 3.3-36V (optional battery power supply)