Meng Hui of radio frequency admittance level meter
Because of the existence of the protective electrode, the detection circuit compares the signals of the detection electrode and the protective electrode, which overcomes the influence of material adhesion on liquid level measurement.
Shanghai Meng Hui: The important difference between point-to-point radio frequency admittance technology and capacitance technology is the adoption of three-terminal technology. A wire is drawn from the measurement signal of the circuit unit, amplified by the noninverting amplifier, and its output is connected with the shielding layer of the coaxial cable and then connected with the shielding layer of the probe. The amplifier is a noninverting amplifier with a gain of "1". The output signal and the input signal are equipotential, in phase and at the same frequency, but isolated from each other. The ground wire is the outermost shielding layer in the cable. Because of the above relationship between the center line of coaxial cable and the intermediate shielding layer, there is no potential difference between them, that is, no current flows, that is, no current leaks from the center line, which means there is no capacitance or zero capacitance between them. Therefore, the temperature effect and installation capacitance of the cable will not affect. In order to solve the problem of hanging material on the probe, a new probe structure is adopted, which has five concentric layers: the innermost layer is the central measuring rod, the middle layer is the central shielding layer, the outermost layer is the grounding installation line, and the middle is separated by insulating layers.
As in the case of coaxial cable, there is no potential difference between the central measuring rod and the shielding layer, and even if the impedance of the suspension material on the sensing element is very small, no current will flow. The electronic instrument only measures the current from the center of the probe to the opposite tank wall, because the central element can prevent the current from flowing upward along the probe to the container wall, so the current to the ground can only flow to the opposite tank wall through the measured substance at the end of the probe. That is, UA = UBLAB = (UA-UB)/r = 0. Because there is a potential difference between the shielding layer and the container wall, although the current flows between them, the current is not measured and the measurement result is not affected. In this way, the measuring end will not be affected by the hanging material. Only when the material level in the container really rises and touches the central measuring rod, the measured current is formed between the central measuring rod and the ground through the measured material.
technical parameter
Repeatability of measurement accuracy of conductive medium
The temperature range is -200℃ ∽+800℃ (select the corresponding sensor probe).
Ambient temperature -40℃ ∽+60℃ Storage temperature -40℃ ∽+60℃
The response time of 0.3s or 0∽20s can be adjusted continuously.
Sensitivity is better than 0.3PF
Temperature affects 0.05pf per10℃.
Signal output DPDT relay output, two groups of normally open and normally closed contacts.
Contact capacity: AC200V5A DC24V5A
The power supply is 220 volts AC or 24 volts DC.
Power consumption 4W
Protection grade IP66
External threads G3/4 "and G 1" for process connection.
Gb-9123-2000dn50pn0.6mpa for flange connection.
The sensor electrode extension rod is 3m long and 0.4m long, and is made of stainless steel 304+PTFE plastic, ceramics or other agreed requirements.
The longest cable type is 35m, and the shortest cable type is 0.5m. Cable type is made of stainless steel 304+PTFE plastic or other agreed requirements.
The standard length of protective electrode is 100 mm or 300 mm stainless steel 304+PTFE plastic, ceramic or other agreed requirements.
Shell type a plastic PBTP
B-type die casting aluminum and epoxy resin spraying
Cable lead-in hole M20x 1.5 with plastic cable sealing sleeve
Explosion-proof standard ExdIICT5
Shanghai Meng Hui Radio Frequency Admittance Level Meter.