1. Overview

The Lingke series RF admittance level switch is a positional control instrument used to detect the level of adhesive liquids, solid particles, dust, other mixed slurries, etc. in silos, chutes, or other containers. It can also be used for interface measurement between two different liquids, such as oil-water interface measurement.

The Lingke series RF admittance level switch has the advantages of simple and fast calibration, stable product performance, strong universality of various models, easy installation, and beautiful appearance. It can be widely used in industrial fields such as petroleum, chemical, metallurgical, power, medicine, food, papermaking, and building materials. And the controller can be used in conjunction with PLC programmable controllers or DCS distributed control systems to achieve automatic detection and control of the process flow.

2. Working principle

1. The Lingke series RF admittance level switch utilizes high-frequency technology to generate a low-power RF signal from an electronic circuit on a probe. The probe acts as a sensitive element and feeds back the signal changes caused by the dielectric constant of the level to the electronic circuit; Due to these changes including changes in capacitance and conductivity, the signals processed in electronic circuits are reactance (signals that combine changes in capacitance and impedance).

The change in reactance also causes a phase change in the high-frequency signal on the pole. Therefore, the phase difference between the high-frequency signal on the pole and the reference signal in the electronic circuit also changes accordingly. After processing this change, the driving output circuit sends out an alarm signal to detect whether there is material in the silo.

3. The Lingke series RF admittance level switch adopts three terminal Cote Shield technology to eliminate the influence of adhesive materials on the detection rod on the control function. The high-frequency signal generated in the electronic circuit is directly sent to the detection rod on one side, and sent to the anti adhesion protective cover on the other side through an RF voltage follower. Its magnitude and phase are the same as the signal applied to the detection rod. When material adheres to the probe, a capacitor is formed between the protective cover and the warehouse wall. Therefore, the high-frequency signal applied to the protective cover will cause the capacitor to tend towards saturation, making it impossible for the high-frequency signal on the probe to flow into the container wall through the adhesive layer. When a large amount of material in the container contacts the probe, the current on the probe bypasses the saturation zone and flows towards the container wall, thereby generating a signal of the presence of material.

Main technical parameters

Working power supply: 24VDC; 220VAC

Relative humidity: ≤ 85%

Output signal: Two sets of normally open and normally closed contacts

Contact capacity: AC220V, 5A;  DC24V，3A

Environmental temperature range: -40 ℃~+60 ℃

Medium temperature: -180 ℃~+500 ℃

Delay time: 0.2 seconds (adjustable from 0.2 to 30 seconds)

Protection level: IP65

Probe material: 316 stainless steel, tetrafluoroethylene, high-temperature plastic, ceramic

Explosion proof grade: ExdIIBT4

Connection method: 3/4 "NPT thread; 3/4 "pipe thread; Flange (optional); 1-1/2 "pipe thread

Installation methods: top mounted, side mounted

Exterior structure diagram

1 . Installation and Debugging

To ensure the normal operation of the instrument, the controller must be installed correctly. The following illustrations will help you choose the correct installation method.

1.1 Probe installation

1. The probe should be installed with a downward inclination (>5 °) in the horizontal direction

2. The installation position of the probe should be away from the feeding port (>10cm)

3. The probe should maintain a certain distance (>10cm) from the container wall

4. The protective cover should protrude from the container wall (>5cm)

5. The coaxial cable between the separated instrument installation probe and the controller should be threaded through a shielded tube

6. The distance between the high and low level probes is greater than 50cm

When vibration equipment is installed in the cylinder groove or conveying pipeline, it is necessary to consider whether it will damage the internal parts of the switch.

8. If the switch is used to detect liquids, do not install the switch on the circuit board with the inlet setting function to avoid misoperation caused by fluctuations.

When installed in a simple tank with mixing equipment, a delay should be selected to avoid liquid impact on the sensing rod and cause misoperation.

The probe installation interface should be selected according to the equipment situation as follows:

1. The instrument is equipped with two types of threaded mounting interfaces, 1-1/4 "NPT and 3/4" NPT

① For equipment with high vibration, a 1-1/4 "NPT threaded installation interface should be selected;

② Equipment used for high temperatures should choose installation interfaces;

③ The maximum working pressure that 1-1/4 "NPT threaded installation joints can withstand is 0.3 MPa, and the maximum working pressure that 3/4" NPT threaded joints can withstand is 1.0 MPa. When the instrument is used to measure liquid levels and pressure vessels, a 3/4 "NPT threaded installation interface must be used.

When using a 3/4 "NPT threaded installation interface to install the instrument, the user must first use a 3/4" NPT internal threaded interface connecting pipe welded to the outside of the warehouse wall, and refer to the processing and installation diagram below to process and weld the connecting pipe (tilted horizontally downwards by 5 °). The length of the connecting pipe for the 3/4 "NPT internal thread interface should be controlled between 40-70mm. When installing 1-1/4 "NPT threaded interfaces, the threaded diameter of the connecting pipe should also correspond to it. When fixing the instrument with the connecting pipe, use a wrench to secure it.

Structural diagram of connecting pipe installed with 3/4 "NPT threaded mouth (unit: mm)

1.2 Installation of Material Level Switch

Installation of integral level switch

1. The installation and on-site wiring of instruments should comply with national standards;

2. The power and signal lines must be wired according to the diagram and cannot be connected incorrectly;

3. To ensure good grounding of the overall instrument, it is recommended to use an independent grounding wire;

① The power supply for the instrument must use the power supply voltage shown on the instrument nameplate. Incorrect power supply will damage the instrument.

② When the power supply of the instrument is 220VAC, the L end is connected to the 220V phase line and the N end is connected to the neutral line.

③ When the power supply of the instrument is 24VDC, the N terminal is connected to the positive pole of 24VDC and the GND terminal is connected to the negative pole of 24VDC.

Special reminder: Instruments powered by AC 220VAC and DC 24VDC cannot be mixed. They must be confirmed to be accurate according to the wiring label before connecting to the power supply.     

Installation of separated level switch

1. A 1.5mm2 single core wire (to be provided by the user) and a dedicated coaxial cable provided by the company with the instrument should be laid in parallel between the separated controller part and the probe junction box. They should be shielded in a metal tube to prevent strong electromagnetic interference from causing instrument misoperation. The grounding wire must not be omitted, otherwise it will seriously affect the stability of the instrument.

2. The cable connection between the instrument controller and the probe junction box shall not exceed 22 meters. When measuring materials with light powder or low dielectric constant, the distance shall not exceed 10 meters. Excess cables cannot be coiled into a circle and need to be cut off to prevent cross interference, and coaxial cables cannot pass through the same shielding tube as the power source line and alarm signal line.

3. The principle of selecting the shortest distance between the instrument controller and the probe should be followed, and the shorter the distance, the more reliable the instrument operation.

Only one coaxial cable and one grounding wire can pass through a metal shielding tube.

1.3 Upper and lower limits and delay settings

The instrument is set to standard state according to the medium (dielectric constant) provided by the user when it leaves the factory. After the instrument is installed, the user must perform hot state (half an hour of power on) debugging. Calibration should be carried out in an empty state (the instrument must be grounded), and the factory setting position of the instrument should be recorded before calibration.

1. The product can set upper and lower limit material level alarms according to user requirements. If not specified, it defaults to upper limit alarms.

When users want to select the lower limit alarm, they can achieve the goal by selecting the relay contact to output the signal in reverse. However, at this time, the status of the alarm indicator light has the opposite meaning. It can also be indicated at the time of ordering that the status of the alarm indicator light has the same meaning.

3. Delay setting: The output response time of the instrument is set to 0.2mS when it leaves the factory. If the surface of the measured medium fluctuates greatly, the delay potentiometer RP2 can be adjusted clockwise to the appropriate delay parameter.  

1.4 Calibration method (alarm setting):

① Turn the RP2 potentiometer counterclockwise to the leftmost position;

② At this time, the red LED indicator light is not on. The delay time is 0.2ms;

③ Slowly rotate RP1 (sensitivity potentiometer) counterclockwise until the red LED indicator light is just on;

④ Slowly rotate the RP1 potentiometer in a clockwise direction until the red LED indicator light just goes out, and then rotate it half a circle in the original direction;

⑤ According to the dielectric constant of the tested material, the RP1 potentiometer can be further rotated clockwise or counterclockwise to a suitable angle, with an insulation medium of 5-30 ° and a conductive medium of 30-180 °. When the material contacts the detection probe, an alarm output is generated, and when the material separates from the detection probe, a normal state is displayed.        

2 . Troubleshooting

2.1 Power Failure

If the instrument malfunctions, please immediately check whether the power supply meets the requirements and whether the power wiring complies with the specifications. Only when the power supply is correct can the following troubleshooting process be carried out. When the instrument encounters the following situations, please refer to the maintenance:

2.2 Probe malfunction

Firstly, please check whether the installation of the probe meets the technical requirements for installation. Only after the probe is correctly installed can the following troubleshooting process be carried out. Secondly, please confirm whether the material is already in the position of the described fault. Otherwise, the following phenomena are normal. When the material level position has been determined but the instrument shows the following situations, please refer to the maintenance: