Capacitive level gauge
  • Capacitive level gauge

Capacitive level gauge

Capacitive level gauges are suitable for continuous detection of various liquids under harsh conditions such as high temperature and pressure, strong corrosion, easy crystallization, and blockage.

Capacitive level gauges are suitable for continuous detection of various liquids under harsh conditions such as high temperature and pressure, strong corrosion, easy crystallization, and blockage. Suitable for measuring the water level of sewage, acid-base solutions, and boilers, the entire machine has no movable or elastic components, is shock resistant, easy to install, has high reliability, and high accuracy. It can replace traditional float type, input type, differential pressure type and other liquid level transmitters in various applications.

The core component of the capacitive level gauge adopts a radio frequency capacitance detection circuit, which is accurately temperature compensated and linearly corrected by a 16 bit microcontroller, and converted into a standard electrical signal (usually 4-20 mA). The system can be configured with optional communication protocols such as Hart, CANBUS, and 485. The entire series of transmitters have self calibration function, and users can perform automatic calibration of "zero" and "range" through two buttons to adapt to different requirements in various complex environments.

The product complies with GB3836.4-2000 "Electrical Equipment for Explosive Gas Environments Part 4: Intrinsic Safety Type" i "and GB3638.1-2000" General Requirements for Electrical Equipment for Explosive Gas Environments Part 1 ", with the explosion-proof mark: Exia IIC T6. It is suitable for areas in Zone 0, Zone 1, and Zone 2, containing Class IIA to IIC, T1 to T6 explosive gas mixtures.

Characteristics of capacitive level gauge:

1. With a simple structure and no movable or elastic components, it has good reliability and minimal maintenance. In general, routine major, medium, and minor repairs are not necessary.

2. Multiple signal outputs for convenient system configuration.

3. Suitable for liquid level measurement of high-temperature and high-pressure vessels, and the measurement value is not affected by the temperature, specific gravity of the measured liquid, as well as the shape and pressure of the container.

4. Especially suitable for measuring highly corrosive liquids such as acids and bases.

5. Complete overcurrent, overvoltage, and power polarity protection.

Performance of capacitive level gauge:

1. Detection range: 0.01~2000m

2. Pressure range: -0.1MPa~32MPa

3. Temperature resistance of probe: -50~250 ℃

4. Environmental temperature: -20~60 ℃

5. Storage temperature: -55 ℃~+125 ℃

6. Output signals: 4-20mA, 4-20mA superimposed with Hart communication, 485 communication, CAN bus communication

7. Power supply voltage: 12-28VDC (requires power supply through safety barrier)

8. Fixation method: threaded installation M20 × 1.5, M27 × 2,

Installation of flanges DN25, DN40, DN50. Special specifications can be customized according to requirements

9. Wet material: 316 stainless steel, 1Gr18Ni19Ti or polytetrafluoroethylene

10. Long term stability: ≤ 0.2% FS/year,

11. Temperature drift: ≤ 0.02% FS/℃ (within the range of 0-70 ℃)

12. Explosion proof level: Intrinsic safety Exia IIC T6 Explosion proof Exd IIC T5

13. Protection level: IP67

14. Intrinsic safety parameter: Ui: 28VDC, Ii:93mA,Pi:0.65W,Ci:0.042uf, Li:0mH 

Wiring of capacitive level gauge:

The capacitive level gauge transmitter is a standard two wire or three wire instrument, and the power (signal) terminal is located on the wiring side inside the instrument casing. The signal line should use shielded wire or two twisted pair wires twisted together. It is recommended not to pass through the conduit or open wire slot with other power lines, nor near high-power equipment.

Installation and commissioning of capacitive liquid level transmitter:

Cable and rod level transmitters have multiple installation and fixing methods to adapt to different on-site conditions. When on-site facilities such as M20 × 1.5 internal threads or flanges cannot be provided, you can choose from three installation methods: wall mounted, horizontal pipe rack, and vertical pipe rack, so that you can easily install on site.

When measuring media with high fluidity, in order to prevent the sensor from swinging violently, users can choose counterweight accessories to stabilize the sensor. When adding counterweights, it is necessary to place the counterweight object at the bottom of the container to avoid damaging the sensing wire.

When the on-site environment is harsh, users should choose a sensor protective cover to protect the sensor from being damaged by foreign objects or affecting the accuracy of measurement.

When using a rod type liquid level transmitter, if it is not a metal container, it is necessary to connect the outer shell of the transmitter to the bottom of the container with a wire, otherwise the measurement will be inaccurate.

If on-site adjustment is required for the product, the following methods can be adopted:

B: Debugging method using intelligent circuits:

On site zero adjustment - When the liquid level is at the low position of * * *, press and hold the "Z" and "S" buttons for 8 seconds, then release them simultaneously. Press the "Z" button again, and the output current will automatically adjust to 4mA.

On site filling - When the liquid level is at a high level, press and hold the "Z" and "S" buttons for 8 seconds, then release them simultaneously. Press the "S" button again, and the output current will automatically adjust to 20mA.

B: Debugging method using analog circuits:

When the liquid level is at the lower limit, slowly rotate the "Z" potentiometer with a screwdriver and observe that the reading on the ammeter is close to 4mA.

When the liquid level is at the upper limit, slowly rotate the "S" potentiometer with a screwdriver and observe that the reading on the ammeter is close to 20mA.

Repeat this process 2-3 times or more until the zero point and range are both accurate at 4mA and 20mA, respectively.

After adjustment, the cover of the transmitter should be tightened.