OW700 RF admittance level meter

The OW700 series is a universal RF admittance level gauge used for continuous level measurement. The product is applied in industrial and mining sites and is suitable for most applications. The instrument consists of a circuit unit, an explosion-proof housing, and rod or cable type sensing elements. There are multiple types of sensors to choose from, and the instrument can be installed as a whole or separately

OW700The series is a universal typeRF admittance level meterUsed for continuous level measurement, the product is applied in industrial and mining sites and is suitable for most application scenarios. The instrument consists of a circuit unit, a set of explosion-proof enclosures, and rod or cable type sensing elements. There are multiple types of sensors to choose from, and the instrument can be installed as a whole or separately.

1、 Measurement principle of RF admittance level meter:

Radio frequency admittance is a new level control technology developed from capacitive technology, which is anti hanging, more reliable, accurate, and widely applicable. It is an upgrade of capacitive level technology. The so-called radio frequency admittance refers to the reciprocal of impedance in electricity, which is composed of resistive, capacitive, and inductive components. Radio frequency is the spectrum of high-frequency radio waves, so radio frequency admittance can be understood as measuring admittance using high-frequency radio waves. When the instrument is working, the sensor of the instrument forms an admittance value with the wall and the measured medium. When the level changes, the admittance value changes accordingly. The circuit unit converts the measured admittance value into a level signal output to achieve level measurement.

For continuous measurement, the difference between radio frequency admittance technology and traditional capacitance technology is not only mentioned above, but also includes two important circuits, which are improved based on an important discovery in conductive hanging practice. The above technology also solves the problem of connecting cables and the issue of hanging materials at the root of vertically installed sensors at this time. The two circuits added to the lock are the oscillator buffer and the AC converter chopper driver.

For a container with a highly conductive test medium, since the test medium is conductive, the grounding point can be considered to be on the surface of the probe insulation layer, which is only a pure capacitance for the transmitter. As the container is emptied, hanging material is generated on the probe, which has impedance. In this way, the previous pure capacitor has now become a complex impedance composed of capacitors and resistors, causing two problems.

The first issue is that the liquid level itself is equivalent to a capacitor to the probe, which does not consume the energy of the transmitter (pure capacitor does not consume energy). However, if the equivalent circuit of the probe contains resistance in the hanging material, the impedance of the hanging material will consume energy, thereby pulling down the oscillator voltage and causing changes in the bridge output, resulting in measurement errors. We have added a buffer amplifier between the oscillator and the bridge to replenish the consumed energy, so as not to reduce the oscillation voltage applied to the probe.

The second issue is that for the conductive tested medium, the grounding point on the surface of the probe insulation layer covers the entire tested medium and the hanging area, allowing the effective measurement capacitance to extend to the top of the hanging area. This results in hanging errors, and the stronger the conductivity, the greater the error. But no tested medium is completely conductive. From an electrical perspective, the hanging material layer is equivalent to a resistor, and the part of the sensing element covered by the hanging material is equivalent to a transmission line composed of countless infinitely small capacitors and resistance elements. According to mathematical theory, if the hanging material is long enough, the impedance of the capacitance and resistance parts of the hanging material will be equal. Therefore, based on the study of the error caused by the impedance of the hanging material, an AC driver circuit is added. This circuit, together with an AC converter or synchronous detector, can measure capacitance and resistance separately. Since the impedance and capacitance of the hanging material are equal, the total capacitance measured is equivalent to C+C hanging material. Subtracting the resistance R equal to C hanging material can actually measure the true value, thus eliminating the influence of hanging material.

C measurement=C+C hanging material

C=CMeasurement - C hanging material

=CMeasurement - R

These, multi parameter measurements, are essential foundations, and the AC phase detector sampler is the means to achieve them. Due to the use of the above three technologies, radio frequency admittance technology has demonstrated extraordinary vitality in field applications.

IIRF admittance level meterProduct features:

Strong universality: It can measure liquid and material levels, meet the measurement requirements of different temperatures, pressures, and media, and can be applied to harsh environments such as corrosion and impact

Anti hanging material: The unique circuit design and sensor structure enable its measurement to be unaffected by sensor hanging material, without the need for regular cleaning, avoiding false measurements.

Maintenance free: There are no movable parts during the measurement process, and there is no mechanical component damage issue, so no maintenance is required.

Anti interference: contact measurement, strong anti-interference ability, can overcome the influence of steam, foam and agitation on measurement.

Accurate and reliable: Diversified measurement quantities make the measurement more accurate, unaffected by environmental changes, high stability, and long service life.

3、 Typical applications of RF admittance level meter:

Conductive and insulating liquids in chemical, oilfield, water and wastewater treatment industries

Conductive and insulating pastes for papermaking, pharmaceuticals, water and wastewater treatment

Powder: ash, powder, power plant, metallurgy, cement

Particles: coal, grains, power plants, metallurgy, grains

Interface: Two different liquids... oilfield, chemical industry

4、 Performance indicators of RF admittance level meter:

Power supply: 18V-30VDC

Spark protection (for sensors): Built in spark protection circuit

Output: 4-20mA

Electrical interface: M20 × 1.5

Output mode: level mode or distance mode

Cable: Special connection cable between split electronic unit and sensor, standard 5m, maximum length 50m

Accuracy: ± 1% ± 0.5%

Environmental temperature: -40 ℃~70 ℃

Process connection: NPT thread installation (standard)

Medium temperature: -100 ℃~260 ℃

Flange installation (optional)

Maximum load: 24VDC 350 Ω

Shell protection: IP66

Load impact: 0.2% (0- maximum load)

Explosion proof: EXID Ⅱ CT4

Response time: 0.5s (watch holder) 0.5-30s (adjustable)

Range: maximum 15000PF, maximum distance 100m (different sensors have different maximum ranges)

5、 Selection Guide for Radio Frequency Admittance Level Gauge

OW700Selection of series RF admittance level switch sensors

6、 Installation instructions for RF admittance level meter:

In non-metallic containers and nonlinear applications, auxiliary reference ground level should also be installed.

When using a soft cable bare probe to measure insulation materials (such as coal powder silo), it is required that the height of the installation pipe seat must be less than the length of the hard rod part of the probe to ensure that the hard rod part is exposed from the installation pipe. Prevent the probe from shaking inside the compartment and causing a short circuit to ground. And the installation pipe and steel reinforcement skeleton should be connected together.