FT8062 Intelligent RF Admittance Continuous Level Gauge

The FT8062 series is a universal intelligent RF admittance continuous level instrument, which can be used for continuous measurement in most application scenarios. Instruments are widely used in industrial and civilian fields, both indoors and outdoors. Compared to other forms of instruments, this instrument has no special requirements for on-site installation conditions.

The instrument consists of an electronic unit, an explosion-proof casing, and pole or cable sensors. The sensors can be made of various materials and can be installed as a whole or in separate units. Integrated installation refers to placing the electronic unit and sensor in the same explosion-proof enclosure, while modular installation refers to placing the electronic unit and sensor separately in two independent explosion-proof enclosures, connected by a specially designed cable from the manufacturer.

　　measuring principle

Radio frequency admittance level control technology is a level control technology developed from capacitive level control technology, which has better anti hanging material performance, more reliable operation, more accurate measurement, and wider applicability. The meaning of "admittance" in "radio frequency admittance" is the reciprocal of impedance in electricity, which is composed of resistive, capacitive, and inductive components. "Radio frequency" refers to high-frequency radio waves, so radio frequency admittance technology can be understood as measuring admittance with high-frequency current. A high-frequency sine oscillator outputs a stable measurement signal source, utilizing the principle of a bridge to accurately measure the admittance of sensors installed in the container under test. In direct action mode, the output of the instrument increases with the rise of the material level.

The difference between radio frequency admittance technology and traditional capacitance technology lies in the diversity of measurement parameters, three terminal drive shielding technology, and the addition of two important circuits, which are improved based on valuable experience in practice. The above technology not only solves the problems of cable shielding and temperature drift, but also solves the problem of hanging materials at the root of vertically installed sensors.

For a container made of highly conductive material, since the material is conductive, the grounding point can be considered to be on the surface of the sensor insulation layer. For instrument sensors, it only appears as a pure capacitor. As the container is discharged, there is a hanging material on the sensor, 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 material itself is equivalent to a capacitor to the sensor, which does not consume the energy of the transmitter (pure capacitor does not consume energy). However, if the equivalent circuit of the hanging material to the sensor contains a resistor, 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 driver between the oscillator and the bridge to replenish the consumed energy, thus stabilizing the oscillation voltage applied to the sensor.

The second issue is that for conductive materials, the grounding point on the surface of the sensor insulation layer covers the entire material and hanging area, allowing the effective measurement capacitance to extend to the top of the hanging area, resulting in hanging errors, and the stronger the conductivity, the greater the error.

But no material is completely conductive. From an electrical perspective, the hanging material layer is equivalent to a resistor, and the part of the sensor 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 and reactance values of the capacitance and resistance parts of the hanging material are equal. Therefore, an AC phase detector sampler can be used to measure capacitance and resistance separately. The measured total capacitance is equivalent to the C level+C hanging material, and subtracting the resistance R equal to the C hanging material can obtain the true value of the level, thereby eliminating the influence of hanging material.

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

The FT8062 series intelligent universal RF admittance level meter fully utilizes the new software and hardware technologies of the 21st century, achieving high reliability, safety, and precision measurement. In addition to retaining the original basic functions, it also adds software processing and digital communication functions, greatly improving the comprehensive capabilities of the instrument such as accuracy, self diagnosis, and stability.

　　characteristic

Intrinsic safety design: Two wire intrinsic safety design, where both the unit and probe are inherently safe

Maintenance free: No moving parts, no wear or damage, no need for regular cleaning, no need for repeated debugging

Anti hanging material: Three end shielding technology allows it to ignore the influence of hanging materials on walls or sensing components

Chemical compatibility: Multiple probe designs to meet various media requirements

Widely applicable: Process temperature ranges from -183 ℃ to+815 ℃, pressure ranges from vacuum to 100bar

No drift: Will not drift due to temperature or density changes in the medium

Reliable lifespan: Unique technology ensures instrument service life of up to 15 years

Safety protection: Built in probe input device, strong protection ability, not easily affected or damaged by static electricity, impact and electrochemical phenomena

Easy installation: The instrument can be installed through the threaded port or flange on the tank, and can be installed as a whole or in separate parts by yourself,

Optional vertical, curved probe or any angle installation, simple and convenient, easy and fast debugging

Intelligence: Data software processing has improved accuracy by one level. The instrument has a self diagnostic function inside

Communication: HART digital communication function

On site key calibration: The instrument provides a key calibration function that can be implemented on-site

　　Typical applications

Liquid: Conductive liquid or insulating liquid (including liquefied gas)

Slurry: conductive slurry and insulating slurry

Particles: grains, plastic sheets, coal, etc

Interface: Two liquid interfaces with different dielectric constants

Powder: plastic powder, cement, fly ash, etc

　　performance index

Measurement equipment level: CAT I level, transient rated voltage 1500V, cannot be used for levels other than CAT I level

Output: 4-20mA HART protocol, software adjustable current output direction

Measurement method: can be set as level/distance measurement method by software

Power supply: 12-35VDC Smart communication requires a power supply of 15-35VDC

Power: less than 0.5W

Accuracy: ± 0.5% FS

Linear correction: Software selectable 10 point nonlinear correction (if necessary)

Temperature effect: 0.25%/10 ℃ (18 ℉)

Load resistance: Output circuit load resistance capacity of 600 Ω at 24VDC

Environmental temperature: T5: -40 to+70 ℃ (-40 to 158 ℉); T6: -40 to+60 ℃ (-40 to 140 ℉) (The influence of medium temperature on ambient temperature cannot exceed the instrument's requirements for ambient temperature)

Response time:<1 second

Delay: Adjustable from 1 to 90 seconds (software adjustable)

Electrostatic spark protection (for sensors): anti surge impact 1000V, anti-static 4kV/8kV

RF protection (built-in filter): The whole machine is tested by injecting current through a 10V/m electromagnetic field and a 3V/m electromagnetic field in space

Range: Maximum 20000pF (when the resistance component is infinite, it can be expressed as capacitance), maximum range distance is about

1000 meters (39370 ″) (the maximum measuring range of different sensors is different)

Cable length: 5m (standard) (197 "), 0.1m (3.9") to 50m (1968.5 ") (optional), 50m (1968.5") to 100m (3937 "). Please consult the manufacturer for more information

Electrical interface: M20 × 1.5 (optional 3/4 "NPT)

Process connection: NPT thread installation (standard, optional BSPT), flange installation (optional)

Shell material: die cast aluminum with epoxy coating

Shell protection: Compliant with IP67 protection standard

Explosion proof grade: Ex ia IIC T5/T6 Ga

Certification: CMC, PCEC/NEMSI. For other certifications, please consult the manufacturer

FT8062 wiring diagram

The FT8062 series level gauge belongs to the intrinsic safety type of instrument. Whether installed as a whole or separately, when installed in hazardous environments, a jointly certified safety barrier needs to be added to its power supply circuit. Both single and double barriers can be used, but the connection method is different. The examples in the intrinsic safety application system and safety barrier wiring diagram are single barrier integral installation and double barrier separate installation. For safety barrier products that have been jointly certified, please consult our company or our agent. The maximum impedance of cables, loads, and safety barriers under 24VDC power supply is 600 Ω.

Please refer to the instructions for the use of safety barriers for grounding requirements. The requirements for safety barriers in this level gauge are:

Uo=28VDC

Io=93mA

Po=0.65W

Co=0.083uF

Lo=4.2mH

Safety parameters of this instrument:

Ui=30V

Ii=100mA

Pi=0.75W

Ci=6nF

Li=240uH

Installation requirements for FT8062

The installation, use, and maintenance of the product should comply with the relevant provisions of the product installation, commissioning, and use instructions, GB50257-96 "Code for Construction and Acceptance of Electrical Equipment in Explosive and Fire Hazardous Environments", GB3836.15-2000 "Electrical Equipment for Explosive Gas Environments Part 15: Electrical Installation in Hazardous Areas (excluding Coal Mines)", and GB3836.13-1997 "Electrical Equipment for Explosive Gas Environments Part 13: Maintenance of Electrical Equipment for Explosive Gas Environments".

When installing instruments, they should be kept as far away as possible from vibration sources, high temperature environments, corrosive air, and any places that may cause mechanical damage. If the requirements cannot be met, please replace the instrument with a new component. The ambient temperature should be at: T5:- 40～+70℃(-40～158℉); T6:- Between 40 and+60 ℃ (-40 to 140 ℉) (the influence of medium temperature on ambient temperature cannot exceed the instrument's requirements for ambient temperature).

The instrument installation area requires lightning protection devices to prevent lightning strikes.

It is prohibited to use single component ambient temperature sulfurized sealant inside the instrument casing. This substance often contains acetic acid, which will corrode electronic components. Special two-component sealant (non corrosive) should be used.

The instrument casing is equipped with grounding terminals, and users should ensure reliable grounding during installation and use. When used for non-metallic cans, a standard ground should be provided on site and cannot be connected to the power ground.

The electrical interface should be equipped with cable sealing joints with a protection level of IP65 that meet the requirements of GB4208 standard to ensure reliable sealing and prevent damage to the instrument electronic unit caused by water ingress or other corrosive gases.

Do not disassemble the sensor or loosen the sealing nut to avoid probe leakage.

The installation of sensors should avoid material flow or inlet/outlet ports. If there are no other installation locations, protective covers or partitions should be added.

The installation of threads or flanges should be firmly connected to the container, reliably sealed, and have good electrical contact. Except for the connection, other parts of the sensor should not come into contact with the container to ensure good insulation.

When installing the sensor horizontally, it should be slightly tilted downwards at an angle of 10-20 °.

When installing hard rod sensors, the installation space should be considered, with a minimum distance of 100mm from the tank wall. After installation, the cable sensor should be straightened and kept at least 300mm away from the tank wall to avoid short circuits to ground.

In situations where there is significant mixing, airflow, and material flow fluctuations inside the container to be tested, in addition to avoiding direct mechanical damage to the sensor, indirect mechanical damage such as long-term fatigue of the sensor material should also be considered. Therefore, it is recommended to install protective measures such as intermediate support and bottom anchor fixation for the sensor. Please note that the support and ground anchor should be insulated from the sensor, and the insulation material should be selected from materials with high insulation strength, low hardness, lubrication function, and no wear on the sensor (such as PTFE). If not, please consider replacing the sensor regularly to avoid sensor damage and chain loss.

When measuring large quantities of solid particles, the heavy hammer at the end of the sensor should be as high as possible above the cone angle of the silo. If it is necessary to enter the conical section, the maximum entry size should not exceed 20% of the diameter of the silo.

The non active section of the sensor should enter the tank at least 50mm. When the cable sensor is installed horizontally, the hard rod part entering the tank should not be less than 200mm, and when installed vertically, the hard rod part entering the tank should not be less than 100mm.

The instrument circuit installed according to intrinsic safety standards must be equipped with safety barriers certified by GB3836.1 and GB3836.4 explosion-proof standards.

The ripple of 24VDC power supply shall not exceed 100mV.

The instrument connection cable shall comply with the requirements of IEC60245/60227 standard. It is recommended to use armored shielded 3-core cables with an outer diameter of no more than 12mm. The cable conductor material is copper, and the cross-sectional area of the conductor is 0.13-2.1mm2 (AWG14-26). The insulation strength of the cable is 1500V. Long distance unshielded cables cannot be used in parallel with AC power cables.

When using and maintaining on site, the principle of "no opening with power on" must be followed, and it is recommended to shut off the power for 10 minutes before operation.