Magnetrol Level & Flow Sensors
For more than 80 years, Magnetrol® level controls and flow controls have been transforming industrial processes. As the innovator of the first magnetic liquid level switch and pioneer of today’s level and flow technology breakthroughs, MAGNETROL manufactures instrumentation that is more intelligent, more reliable and simpler to install and operate – making it far more easy for you to improve safety, drive efficiency and grow your business. The Extensive Magnetrol range covers many different forms of level and flow control enabling the V-Flow engineers to provide the right solution for almost every application.
Guided Wave Radar
Guided Wave Radar is based upon the technology of Time Domain Reflectometry (TDR). TDR utilises pulses of electromagnetic energy, which are transmitted down a probe. When a pulse reaches a liquid surface that has a higher dielectric than the air/vapour in which it is travelling, the pulse is reflected. An ultra high-speed timing circuit precisely measures the transit time and provides an accurate measurement of the liquid level or the liquid-liquid interface. All these devices are overfill safe due to the fact that the reference signal is generated above the process seal.
Pulse Burst Radar
Pulse Burst Radar emits short bursts of energy to a liquid surface. An ultra-high-speed timing circuitry measures the time of the signal reflected off the liquid surface. Sophisticated signal processing filters out false reflections and other background noises. The exact level is then calculated, by factoring tank height and sensor offset information.The circuitry is extremely energy efficient so no duty cycling is needed like with likewise radars. This allows to track high rates of level changes up to 4,5 m/minute (180″/min).
Echotel® ultrasonic contact operates on a two crystal pulsed or “transmit-receive” principle which applies a high frequency electronic burst to the transmit crystal. The signal is then converted into ultrasonic energy and transmitted across the sensing gap towards the receiver crystal.When there is air in the gap, the high frequency ultrasonic energy will be attenuated, thereby not allowing the energy to be received. When there is liquid in the gap, the ultrasonic energy will propagate across the gap and the current shift or relay output will indicate a reception of the signal.
The level measurement is accomplished by emitting an ultrasonic pulse from the transducer face and measuring the elapsed time between sending this pulse and its reflected echo from the liquid surface. Since the speed of sound is temperature dependant, the transducer also measures ambient temperature to compensate for the changing velocity.
Acoustic Volume Mapping
Acoustic Mapping Technology uses an array of three antennas to transmit low frequency pulses and to receive echoes of the pulses from the contents of the silo, bin or other container. Using three antennas the unit measures not only the time/distance of each echo, but also the direction each echo comes from. The device’s digital signal processor samples and analyses the received signals to provide very accurate measurement of the level, volume and mass of the stored contents and generates a 3D image of actual allocation of product within the container for display on remote computer screens.
Two Resistance Temperature Detectors (RTD) sensors are fixed at the end of a probe. One sensor measures the ambient temperature; the second sensor is heated to a given temperature.For level applications the cooling effect of the contacting media reduces the temperature difference between the two sensors (TD and TG product series) and will activate a switch.In flow applications the change in flow will create a temperature difference depending on the amount of gas passing through the pipe.
Thermal Dispersion (Mass Flow Measurement)
Similar to our thermal dispersion switches also here two resistance temperature detectors (RTD) are fixed at the end of a probe. Specific for this device is that the sensors are protected to prevent damage if inserted into a pipe/ channel. One sensor measures the ambient temperature; the second sensor will vary in temperature to make sure that the temperature difference between the two sensors remains constant. The energy needed to do this is measured and recalculated to a mass flow of the known gas passing through the pipe/channel.
Electromagnetic Flow Meter
The function of an electromagnetic flow meter is based on Faraday’s law of induction. The sensor consists of a nonmagnetic and non-conductive tube with two embedded measuring electrodes. To create an alternating magnetic field, two coils are fitted onto the tube in parallel with the plane defined by the active parts of the measuring electrodes. If a conductive liquid flows across the magnetic field, a voltage will appear on the measuring electrodes proportional to the flow velocity and the conductor length.
The liquid acts as an isolator between two conductors (probe and tank wall). When level rises, there is more gain of capacity into an analogue or digital signal.
Enhanced Jupiter® transmitter utilises the effect of a magnetic field on a magnetostrictive wire as the basis for operation of the instrument. The primary components are the probe assembly containing the wire and the electronics assembly.
1. A low energy pulse which is generated by the electronics travels the length of the magnetostrictive wire.
2. A return signal is generated from the precise location where the magnetic field of the float intersects the wire.
3. Interaction between the magnetic field, electrical pulse and magnetostrictive wire cause a slight mechanical disturbance in the wire that travels back up the probe at the speed of sound.
4. A timer precisely measures the elapsed time between the generation of the pulse and the return of the mechanical or acoustic signal. This is detected by the acoustic sensor located below the electronics housing. The software is set up to measure the time-of-flight data and to display and convert to level and/or liquid interface measurement.
Magnetic Level Indicator
The Magnetic Level Indicator (MLI) consists of a sealedbypass cage, a float containing a magnet and a visual indicator rail with bi-coloured flags that individually contain a magnet. The indicator rail is external mount on the cage and its flags are magnetically coupled/aligned with the magnet of the float. As the level changes, the float will follow and its magnet will attract the magnets in the flags. This will cause the flags to rotate showing their opposite coloured side. The same electro-magnetic coupling will activate/deactivate switches or change the output of an externally clamped on magnetostrictive transmitter.
The buoyancy force works on the displacer which will vertically move in (increasing liquid level) and out (decreasing liquid level) the linear differential transformer (LVDT). Due to this movement voltages are induced in the secondary windings of the LVDT. These signals are then processed in the electronic circuitry and used to control the output signal.
A permanent magnet is attached to a pivoted switch actuator. As the float/displacer rises following the liquid level, it raises the attraction sleeve into the field of the magnet, which then snaps against the non-magnetic enclosing tube, actuating the switch. The enclosing tube provides a static pressure boundary between the switch mechanism and the process. On a falling level, the float/displacer deactivates the switch.