Capacitance Level Sensor Working Principle

Capacitance Level Sensor Working Principle. The capacitive fuel level sensor refers to a capacitive liquid level transmitter used to measure the oil level According to the principle of capacitance sensing when the height of the measured electrode dips and changes the capacitance of the measured electrode changes It can convert the change of oil level into a standard current signal.

Capacitance Level Transmitter Use CasesThe Working Principle of Capacitance Level TransmittersContinuous Level Measurement and Level SwitchesConclusionAfter you’ve spent a while in this business you’ll have a good idea of which devices will work best in your process For instance if you need the level in an ice cream tank then you’ll want a noncontact device That way you’ll reduce the risk of contamination and avoid certain types of process connections Makes sense right? Nonetheless most ice cream tanks today use pressure transmitters with flush connections and hygienic approvals Because even though a noncontact solution like a freespace radar looks better for the process the industry typically uses transmitters designed for food application The pressure device will operate just fine but if you have unstable product density it can affect the readings A change in the density will increase the error margin and reduce accuracy If you choose a freespace radar density won’t affect the measurement But wait you might say Those tanks usually have agitators and those disrupt radar devices right? Not exactly Yes m As it says in the name suggests capacitance level transmittersoperate as a capacitor The probe acts as one of the capacitor plates and the metallic vessel wall as the second one We call the medium that separates these plates the insulating material (dielectric constant K) The capacitance or storage capability of the capacitor (C) depends on the plate areas (A) their distance apart (d) and the dielectric constant (E) C= E(K A/d) 1 C = capacitance in picofarads (pF) 2 E= constant 3 K = relative dielectric constant 4 A= effective area of the plates 5 d= distance between the plates When you have a tank with the level at zero percent then you have only air as your insulating material As the product begins to fill the vessel that material will change to a liquid or solid thus changing the capacitance So the capacitance measured by the sensor is directly proportional to the level of the tank This principle can work in many process conditions such as slurries foams h This principle applies to continuous measurement and level switches When you have a continuous measurement the probe should cover the whole measurement range With a level switch the installed rod only detects level in a particular area Many vendors offer these solutions on the market – Endress+Hauser VEGA OMEGA Siemens and others Depending on the vendor you may have to get a model for liquids or solids with fully or partly insulated material in PE PTFE PFA and more Capacitance level transmitters are simple yet flexible If you need to calibrate the device in the field for nonconductive media then you might have a bit of difficulty But in conductive media it installs fairly easily Scale out a device and compare its pros and cons to others to decide the best for your process Buy capacitive level transmitters in our online shop.

Capacitance Level Sensor Principle, Limitations, Installation

Measurement PrincipleLimitationsSelectionDesignInstallationCalibration and ConfigurationThe capacitive measuring principle is based on the method of the operation of a capacitor A capacitor is formed by two differently charged electrodes isolated from each other Applying an alternating current between the electrodes will create an electric field This electrical field depends on the distance between the electrodes the size of electrodes surface and the isolating medium between the electrodes If the distance between electrodes and size of surface of the electrodes are kept constant only the medium would have an effect on the electrical capacitance When the medium change the electrical field changes also consequently the capacitance evolves as follows 1 Capacitance (C) = Dielectric constant (Ɛ0) × Relative Dielectric constant (DC) × Electrode Surface Area Where the dielectric constant (Ɛ0) is the electric field constant (Ɛ0 = 88 × 10‐12C/(Vm) Figure – Capacitance measurement principle Media with a low dielectric constant (DC value) cause very small changes of Figure – Capacitance operating range If a process coats or fouls a capacitance probe a compensation option may be required to prevent false highlevel readings Continuous level capacitance transmitters require that the liquid being measured remains at a constant dielectric value If this is not the case the transmitter should have the capability to compensate for the liquid dielectric variation Probes mounted directly in the vessel typically cannot be replaced with the process in service unless they are mounted in a sensor cage with isolation valves The rod probes require sufficient height clearance depending on the length of the probe It cannot measure liquids which have a viscosity above 2000 cst The capacitive level measurement can be used in aggressive media when a fully coated probe (eg PTFE) is used Capacitive measurement has a very fast response time which makes it ideal for processes with fast level changes and small containers The measurement principle is not affected by the density variation of the media For interface measurements a conductive and non‐conductive media is required At this interface the difference between the conductivity of the conductive media should be greater than 100 μS/cm and the conductivity of the non‐conductive media should be lower than 1 μS/cm An oil‐water emulsion has all the conductivity range between 1 and 100 μS/cm depending on the oil‐water bubble repartition This means that a capacitance probe will detect the media above 100 μS/cm (ie conductive media) and will not detect the emulsion layer (between 1 and 100 μS/cm) as well as the nonconductive media layer (ie.

How does a capacitive liquid level sensor work? SinoInst

Working Principle The principle of capacitive level measurement is based on change of capacitance An insulated electrode acts as one plate of capacitor and the tank wall (or reference electrode in a nonmetallic vessel) acts as the other plate The capacitance depends on the fluid level.