Glossary of Level Sensor Terms
By Dhananjay Palshikar on April 26, 2019Beginner
Context is Important
Even Industry veterans cannot keep up with the changing lingo in the automation industry. The challenge with the lingo in automation is that common english words have nuanced contextual meaning.
e.g An Alarm Signal is raised under undersirable condition. Fire Alarm is signaled in case of Fire. For Level Measurement an Alarm Condition is different for a :
- High Level Sensor: In most cases Alarm condition is considered when material overflows from the vessel or when level sensor is covered
- Low Level Sensor: In most cases Alarm condition is considered when the vessel is empty or when the level sensor is uncovered
If you find mistakes or if something is missing, readers are encouraged to add your thoughts in the comments section below
|Level sensors are used in various application media according to which design and products varies and the construction of product is also depend on the application media.
|Conductive material are those that allow flow of charge in one or more directions and materials made of metals are most common conductive materials. When the process material is conductive then the PTFE insulation is provided with sensor.
|Corrosive material is one that destroy the substance that comes in contact with it. Most common corrosive material are acids which includes sulphuric acid, hydrochloric acid etc. As it can harm the metal body so the level sensors are insulated with halar coating.
|Non-conductive or insulators in which electrons does not flow freely and it prevent the flow of electric current so a very low amount of current is flowing in it. Glass, Plastic or rubber is the example of non-conductive materials.
|A mechanism or arrangement is constructed to allow the entry of cable in a electrical device which provide sealing, grounding, earthing, insulation etc.
|Single Compression Gland
|SC gland is used for light armored cables as it provide compression only at one place i.e. at the cable shield so there is a chance of moisture to enter into cable gland.
|Double Compression Gland
|It serve extra support to the shielded cables entering or exiting the panel and it give compression at cable shield as well as at the inner covering which minimizes the scope of moisture entering.
|Polyamide Cable Gland
|The polyamide PG gland provide a water tight seal for round cables and it gives a better strain relief. These cables are shock resistance.
|Sapcon products are certified and approved by various organisations to work better in any environmental and hazardous conditions.
|It is a abbreviation of Bureau of Indian Standards (BIS) formerly known as ISI, is a National Standard Body of India which provide flexibility and importance to standardization, appropriate recognition for development of production in different sectors and certification marking.
|PESO & CCOE
|The Petroleum and Explosives Safety Organisation(PESO) is a regulatory authority control by Chief Controller of Explosives(CCOE) approves various electronics and mechanical products for hazardous area. This certification is mandatory for all products installed in explosive environments.
|CE marking is the abbreviation of a phrase Conformité Européene" which means "European Conformity". This certification acknowledge that the product signify all requirements of European health, safety and environmental protection.
|EIL a public sector undertaking and is reposible for undertaking inspection of all major equipment manufacturers in India. The company is under the Ministry of Petroleum and Natural Gas.
|European Hygience and Design Group is not a regulatory body but a consortium of companies devoted to the advancement of hygienic design and food engineering.
|RoHS is the abbreviation of Restriction of Hazardous Substances. It restricts the use of specific hazardous materials found in electrical and electronic products that are dangerous.
|The instruments measure or sense the material properly and give the correct output when correct dimensions are taken into account while designing the electronics and mechanical parts.
|It is the length of ground section which comes between sense and mounting connection to give the extension to sense or shield.
|The Nozzle is pipe or tube having varying cross-section area which differ in length it depends on vessels and grounding length.
|It is the length of sense part which make contact with the material and detect the material on a required point.
|Sensing Point/Switching Point
|A point around which sensing/switching takes place.
|It is the length of non contact part of probe which is not in contact with the material. It is just used to provide extension to sense part.
|The summation of Ground Length, Shield Length and Sense length is known as Probe Length.
|It is the length of shield part which isolate the grounding and the sense part and it help to immune the build-up on the probe.
|Build-up on Level Sensor
|Some amount of material stick on the probe and creates coating on it and level sensor treat as real material which cause malfunction in level sensor and gives false alarm. This coating on probe is known as Build-up on level sensor.
|Calibration of an instrument means to set the level of 0% and 100% which help level sensor to understand the high and low level of a vessel.
|The dielectric is an insulator or a bad conductor of electric current. When the dielectric is placed in a electric field, electric charges do not flow through the material.
|It is the method of providing a path for transferring the electricity discharge directly to the earth. It is used to protect us from electric shock.
|The non-inductive loads are those which has negligible or low inductance and it's current does not changes promptly.
|A shielded cable is an electrical cable which enclosed group of wires or cables by a common conductive layer and it efficiently block the noise or interference.
|A socket is used to connect the electrical equipment which differ in voltage, current ratings, shape and size.
|It is define as the change over of voltage with respect to given temperature.
|The voltage which is required to on the device is known as threshold voltage.
|The flow of fluid which undergoes irregular motion, disturbance or fluctuations when fluid flow in parallel path.
|viscosity is the quantity which illustrate the opposition of flow of liquid. It means resistance of liquid to change in shape related to other.
|Some unique features are implemented in our various products.
|A Gas filled Surge arrester, commonly known as discharge device in probe head discharges the static charge or limiting surge voltages on device.
|In a condition of device failure, known errors and input power failure the outputs of the device resemble the ALARM condition.
|This feature is available in vital which means that the level sensor changeover its condition or switch in just 0.5 to 0.8 seconds.
|Internal Temperature Compensation
|This feature are commonly used in level sensor resembles that the performance or output of level sensor does not affected by change in temperature. It compensate the system and gives the true value of output.
|Pump Control Logic
|Pump Control Logic interpret that one relay control two points i.e. Low and High. When material goes below low point then the device connected to it gets on and when the material goes above high point then the device connected to it get off.
|Single Point Switching
|In single point switching the level sensor change over its output at one point. It means that when material touches the probe it will switch or change the output.
|Three Point Switching
|In three point switching, the level sensor calibrated at three points i.e. Low, High and very High and then it gives alarm at these three points.
|Two Point Switching
|In two point switching, the level sensor calibrated at two points i.e. low and High and then it gives alarm at these points
|In industries it is commonly refer as Enclosure. These are used in level sensors to protect internal electronic components from humidity, dust, moisture etc.
|The meaning of flameproof housing is that if some explosion occurs due to faulty components, the effect of explosion should be enclosed within the enclosure only it should not affect the surroundings.
|The weatherproof housing is used to provide the degree of protection to the internal electronics component from rain,dust and splashing water. With the help of this housings.
|The place where there is a chance of explosion due to present of hazardous gases or other environmental conditions is known as hazardous area.
|The international protection which provide various degree of protection for mechanical castings and enclosures against dust, moisture, water etc.
|Ingress Protection Rating
|The IP ratings are used to define the level of sealings or effectiveness of enclosures against dust, water. These ratings consist of two letters IP followed by the 2 digits. The first digit indicates the level of protection against solid bodies and second digit represent the degree of protection of device inside the enclosure from water.
|Sometimes insulation protection for probe is needed to work properly in particular media as conductive and corrosive material may harm our instrument.
|It is a abbreviation of Ethylene Chloro Tri Fluoro Ethylene, also known as halar coating is used to protect metal body of level instrument from acidic or other chemicals.
|It is the abbreviation of Poly Tetra Flouro Ethylene. The furnish product with PTFE coating will be convenient for conductive material as this material can cause short circuit between sense probe and the vessel wall.
|The ceramic material is non-metal which is brittle and strong that withstand in high temperatures. The Level sensor's electronics need protection against high temperature material so it is advantageous to use ceramic insulation where process material heated upto high temperature
|A level sensor is a device which detects and monitor the level of liquid, solid, and other substances including slurries, granular material and powder that flows freely in vessels.
|It is the type of level sensor that measures the level at a certain point and monitors the high and low level to prevent from dry run and overspill detection.
|The level transmitter is the type of level sensor which monitors the level at every point and show the level continously to provide accuracy in process control system.
|The instruments parts like mounting arrangements, probes, housing are constructed with different materials which are as follows
|This is belongs to austenitic stainless steel group that are used very commonly used. This stainless steel has excellent corrosion resistance and good weldability.
|This is also belongs to austenitic stainless steel group. It has better mechanical properties which can withstand over high temperatures used in typical applications.
|Mild Steel is also known as low carbon steel due to low cost and mechanical properties which is suitable with many applications.
|The iron or steel on which the protective layer of zinc is applied to prevent from rusting is known as Galvanized Iron.
|Polyvinly Chloride is widely used synthetic plastic polymer. The rigid form is used for construction pipes whereas the flexible form is used for making electric cable insulation etc.
|Perfluoroalkoxy alkanes (PFA) are fluoropolymers. As compare with PTFE, PFA have better anti-stick properties, higher chemical resistance on expense of a lesser scratch resistance.
|Polycarbonate is a plastic material which have heat-resistant and flame-retardant properties for various applications that demand high temperature and safety feature. It is dimensionally stable and durable material.
|Flame retardent is a variety of substances that are added to combustible material to prevent fires or to slow the spread of fire.
|A baffle is a surface which is placed inside the vessels to prevent the application media falling on the instrument directly.
|The terminals made from ceramic materials are used in the electronics when instrument is used in extremely high temperature application like in furnace, heaters etc.
|Some amount of clearance or space should be given between the vessel and the wall to install the instrument properly. This clearance is known as head clearance.
|Hygienic Design must be ensures that the vessel should be clean properly with the selected design and the deposition in the vessel should be minimize.
|It is the type of model in which the sensor is situated in the same unit or in probe of product.
|The standard level of pressure on which the electronics device operates and the pressure is not too low as device is not function properly and not too high as there is a chance of explosion.
|In this model, the evaluation unit is remotely wall mounted with the help of special cable.
|Roughness Average is the one of the method for calculating the surface roughness. Ra is the arithmetic average of surface height measured across the surface.
|In this model, the sensor is situated in the probe and the evaluation unit is mounted on a wall via cable.
|It standoff is an extension provided to protect the electronics from high temperature.
|The wetted parts are active parts or the measurement side of the sensing device which is in contact with the application media.
|All mounting arrangements are not suited for various vessels, tanks and other system so it requires different arrangement depend on tanks parameters.
|Flange is the one of the mounting arrangement which is used to joint two objects and giving the strength which are usually welded or screwed.
|This is the mounting arrangement used in hygienic applications which is made by joining two tri-clover fittings and a clamp holding them together.
|The mounting arrangement consist of threads in the mounting which should be tighten on the vessel easily.
|All mountings arrangements uses international standards which taken into account while designing the probe.
|The American National Standard Institute(ANSI) is one of the flange dimensional standards for threaded, slip-on, socket weld and blind flanges.
|The American Standard Association(ASA) is also a type of flange dimensional standard.
|British Standard Pipe is a technical standard for screw threads that has been internationally approved for interconnecting and sealing pipes and fitting.
|American National Standard Pipe Thread frequently called National Pipe Thread are technical standards for screw threads used on threaded pipes and pipe fittings.
|The noise is unwanted disturbance or error in an electrical signal. It is a type of distortion.
|Any noise or interference of electrical nature either isolated or radiated which present in the environment, signals or power lines is known as electrical noise.
|Conducted EMI is caused by the physical contact of the conductors as opposed to radiated EMI which is caused by induction.
|RF Noise is interference or disturbance created by various external source like power supply, electric signals and probe and it causes due to leaky rectifiers, variable frequency deviation and wireless radiation which affect the internal circuitary.
|Level Sensors proposed various types of outputs according to customer's requirements
|4-20mA are frequently used to provide a strong electronic signalling with two values i.e. 4mA and 20mA which represent 0-100% range of measurement or control. The sensor generating signal act like a current source providing a constant current output signal. The current output is same at any point in the circuit.
|The current output is a maximum load current that a power supply can provide at a specified temperature.
|DPDT is the abbreviation of Double Pole Double Throw Relay. It comprises of two Normally Open (No) terminal, Normally Closed (Nc) and two Common (COM) terminal. Normally common terminals of both relay is connected to the Nc when initially relay is de-energized and when both relay is energized then the common terminal get connected to the No terminal.
|MODBUS Protocol is a messaging structure, widely used to establish master-slave communication between intelligent devices. A MODBUS message sent from a master to a slave contains the address of the slave, the ’command’ (e.g. ’read register’ or ’write register’), the data, and a check sum (LRC or CRC).
|It is a signaling standard used for 2-wire connections to switching instruments. It outputs a current signal depending upon state of switch. It operates at two distinct current levels. The current flow through the sensor drops less than 1.2mA when sensor detects the material whereas the current flow increases to 2.1mA when the material is not present.
|It is generally known as sinking output. The output will be connected to the negative terminal if sensor sense the presense of material.
|It is also called as Open Collector output. It is one of the output offered by level sensors. The Open Collector output pin is directed by single transistor which drag the pin to only one voltage. The output made either open circuit or connection to ground. It consist of external pull-up resistor which boost the output voltage when transistor is turned off. When the transistor connected to this resistor is turned on, the output is forced to nearly 0 volts.
|SPDT is the abbreviation of Single Pole Double Throw Relay. It consist of two contacts .
|Power Supply is used to convert electric current of a current source to correct voltage, current and frequency to power the load.
|Universal Power Supply
|A power supply which detects the incoming voltage and its type AC/DC and arrange itself to provide the correct power to the device. Sapcon provides universal power source input range within 90 ~ 265 Volt AC / 24 V DC and capable of operating at 50 and 60 Hz. This makes it easy for clients to use the instruments directly on the AC mains and DC both.
|AC Power Supply
|AC Power Supply takes the voltage from main supply and uses a transformer to step up and step down the voltage to the desired voltage.
|DC Power Supply
|DC Power Supply is one that supplies constant DC voltage to its load. DC power supplies uses AC mains electricity as an energy source.
|Our instruments are differentiated through different principles on which it works
|Active shielding is used to measure the capacitance by applying the positive voltage to the shield. It reduces the external noise.
|Galvanic Isolation is the term used to isolate functional sections of electrical systems to prevent current flow which means that no direct conduction path is permitted but the information still exchanged with the help of electromagnetic waves or by other means.
|It is defined as the measurement point within the sensor's specified range when approaching the swiching point during high and low level.
|This principle is used in vibrating fork level sensors. It convert mechanical signal into electrical signal and when sound waves strikes to one or both of the tines, tines vibrates.
|The level instruments uses two types of probe arrangements
|The rod arrangement is usually made by stainless steel which act as rigid support to increase the strength and also it resist corrosion.
|For large tanks which required probe length higher than 3m then the rod probe arrangement is not a good idea. Instead of rod, rope probe is better option.
|With the help of LED, product shows the status of the device.
|Two types of LED indication is provided to show the status i.e. normal and alarm condition of the device.
|This condition occurs when the material touches the probe and the device switch its condition from normal. The alarm condition is indicated by RED LED.
|The normal condition is indicated by Green LED. The device is in normal condition when the material is not touching the probe or material tends to fill.
|Sapcon uses two types of switches in electronics assembly
|The dual inline package (DIP) switch is a electric switch designed to change the operating mode of a device.
|The toggle switch is a type of electric switch which is manually handle through a lever to control the flow of electrical current.
|The operating temperature is the temperature at which electronics and electrical device operates.
|The ambient temperature is the temperature of surroundings or environment.
|The change over of the output can be delayed by some amount of time is known as time delay.
|When the application material covers the instrument, the changeover of the output can be delayed by a pre-determined time. This time is called Cover Delay.
|When the application material uncovers instruments, the changeover of the output can be delayed by a pre-determined time. This time is called Uncover Delay.