March 14th, 2012
A new range of water-approved submersible level transmitters is now available from instrumentation specialist Impress Sensors & Systems Ltd.
The new IWSL range of WRAS-approved submersible level transmitters is suitable for continuous submersion in water, for a wide range of level measurement applications in reservoirs and drinking water storage tanks, but also for use in rivers, boreholes, aquifers, environmental monitoring and V-notch weir flow measurements.
IMSL WRAS Approved submersible level transmitter
Manufactured in the UK by Impress Sensors, the IWSL sensors use a piezoresistive media-isolated, silicon sensing technology and a stainless steel diaphragm, which provide excellent stability, repeatability and resolution. The sensor housing is 316L stainless steel, making it ideal for reliable, repeatable hydrostatic level measurement. The sensors are available in nominal pressure ranges from 1mWG to 100mWG.
When installing a product that will carry, receive or be submersed in water from the public mains water supply in the UK, it is a criminal offence if that device does not comply with the Water Supply Regulations or Scottish Byelaws. The Water Regulations Advisory Scheme (WRAS) requires that these devices should not cause waste, misuse, undue consumption or contamination of the water supply and must be of an appropriate quality and standard. WRAS approval is the best way to demonstrate compliance as it is granted directly by representatives of the water suppliers and is therefore accepted by every water supplier in the UK.
All IWSL sensors are WRAS-approved with a single WRAS approval number and are temperature-compensated, calibrated and supplied with a traceable serial number and calibration certificate. Operating (media) temperatures are from -20 deg C to +60 deg C in non-freezing media. Cable material is PUR, with elastomeric (EPDM) O-ring seals that are carefully selected for compliance with WRAS.
Sam Drury, Sales & Marketing Director at Impress Sensors & Systems comments: “The electronics on the IWSL incorporate a microprocessor-based amplifier, which means no adjusting pots are required, which in turn means the electronics are very stable. The IWSL can also be custom engineered for specific applications, including various output options, accuracy levels and pressure ranges. The sensor is also suitable for battery operation when output options of millivolt or SDI-12 are selected.”
Impress Sensors will be exhibiting at IWEX 2012 (International Water & Effluent Exhibition) at the NEC from 22-24 May 2012 (stand E48), and at the WWEM (Water, Wastewater & Environmental Monitoring) exhibition, from 7-8 November 2012 at the Telford International Centre (stand 58).
For more information on the IWSL range of water-approved submersible level transmitters, please visit www.impress-sensors.co.uk or call the sales team on 0118 981 7980.
March 3rd, 2012
A new range of submersible dual output level and temperature transmitters is now available from instrumentation specialist Impress Sensors & Systems Ltd.
Manufactured in the UK by Impress Sensors, the new transmitters are suitable for continuous submersion in liquids such as water, oils and fuels. The sensors are available in ceramic (IMCTL) or silicon (IMSTL). All sensors provide dual independent, 2-wire, 4-20mA outputs: one for level and one for temperature, with no signal loss over long cable lengths. The sensors offer nominal pressure ranges from 10mWG to 100mWG (ceramic) and 0.5mWG to 100mWG (silicon).
Dual output Submersible level transmitter with integrated temperature sensor
The temperature sensor is based on a platinum resistance thermometer with Class ‘B’ accuracy (other accuracy classes are also available). The sensor housing is either 316L stainless steel, high grade Duplex stainless steel or a Marine bronze option for the IMCTL, making the transmitters ideal for hydrostatic level measurement, where temperature is also a critical factor in measurements.
All sensors are temperature-compensated and calibrated and supplied with a traceable serial number and calibration certificate. Operating (media) temperatures are from -20 deg C to +60 deg C in non-freezing media. Cable material is PUR, with PVC, FEP or TPE as options.
The IMSTL is the higher accuracy version and uses the latest piezoresistive media-isolated silicon sensing technology and a stainless steel diaphragm. This provides excellent stability, repeatability and resolution, particularly for high accuracy level and temperature measurement (including V-notch weir flow measurements) in rivers, canals, reservoirs, boreholes and aquifers.
The IMCTL is also designed for submersion in liquids such as water, oil and fuels. This device uses a ceramic sensor for level measurements, which provides excellent corrosion resistance, particularly where the media may be aggressive. Applications include level and temperature measurements in storage tanks, rivers, boreholes and aquifers, as well as environmental monitoring in estuaries and seawater applications (when used with the marine bronze housing).
Sam Drury, Sales & Marketing Director at Impress Sensors & Systems comments: “Because we manufacture the IMSTL and IMCTL sensors in-house, we can offer different versions of the sensors tailored for specific customer applications. For example, we can provide different level and temperature ranges, sensors for drinking water applications or WRAS-approved versions with special cable materials.”
For more information on the IMSTL and IMCTL sensors, please visit the website at www.impress-sensors.co.uk or call the sales team on 0118 981 7980.
February 21st, 2012
Impress Sensors also offer a full range of pressure transmitters, screw-in transmitters, submersible probes and level control switches, all with SIL2 (Safety Integrity Level 2) approval for hazardous environments.
The product range is is targeted at safety and hazardous area applications, including process manufacturers, chemicals, oil and gas, nuclear and Atomic Weapons establishments. The devices are also suitable for medical device applications.
The process industry demands the highest degree of safety and reliability these days. The current Safety Integrity Level (SIL) international safety standard provides suppliers and users with a common framework on which to design products and systems for safety related applications. The standard also provides a more scientific, numerical approach to specifying and designing safety systems, enabling the nature of the risk to be quantified.
SIL means risk reduction to a tolerable level. The required safety level of a process plant is classified in accordance with the international IEC 61 511 standard and depends on the risk constituted by a plant. The IEC 61 508 standard describes the requirements of electrical, electronic and programmable electronic devices used in such plants. Both standards subdivide plants and devices into 4 safety levels, from SIL1 for low risks, to SIL4 for very high risks. The allocation to these safety levels is based on the use of a risk graph and depends on:
• Extent of possible damage
• Frequency of persons present in hazardous areas
• Possibility of damage prevention
• Probability of an unwanted event occurring
The standards also describe the type of risk assessment and procedures for integrating certain safety functions into sensors and plants. Generally, the significant hazards for equipment and any associated control system have to be identified by the specifiers or developers via a hazard analysis. The analysis identifies whether functional safety is necessary to ensure adequate protection against each significant hazard.
Examples within safety related systems for mechanical engineering include auxiliary disconnected systems; fire detector and gas warning systems; monitoring of turbines; safety interlock and auxiliary disconnected systems for machines; devices for medical applications; and remote monitoring based on network, handling and programming of procedural constructions.
For more information on Impress Sensors’ range of SIL2-certified pressure, temperature and level control switches, contact the sales department at Impress Sensors & Systems Ltd on 0118 981 7980 or visit the website at http://www.impress-sensors.co.uk/sil-products.htm
January 14th, 2012
Marine-Approved Level and Pressure Sensors now available from Impress
Instrumentation specialist Impress Sensors & Systems Ltd has launched two new marine-approved sensors for level and pressure measurement of storage and ballast tanks. Both sensors are approved by DNV and Germanischer Lloyd.
The new LMK 458 is a hydrostatic probe with ceramic (Al2O3) diaphragm that is suitable for level measurement in marine storage/ballast tanks and draught monitoring, as well as applications in the water industry such as desalinization plants and drinking water filtration.
The probe uses a capacitive ceramic sensor element that provides a high resistance to overpressures. The transmitter is protected to IP68 and provides good resistance to chemicals and high long-term stability.
Marine Approved Pressure Transmitters
An optional intrinsically safe (IS) version of the LMK 458 is also available. This version is ideal for measuring the pressure of various fluids in harsh marine environments, including Zone 0 ATEX areas. Other options include different housing materials, either stainless steel as standard or a Cupro-Nickel (CuNiFe) sea water-resistant version. Other options include screw-in or flange-mounted versions, as well as other accessories such as probe flanges and mounting clamps.
The LMK 458 has a diameter of just 39.5mm and is able to operate in temperatures from -25 deg C to +125 deg C. The sensor is accurate to 0.25% FSO (to IEC 60770). Nominal pressure ranges are from 0-40 cmH2O, up to 0-200 mH20.
In addition to the LMK 458, Impress Sensors has also launched a marine-approved pressure transmitter. The DMK 458 is a pressure transmitter with ceramic diaphragm that is suitable for monitoring pressures in a variety of marine and offshore applications, including loading and unloading systems, level measurement in ballast and storage tanks, draught monitoring, and anti-heeling systems used on ferries and cargo ships, which prevent heeling of the ship during loading and unloading.
The DMK 458 offers high overload pressures, excellent accuracy and high temperature resistance. The transmitter is available in nominal pressure ranges from 0-40mbar up to 0-20bar. As well as threaded versions, the transmitter is also available in various flush mounted versions, which are ideal for measuring pressures of viscous, pasty and polluted media.
The DMK 458 can operate in temperatures from -40 deg C up to +125 deg C. The sensor is accurate to 0.25% FSO to IEC 60770. An optional IS-version for Zone 0 applications is also available.
For more information on the LMK 458 or DMK 458 pressure transmitters, please visit the website at www.impress-sensors.co.uk or call the sales team on 0118 981 7980.
February 28th, 2011
Level sensors are widely used across different industrial sectors. Their application includes determining level of substances that flow including powders, liquids, slurries and granular materials. Due to gravity, these substances flow into their respective containers. The measuring substance can be in the natural form like a river or lake or within a container.
Level measurement can either be continuous or point value. The continuous level sensors measure level of the given medium in a specified range. On the other hand, point level sensors only determine whether or not, the substance is above or below the sensing point. The main purpose for using point level sensors is to detect extremely high or low levels.
Numerous physical variables and applications affect the selection of level monitoring techniques. When selecting level sensors for industrial or commercial purposes, look for the following specifications;
• Pressure or vacuum
• Physical phase (slurry, liquid or solid)
• Acoustical or electrical noise
• Dielectric constant and density of the medium
The application of level sensors is also an important consideration. Ease of calibration and programming, appearance, cost, accuracy and response rate are other specifications to look for. The mounting of level sensor instruments, its physical size, monitoring or controlling of continuous or discrete levels are other important considerations.
The measuring range, process operating conditions, communication interface and instrument style are some specifications that can help you choose the right level sensors that suit your application needs.
February 15th, 2011
Level sensors are widely used for determining powder or liquid levels. They are also used to find out interfaces between liquids. Two basic types of level-measurements are available – multi-point or point and continuous.
The multi-point or point level sensors mark a particular level and are mostly used as a switch or a high level alarm. On the other hand, continuous level sensors are used for measuring dry or liquid material levels within a specific range. They also offer outputs that constantly indicate the level.
Both continuous and point level sensors can be incorporated into a single device to provide a stepped version of constant level or add a low alarm. Output options include analogue current signals, modulated frequency or frequency, analogue current signal, visual or alarm indicator.
Level sensor technology
Different types of level sensors are manufactured. Options include radio frequency (RF) admittance or capacitive, air bubbler, resistance or electrical conductivity, magnetic or mechanical floats, differential pressure and resistance or electrical conductivity. These sensors can also use microwave or radar, ultrasonic or sonic meters, pressure membrane and radio frequencies.
Sensors that use tuning forks make use of different technologies to vibrate a probe. They continuously monitor the absence or presence of that vibration. Level sensors are basically designed for applications that need a controller, a locally-programmable unit or a simple gauge.
January 11th, 2011
Ultrasonic level transducers transmit and receive waves from different types of sensing devices.
These sensors read the echo to find out specific variables like proximity, distance, level or speed in different applications such as non-destructive evaluation, security applications, web break detection, welding and cutting. Ultrasonic transducers operate at a specific resonant frequency with different beam patterns, construction options and power levels.
Angle beam ultrasonic transducers, delay line ultrasonic transducers and electromagnetic acoustic transducers (EMAT) are the different available types. When it comes to selecting ultrasonic level transducers, you need to make sure that you choose one that suits your application needs.
Some features of ultrasonic transducers
Ultrasonic transducers are available in different types to suit different applications. General purpose ultrasonic transducers including air transducers do not usually come with any special features. However, more specialised ones like contact transducers need to be directly placed on the surface that is to be measured.
Dual element transducers have two different elements which allow the receiver and transmitter to operate independently. As the elements are angled towards each other, they create a reflective receive/transmit pathway.
A range of configurations are available for connecting the ultrasonic transducer to one or more transducers in parallel or in series. While most transducers offer analogue output voltage, they can have provision for current loop output.
January 11th, 2011
With a huge number of different ways to monitor levels needed by industry, a range of different level measurement devices and sensors are available to suit different applications. Thus, selecting the right level measurement device for your needs is easy, if you know what you are looking for. The level-measurement instruments available today can include configuration and diagnostic system as well as just monitoring the level of a liquid. They can also process and communicate the data they obtain over a network for control and monitoring applications.
The PID or proportional integral derivative sensor is one model of sensor that is commonly used in liquid-level measurement. Different methods for liquid level measurement include.
• Conductance (conductivity)
• Hydrostatic tank/head gauging
• RF capacitance
Prior to selecting a device for your application, you must initially understand the working of each device as well as the theory behind it.
Things to know about interface level measurement devices
Interface level measurement devices include meters and sensors that can measure and detect levels between different media like water/oil and solid/liquid. There are some interface level measurement devices that can also measure the interface between a settled bed of solids and a liquid.
Sometimes, interface level measurement equipment is also referred to as water oil analysers, oil water analysers, oil level measurement equipment or liquid solid analysers, depending on the application. A vibrating probe extending through a wall of a vessel or tank to detect the level of the interface materials is one type of interface level measurement device.
Hydrostatic ‘screw-in’ level transmitters, hydrostatic ‘submersible’ level transmitters, radar level transmitters and TDR level transmitters are some of the options you can choose from.
August 12th, 2010
The basic operating principle for all vibrating probe level switches is almost the same. These level switches operate by using two piezoelectric elements constructed on a vibration kit inside the tube. The piezoelectric element receives pulse signals from the PCB (printed circuit board) which causes the tube to vibrate. The vibration is transmitted to the PCB in order to get an electrical output signal.
If the vibration of the tube is stopped by the rising material, the PCB cannot receive any vibration signals from the piezoelectric element. Thus, the relay gets activated. Most vibrating probe level switches are well equipped to prevent malfunctioning that is caused due to a power shortage.
The vibrating probe level switches offer a trouble-free and reliable level sensing for bulk solids. With simple calibration, mounting and high stability working principle, it can survive high lateral loads and cannot be affected by static electricity and material build-up.
The following are some of the key benefits of vibrating probe level switches:
• No maintenance required
• Maximum versatility
• Absence of mechanical moving parts that wear out
• Easy to install
• No adjustments needed
• Unaffected by environmental changes, agitation and dust clouds.
Such benefits have added to the wide-scale use of vibrating probe level switches. Given below are some features of vibrating probe level switches which have enhanced the performance of the device.
• Durable and sturdy design
• No calibration needed
• Low / high fail safe modes provide reliability and safety
• No fear of accumulated materials on the sensor
• Adjustable sensitivity can be set depending on different density of materials.
Applications include the detection of powdered materials, dry milk, powdered coffee, powdered coal, chocolate, salt, sugar, dry bulk, glass material, wheat and cement. Vibrating probe level switches are also helpful in detecting the sludge level in waste water.
August 4th, 2010
Level transducers or level transmitters are used for measuring the level of a bulk solid material or liquid within a particular space. They are also used to measure the electrical output that is proportional to the input level. Level transmitters are specially designed to measure these levels based on continuous or point level readings.
Point level transmitters offer an output after reaching a particular level of measurement. Basically, this output is in the form of an electrical charge or an audible alarm that activates the switch. Numerous point level sensors can be integrated together to provide a stepped version of a continuous level.
On the other hand, continuous level transmitters determine the level within a particular range and offer a continuous reading of the level. Most level transmitters can operate through an extensive range of pressures, temperatures, process conditions and vapour gas mixtures.
Advantages of using vibrating probes for level measurement
• Needs no maintenance
• No mechanical moving parts to wear and tear
• Easy to install
• No adjustments required
• Unaffected by agitation
• Unaffected by environmental changes
• Offers maximum versatility.
Level transmitters use different technologies for measuring or sensing levels. Some of these include air bubblers that utilise a constant volumetric rate of gas flow. This is generally fed through a bubble tube that is submerged in a liquid. RF admittance or capacitive transmitters utilise a radio frequency technique depending on the inconsistent dielectric constants.
Tuning fork or vibrating level transmitters use different technologies (usually piezoelectric) to vibrate the probe and constantly monitor the absence or presence of that vibration.