FOR THE past few years, Control’s annual level-instrumentation roundup has observed many non-contact radar and ultrasonic-level instruments, and a scarcity of new versions of traditional instruments. Market researchers were probably gloating (or surprised!) to note that one of their predictions had actually come true: that radar and ultrasonic sensors would be the fastest-growing segments.
For instance, Venture Development Corp. (VDC) recently reported in executive editor Jim Montague’s “Rising Levels of Process Level Measurement Devices,” Control, Nov.’05, that, “The largest relative gains in continuous measurement technologies are expected for microwave/radar contact/guided (10.6%) and non-contact sensors (8.4%).”
Though true before, this trend isn’t reflected in the products in this year’s roundup. Now, there are more non-non-contact sensors in our roundup than ultrasonic and radar sensors. And, despite contributing author David Spitzer’s glowing coverage of laser sensors in “Zap! How Do It Know?” Control, Feb. ’06, we see no new laser-based sensors in this roundup.
In fact, because not all of the non-contact sensors listed below are actually new—some are enhancements to existing products—this year’s roundup may indicate a return to relative normalcy in the level industry.
This year’s roundup shows more agreement with VDC’s forecast that, “While there likely will be a barely perceptible shift from mechanical to electronic sensing technologies in continuous measurement, shipments of mechanical point measuring/sensing devices will outstrip electronic types.” VDC’s global study, “Worldwide Process Level Measurement and Inventory Tank Gauging Markets, October 2005,” also anticipates above average growth for float switch (6.7%), vibration (6.4%), and paddlewheel (6.1%) measurement devices.” We’re again seeing some of the devices below for the first time in a coon’s age.
You’ll see a mixed collection of all sorts of level sensors in the following roundup, including radar, ultrasonic, float, magnetostrictive, weight-based, vibrating fork, thermal and pneumatic devices. That’s the way it should be. Instead of rolling over and playing dead in the face of increasing non-contact sensor sales, other vendors see a growing economy, have more confidence in the market, and are starting to roll out new, contact-type sensors. Hooray!
Level Transmitter Sounds Good
Type 8175 ultrasonic level transmitter has 0.25% FS accuracy over a 1.0 to 32.0-ft range, with resolution of 1/8 in. The non-contact transmitter is suitable for continuous level control, on/off level measurements of fluids/solids, flow measurements in open channels, and volume and distance measurements. It includes an ultrasonic sensor, transducer and eight-digit, multi-language display protected by a NEMA 4 enclosure. More info at controlglobal.com. Burkert; 800/325-1405; www.burkert-usa.com
Unchain My Sensor
RP resistive-chain level measurement sensors are shock resistant, have an anti-stick float, and are suitable for bulk-liquid product applications. The sensors operate with a float that travels up and down a vertical stem. A permanent magnet inside the float acts on a series of closely set reed switches and resistors inside the stem. The sensor converts the resistance value into voltage, providing current signals proportional to the level of the liquid. Scientific Technologies; 888/349-7098; www.stiapg.com.
BW Controls 7230 explosion-proof sensor measures total level, interface level, and up to five temperatures. The temperature sensors are distributed evenly over the active length of a stainless steel tube. It has a Modbus RTU digital output and optional analog converter, and is suitable for applications where the dielectric constant or density of the liquid is unstable. Ametek Automation & Process Technologies; 800/635.0289; www.ametekapt.com
Pushbutton, Plug-in Programming
SmartPress Model LP-D pressure/liquid level transmitters come with a 10-year warranty. The two-wire, loop powered transmitters provide pushbutton programming, and can be supplied pre-calibrated by the factory at no added cost. An optional plug-in programming/display module, which can be moved from unit to unit, provides full setup and display capability. More info at controlglobal.com. Princo Instruments; 800/221-9237; www.princolevelcontrols.com
TIP, Remote Point-level Control
RF Series point-level indicator has no moving parts, and isn’t affected by material coating. One-step calibration eliminates many steps formerly needed to calibrate and test level controls. “Test-In-Place” allows users to test level controls without removing the cover, or from a remote location. This is especially important for hazardous applications or where fugitive emission releases must be prevented. Bindicator; 800/778-9242; www.bindicator.com
Ultrasonic Point-level Sensor
Levelprox non-invasive, ultrasonic sensor provides point-level detection of liquids through metal containers, making it suitable for high pressure, hazardous, or hygienic applications. It compares the analyzed signal to empty and full conditions previously programmed. Models T50, with a 316L stainless-steel housing and sanitary connection, and M30, with a standard 30-mm barrel, are both FM-approved for Class I, Division 2 applications. Turck; 800/544-7769; www.turck.com
Multiple-tank Level System
King-Gage LP3 system works in processing environments with multiple tanks or process vessels requiring level measurement and inventory monitoring. It handles up to 32 analog channels and optional RTD inputs. Transmitter inputs are scaled for specific tank geometries to generate volumetric or mass measurement. More info at controlglobal.com. King Engineering; 800/242-8871; www.King-Gage.com
Model 5318B microprocessor based level instrument has pushbutton calibration and a digital display. For point-level operation, calibration may be accomplished without raising or lowering the process. It has an adjustable differential mode for pump on/pump off operation, is available for AC or DC power, and has a NEMA 4 explosion-proof enclosure. Robertshaw Industrial Products; 865/ 981-3100; www.robertshawindustrial.com
Self-testing, Ultrasonic Switches
Echotel Model 961 single-point and 962 dual-point ultrasonic level switches require no density adjustments, work in aerated or foamy liquids, perform self-testing of electronics, piezoelectric crystals and transducers, and check for the presence of EMI/RFI electrical noise. The switches are suitable for Safety Integrity Level (SIL) 2 loops. Options include a selection of transducer materials for various process media. Magnetrol; 800/624-8765; www.magnetrol.com
Models 2110 and 2120 level switches are based on a vibrating short-fork technology that’s suitable for virtually all liquid applications. The switches are unaffected by flow, turbulence, bubbles, foam, vibration, or product variations. A “Fast Drip” fork means any remaining liquid is drawn away from the fork tips, allowing for quicker, more reliable detection, especially in high density liquids. More info at controlglobal.com. Rosemount; 800/999-9307; www.rosemount.com
Wireless Sensors Go 1,000 Feet
RF10 RF event transmitters are suitable for monitoring fluid levels in tanks and drums. The portable, battery-operated units transmit up to 1,000 feet from the receiver, depending on environment. Transmitters are available in 1, 4 and 8-channel models. APT Instruments; 877/324-5444; www.aptinstruments.com
How Deep is Your Sludge?
Model 602 sludge-depth meter can be used in clarifiers, tanks, inclined plate clarifiers (Lamellas), SBRs and dissolved-air flotation tanks. The company offers free testing of your materials at its plant, so you can prove the meter will work. Markland Specialty Engineering; 416/244-4980; www.sludgecontrols.com
Hot Level Switch Uses RTDS
Innova-Switch level switch uses a high-resolution thermal differential technique, involving a pair of matched RTDs. The thermal differential created between the reference and the heated RTD pair is a function of the density of the media that the sensor is contacting. It switches on a level change of 0.03 in. More info at controlglobal.com. Sierra Instruments; 800/866-0200; www.sierrainstruments.com
Pneumatic Level Switch
Model 1540 non-bleed, side-mount pneumatic level switch is suitable for plant and OEM applications where pneumatic valve operation is required to signal presence or absence of liquid at a discrete level. The float-operated level switch has all-316SS body and wetted parts, and a magnetic coupling. SOR; 913/888-8150, x3303; www.sorinc.com
IMV31 provides tank-level measurement when fluid density varies. It works in open (vented) and closed (pressurized) tanks and compensates for density changes in the tank liquid and vapor. This makes the transmitter suited for applications such as boiler drum level and other applications where fluid densities are affected by variations in pressure and temperature. More info at controlglobal.com. Foxboro Measurements and Instruments; 866/746-6477; www.foxboro.com/instrumentation
Solid-Signal Radar Sensor
PULS 68 two-wire radar level instrument uses a frequency of 26 GHz to achieve a strong return signal from solid materials. It’s able to see and evaluate echoes in low dielectric conditions, and at up to 230 ft. Its swivel antenna allows for mounting to match the angle of repose created by fill or empty conditions. The sensor is unaffected by dust or buildup, angle of repose, and temperature. Applications include flour, sugar, cement, grain, plastic pellets, and aggregates. Ohmart/Vega; 513/272-0524, x143; www.ohmartvega.com
Sitrans LU 02 ultrasonic sensor scans liquids, solids or a combination of both in one or two vessels of different size, shape and configuration up to 200 ft high. It measures level, space, distance, volume or average/differential. Transducers can be mounted up to 1,200 ft from the monitor. Readings are displayed in linear engineering units on the backlit LCD. More info at controlglobal.com. Siemens Energy & Automation; 215/646-7400 x2592; www.siemens.com
Magnetorestrictive Level Sensors
Level sensors use magnetostrictive linear measurement technology. Options include 3A (74-03) sanitary configurations, NEMA 4X- or IP68-rated housings, analog and digital outputs, and level and interface measurements. All have remote programming and diagnostics, via serial communication over standard cabling. Programming software is free. Other output available include digital pulse, high speed serial, and CANOpen, DeviceNet and Profibus fieldbuses. MTS Sensors; 919/677-2332; www.mtssensors.com.
Waveguide Aids Radar Transmitter
MT5000 Series guided-wave-radar level transmitters have a concentric waveguide that directs the radar beam, alleviating divergence problems and echoes from tank walls and surrounding structures. The devices are unaffected by variations in specific gravity due to temperature or pressure changes, and work at pressures up to 5,000 psi and temperatures up to 800 F. More info at controlglobal.com. K-Tek; 225/673-6100; www.ktekcorp.com
Where Ultrasonic Won't Work
LVRD500 Series are suitable where vapor, dust, or a foaming surface prevents ultrasonic measurement. The radar sensor uses microwave pulse technology to track target liquids from the antenna tip to the bottom of a tank. RS-232 and RS-485 models are available. Omega Engineering; 203/359-1660; www.omega.com
More Good Vibrations
Optiswitch 3000 vibration level switch works in bulk solids and model 5000 detects liquids. Both have a tuning fork that is energized piezoelectrically, and vibrates at the mechanical resonance frequency. When the tuning fork is immersed in the liquid or solid, the vibrating frequency changes, is detected by the integrated oscillator, and is converted into a switching command. Krohne; 800/FLOWING; www.krohne.com
Submersible Model 700 level transducers are shipped with an installed vent filter for moisture protection, or with an optional unattached aneroid bellows for applications where periodic maintenance isn’t practical and high accuracy isn’ot required. Transducers are available with 4-20mA output in level ranges of 10, 23, and 35 H2O ft. with cable lengths of 25, 50, and 75 ft, respectively. More info at controlglobal.com. Pressure Systems; 800/678-7226; www.pressuresystems.com