Continuous level sensors are used to measure the level within a specific range and provide continuous monitoring of level conditions.

With a wide variety of approaches to point level and continuous level measurement of liquids and solids,  Sigma Hellas can assist to solve the needs in many level applications. The sensors and systems we offer are based on the following measuring methods:

• RF capacitance
• Capacitive
• Magnetostrictive
• Magnetic
• Hydrostatic
• Radar
• Ultrasonic
• Laser

Level Transmitter Overview

Magnetostrictive Level Transmitters

Magnetostrictive Level Transmitters (MLT) are used extensively around the world to accurately measure level in process vessels. High accuracy and no maintenance are two of the most common reasons for choosing this technology. With ratings to 800ºF / 427ºC and 3000 psig / 207 bar, MLT's are suitable for almost any application. The MLT versatility allow direct in-tank installations or attached to a magnetic level gauge. HART, Foundation Fieldbus and Honeywell DE protocol options make the MLT's easy to connect digitally to most control systems.

Model 100

The 100 is suitable for product and/or interface level measurement. Featuring
HART or Fieldbus protocol & an accuracy of +/- 0.01% FS.
2 wire loop powered, 24 Vdc
ATEX Approved
+/- 1mm Accuracy
Product Level and Interface with one Gauge
60 Year MTBF (FMECA Reports)
No field calibration
316L / Monel / Hastelloy
Gauge length from 0.3 to 22m
Operating temperatures - 200°C to +430°C
Operating pressure up to 207 Bar

Model 500

The 500 is a cost effective alternative to capacitance probes,
displacers, ultrasonic meters and radar transmitters.

2 wire loop powered, 24 Vdc
ATEX Approved
+/- 1mm Accuracy
No field calibration
316L
Gauge length from 0.3 to 4.8m
Operating temperatures - 40°C to +121°C
Operating pressure up to 124 Barg

Model 100S  

The 100S Magnetostrictive Transmitter is based on the Same Magnetostrictive Principle as the 100 Model. The 100S is a High Accuracy Sanitary Magnetostrictive Liquid Level Transmitter Suitable for CIP and SIP Applications.
High Accuracy: 0.01% of Full Scale
Single and Double Tri-Clamp Installations
Suitable for CIP and SIP Applications
180 Grit Polish Standard
Simple Calibration: Pushbutton or HART Protocol
Never Requires Re-Calibration: Set it and Forget it
Dual Compartment Housing with Separate Field Terminal Compartment
No Drift Due to Dielectric Constant Changes, Temperature Changes, Vapor Composition Changes or Pressure Changes
Loop Powered to 50 ft (15 m) Probe Length
Pressure to 950 psig (66 bar)
Temperature Range: -320ºF to 450ºF (-196ºC to 232ºC) with Options
Field Replaceable Module - No Recalibration Necessary
Built-in RFI / EMI Filter
Total or Interface Level Measurement

Radar Level Transmitters

Unlike conventional through-air radar (also known as FMCW – Frequency Modulated Continuous Wave), Guided Waves Radar  utilizes a wave-guide to direct or guide very low power microwave pulses. FMCW radar sensors emit higher frequency microwave pulses through-air to reflect from the product surface.

Guided Waves Radar directs a pulse down a probe that is reflected at the material to be measured. Transit time is measured and level calculated. Use of a probe or wave-guide permits very efficient energy transmission, use of compact, low power electronics resulting in higher efficiency and lower costs.

700 series Guided Wave Radar

Bulk Solids Level Transmitter

The 700 series uses guided wave radar to make measurements, which means no moving parts and therefore, virtually no maintenance. A waveguide directs the microwave pulses, eliminating the beam divergence problems common to conventional non -contact radar transmitters.

Model 701 with a stainless steel cable probe is designed specifically for bulk solids in Silos.

FEATURES

• Radar Signal Travels Along the Waveguide –

Eliminates False Echoes and Minimizes Signal Loss

• No Moving Parts
• 2 Wire Loop Powered
• Linearization Table
• Lengths up to 30 meters
• Flexible Cable Probes
• Remote Display (optional)
• IP68 Protection rating
• All Digital Electronics
• EXiaIICT6

OPTIONS

• HART Protocol
• 316L Stainless Steel Enclosure
• Remote display

SPECIFICATIONS

Housing Aluminum or Stainless Steel

Power 18 – 30 VDC

Wiring Standard - 2 wire

Output Single 4-20 mA, HART

Accuracy ±1mm

Resolution +/- 0.063 in / 1.6 mm

Range up to 30 meters (­exible probe)

Sensor Material 316L SS Standard

Process Pressure -1.0 to 40bar

Process Temperature from -40C up to +250C (-20…150C standard)

Housing rating IP68

Dielectric Constant 1.3-2.3; 3-100 Direct Mode

Model, Probe,                           Length,             Material

701       8mm cable probe          30000mm         Stainless steel

702       10mm rod probe            6000mm           Stainless steel

703       Two-rods probe             6000mm           Stainless steel (Flange mounting)

Magnetic Level Gauges

A hermetically sealed float with an internal magnetic ring is housed in a non-magnetic float chamber. The float will move up and down in the chamber as the level rises or falls in the vessel on which it is attached. A magnetic, highly visible "shuttle" or Bar graph indicator encapsulated in a hermetically sealed glass tube, is attached in a scale housing to the outside of the float chamber. It indicates the liquid or interface level without being in contact with the process fluid.

Model 26

Model 26 Magnetic Level Gauge has proven (more than 100 000 installed internationally) itself safe for total and interface applications that are toxic, corrosive, flammable, or high-pressure and is easy to maintain with no sight glasses to clean, superior in design, operability, long-term safety and cost of ownership For accurate measurement of liquids such as oil, water, acids, solvents, petrochemicals or most liquid-to-liquid interfaces across a variety of industries, The product range includes the standard model 26 magnetic level gauge (MLG) with a chamber of virtually any non-magnetic material, extruded process connections, a custom engineered float and all accessories with 316 stainless steel construction.
* Highly Visible Level Indication with No Process Fluid in Contact with the Glass
* All Construction In-house by Code Certified Welders
* Float Designed and Weighted for Maximum Accuracy
* Transmitter and Switch Options, which Can Be Installed, Adjusted and
Maintained with No Process Interruption
* Safe for Corrosive, Flammable, Toxic, High Temperature and High Pressure
Applications
* Rugged Design - Low or No Maintenance
* 5 year warranty

Approvals 
•  ANSI - ASME B31.1, B31.3
•  ASME Code S, U, UM
•  CRN
•  Lloyds Registration
•  NACE MR0175
•  PED

Magwave Dual-Chamber Level System

The MagWave is a level measurement system which combines a highly visible magnetic level indication with an output from a Guided Wave Radar Transmitter. The MagWave features two separate close-coupled chambers for the level indicator float and the Guided Wave Radar antenna. Using single probe radar transmitters in the

standard 1-1/2 inch chamber provides the measurement capabilities of coaxial style probes without the potential for fouling due to buildup. The separate float chamber allows the float to travel unobstructed throughout the range of measurement. Redundant level control can be achieved by adding a magnetostrictive transmitter or switches to the float chamber.

* Highly Visible Level Indication
* Single Probe Guided Wave Radar Transmitters (No need for coaxial probes)
* Compact Close-Coupled Chambers
* Separate Chambers Provide Unobstructed Float Travel
* Extruded Outlets and Smaller Chamber Sizes
* Precision Fabricated Floats
* Temperature Range -60 F to 800 F (-51 C to 427 C)
* Pressures to 3000 psi (207 bar)
* Additional Transmitters And Switches May Be Added for Redundant Measurement
* Optional Vent, Drain, and Isolation Valves
* Insulation for High and Low Temperature Applications

Hydrostatic Head

One of the oldest and most common methods of measuring liquid level is to measure the pressure exerted by a column (or head) of liquid in the vessel. We offer solutions with submersible sensors and through the tank wall sensor options.

400 series

The 400 series of submersible pressure transmitters includes a number of completely submersible pressure-sensing transmitter models ranging  from 0 to 1m water column to 0 to 500m, that contain an air vent tube for providing a pressure differential relationship between the hydrostatic head and the atmosphere. The transducer contains associated electronic circuitry for providing an analogue output, has an IP 68 protection rating, and requires a  24 Vdc ± 10% Power Supply
These transmitters can be used in applications such as:
• Tank Level Measurement
• Level measurement of liquids with foams
• Level measurement of muddy liquids
• Well / borehole Level Monitoring
• Surface Water Monitoring
• Hydraulic monitoring in rivers and seas
• Reservoirs
• Research
• Water treatment

Plumb Bob Device - for difficult level measurements in Silos.

The Plumb Bob Device is Used for "On-Demand" Level Measurement in Silos and Vessels. Even Prec

ise Volumetric Measurements and Long Measuring Distances are no Problem.

Model SLT

The Model SLT is an Electro-Mechanic Level Measuring Instrument for the Continuous Measuring of Level in Hoppers, Silos or Tanks. This Top Mounted System is used for Monitoring the Level in Applications, such as Powders, Small Grain Bulk Materials or Coarse Grain Bulk Materials. A Bob Weight is Mounted at the End of a Measuring Rope or Tape, which is Wrapped on a Motor Driven Rope Roller. Upon Contact with the Bulk Material, the Bob Weight Returns and is Drawn Back to its Upper Stop Position.

       Product Features
* Appropriate for Nearly All Kinds of Bulk Solids
* Insensitive to Changes in Product Density, Dust in the Silo, Changes in
Moisture of the Material and Products that are Inclined to Stick
* Very Simple Installation and Set-up
* Very Accurate Measurement
* Internal Tape Cleaner (Tape Version)
* Variety of Sensor Weights
* Robust Die Cast Housing
* Two Versions: Rope and Tape
* Measuring Range: Max 98.4 ft. (30 m) rope version;
Max 75.5 ft. (23 m) tape version;
For max overall height of silo 82.0 ft. (25m)
* Power:  110/120 VAC 50-60 Hz or 220/240 VAC 50-60 Hz
* Signal Output : floating relay contact max 250 VAC, 2 A, 500 VA
or floating current output; 4—20 mA +/- 0.1 mA; max load 500 ohm

Laser Sensors

All Digital Designs that Combine Accuracy and Speed for Non-Contact, Continuous Level Measurement. Applications Include: Pellets (Converters), Slurries, Opaque Liquids and tall Bin and Silos.

Model 80

Model 80 Laser is a High Performance Laser Transmitter that can Accurately Measure Level, Distance and Position Over Long Ranges in Extreme Environments. Model 80 Features Advanced Timing and Sophisticated Signal Processing for Pinpoint Accuracy at up to 30m / 100ft. (Level Applications) and to 150m / 500 ft. (Positioning Applications).

o Long Range to 150m / 500 ft. (positioning applications)  and Up to 30m / 100ft. (level applications)
o No Beam Divergence = No False Echoes
o Measures any Surface at any Angle with Narrow Beam

o Rugged and Robust Enclosure
o Built-in Purge Port (1/8" FNPT)
o Last Pulse Detection for Measurement with Light Dust
o Ideal for Plastic Pellets, Grain Silos, Food Processing Industry, Crushers & Rock Silos, Indoor/Outdoor Positioning Applications- Overhead Crane, Tripper Cars
o Optional: Variety of Mounting Solutions

Model 200

Model 200 Laser is a Robust Laser Transmitter that can Accurately Measure Level, Distance and Position Over Long Ranges in Extreme Environments. Model 200 Features Advanced Timing and Sophisticated Signal Processing for Pinpoint Accuracy at up to 60 m / 200 ft (level applications) and up to 400 m / 1312 ft.  (positioning applications)
* No Beam Divergence = No False Echoes
* Long Range to 60 m / 200 ft (level applications) 400 m / 1312 ft.  (positioning applications)
* Dust Penetration Mode
* Rugged and Robust Enclosure
* Built-in Laser Pointer
* Field Upgradable Firmware Via ISP / IAP Flash
* No Calibration Required
* No Special Configuration Software Required
* Optional Flanges, Dust Tubes and Hand-Held Programmer (PDA) Available

Ultrasonic Level sensors –  a non contact technology

Ultrasonic sensors provide a cost effective sensing method with unique properties not possessed by other sensing technologies. By using a wide variety of ultrasonic transducers and several different frequency ranges, an ultrasonic sensor can be designed to solve many application problems that are cost prohibitive or simply cannot be solved by other sensors. Ultrasonic sensors continuously emit high frequency sound pulses inaudible to the human ear  which travel away from the sensor, hit the surface of the target and are reflected back to the sensor. The sensor electronics measure the time taken by the signals to return after being reflected by the target surface.

Since the speed of sound is affected by air temperature, our ultrasonic sensors include a built-in temperature sensor. Level/distance measurements are automatically temperature compensated throughout the operating temperature range of the sensor.

Sigma has a variety of sensors available to satisfy the requirements of most applications including Micro, a compact, ultrasonic level transmitter/switch that features Variable GAP technology that allows the instrument to work even in the presence of dust, vapour or foam. Variable GAP ensures accurate measurements by always working with the smallest return signal.
The gain is automatically increased if the return echo is being absorbed by dust or foam in the environment. Variable GAP technology also provides the narrowest beam angle in the industry, at less than four degrees. This allows the transmitter to make accurate measurements in narrow vessels. This transmitter measures liquid levels to 10m and bulk solids to 5m.