A magnetostrictive Level transmitter is a continuous level measurement device. It mounts externally to a magnetic level indicator (MLI) chamber and reads the magnetic field of the float. From there, it outputs a high-resolution analog signal to a PLC or DCS. No vessel penetrations required. No process contact.
How Does a Magnetostrictive Level Transmitter Work?
The Role of the Waveguide
Inside the magnetostrictive Level transmitter, a wire called a waveguide runs the full length of the measurement range. A current pulse travels down that waveguide. At the float position, a permanent magnet creates a localized magnetic field. When the current pulse reaches that field, it generates a torsional stress wave. That wave travels back up the waveguide at a known speed.
How Position Is Calculated
The transmitter measures the time between the outgoing current pulse and the returning wave. From that measurement, it calculates the exact position of the float. The result is a continuous level output accurate to within millimeters.
No Moving Parts in the Transmitter
Crucially, the transmitter contains no moving parts. Only the float moves. Position detection happens without physical contact between the transmitter and the float.
What Is a Magnetic Level Indicator?
How the Chamber Works
A magnetic level indicator is a sealed float chamber that connects to a process vessel. Inside the chamber, process liquid enters through process connections. It rises and falls at the same rate as liquid in the primary vessel. A float inside the chamber tracks that level. Magnets inside the float interact with an external flag indicator, flipping color-coded flags to show the current level in real time.
Process Containment and Operator Safety
Because the process stays fully contained, operators read the level from the external indicator without any process exposure.
Compatibility With External Transmitters
Beyond containment, engineers design MLI chambers to accept external transmitters and switches. That design makes them a direct mounting point for continuous level measurement devices, with no additional vessel penetrations needed.
Why Pair a Magnetostrictive Level Transmitter With an MLI?
Why Control Systems Need More Than Visual Indication
Visual indication alone does not feed a control system. Specifically, a PLC or DCS needs a continuous analog signal to automate control loops and trigger alarms. It also logs level data over time. A magnetostrictive transmitter mounted to the MLI chamber delivers that signal without adding process penetrations to the vessel.
Three Capabilities in One Installation
Together, the combination gives you three things in one installation:
- Real-time visual level indication from the flag indicator, readable without power
- Continuous high-resolution analog output for control and monitoring
- A single sealed pressure boundary, maintained throughout
Independent Verification During Instrument Conflicts
When radar or differential pressure readings conflict, operators use the MLI to verify level mechanically, independent of power or electronics. At the same time, the magnetostrictive transmitter continues to provide the signal the control system needs alongside that visual verification.
Common Applications
As a result, this configuration is standard in high-pressure separators, boiler drums, feedwater heaters, condensate collection tanks, slug catchers, and inventory management applications.
What Output Options Does a Magnetostrictive Level Transmitter Support?
Standard Output Protocols
Most magnetostrictive Level transmitter support three output protocols:
- 4-20 mA analog output for direct integration with PLCs and DCS systems
- HART communication for digital configuration and diagnostics over the 4-20 mA loop
- Modbus for serial communication in systems using RS-485 networks
Mounting and Field Serviceability
For installation, transmitters mount to the MLI chamber using non-ferrous hardware. Specifically, non-ferrous mounting prevents interference with the magnetic field interaction between the transmitter and the float. It also allows removal of the transmitter for calibration or replacement without taking the vessel offline.
What Applications Use This Technology?
Industries and Process Units
Magnetostrictive Level transmitter appear across process industry applications that require continuous level output alongside visual indication:
- High-pressure separators in oil and gas production
- Boiler drum level monitoring in power generation
- Feedwater heater level control
- Custody transfer and inventory management applications requiring high measurement resolution
- Condensate collection tanks in chemical and pulp and paper applications
- Slug catchers and liquid accumulators in gas processing
Material Options for Demanding Service
For demanding service, MLI chambers come in carbon steel, stainless steel, and exotic alloys for corrosive, high-temperature, and cryogenic applications.
Frequently Asked Questions
Magnetostrictive vs. Guided Wave Radar: What Is the Difference?
Both technologies deliver continuous level output and mount externally to an MLI chamber. Guided wave radar sends a microwave pulse down a probe inside the chamber. It measures the time of flight to the liquid surface. Magnetostrictive Level transmitter technology uses the magnetic field of the MLI float and does not require a probe inside the chamber. For standard liquid level applications, magnetostrictive transmitters typically cost less than guided wave radar. Engineers prefer guided wave radar in applications with foam, vapor, or where interface level measurement between two liquids is required.
Does a Magnetostrictive Level Transmitter Require a Vessel Penetration?
No. The magnetostrictive Level transmitter mounts to the outside of the MLI chamber. It reads the position of the float through the chamber wall using magnetic field interaction. The pressure boundary stays intact. No additional process connections or vessel penetrations are needed.
What Is a 4-20 mA Level Transmitter?
A 4-20 mA level transmitter outputs a continuous analog current signal proportional to the measured level. The bottom of the measurement range corresponds to 4 mA, and the top corresponds to 20 mA. PLCs, DCS systems, and safety instrumented systems across process industries support the 4-20 mA standard.
Can a Magnetostrictive Transmitter Be Used for Custody Transfer Measurement?
Magnetostrictive level transmitter technology delivers high-resolution level measurement suitable for inventory management and custody transfer applications. Whether it meets accuracy requirements for a specific custody transfer use case depends on the application conditions. Consult the transmitter manufacturer with your specific process data.
Can a Magnetostrictive Transmitter Be Added to an Existing MLI?
Adding a magnetostrictive Level transmitter to an existing MLI is possible in most installations. The transmitter mounts externally to the chamber using non-ferrous hardware, with no vessel penetrations required. Compatibility depends on the chamber model, float magnet configuration, and measurement range. Contact the manufacturer with your existing chamber model number and operating conditions.
Product Q&A:
The SOR Measurement and Control 1310 Magnetostrictive Level Transmitter and SOR 1100 Series MLI
Who Manufactures the SOR 1310?
SOR Controls Group designs and manufactures the SOR 1310. It is the only magnetostrictive level transmitter designed by the same manufacturer as the MLI it mounts to. SOR builds the 1310 specifically for the SOR 1100 Series MLI.
Why Does It Matter That the Transmitter and MLI Come From the Same Manufacturer?
Most MLI suppliers source their magnetostrictive level transmitter from a third-party manufacturer. When the transmitter and chamber come from different companies, you coordinate compatibility between two separate product lines. You also manage two separate support relationships. When both products come from the same manufacturer, the float and transmitter work together by design. The combination ships assembled and calibrated. One point of contact covers support throughout the installation lifecycle.
What Does the 1100 Series MLI Include?
The 1100 Series includes a patented Vista indicator with a 200-degree viewing angle and forward visibility of 250 feet or more. SOR builds the chamber to ANSI/ASME B31.1 and B31.3 guidelines. The design accepts external transmitters and switches without additional vessel penetrations.
How Do I Specify the SOR 1310 With the 1100 Series MLI?
SOR specifies, manufactures, and calibrates both products together at SOR Measurement and Control. They ship as a complete assembly. To configure the right combination for your application, contact SOR or find your local representative at sorinc.com.
To configure the right combination for your application, contact SOR or find your local representative at sorinc.com.
View the 1310 Magnetostrictive Level Transmitter
