Micro Motion FVM Fork Viscosity Meter

Viscosity, density and temperature from one insertion meter

The Micro Motion Fork Viscosity Meter (FVM) is a multivariable direct-insertion meter that measures liquid viscosity, density and temperature continuously. The datasheet quotes viscosity accuracy of ±1 percent of full scale and density accuracy of ±1 kg/m3, with stem lengths up to 13 ft (4 m). It is used in product detection, fuel blending and heater combustion control, and in pipelines, bypass loops and tanks.

Technical specifications

Outputs, calibration and selection

The meter reports dynamic viscosity, kinematic viscosity, referred kinematic viscosity (ASTM D341-03), density, referred density including API tables with a live pressure input, and temperature. The tine bandwidth changes with viscosity and is converted with up to 11 viscosity calibration fluids, while three fluids calibrate density. Pick the calibration range that matches the viscosity window, because accuracy is stated against the range maximum rather than the reading. Known Density Verification supports health checks. For density only, see the Micro Motion fork density meter; for flow with density see the Micro Motion ELITE CMF400.

The fork temperature is read by a class B 100 ohm RTD, and the transmitter uses it to optimize performance. Newly shipped devices carry a QR asset tag that links to serialized drawings and documentation, and ProLink III software is the configuration and service tool.

What to confirm before ordering

• Fluid, viscosity window and the calibration range code required
• Operating temperature and pressure, and the stem length (code 1 or 2, or special order)
• Wetted material and tine finish for the fluid
• Transmitter output, display requirement and hazardous area approval
• Installation position, because the fork needs the tines fully immersed in the flowing process stream

How the Micro Motion FVM works

The FVM is a probe that is pushed into a liquid. At its end is a pair of tines, like a tuning fork, that a drive coil keeps vibrating at their natural frequency. A thicker liquid damps the vibration more and changes how the tines move. A heavier liquid changes the vibration frequency. The electronics read both changes and calculate viscosity and density. A temperature sensor in the probe adds the temperature and corrects the readings for it.

Where the Micro Motion FVM is used

• Product detection in pipelines
• Fuel blending
• Heater combustion control
• Bypass loops and tanks
• Replacement of older Visconic viscosity meters

Selection checklist for the Micro Motion FVM

• Viscosity range in cP
• Short stem or long stem
• Process temperature and pressure
• Tine finish: standard, electro-polished or DLC
• Transmitter housing material
• Hazardous area marking required
• Process connection and insertion length
• Output signals needed

Installation, commissioning and maintenance notes for the FVM

Insert the probe where the fluid flows past the tines and where air bubbles do not collect. Keep the tines clear of the pipe wall. Wire the transmitter and enter the calibration data from the sheet supplied. Check the readings against a lab sample. Clean the tines when the fluid leaves a film, taking care not to bend them.

Requesting a quotation for the Micro Motion FVM

Please send the viscosity range, the temperature, the pressure, the connection and the quantity. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

FVM viscosity ranges

Calibration ranges are 10 to 100 cP, 100 to 1,000 cP and 1,000 to 12,500 cP. A 0.5 to 100 cP range is also offered.

FVM density performance

Density accuracy is plus or minus 1 kg/m3, with repeatability of plus or minus 0.1 kg/m3.

FVM temperature and pressure

The short stem works from minus 50 to plus 200 degrees C at up to 207 bar. The long stem works to 150 degrees C at 100 bar.

FVM materials

Wetted parts are 316L stainless steel. The transmitter housing is stainless steel or painted aluminium.

FVM measured values

The meter reports dynamic viscosity, kinematic viscosity, density and temperature.

Meter records for the FVM

Record the calibration range, the tine finish and the lab check results.

Choosing the right FVM stem

Choose the stem length from how deep the tines must sit in the line or tank.

Documents and quotation

The Micro Motion Fork Viscosity Meters datasheet (PS-001486 Rev I, February 2024) is available from the product documents on this page. Seven Star LLC is an independent supplier in Muscat; send the complete order code from the nameplate or your specification and we will check it against the manufacturer documentation before quoting. Browse more flowmeters in the catalogue.