M3900 In-Line Viscometer


  • Height: 12 in.
  • Width: 4.5 in.
  • Depth: 5 in.
  • Weight: 15 lbs (25 lbs if attached to base)
  • US Patent: 8,850,874

Single rotating element submerged in test fluid without a dynamic seal
The only moving component in contact with test fluid is the rotating bob. This patented design ensures reliability of test results over a longer period of time than any competing model can provide, without the use of any dynamic seal.

Easy breakdown for cleaning and maintenance
Access to all internal components is accomplished by a one-action dismount, providing fast access for maintenance and cleaning, maximizing performance and minimizing maintenance.

The Grace Instrument M3900 In-Line Viscometer is designed to be easy to operate in process while providing a dependable and powerful viscosity measurement system. The simple, streamlined structure allows for long periods of low maintenance operation, during which time the unit is in constant service. Stainless-steel construction ensures that the M3900 will provide years of functionality.

When maintenance is required, the patented design of the M3900 provides quick access, making maintenance easy and efficient. The M3900 In-Line Viscometer is intended for use with a wide variety of fluids, with a special emphasis on fracturing fluid and drilling mud.

U.S. Patent: 8,850,874
Dimensions: 12" height x 4.5" width
Weight: 15 lbs (25lbs if attached to base)
Viscosity Range: 5 cP to 300 cP - mPa.s
Pressure Range: Atmospheric pressure up to 2,000 psi
Speed Range: 3 and 6 rpm; 50 to 600 rpm continuous
Output: 0 to 5 VDC analog output or RS485 Modbus output
  • Compliant with API 13 and API 39
  • Viscosity measurement unaffected by fluid flow
  • Computer-controlled speed, viscosity measurement and calibration
  • Multiple data export formats
  • Easy to operate and calibrate
  • Unique and durable design with fast cleaning and simple maintenance


Comparison results between Grace M3900 and Leading Competitor
No. Feature Grace M3900 Competitor's In-Line Viscometer
1 Compliant with API 13 and API 39 Yes No
2 API Testing speeds: 3, 6, 100, 200, 300, 600 rpm Yes No
3 Viscosity measurement unaffected by fluid flow Yes No
4 Patented design without dynamic seal enables minimum maintenance and instant repair.

M3900 has patented magnetic drive motor for more accurate readings, and therefore no dynamic seal, so it is much easier to clean.
Yes No
5 M3900 minimum viscosity reading of 5 cP Yes No
6 M3900 thick wall pressure rating up to 2000 psi Yes No
7 M3900 has analog or modbus output Yes No
8 M3900 includes control panel with LCD viscosity reading Yes No
Downloads for the Lubricity Dynamic Filtration Drilling Simulator: