The DON is a positive displacement oval gear flow meter that measures clean, viscous, and non-abrasive liquids by volume, delivering accurate volumetric readings across flow rates from 0.13 GPH to 660 GPM (0.5 L/h to 2500 L/min). Available in aluminum or 316L stainless steel, the series is the preferred choice for highly viscous fluids in industrial process applications, and its compact body installs economically in tight spaces.
How the DON Oval Gear Flow Meter Works
Two oval gear rotors turn inside a precisely machined measuring chamber, capturing a fixed volume of liquid with each rotation. Magnets embedded in the rotors sense that rotation and transmit a high-resolution pulse output, which a remote controller, PLC, or local display converts into flow rate and total. Because measurement is volumetric, media conductivity does not affect the reading. A range of output and display accessories mounts directly to the meter for local indication.
Flow Ranges, Line Sizes, and Connections
The DON spans 13 model sizes covering 0.13 GPH on the smallest meter up to 660 GPM on the largest, in line sizes from 1/8 inch to 4 inches. Process connections include NPT or BSP threads and ANSI or DIN flanges, so the meter drops into most existing pipework without adaptation.
Viscosity and Media Compatibility
Standard rotors handle viscosities up to 1000 cP, and special cut rotors are available for significantly higher viscosities. The DON suits clean, non-abrasive liquids such as petroleum, oils, fuels, greases, inks, chemicals, and pastes. On thicker media the maximum flow rate is derated according to KOBOLD's published multiplier table.
Pressure, Temperature, and Accuracy
Maximum pressure ratings reach 1450 PSIG (100 bar) on smaller and stainless models and step down to 230 PSIG on the largest sizes. Media temperature capability spans -4°F to 302°F (-20°C to 150°C) depending on the seals and electronics selected. Typical accuracy ranges from ±0.2% to ±1% of reading, by model and electronics.
Materials of Construction
The DON is built in aluminum or 316L stainless steel. Aluminum-body meters are compatible with fuels, fuel oils, and other lubricating liquids, while stainless steel meters suit most water-based products and chemicals. Rotor and gear materials include PPS, PTFE, PEEK, or stainless steel depending on the model and viscosity. Confirming that the wetted materials match the process media is important for reliable, long-term measurement.
Output, Display, and Communication Options
Output choices include reed switch and Hall-effect pulse outputs, a loop-powered 4-20 mA analog signal, and quadrature outputs for bi-directional flow. Local options add LCD rate/totalizers and batch controllers, a mechanical totalizer on 1/2-inch through 4-inch meters, and U-PACE electronics with a configurable TFT display, integrated temperature measurement, and IO-Link communication.
Certifications and Installation
The DON carries ATEX and IECEx approvals for hazardous areas, with CSA-certified U-PACE electronics for ordinary locations. Its positive displacement design needs no straight pipe runs or flow conditioning, simplifying installation in space-constrained systems. An inlet filter is recommended, with mesh sizing selected to match the meter size.
See It in Action: Dosing Viscous Fluids
Wondering how this meter performs on a real dosing application? Our use case walks through a lubricant blending skid dosing an 800 cP additive to a 50-gallon target, and explains why oval gear measurement holds its accuracy where velocity-based meters struggle. Read Precise Viscous Fluid Dosing with the KOBOLD DON.
Common Questions about DON - Positive-Displacement Flow Meters
The DON handles clean, non-abrasive liquids, including petroleum, fuel and lubricating oils, greases, inks, pastes, and many chemicals. Aluminum bodies fit fuels and lubricating oils; stainless steel versions cover water-based media and most chemicals. Abrasive or particle-laden fluids should be filtered upstream to protect the oval rotors.
With standard rotors, the meter measures fluids up to 1000 cP. For thicker media, special cut rotors extend the range much further, though maximum flow is reduced per a published multiplier—for example, a DON-x25G on 8000 cP oil derates from 40 GPM to about 20 GPM.
Typical accuracy is ±0.2% to ±1% of reading, set by the model, rotor material, and electronics. Stainless steel rotors reach ±0.5% of reading, improving to ±0.2% with optional linearization electronics; PPS rotors are rated ±1%, improving to ±0.5%. The smallest x04 meters are rated ±1% to ±3%.
No. Because it meters by positive displacement rather than inferring velocity, the DON needs no upstream or downstream straight-run piping and no flow conditioning. That makes it well suited to compact, space-constrained installations. Mounting orientation and flow direction should follow the model's ordering configuration and the installation manual.
Yes. The DON is certified to ATEX and IECEx and can be installed in hazardous areas when ordered with the appropriate approval, such as flameproof (Ex d) electronics or an intrinsically safe reed-switch pulse output used in an I.S. loop. U-PACE electronics additionally hold CSA certification for ordinary locations.
Pulse signals are available as reed-switch or Hall-effect types, alongside a 4-20 mA loop-powered analog output and a two-channel quadrature output that indicates flow direction. For local readout, choose an LCD rate/totalizer or batch controller, a mechanical register on larger meters, or U-PACE electronics offering IO-Link and on-board temperature measurement.
An upstream filter is recommended to keep particles away from the gear set. KOBOLD suggests roughly 75 µm (200 mesh) for the smallest x04–x15 meters, 150 µm (100 mesh) for x20–x35, and 350 µm (45 mesh) for x40–x60. Matching filtration to meter size protects accuracy and service life.
Yes. Ordered with the quadrature Hall-sensor option, the DON provides two phased outputs that detect flow direction, so it can read bi-directional flow and support batching or fill-and-dispense control. Standard single-channel pulse versions read flow in one direction and are typically specified for continuous, unidirectional processes.
Line sizes run from 1/8 inch on the DON-x04 to 4 inches on the DON-x55 and x60. Threaded ports are offered in NPT or BSP, and flanged versions in ANSI (150 lb and 300 lb) or DIN (PN16, PN40, and larger) ratings, letting the meter match existing process piping.
Product Specifications
Flow Ranges
0.13...9.5 GPH to 40...660 GPM
Fittings
NPT or BSP Threaded, ANSI or DIN Flanged
Max. Operating Temperature
Up to 300 °F (150 °C) (Output Option Dependent)
Product Features
Aluminum or Stainless Steel Bodies
Viscosity range up to 1000 cP (standard), higher viscosities with special cut rotors
Operating Pressures to 1,450 PSIG (Model Dependent)
Electronic Output Options Include Analog and Frequency Outputs, LCD Totalizers, Batch Controllers, U-Pace Electronics: IO-Link and Temperature Measurement
Mechanical Totalizer (½"...4" Meters Only)
Bi-directional Flow Sensing with Optional Quadrature Output
Certifications/Approvals: ATEX
Documents
Software Downloads
There are no downloads to display at this time. If you think this is incorrect, please contact us and let us know the issue you are having.
Videos
C3T0 Electronics Technology Explained
Join KOBOLD Applications Engineer Michael Besser for a comprehensive look at C3T0 technology and its practical applications in flow measurement. In this informational session, we'll explore how C3T0 technology works and where it's implemented across KOBOLD's product line. There are two configurable outputs and a grand and resettable totalizer. Temperature measurement is also integral and bi-directional flow measurement is also possible. To learn more about our U-PACE C3T0 electronics package,
view our U-PACE Video.
U-Pace: KOBOLD's Universal Flow Control Electronics for Industry 4.0
Discover KOBOLD's cutting-edge U-pace electronics for flow meters, designed to seamlessly integrate with Industry 4.0 standards. This video showcases our state-of-the-art technology that combines precision flow and temperature measurement with advanced communication capabilities.
Accessories
There are no accessories to display at this time. If you think this is incorrect, please contact us and let us know the issue you are having.