The KOBOLD DOE is an oval gear (oval wheel) positive displacement flow meter designed for measuring viscous, non-abrasive, clean liquids such as lubricating and hydraulic oils, petroleum, grease, pastes, diesel fuel, ink, chemicals, solvents and resins. This compact meter handles viscosities from 2 to 1000 cP, pressures to 928 psi (64 bar) and temperatures to 176°F (80°C). It is sold only in quantities of 25 pieces or more per purchase order.
How the DOE Oval Gear Flow Meter Works
As liquid flows through the DOE, two oval geared rotors turn inside a precisely machined measuring chamber, and each rotation passes a constant volume of liquid. Magnets embedded in the rotors are used to sense their rotation, producing a high-resolution pulse output. With the Hall sensor, this is a square wave frequency signal linearly proportional to volumetric flow.
No flow profile conditioning or straight pipe runs are needed, which makes the meter simple to install in tight spaces.
Measuring Ranges and Accuracy
The DOE is available in five measuring ranges covering 0.14 GPH to 634 GPH (0.5 l/h to 40 l/min). Accuracy is ±1% of reading under reference conditions, with typical repeatability of ±0.03%. The one exception is the low end of the DOE-x04: ±3% of reading from 0.14 to 0.95 GPH, then ±1% of reading from 0.95 to 9.5 GPH.
- DOE-x04 and DOE-x05: 0.14 to 9.5 GPH (0.5 to 36 l/h), G 1/8 or 1/8" NPT
- DOE-x10: 0.5 to 26.5 GPH (2 to 100 l/h), G 1/4 or 1/4" NPT
- DOE-x15: 4 to 145 GPH (15 to 550 l/h), G 3/8 or 3/8" NPT
- DOE-x20: 16 to 634 GPH (1 to 40 l/min), G 1/2 or 1/2" NPT
Pressure, Temperature and Viscosity Ratings
The DOE is rated for a maximum pressure of 928 psi (64 bar) and for medium and ambient temperatures from -4°F to 176°F (-20°C to 80°C). It handles liquid viscosities from 2 to 1000 cP, and the housing is rated IP65. Exceeding the 15 psi (1 bar) maximum differential pressure or the maximum rated flow rate may damage the meter.
Materials of Construction
The DOE body and rotor axes are stainless steel 1.4404. Oval gear rotors are PEEK on the x04 through x15 and PPS on the x20. Rotor magnets are encapsulated in PEEK on the x04 through x10 and in stainless steel 1.4404 on the x15 and x20. O-rings are FKM or NBR, both rated -4°F to 176°F (-20°C to 80°C).
Pulse Output and Electrical Options
Every DOE electronics option delivers a calibrated pulse output. The Hall sensor output is a 3-wire NPN open collector connection powered by an external 5 to 24 V DC supply, with a maximum output current of 10 mA (not short circuit protected). Connection is a valve plug to EN 175301-803 form A or a 2 m (6.6 ft) UL/cUL cable.
- T0: Hall sensor pulse output
- H0: Hall sensor pulse output plus a reed switch (2-wire, normally open SPST, voltage-free)
- B0: bipolar Hall sensor pulse output for pulsating flow (x15 and x20)
- BP: bipolar Hall sensor pulse output for pulsating flow with a 3-wire Pt100 (x15 and x20, 2 m cable only)
Approximate T0/H0 pulse rates are 10,107 pulses per gallon (2670 per liter) for the x04 and x05, 3,990 (1054) for the x10, 2,688 (710) for the x15 and 617 (163) for the x20. B0/BP have half the K-factor: 1,344 (355) for the x15 and 310 (82) for the x20. Each meter ships with a calibration certificate stating its actual value.
Fuel Consumption Measurement
Sample applications for the DOE include fuel consumption measurement on small aircraft, motor boats and mobile power generators. With the BP option, a Pt100 sensor measures the temperature of the fuel inside the meter, so volumes at the inlet and outlet of an engine's fuel system can be temperature compensated for high accuracy consumption measurement.
Installation Requirements
A filter should be installed immediately upstream of the DOE: 200 mesh (75 µm) for the x04 through x15 and 100 mesh (150 µm) for the x20. Filters are sold separately. Flush debris from new piping before installation, mount the meter in its specified orientation, and purge air at a low flow rate.
- Locate the meter on the discharge side of the pump and before any flow control or shut-off valves.
- Install surge dampeners or pressure relief valves where hydraulic shock or pressure spikes occur.
- Do not allow the liquid to freeze or flash inside the meter.
Minimum Order Quantity: 25 Pieces
The DOE is not sold as a single unit. The minimum order quantity is 25 pieces per purchase order, and different DOE models may be combined to reach it. For projects requiring fewer than 25 units, please review our DON oval gear flow meters.
Common Questions about DOE - Oval Gear Flow Meter
DOE Oval Gear Flow Meter FAQ
The DOE is a positive displacement meter. Two meshing oval rotors sweep a fixed volume through a machined chamber on every turn, and magnets in the rotors trigger the pulse signal, so counting pulses gives the volume that has passed. Liquid conductivity does not affect the reading, and other fluid properties have only a minimal influence on performance.
The DOE is suitable for clean, non-abrasive liquids with a viscosity of at least 2 cP and no more than 1000 cP. Its accuracy rating is based on calibration oil of 10 cSt (x04 and x05) or 4.6 cSt (x10 through x20), and that rating holds for liquids at those viscosities or thicker. Typical liquids include oils, grease, pastes, fuels and ink.
Maximum operating pressure is 928 psi (64 bar). Both the process liquid and the surrounding air may range from -4°F up to 176°F (-20°C up to 80°C). Keep the pressure drop across the meter at or below 15 psi (1 bar). When using the reed switch, liquid temperature must not change faster than 18°F (10°C) per minute.
Connect red to +Vs, black to 0 V/GND and white to signal, powered from 5 to 24 V DC. If your counter or PLC input lacks an internal pull-up resistor, fit one between the white and red wires: 10 kΩ is recommended, 2.4 kΩ minimum. On BP units, the yellow, green and blue wires carry the Pt100.
No. An oval gear meter needs no upstream or downstream straight run and no flow conditioning. What it does need is clean liquid: place a filter directly ahead of the inlet (a 200 mesh, 75 µm screen suits the x04 to x15, while the x20 takes 100 mesh, 150 µm) and flush new pipework first.
Choose B0 or BP. These options use bipolar Hall sensors with alternating polarized magnets, are offered on the x15 and x20 ranges, and have half the K-factor of the T0/H0 versions. BP adds a Pt100 temperature sensor. For highly pulsating flow, such as from diaphragm pumps, install proper pulsation dampers as well.
Each range has one port size, offered with either G or NPT threads. The x04 and x05 use 1/8", the x10 uses 1/4", the x15 uses 3/8" and the x20 uses 1/2". Select R for G threads or N for NPT in the connection field of the order code.
No. Each purchase order for the DOE must total at least 25 pieces, so single units are not available. You can mix different DOE models in one order to reach that minimum, combining measuring ranges, thread types and electronics options. If your quantity is under 25, take a look at the KOBOLD DON oval gear flow meter line instead.
Product Specifications
Measuring Range
0.14...9.5 GPH to 16...634 GPH
Process Connection/Type
1/8"...1/2" NPT Thread, G1/8...G1/2
Maximum Pressure
928 PSIG (64 Bar)
Maximum Temperature
Up to 176 °F (80 °C)
Housing Material
Stainless Steel
Rotor Material
PEEK or PPS
Minimum Order
25 Pieces per PO
Product Features
Pulse Frequency Signal Output
Stainless Steel Body w/PEEK or PPS Rotors
Media Viscosities from 2...1000 cP
Sample Applications: Fuel Consumption Measurement for Small Aeroplanes, Boats, or Generators
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